RFIC46 system user manual
Contents
1. Connect the system as indicated in fig 18 Select the appropriate injection device and mode in the Main menu Transducer Page 27 Laplace Instruments Ltd User Manual RFIC46 iss E screen The calibration data for the relevant device must be entered Once the EUT is fully connected and operating normally in the required mode the test can commence Click the Enhanced Test RUN button The progress of the test can be monitored on the RESULTS screen and on the MONITOR screen When the test is completed the test data can be saved to file using the File Save menu This will save the setup information the actual stress level data and the EUT monitor results Scan Modes The RFIC system has three modes for running the test in terms of frequency and stress level Mode Details Standard Steps through the specified frequency range from start to finish frequency with a fixed stress level Step size and dwell time are user selected Single Applies the stress at a single frequency The frequency and or stress level can be entered manually or can be stepped in pre set increments using Up Down nudge buttons In addition an Auto Increase mode can be selected in which the stress level can be automatically incremented after a specified dwell period This can be set to stop when an EUT failure is detected Note that this mode cannot be used in Conventional mode Custom Similar to Standard except that the stress level can2. That plotted in Figure 5 exhibits a fall of 5 to 6dB over a wide range of frequencies around 15 and SOMHz whilst that in Figure 6 shows a 9dB fall in coupling in a narrow frequency Page 36 Laplace Instruments Ltd User Manual RFIC46 iss E range at about 67MHz In CDN B the wires occupied separate sections of the core perimeter The resulting large leakage inductance resonates with stray capacitances but is damped by the core losses producing the broad resonance bands that may be seen in Figure 5 O foo eh TTT es L In contrast CDN A embodied a choke constructed with its three wires twisted together before winding This minimises leakage inductance but there is still a Sa Sen narrow band resonance at 67MHz at which Sees the wire being measured is almost totally ee disconnected from the other two wires It Lane can only see its own 3R injection resistor At this frequency the length of the wires that form the CDN choke is an electrical quarter wave The wires are short circuited to rf at the AE end by the capacitors CD see Figures 3 or 4 This short circuit is transformed by the quarter wavelength into a very high mutual Figure 6 Loss through M3 CDN A with unbalanced impedance at the EUT end This is purely load a differential mode effect in which the ferrite choke core plays no magnetic part The Q factor of the resonance is high since the only losses involved are t
3. can be used to display the stress Enhanced a level if required Note that this is mode 7 not used for level control ol feedback Optional vee monitor oA probe The system can be used in the AE sa ran EUT Enhanced mode The calibration A data for the monitoring probe m should be entered into the Femite Gem software and then the test can Ground reference plane be run in one operation subject to the cautions explained in section 3 Figure 23 BCI Phase 2 EUT Monitoring The RFIC46 is equipped with 4 analogue input channels A B C and D These are all identical They have a range of 0 10v input impedance 100Kohm single ended These inputs are sampled at a rate of approx 1Hz during the dwell time at each frequency The resulting measurements are plotted on the PC screen in graphical and bargraph format See section 7 for more details EUT Prompt This facility enables the EUT to be prompted at the start of each dwell period This is to synchronise any cyclic operation of the EUT with the stepping of the test through the frequency range If selected in the test setup screen a 4 pole relay inside the RFIC46 unit operates a 4 pole c o relay for 1 second at the beginning of each dwell period The 12 contacts are brought out to the 15 pin D type connector on the front panel Page 18 Laplace Instruments Ltd User Manual RFIC46 iss E 6 Hardware The RFIC system comprises 3 elemen
4. e Because it uses a series of ferrite sleeves to provide the inductive coupling it is quite long and to provide good capacitive coupling it has a relatively narrow inside diameter This makes it bulky to use and restricts its application for short or large diameter cables e Below 10MHz its directivity is negligible and therefore the AE low frequency common mode impedance is not decoupled e It does not provide an accurate source impedance of 150Q across the frequency range Page 38 Laplace Instruments Ltd User Manual RFIC46 iss E Current injection probe The current injection probe or Bulk Current Injection BCI probe was not part of the original method but was added before the standard was published at the insistence of several laboratories who were already using it for military standard tests It acts as a current transformer whose secondary is the cable under test it provides inductive injection only Advantages e Its main advantage and the reason it is widely used by many labs is that it is both convenient and non invasive Because it is compact and can be made with quite a wide aperture it can be used on virtually any cable even short runs with limited access This makes it the transducer of choice for in situ tests Disadvantages e Balancing this practical advantage are several technical failings There is absolutely no decoupling of the AE since the current induced on the cable must flow both into
5. Laplace Instruments Ltd User Manual RFIC46 iss E EUT Interface Conducted RF immunity test system controller User Manual Page 1 Laplace Instruments Ltd User Manual RFIC46 iss E Page 2 Laplace Instruments Ltd User Manual RFIC46 iss E CAUTIONS ALWAYS ENSURE THAT THE SYSTEM IS FULLY CONNECTED PRIOR TO START OF ANY TEST OR CALIBRATION SEQUENCE This system can generate significant levels of RF power The amplitude of this power is controlled via feedback from the relevant transducer If this feedback is not correctly connected the applied RF power may rise to maximum which may damage your test equipment and or EUT RF power amplifiers must always be connected to a suitable matched 50 ohm load or transducer before any power is applied Failure to ensure this may result in damage to the power amplifier CHECK THE MAINS VOLTAGE RATING OF THE RFIC46 SYNTHESISER BEFORE CONNECTING THE MAINS POWER This item is not dual voltage ALWAYS CHECK THE GROUNDING ON CDNS AND OTHER INJECTION DEVICES AND ANY CALIBRATION ADAPTORS Failure of any grounding may cause loss of control and potential damage to injection devices and or EUT Page 3 Laplace Instruments Ltd User Manual RFIC46 iss E Page 4 Laplace Instruments Ltd User Manual RFIC46 iss E CONTENTS 1 Introduction 1EC61000 4 6 Compliance Criteria 2 Stress injection devices CDN EM Clamp BCI Bulk Current Injection 2 1 Cable matching
6. overload The operation of the RFIC46 is entirely controlled by the RFIC software supplied with the unit There are no controls on the hardware itself Indications The bargraphs for RF output level and Feedback level are for indication only These are provided to give an approximate indication of operation of the system The red levels are simply an indication that the levels are approaching the maximum levels not an indication of overload When the feedback is being used for level control the indications will not generally be equal This is normal The feedback level will be driven by the feedback input that is currently selected as indicated by the green LEDs adjacent to the input BNC connectors Status Indications Standby RF output is switched off and the system is dormant PA Status This will indicate if the PA is switched into standby mode EUT Prompt Prompt relay energised Running System is in dwell mode Front panel layout RF output Feedback Analog inputs Mains power level signal level for EUT power indicator indicator monitoring indicator Laplace Instruments Ltd RF OUTPUT FEEDBACK A O B ro c D Max 30dBm P A Interlock Q EuTimerace CO RFIC 4 6 SYNTHESISER 100KHz 250MHz 6 SYNTHESISER 100KHz 250MHz Page 20 RF output to Feedback Power EUT Pr
7. EUT monitor channels Details Area A Status Indicators show the status of the hardware Ready System OK and operational Running Test running in dwell mode Settling System adjusting the stress level to the required level Modulation Modulation running Standby System in standby mode RF output switched off EUT OK No EUT fail detected Fail EUT failure detected Prompt EUT prompt activated Page 23 Laplace Instruments Ltd User Manual RFIC46 iss E ot Laplace instruments Ltd RFIC 4 6 Cle Gecplay ode Jransdce Configre teip STATUS Ready TANDARD SETTINGS l 2 Start 0 20 MHz EUT Status i A D op f Continue Modutstion O Finish 000 MHz EUT Prompt Standby C OF Pulko EUT Stress E1 vate E2 OK a Modulation None a Fault D v C 200Hz G thHe P t 0O ateka Sip 50 Modulation 20 FAULT Synth oO Dwell j2 secs PA oO Reset Continuous Hortons Estimated Time 25 03 Channel A Active i Channel B Acte F Channel C Actne V Channel D Active Standard Test MONITORF e gt testall RF Curent 0 645 MHz DwelfO Secs Target 0 0 D Control EE Btempersturc be REE Modulation dkHz Total 01 17 Actua O00 gt Fee M 100kHz 10MHz Frequency Elapsed Time Stress Level bots lt F 1MHZz 250MH2 Conventional IRF how trom Cainration OAS a a C AE SETE Test ride amp Osan Peak Re an TEST STANDARD SINGLE CUSTOM TEST MODE Enhanced Feedback vis Enhanced CDH ard Test DC nopia or Celbrate
8. In this instance if using the Laplace Versatile CDNs the following models could be used Cable type Conventional CDN Versatile CDN Other cables covered by versatile CDN 2 core mains M2 M3 M1 M3 Page 12 Laplace Instruments Ltd User Manual RFIC46 iss E 5 TEST Set out the test equipment EUT and AE as described in the previous section Reference to EC61000 4 6 is recommended to ensure the arrangements are compliant Selecting the injection device and mode Generally the choice of injection device will have been made according to the constraints of the product and cabling The key choice may then be test strategy Conventional or Enhanced To enter these factors go to Main menu Transducer A selection screen will be shown see fig 13 Laplece festruments Lid Hi iC 4 4 input Device Selection Select Input Orrice Setect Mode Salat Caltration Fils fan CON Btandardj Load Naw Efteantad CON Calteation Filo C CON nhan et EH Clare id Load New Curent Proge Calitewion Data A EM Claro wth Current Probe Bu 2 Load New Current Proba Calibration Data C Bwth Current Probe 1 Cane Dore Figure 13 Test setup selection screen Click on the appropriate input device as listed on the left side Once this selection has been entered the appropriate mode and calibration options will be enabled For example Leplece lretrerrents Lid KE IL 4 6 lopat Devine Selection Bact
9. agar Ocke actactMces aera The conventional of ad Comastonal Load Naw intared CON CatestonFis standard CDN has been CEEA IE Ha veat selected In this case there are no further choices as jr i Kinet Rina Saa Posie 5a Meath Saks this can only be used in ENS ATEN the conventional mode and no calibration file is Loyi Nw Suert Probe Cattention Data required Figure 14 Conventional selection Page 13 Laplace Instruments Ltd User Manual RFIC46 iss E In this next instance the Enhanced model of CDN is selected This may be used in a Conventional or Enhanced mode so both these options are made available If Enhanced is selected the options to select the relevant calibration file or to load a new file are available If Conventional mode is selected No Cal file required is highlighted Selecting Enhanced mode activates the options to load a calibration file or to select one from the existing list A window is displayed in which any previously loaded CDN can be selected from a list or a new CDN loaded A browse feature is included so that the relevant file can be selected from for example the CD and installed x EAT change the selection SclartCesbeatins Fa click RESET ALL and the page will return to its initial state Leplece lpetrerents Lid HI IL 4 6 lepat Devine Selecton Satis Opata Botariw oda CON Dian cand Cora rtonal Load Nzw Entana dCEN Caterionf is w COM IE t
10. be varied against frequency Data Entry is via a table in which key nodes are entered The software will automatically interpolate between nodes EUT monitoring There are 4 channels of analogue inputs available Each is a O 10v input To configure these inputs select Configure EUT input setup from the main menu The window shown in fig 33 will be displayed EUT Settings Each channel can be Display given a name a colour Name Low Limit High Limit All parameters are scaled emPerature 2 000 7 000 Colour aii he Mira Im Im f Any excursion outside level foo Boo Colour the limits will e treated by the software as an Limit Colour EUT failure The action on EUT Failure is defined by the user in Fig Accept Data Change 30 section E2 EEE TELLI Fig 33 EUT monitor setup screen Page 28 Laplace Instruments Ltd User Manual RFIC46 iss E The inputs can be checked by using the Single button in area E3 on the main screen This will display the current values of the input channels Once a test is in progress these inputs can be plotted on the Results page available by clicking on the REPORT RESULTS SCREEN button Laplace Instruments Lid RFIC 4 6 Fe ipay Mode Transducer Configure Hep STATUS TITLE Ready REPORT Running Settling Modulation Hardware CG Bi control PBtemperture F Bl Feed So Bie B E presen 6 sero gt Control Limits temperate Limits Feed Limits tevel Limits No
11. impedence 100R Power amplifier Figure 7 Setting the level 3 Testing Strategies Basic choices There are two sets of alternative techniques one set related to the test strategy and one Set related to the injection technique Test Strategy The Standard EC61000 4 6 specifies the use of a substitution technique for setting the stress level The RFIC system offers that technique strategy plus an alternative technique based on the use of Enhanced CDNs This alternative strategy is not described in the standard but does offer several advantages Key differences are The conventional strategy is strictly compliant But the alternative technique will generally provide a more consistent stress level This may not be a good feature The actual stress level imposed on the EUT in the real world will be very dependant on the EUT input impedance If this is high the voltage stress level will be high The conventional technique allows this variation due to the EUT characteristics So the imposition of a more consistent stress may be retrograde The Enhanced CDN overcomes this issue by monitoring the stress level at the RF input to the CDN not at the EUT cable This problem does however apply to the use of an enhanced mode when EM Clamps or BCI probes are used In these Page 9 Laplace Instruments Ltd User Manual RFIC46 iss E L Test strategy I 1 i ti F Alternative ml Test strictly according technique to
12. the EUT and the AE Therefore the AE is being tested just as much as the EUT e The applied stress is very dependent on cable layout and AE impedance The current flowing into the EUT is determined by the impedance of the cable which acts as a transmission line at high frequencies and so may have standing waves due to mismatches and by the impedance to the reference plane of the AE So this offers the highest uncertainty and least repeatability of all the methods e The probe is lossy and has a high power requirement The higher its internal turns ratio the more power is needed but low turns ratios affect the coupling of the probe to the cable and are effectively forbidden by the standard Equivalence of results The standard does not categorically specify which transducer method to use Its Figure 1 Rules for selecting the injection method asks the first question Are CDNs suitable to which if the answer is yes they should be used Criteria for suitability are not defined Clause 6 2 of the second edition says that CDNs are to be preferred but are not mandatory In the European pre standard ENV 50141 they were mandatory for all AC and DC power supply cables but only a recommendation appears in IEC 61000 4 6 in clause 6 2 1 1 It must therefore be assumed that if one laboratory decides that for a particular port a CDN is suitable and uses it while another does not and uses an EM clamp and a third elects for the current injec
13. 0cm above the ground reference plane These problems have been addressed in A1 to the second edition 5 This adds an informative Annex F Test set up for large EUTs The modified set up uses either an elevated horizontal ground reference plane to which the CDNs are bonded and which allows the CDN EUT cable length to be maintained at less than 30cm or a vertical ground reference plane again used for bonding of the CDNs The vertical GRP for instance a screened room wall is likely to be the more attractive to test labs since it can be used for all types of EUT regardless of the actual height of their cable entries It will also give more repeatable results than an elevated horizontal plane which is likely to suffer from resonances caused by its own capacitance and an inductive connection to the main ground reference plane In all cases the dc or low frequency current path through the transducer should be controlled to prevent saturation of the ferrite This requires that for all circuits the flow and return conductors must go through a single transducer For example even if a high power dc supply uses separate cables for its positive and negative wires these should both pass through a single M2 CDN CDN Selection Use the right one for the cable don t use M3 for M2 M5 for M3 etc unless the CDN supplier specifically recommends this For details see CDN Cautions above Grounding Ground it properly The disturbance voltage
14. 2 2 Setting the stress level 3 Testing strategies Conventional Enhanced 4 Test setup CDNs 5 Testing Selection of injection device and mode Setup with CDN EM Clamp and BCI EUT interface 6 Hardware 7 Software reference 8 Annex A Best Practice B Shipping list C Software installation D File organisation Page 5 Laplace Instruments Ltd User Manual RFIC46 iss E 1 INTRODUCTION EMC compliance testing requirements include a check of the susceptibility of a product to RF interference coupled into it via any cables that may normally be connected The standard that defines this test is 1EC61000 4 6 This test normally covers the frequency range 150KHz to 80MHz or sometimes to 230MHz The level of applied RF the stress level may be defined by the particular product specific standard but otherwise the default values are 3V rms for products intended for domestic amp commercial environments and 10V for Industrial environments Although the test seems at first sight to be very straightforward in practice it requires great care in terms of setup and application Key issues are Repeatability Coupling Stress level calibration The first two issues are dependant on the test setup especially given the high frequencies involved At the higher frequencies capacitive coupling to surrounding objects and impedance matching become critical For these reasons test configuration and setup are critical Figure 1 sho
15. F and UHF impedance measurement Richard Marshall to be published in the May issue of the EMC amp Compliance Journal Tim Williams is with Elmac Services www elmac co uk Richard Marshall is with Richard Marshall Limited www design emc co uk Page 43 Laplace Instruments Ltd User Manual RFIC46 iss E This page is intentionally blank Page 44 Laplace Instruments Ltd User Manual RFIC46 iss E ANNEX B Shipping list Item RFI C46 RFO250 Software Supplied on CD CDNs As ordered 6dB attenuator As ordered Cable BNC BNC RFIC46 to RFO250 Cable N N RFO250 Atten if used Cable N BNC Atten to CDN Cable BNC BNC Feedback signal BNC right angle CDN connections adaptor 50o0hm termination 462ZZ As ordered Calibration adaptors 46GP As ordered Ground plane 46XP As ordered Extension ground plane USB cable PC to RFIC46 15 pin D type For EUT prompt plug Cable cover for above 4 pin DIN cable RFIC46 to RFO250 interlock Page 45 Laplace Instruments Ltd User Manual RFIC46 iss E This page is intentionally blank Page 46 Laplace Instruments Ltd User Manual RFIC46 iss E Annex C Software installation The software is supplied on a CD together withy any relevant calibration files required for CDNs and a copy of this manual in pdf format CD Contents RFIC_4_6 msi Main program install file USB_Drivers DeVaSys_UsbI2clo_Drivers_32_bit msi D
16. IEC61000 4 6 Use monitor probe EM and 150R calibration Pre scan not required Clamp i fixture Use monitor probe i Use monitor probe BCI and 50R calibration probe fixture Pre scan technique Figure 8 Overview of test techniques instances the feedback is obtained from current monitor clamps fitted to the EUT cable and are thus measuring the stress level at the EUT cable This negates the effect of the EUT input impedance Alternative technique is quicker no need for a calibration pre scan Alternative technique does not require the 6dB attenuator in the RF output feed to the CDN This halves the required power rating of the power amplifier The alternative technique cannot be used with MDM a A i conventional CDNs but can ORE milli be used with Enhanced CDNs voltmeter f 6dB and subject to some further E j ane Signal Power attenuator A considerations EM Clamps and enerator amplifier BCI probes too j i l L IEC61000 4 6 Standard technique The conventional strategy requires 2 Note a scans through the frequency range 6dB attenuator to match con LY gt EUT An initial scan with the EUT generator source impedence to AE oi substituted by a calibration fixture pete pls ia baad This fixture involv
17. Limit Display Stress Levely E MONITOR Enhanced Standard Test Curent 100 000 MHz Dwell 0 0 Secs Tage O0 Vols A Contral E5 B temperature ee 250MHz Modulation None Total 11 01 Actual 0 0 Vols Food HO ls i O0kHz 10MH2 Frequency Elapsed Time Stress Level Stats i MHz 250MHz Cemventional RF reut trom Cn bra on gt j T l dean comarca STANDARD SINGLE CUSTOM TEST MODE Enhanced Pescback vis Enhanced ODM and Tua Goraua casein _Test REPORT RESULTS SCREEN EUT Settings On this screen the following parameters can be observed by clicking on the tick boxes across the bottom of the graph area Set point stress level Actual stress level This shows the measured values during an enhanced test If a conventional test then this shows the values obtained during the pre scan EUT monitor levels EUT monitor limit levels In addition the Monitor area provides readouts of the frequency actual stress level timing and EUT status OK or Fail The above screen shows the 4 analogue input channels plotted Note that each channel may show as 2 lines These represent the max and minimum measured values during each dwell period So if an input varies widely due to noise or instability the effects can be clearly seen The straight lines at 10V indicate the set level and the achieved level Page 29 Laplace Instruments Ltd User Manual RFIC46 iss E Within the main control
18. a given case Summary of best practice The drawing below is a reproduction of fig 2b of the second edition of IEC 61000 4 6 The annotations should be self explanatory These cable hengihe truhi a Shag bet Him AR i grounding a portant oa ba oe CES I sharin C Tiia cate kh mA be lt Hiem af i EM clang preierredl cure yit ai iiih if teed ued here to herr Pune i Fi a yi F Observe thes spacings even far AE CON meki bee mo came AEI Arni References 1 Uncertainties of immunity measurements Schaffner EMC Systems Ltd and Elmac Services DTI NMSPU project R2 2b1 main report 2002 downloadable from www elmac co uk 2 A non invasive Coupling Decoupling Network with inherently good balance Honkala Repo and Marshall EMC and Compliance Journal January 2005 pp14 18 3 Reducing errors due to resonances in radiated and conducted EMC testing Richard Marshall 15th Intl Zurich Symposium on EMC February 18 20 2003 paper 4F1 pp 267 272 4 IEC 61000 4 6 second edition 2003 EMC Testing and measurement techniques Immunity to conducted disturbances induced by radio frequency fields 5 Amendment 1 to IEC 61000 4 6 second edition Define a new set up for large EUTs 77B 426 FDIS 6 A new approach to Coupling Decoupling Networks for EMC testing Richard Marshall EMC York 1999 UK July 1999 See also www design emc co uk 7 Use of a tee attenuator for VH
19. across the frequency range for every test set up While a procedure for doing so can be envisaged using a spectrum analyser tracking generator a small coupling jig and some data reduction software 7 this would noticeably extend the time taken to complete what is already a potentially long drawn out test It is also equally unrealistic to verify the EUT port CM impedance So under real life constraints labs tend not to ensure that the common mode impedance of the AE is less than or equal to the common mode impedance of the EUT port Although the current limiting method ensures against over testing if the EUT port impedance drops to zero it would only ensure against under testing if the AE port impedance was in fact maintained at less than 150Q Thus laboratories are left largely without guidance in this crucial aspect of the test and as a matter of practice it is easy for them to pay insufficient attention to controlling the AE CM impedance as the standard requires secre The threat is mainly that if the AE is left floating coment bebe because for instance it is battery powered or passive and there is nowhere to connect a grounding resistor the return path for the stress at low frequency is high impedance being only provided by stray capacitance from the AE to the this resistor necessary to provide stress current retum path ground plane Figure 8 Thus the EUT cannot avoid being under tested at low frequencies since Figure 8 The problem of f
20. an The setup shown could be used connected as shown after pre scan phase phase 1 has been Enhanced alternative strategy completed as per fig 19 In this instance the system is now running in phase 2 of AE EUT port port conventional mode and the current probe is used only as a eucam _ Ferrite Clamp monitor of the stress level applied but not used as part of the feedback system BCI Conventional substitution The preferred technique is now to Ground reference plane Figure 21 EM Clamp enhanced l e K e use the substitution technique ie a technique similar strategy to the CDN in conventional mode Feedback The calibration fixture in this case signal comprises a conductor terminated 6dB attenuator at one end with a 500hm load of adequate power rating and the BCI feedback to the RFIC from the other A ale injection end Using this setup the pre scan AE lac a Prope EUT is run and then the target cable replaces the calibration fixture and Ground reference plane Figure 22 BCI phase 1 Page 17 Laplace Instruments Ltd User Manual RFIC46 iss E test is run as shown in Phase Phase 2 e napasa j The current monitoring probe Sein for
21. can be monitored on the bargraph and on the results screen This level is not used for level control purposes The EUT status inputs are plotted on the PC screen and any deviations outside the pre set thresholds will be classed as a failure The response of the system to a failure will be as prescribed by the user in the setup screen E2 Conventional mode using EM Clamp or BCI probe The procedure will be as described for the CDN above except that the calibration fixtures will be appropriate for the injection device used Ensure that the correct device is selected in the main setup screen because the feedback levels are calculated differently according to whether it is an EM Clamp or BCI probe fitted Enhanced Mode The Enhanced CDNs are designed to feedback the applied stress level as input to the CDN Not the level actually applied to the EUT cable This is closer to the requirements of EC61000 4 6 in which the pre scan levels ignore the effect of the EUT cable Using Enhanced mode with EM Clamps and BCI probes with the feedback obtained from a current probe will be less compliant with the standard This is because although this technique delivers a more stable stress injection it does not allow for the effect of the EUT input impedance See section 3 However the RFIC system does allow for enhanced mode to be used with all types of injection device but the CDN is preferred as this is the only one specifically designed for this mode
22. d E3 E1 is the frequency setup information Start stop frequency step and dwell time are entered here It will change according to the test mode selected in area C The choices are Standard Custom and Single Standard Enter parameters for a standard sweep with a fixed stress level for the whole test Custom This enables the stress level to be changed during the scan The required parameters can be entered as nodes in the table The software will automatically interpolate between nodes Single Only available in Enhanced mode Frequency and stress level can be entered and these parameters nudged up and down in increments entered in the Inc fields An auto Increase feature can be selected which will automatically gradually increase the stress level in increments set in the Level Step inc field until End Level is reached or the EUT fails E2 remains the same for all setup modes It enables selection of EUT status interaction EUT prompt activity modulation selection and an activity area E3 displays the 4 channels of EUT monitor inputs in bargraph format During a test Aera E can be switched to show a chart format Report Results Screen which shows the target stress level the actual achieved level and the EUT monitor channel results all plotted against frequency in real time Operation In this section operation with CDNs is assumed as this is the preferred technique according to the standard The operation with EM C
23. d Probe REPORT RESULTS SCREEN EUT Sattings Figure 30 Key screen composition NOTE Section E will change according to the mode of operation that is currently selected These modes relate to either setup information or display of test results FAULT Synth Synthesiser responding abnormally PA Power amplifier fault detected Hardware Comms problem If this occurs a Re connect button will be available Area B Main Menu bar File Storage and retrieval of results and setups plus Printing options Display Colour and formatting options Mode Operating modes Standard Settings Custom and Single Transducer Select injection device and test mode Configure Check USB install CDNs define EUT monitor inputs Help Page 24 Laplace Instruments Ltd User Manual RFIC46 iss E Area C Operating controls These are the controls that initiate test sequences and which select the test mode Standard Single and Custom and screen mode as shown in screen section E EUT Settings button shows the screen where the EUT monitoring parameters can be set Area D Monitor Section This shows the current status of the test It includes current frequency and stress level type of modulation and elapsed time current dwell time and total elapsed time Also shown are the status of the EUT monitoring channels and a selector for the frequency range shown on the Results page Area E Setup and EUT monitor This section has 3 sub sections E1 E2 an
24. e 150Q terminations to only a single one Conceptually we can imagine the tests applying to a range of different products Figure 2 e a simple mains powered apparatus with no other signal or power connections e g household appliances RF returns only through stray capacitance to the ground plane remember that the RF is applied in common mode to L N and E together with respect to the ground plane e b mains or DC powered apparatus with one other signal or power port e g power supplies some instrumentation RF returns through stray capacitance and through the untested but terminated port e c apparatus with more than two ports for power and signal e g most IT equipment RF returns through stray capacitance and all untested but terminated ports Page 33 Laplace Instruments Ltd User Manual RFIC46 iss E The issue here is whether in the third case above more than ee one untested port needs to be terminated The first edition 2 Figure 9 shows that all non excited Coupling Decoupling Network CDN ports shall be terminated by 50Q loads implying a 150Q termination for each cable so that b potentially the RF return path could have a low impedance EUT if several terminated CDNs are used In the second edition this has been changed to insist that in any one test only two 150Q networks are required one CDN shall be connected to the port to be tested and one CDN with 50Q termination shall be connected to another po
25. e 7 Note that the damping components X are applied at the AE end of the transmission Figure 7 Resistors X provide damping of transmission line line choke adjacent to the rf short circuits resonance in a CDN provided at CD At this point rf current is highest and the damping resistors will have greatest influence Because the coupling between the wires of the main choke is now much more effective this solution does allow a single CDN to serve almost any conceivable ac or dc single phase or three phase application up to 100 amps with or without associated voltage or control circuits overcoming for power applications all the disadvantages of CDNs listed earlier EM Clamp The EM clamp is a clamping device that subjects the cable under test to both capacitive and inductive coupling of the RF stress It was invented largely for this test by Bersier and Ryser at the Swiss PTT Advantages e Its principal advantage is that it is entirely non invasive No connection need be made to the cable under test e Its second main advantage is that it allows adequate decoupling of the AE at high frequencies The design is arranged so that the capacitive and inductive coupling paths reinforce one another at the EUT end and cancel at the AE end This gives the clamp about 10 15dB of directivity above 1OMHz e Thirdly it is reasonably power efficient although not as good as a CDN for the same stress about 6dB more power is needed Disadvantages
26. e E impedance requirements Fig 3 shows the Figure 2 Basic CDN concept arrangement for a 3 core mains RF input E ean cable This is a type M3 CDN The Dohm source net result is that each type of cable pegi requires its own specific CDN So for inductor 300R instance an M3 type cannot be used 000 oe with a 2 core mains cable this AE Ne 0000 pe leur requires an M2 CDN The However Ee 0000 E the Laplace range of Versatile CDNs is able to cope with multiple cable types so for example the M3 type will work correctly with M2 and M1 RF input Figure 3 M3 CDN simplified schematic 0ohm source C ieee Coupling o g y capacitor cables This is achieved using a technique i i that incorporates programming features in the cable connectors Decoupling 100R 2 Fig 4 shows the RF signal path Note how the inductor prevents the RF coupling to the AE and the internal link in the CDN for the port ground connection This makes it imperative that the CDN enclosure is properly bonded to a the ground plane otherwise incorrect stress levels are likely to be applied to the EUT ope RF stress signal i EUT a Wt port Figure 4 RF signal path Page 7 Laplace Instruments Ltd User Manual RFIC46 iss E RF voltmeter Monitor probe EM Clamp This technique has the advantage of not requiring a break in the cable although more RF power is required to create a given stre
27. e inputs are O 10V 100Kohm impedance and are sampled at approximately 5Hz rate Each channel A D can be assigned a name a colour and have high and low thresholds defined These should be the limits of acceptable operation during the stress test Excursions outside these thresholds will be treated as an EUT fail Once the EUT monitor inputs are connected operation can be checked prior to the test with the bargraph display to the right of the selection areas Single will update the measurement once whilst continuous will measure in real time until Stop is clicked The Reset button resets the max min indications CONNECTIONS CDN used in the Conventional mode This mode can be used with ANY CDN including third party and Enhanced CDN Prior to testing the EUT the connections from the CDN to the EUT and the AE are removed and calibration fixtures type 46ZZ are plugged into the EUT and AE ports on the CDN The AE fixture is fitted with a 500hm terminator and the output from the EUT fixture is connected to the RF feedback port on the RFIC46 The pre scan is then run over the frequency range required This automatically adjusts the output level at each frequency step so that the desired stress Phase 1 Calibration 6dB attenuator Feedback signal Cal Fixture Cal Fixture Ns 46ZZ j port CDN EUT port 46ZZ 500ohm termination Figure 16 CDN
28. eVaSys_UsbI2clo_Drivers_x64 msi Calibration Files txt device serial number The main software is provided as the msi install file Running this file will automatically create the correct directories and install the necessary files This install should work on any current version of Windows Once the main program is loaded the USB drivers must then be loaded There are 2 driver install msi programs on the CD One is for 32 bit operating systems the other for 64 bit Run the install to suit your PC The directory structure Program Files Laplace Instruments Ltd RFIC 4 6 This contains Program file RF46 exe Initialisation file RF46 1NI USB interface file Laplace USB txt USB driver Usbi2cio dll My Documents Laplace Instruments Ltd RFIC 4 6 Results This is the default directory for all saved results files My Documents Laplace Instruments Ltd RFIC 4 6 User Apps Data This contains Analyser calibration file pscan csv Any other calibration files eg for enhanced CDNs These are loaded when the relevant utility on the main program is selected Page 47 Laplace Instruments Ltd User Manual RFIC46 iss E This page is intentionally blank Page 48 Laplace Instruments Ltd User Manual RFIC46 iss E INDEX AE Associated Equipment Analogue inputs Auto increment level BCI probe Calibration fixture Calibration phase CAUTIONS Compliance criteria Conventional technique CDN Curr
29. each method It refers throughout to the second edition for relevant paragraphs although where this has made changes the first edition is also quoted CDN The Coupling Decoupling Network CDN is designed to couple the disturbance signal directly to the EUT cable while at the same time preventing it from passing towards the AE associated or auxiliary equipment It must also provide a fixed common mode source Page 34 Laplace Instruments Ltd impedance towards the EUT The discrete components allow a more compact assembly than the other transducers to be discussed in the assembly shown above the EUT and AE connections are at the top and bottom respectively of the picture and the rf injection is to the BNC connector on the left impedance reference to from Associated Equipment Figure 3 shows the schematic of a CDN for a mains three wire M3 circuit It comprises an assembly of a multi turn common mode choke for insertion in series with the EUT cable together with shunt rf filter capacitors CD on the AE Figure 3 An M3 Coupling Decoupling Network side and injection coupling components nae on the EUT side In general if there are n wires then each is coupled to the tester via an equal resistor of value nR ohms with an appropriate blocking capacitor CC in series R is 100Q in the standard specification Advantages e Its prime advantages are near perfect decoupling of the AE and low uncertainty of the appl
30. ee ren Pitman Select CDH Cabia sihan EGWI J25 1025 Date bern Ede Ev Gare Lant New Tieri Prete Cathain fats EN Glare wth ny Cuni Probe Bc Loyi New Surert Probe Cetbeation Data Bliwih Casrent Frote Figure 15 Enhanced selection In order to repeat a previous test assuming that the test had been Saved the settings calibration and pre scan data can be loaded using the File Open menu Page 14 Laplace Instruments Ltd Entering the test parameters User Manual RFIC46 iss E First the type of test can be selected The choice is Standard Custom and Single These are selected from the buttons displayed near the bottom of the screen Note that Single is only available in Enhanced mode These choices are explained in section 7 page 25 Normally Standard will be used Single is only required for investigative work and custom used only when the stress level must be varied with frequency during the test Then the Start frequency Finish frequency Stress level Frequency step the standard specifies 1 or less and dwell period must be entered in the left hand section The estimated time for the test is displayed In the central section EUT Status parameters EUT Prompt and modulation requirements are entered For most tests the 1kKHz 80 deep AM modulation is required If EUT monitoring is to be used select main Menu EUT Monitor to display the monitor settings page Note that th
31. ent probe Custom mode Dwell time EM Clamp Enhanced technique EUT monitor EUT Prompt EUT status Feedback inputs Frequency selection Front panel 20 25 o 0 10 17 25 15 10 28 21 28 20 25 20 Fuses Ground reference plane TEC61000 4 6 Impedance matching Levelling Modulation Pre scan mode Rear panel Single frequency mode Software file definitions Software Installation Software selecting injection device Software selecting test technique Saving results Opening previous results Software updates Stress injection Stress level standard levels Stress level setting Test Setup Test Strategy Page 49 21 15 10 21 28 47 47 13 13 24 24 via web site 7 6 12 Laplace Instruments Ltd User Manual RFIC46 iss E LAPLACE INSTRUMENTS LTD 3B Middlebrook Way Cromer Norfolk NR27 9JR UK Tel 44 0 12 63 51 51 60 Fax 44 0 12 63 51 25 32 E tech laplace co uk Web www laplace co uk Page 50
32. es a 150R to SOR milivoltmeter required to pre set Calibration adaptor The output from this the signal levels before applying adaptor adaptor is monitored with an RF testto EUT Millivoltmeter and the applied RF level adjusted so that the monitored level maintains the correct stress level See Fig 9 The power settings required to achieve this correct stress level are recorded The EUT is then connected and the second scan performed using the recorded power settings The RFIC46 hardware includes the millivoltmeter and the control system necessary to level the RF output as required Figure 9 Conventional operation with CDN Page 10 Laplace Instruments Ltd IEC61000 4 6 Modified technique RFIC46 RF0250 Signal Power generator amplifier Enhanced CDN Note 6dB attenuator eliminated Control of level achieved during lt the test using monitor output of AE enhanced CDN and control cct Associated within the RFC4 6 sig genny Calibration adaptor and RF equipment millivoltmeter eliminated p EUT Figure 10 Enhanced operation Injection Technique User Manual RFIC46 iss E The alternative strategy involves monitoring the applied stress level during the test scan There is no pre scan requirement To facilitate this the CDNs must be fitted with a system which monitors the applied stress level
33. hose of the dielectrics surrounding the wire and within the capacitors CD Figure 5 Loss through M3 CDN B As stated above both these CDNs work well when the EUT circuits offer the same impedance to each wire but give unquantifiable errors in other cases We have taken as an example the case of the 3 wire mains lead but other important cases are process control cables with varied circuits within the same cable and 4 pair data circuits such as Cat 5 UTP where some pairs are used for balanced data and the remaining wires are either used for unbalanced power or not used at all There are only two CDN design solutions to this problem the length of wire in the choke must be short enough to push the resonance above the maximum frequency of test or the resonance must be damped by introducing extra resistive impedance at the AE end A reduced length of wire is possible for some varieties of low power CDNs but since IEC 61000 4 6 edition 2 Annex B extends the common mode impedance specification from 80MHz to 230MHz the scope for this method is now limited Page 37 User Manual RFIC46 iss E Laplace Instruments Ltd to from Associated EUT Damped resonance CDNs are available 3 for the particularly difficult high current applications where the choke must be a physically large component Damping is achieved by resistors that are transformer coupled to the individual choke wires as may be seen in Figur
34. ied stress e Minimal power is required and there is minimal radiation or environmental influence e Additionally it defines a 150Q common mode cable impedance formed from the 50Q generator impedance in series with 100Q resulting from the injection resistors in parallel This impedance damps cable resonance to increase the repeatability of the test and approximates to real life giving a very credible test Disadvantages e It is invasive that is it requires an electrical connection to the cable shield if there is one or to each core of an unshielded cable Accordingly different networks are required for different cables increasing the capital investment required for general test house use e This disadvantage has been partially overcome by versatile CDNs 6 in which a variety of CDN configurations can be achieved by patching links within the AE and EUT connectors The CDN pictured here may properly be used with coaxial and shielded cables of to 6 cores and with unshielded cables of 1 2 3 and 6 cores e Serious errors may result if an ordinary CDN is used with fewer than its intended number of wires such as for instance using an M3 CDN for a mains port with only live and neutral The reasons for this are set out below under CDN Cautions Page 35 Laplace Instruments Ltd User Manual RFIC46 iss E CDN Cautions The standard for the CDN only specifies its common mode impedance The coupling between the individual conducto
35. ing ferrites to the cable The CDN has the advantage that it is a known impedance and covers the required frequency range Ferrites will be an essentially unknown quantity but will offer a lower cost solution Where multiple cables are involved each must be tested so a full set of CDNs are required anyway Note that only 1 matching CDN should have a 50ohm terminator fitted See annex A for a discussion regarding Best Practice Page 8 Laplace Instruments Ltd User Manual RFIC46 iss E 2 2 Setting the stress level The standard EC61000 4 6 specifies that the stress level is defined as the open circuit source voltage Vs This voltage will have a source impedance of 500hm It is then connected to the test system which nominally has an impedance of 150ohm except that the BCI probe will have an input impedance of 500ohm The calibration fixtures replicate these requirements It is clear that the actual voltage applied to the EUT cable is a fraction of this source voltage For 1500hm systems CDN and EM Clamp the voltage at the output of the 150 50o0hm calibration fixture is 1 6th of Vs 15 6dB lower and for the 50ohm BCI system the voltage is 1 2 of Vs 6dB lower So when calibrating a test in the conventional technique the stress level at the output of the calibration fixture is set either 15 6dB or 6dB lower than the nominal stress level CDN and EM Clamp BCI probe 50R source impedence 50R source
36. ires than on the lower one Unless the multi wire choke acts as an effective transformer to equalise the voltages on these three wires there will be transducer errors but if the choke were perfect in this respect then much less intrusive CDNs could have been specified in the immunity standard which used only transformer action and a primary circuit with a single injection resistor The magnitude of this effect with commercially available CDNs can be measured with the test set up of Figure 4 in which the desired selection of the CDN EUT wires 1 of 3 2 of 3 or all 3 of 3 are connected to the input of a spectrum analyser and the CDN is driven from the ta output of the tracking generator If the ement transformer action of the common mode choke were perfect then we would expect Figure 4 Test of a CDN with an unbalanced load the same voltage measurement in each case Figures 5 and 6 show how the output varies with frequency for two different implementations of the standard M3 3 wire CDN In each chart the OdB ordinate represents the theoretical loss of a 100Q resistor between a 50Q source and a 50Q load The dotted 3 of 3 plots represent the uniform loading of the wires as envisaged in the standard and show less than 1dB of additional loss which would be partially calibrated out by the normal calibration set up with a 150 load The 1 of 3 lines in each case correspond to only one wire being connected to the analyser
37. lamps or BCI probes is very similar same connections unless otherwise indicated and procedures See section 4 for the preparation of the test equipment and the selection of the injection device and mode in the software It is assumed that these choices and settings have been entered in the selection screens shown in fig 13 Page 25 Laplace Instruments Ltd User Manual RFIC46 iss E Conventional strategy Phase 1 Pre scan Connect the system as shown in figure 31 Take care to arrange the setup correctly as described earlier and in the standard 1EC61000 4 6 Both the AE and EUT ports on the CDN are connected to calibration fixtures The output from the EUT side is connected to the RF feedback input on the RFIC46 The AE calibration fixture must be fitted with a 500hm termination On the control screen under the Transducer item in the main menu Section B enter the serial number and parameters of the CDN which will be used for the stress injection Then enter in section E1 e start frequency finish frequency stress level step size dwell time The screen will provide an estimate of the total test time In section E2 enter termination e EUT status mode r Calmretion e EUT prompt mode Calibration e modulation ay ey To see the setting graphically Fig 31 Phase 1 of conventional technique Pre scan click on Report Results Screen section C The screen will show a plot of the target stress level again
38. loating AEs both types of clamp device inject mainly current rather than voltage at this end of the range The lab will ignore this since there is no requirement on them to control the minimum injected level and the customer won t object if their equipment passes At higher frequencies the situation improves because the stray capacitive impedance of larger AEs is low enough for a real test to be made For a correctly implemented test it is essential to find some way of ensuring an AE common mode impedance of at most 150W Manufacturers labs who regularly test only a few types of interface can create jigs for this purpose but for a general test lab who may be faced with a wide variety of products from day to day this is a major overhead The article in the previous issue of EMC Compliance Journal 2 offers one solution to this problem for both the EM clamp and the probe Page 42 Laplace Instruments Ltd User Manual RFIC46 iss E Conclusions This paper has discussed several issues that arise from the application of IEC 61000 4 6 It is a very complex and difficult test to perform properly especially if the EUT AE and their cables do not conform to the simple set ups envisaged by the standard There is no universal guidance that can be applied for all cases but an understanding both of the principles of the test and of the coupling transducers that it allows can guide a laboratory towards applying it in the most effective way for
39. must be applied with respect to the GRP but the voltage feed from the generator is actually connected via the BNC socket on the CDN case Therefore there must be minimal impedance between the case and the GRP since this impedance appears directly in series with the applied stress A metal to metal contact is best any grounding strap must be short and wide since its inductance must be negligible all the Page 40 Laplace Instruments Ltd User Manual RFIC46 iss E way up to 80MHz or 230MHz Green and yellow wires always the bane of EMC engineering are outlawed EM clamp AE CM impedance With the EM clamp it is necessary to constrain the AE CM impedance Zagat low frequencies At these frequencies to 150Q generally below 1OMHz the EM clamp acts mostly like the current injection probe in that it applies current more than voltage to the cable under test so that the impedance of the total loop is important However the directivity of the clamp above 10MHz means that this requirement largely vanishes and the ZAE may be uncontrolled This is actually a happy result because the principal difficulty in controlling Zag is at high frequencies where stray capacitance of the AE to the ground plane and resonances in unavoidably long cables to and from the AE cause the most problems but see 2 Provided that the LF impedance is maintained at 150W which can most easily be done if the AE is mains powered with a mains CDN on its input and all
40. nder test EUT to determine its immunity to this stress The principle of the test is to excite both electric and magnetic disturbance fields within the EUT by applying the stress in common mode with respect to the ground reference plane GRP to certain selected cables entering Sse the EUT Therefore we must use networks to stabilise this impedance or to decouple it so as to ensure that unwanted variations have little effect on the test and also make sure that the layout of the core SHH vonage reson test is controlled so that variations due to stray coupling are minimised Clause 7 of the standard covers these issues Sigrai Current ejection Love it Figure 1 The stress is applied m il through a defined source impedance of Deccuste ypesarce 150Q which is also taken to be the Inecton probe Moret prove stating networks on M ia eur pean impedance of other cables connected to Figure I Principle of conducted immunity testing according to the first edition The second edition IEC 61000 4 6 has recently been republished in its second edition 4 although at the time of writing this has not yet been published in Europe as an EN There are numerous changes from the first edition ranging from merely editorial to fundamental changes in the method and anyone who is familiar only with the first edition will need to revisit the standard to upgrade themselves One of the most important changes is the move from multipl
41. ompt System status power inputs RF and amplifier output indications amplifier DC selected standby according to interlock mode Figure 26 Front panel Laplace Instruments Ltd User Manual RFIC46 iss E Rear panel layout USB RS232 Do not cover Power T2A Mains input interface options ventilation ON OFF 20mm 110 240V only slots switch fuses 50 60Hz Figure 27 Rear panel Power Mains power is applied Connections EUT Prompt The prompt output from the RF1000 is a 4 pole c o relay All the contacts are brought out to a standard 15 way Dee type connector Pin numbering Connection detail 8 1 15 9 Figure 28 EUT prompt connections Notes e NO contacts are closed when EUT prompt operates e NC contacts are opened when EUT prompt operates e Contact rating is 20v rms or 40v dc 300mA e When pulsed prompt is used contacts close for 1 second at the start of each dwell period Page 21 Laplace Instruments Ltd User Manual RFIC46 iss E PA Interlock 2 To P A standby interlock sic standby mode Ov Figure 29 PA interlock connections The RF0250 power amplifier can be set to standby remotely by the RFIC46 or can be switched locally on the PA front panel in which case the interlock will report status back to the RFIC system Page 22 Laplace Instruments Ltd User Manual RFIC46 iss E 7 Software The RFIC46 is shipped with RF46 softwa
42. on the EUT port Enhanced CDNs have this feature This level is output as a DC signal on the monitor port The control system must also be capable of accepting this DC feedback signal and controlling the output RF level during the test run See the choices described in section 2 These are CDN EMClamp and BCI probe CDNs are the preferred technique but the other two could be used with the RFIC system Note that the BCI technique does require higher RF power levels and these probes may require higher power levels than the 25W offered by the RF0250 power amplifier Page 11 Laplace Instruments Ltd User Manual RFIC46 iss E 4 Test Setup CDNs Figures 11 and 12 show a typical test arrangement 50R terminator fitted to only 1 CDN Safety ground Ground Reference Plane connection Figure 11 Typical test arrangement plan view To power 50ohm termination amplifier Ground Reference Plane Insulating blocks 10cm high Figure 12 Typical test arrangement side view Points to note are All CDNs are firmly bonded to the ground reference plane The stress injection is applied to one cable at a time All other cables are fed through CDNs to maintain the 150R impedence Even the earth point on the EUT if fitted is grounded via CDN The EUT and AE are spaced 10cm off the ground plane Just one CDN is fitted with a 500hm terminator Note that each cable is connected via the appropriate CDN
43. ote the critical importance of the grounding of the fixtures to the ground plane Suitable calibration fixtures are available from suppliers of the clamps Phase 1 Calibration Feedback signal 6dB attenuator Cal Cal Fixture Fixture 1000hm p AE Eur oohm port port EM Clamp Le Ground reference plane 50o0hm termination Figure 19 Operation with EM Clamp 1 Page 16 Laplace Instruments Ltd Once the calibration phase is completed the fixtures are removed and the cable to be tested can be installed Note the requirements for spacing the EUT and AE above the ground plane by 10cm Cables on the EUT side should be kept as short as possible The inclusion of a ferrite clamp on the AE side is recommended as this avoids excessive stressing of the AE and if the AE has low RF impedance avoids understressing the EUT Enhanced Strategy User Manual RFIC46 iss E Phase 2 Test 6dB attenuator AE AE EUT SeA port port Ferrite Clamp EM Clamp Ground reference plane Figure 20 Operation with EM Clamp 2 A current probe can be used to provide feedback to the RFIC system during the test The setup is shown in Fig 21 The calibration factor for the probe must be entered into the RFSynth software This removes the requirement for a pre sc
44. phase 1 Ki Ground reference plane level is achieved The software maintains a record of the power levels required Page 15 Laplace Instruments Ltd Phase 2 Test 6dB attenuator CDN AE port port User Manual RFIC46 iss E Once this pre scan phase is completed remove the calibration fixtures reconnect the cables and run the test See fig 17 ic Ground reference plane Figure 17 CDN phase 2 CDN Enhanced mode If using an Enhanced CDN Model E46xxx then the test can be accomplished in one phase Connect the system as shown in fig 18 Note that the CDN Monitor output is connected to the DC feedback input on the RFIC46 unit The calibration file should be entered or selected in the setup mode page Each CDN will have its own calibration file nnnn enh This test will now run without any pre scan EM Clamp Conventional Strategy Enhanced Test AE Monitor port Ground reference plane Figure 18 CDN Enhanced mode As with the CDN there is a Calibration phase then a Test phase The calibration is performed with the clamp driving into a conductor terminated in 150o0hms The 100ohm in the fixture is supplemented either with a 500hm terminator or the 50ohm input impedance of the input port on the RFIC46 The arrangement is shown in Fig 19 N
45. ports other than the cable under test left floating then the HF impedance can be left to look after itself Grounding Like the CDN the EM clamp applies a form of voltage injection with respect to the ground reference plane Therefore it is again necessary to ground it properly with a short direct strap and preferably with the ground plate making direct contact It cannot be used correctly if it is not placed on and connected to the GRP This differentiates it from other forms of clamp such as pure decoupling clamps common mode absorbing devices or the MDS 21 absorbing clamp used for some emissions tests These devices use only ferrite to increase the common mode series RF impedance of the cable without reference to ground Current injection probe AE CM impedance With the current probe it is necessary to constrain the AE CM impedance to 150Q at all frequencies This of course is fundamentally difficult to achieve and even more to confirm The actual CM impedance at the AE port is out of the hands of the test laboratory only the impedance of the AE itself to the GRP can be controlled most easily using a CDN on its power supply but at high frequencies this is compromised by its stray capacitance to the GRP Add to this the effect of longer cables between the AE and the probe and it can be seen that at high frequencies typically 26MHz and above predictability and repeatability of the stress induced by the current probe is very unlikel
46. re This software should be loaded onto your PC and will provide all the user interface requirements for EC61000 4 6 testing Installation of the software is described in annex C The interface between the PC and the RFIC46 synthesiser is via USB bus Any USB port on the PC may be used Connect the supplied USB cable between the PC and the synthesiser If this is the first time that the PC has seen this synthesiser it may request details of the relevant driver See annex C for details When the software is run it will first check that the hardware is connected and switched on If this is not the case a warning message will appear Check the connection and ensure that the hardware is powered up The software can be used without the hardware for display of results and producing hardcopy In this case just accept the warning and continue Once the software is running the main screen will be displayed Note that the settings will match those that applied when the software was last used The main screen comprises 5 areas see figure 30 Status area A Main menu bar B Operating controls C Monitor area D And The main setup and results display area E This area E will switch between modes according to the users requirements These modes are Setup controls E1 and E2 Standard settings Custom settings Single point settings Monitoring screens E3 Chart showing all parameters of the test in real time Bargraph display of
47. rs is not specified This leaves the choice and arrangement of the ferrite cores and the construction of the winding entirely to the test equipment manufacturer Consequently a variety of solutions are in use that meet the common mode requirements but have varying differential mode characteristics Leakage inductance and transmission line resonance within the choke are both important but unspecified sources of error since both effects allow the individual wires through the CDN to exhibit individual impedances that is they may carry different rf voltages if the circuit conditions allow This may be understood from Figure 3 where the EUT has an isolated transformer winding connected to two wires of its mains cable whilst its chassis and hence most of its circuitry and any other cables is connected to the third The impedance seen looking into the EUT from the CDN at the reference points is quite high for the upper two wires being dominated by the effect of the stray capacitance of the transformer winding to its surroundings The impedance of the lower ground wire may be very low being dependent upon the capacitance from the EUT to the ground plane below and on any other cables connected to the EUT but not shown on this simplified drawing If the CDN s isolating inductor comprised three un coupled chokes then because of the source resistors 3R the immunity test voltage injected into the EUT would clearly be much higher on the upper two w
48. rt Decoupling networks shall be installed on all other ports to which cables are attached In this manner there is only one loop terminated with 150Q at each end new 7 1 2 7 2 This change will mostly affect small multi port devices Figure2 Terminating different since the untested but terminated port will now be the only types of EUT one passing RF current out of the EUT All other ports are decoupled but not terminated The change will increase the capacitively coupled voltage stress and decrease the magnetically coupled current influence Decoupling networks just provide a high series impedance they are usually clamp on ferrite absorbers but you have to be sure you are using an absorber which has a high impedance down to 150kHz This is not an everyday item even in an EMC test lab although it is possible to build or otherwise procure one 2 For a large EUT in a metallic enclosure the changed method of the second edition will make little difference since the capacitance to ground of the EUT will typically be sufficient to bypass current away from the non excited ports Choice of transducers The standard allows three methods for injecting the stress and assumes that results from each will be equivalent although it is now stated that the CDN method is preferred e CDN including direct injection e EM Clamp e Current probe This paper discusses the pros and cons as well as the precautions to take for best practice for
49. screen E3 the state of the EUT inputs can be monitored on a bargraph display This shows all 4 inputs together with the thresholds shown as background colour This display is updated continuously during a sweep showing the max and minimum measurements during a dwell period so that all excursions can be observed The thick black line is the current reading the white centre shows the precise value The thin red lines are the maximum and minimum readings during the test The red and green background bands show the thresholds of the high low limits The Reset button will reset the max and min memory i Reset Continuous MV Channel A Active V Channel B Active MV Channel C Active MV Channel D Active Page 30 Laplace Instruments Ltd User Manual RFIC46 iss E ANNEX Annex A Best practice Annex B Shipping list Annex C Software installation Page 31 Laplace Instruments Ltd User Manual RFIC46 iss E This page is intentionally blank Page 32 Laplace Instruments Ltd User Manual RFIC46 iss E Annex A Pitfalls and practice of IEC 61000 4 6 conducted immunity testing By Tim Williams Elmac Services and Richard Marshall Richard Marshall Ltd Introduction IEC 61000 4 6 is widely used for compliance testing of RF immunity of apparatus for the EMC and R amp TTE Directives It applies an RF stress over the frequency range 150kHz 80MHz to the cables connected to the equipment u
50. ss level The stress is applied by capacitive and inductive coupling into the cable and a series of split ferrite rings provide the 1500hm impedance matching over much of the required frequency range The length and size of the clamp can be a problem in some circumstances The overall impedance is not so well defined as with the CDN Control system amp sig genny i i i 1 EUT ites A Figure 5 EM Clamp technique BCI Bulk Current Injection clamp This is generally only used when other techniques are impractical It is non Control system invasive does not require a break in amp sig genny the cable but Requires a significantly higher level of RF power for a given RF stress level volimeter Does not provide any impedance matching The AE is stressed equally as the EUT 4 RY Monitor r i i probe Cables resonances are virtually External i unavoidable at the higher IEO ohm frequencies i An additional current probe is AE required to monitor the applied stress level BCI probe EUT Figure 6 BCI probe technique BCI and EM Clamp techniques are often specified for military or automotive tests One key advantage is that they can be used on complete cable bundles 2 1 Cable matching When more than one cable is attached to an EUT the untested cables need to be impedance matched to 1500hm This can be accomplished by using a CDN or by add
51. st frequency If all is now ready Click PRE_SCAN The system will commence the calibration scan Progress can be observed on the 2 bargraph displays on the RFIC46 front panel These given an indication of RF output level and feedback signal level These are for indication only and will not generally be equal in level Section D will show actual and target levels achieved The Pre scan will not include any dwell periods as there is no product to stress thus saving time Once the Pre scan is completed the pre scan settings can be saved to disk if for later use if required Note that if this is done any future use of this file must be done with care ensuring that the test setup is exactly replicated Page 26 Laplace Instruments Ltd User Manual RFIC46 iss E Phase 2 Test The calibration fixtures can now be removed and the EUT cables connected to the CDN See fig 32 Any EUT monitoring inputs should be connected and checked for operation See later in this section 6B atternestor The TEST button will now commence the EUT test using the power settings stored TEU during the pre scan phase As there are no feedback inputs at this stage the Fig 32 Phase 2 of conventional techinidiieTest feedback level indicator will be dormant although if using an enhanced CDN in Conventional mode the monitor output on the CDN can be connected to the DC feedback input on the RFIC46 and the stress level
52. tion probe then the results of all three laboratories are deemed equivalent Reference 1 investigated this equivalence and concluded e Ifthe Za see later is maintained accurately at 150Q then all three transducers can give very similar results the two clamp methods differ from the CDN reference level Page 39 Laplace Instruments Ltd User Manual RFIC46 iss E by less than 2dB over the range up to 1OMHz unless the current probe turns ratio is as low as 1 1 e Any departure from 150Q of Zar causes a deviation in the injected stress corresponding to the ratio of the total impedances for each of the clamp methods but no change for the CDN The deviation is equivalent for the EM clamp and current injection probe at low frequencies but reduces markedly for the EM clamp at high frequencies Aspects of best practice This section discusses precautions which must be taken in the test method for each of the above transducers in order to get the best repeatability In all cases you must respect the rule that says the transducer to EUT cable length should be 10 30cm Anything longer contravenes the standard It will become resonant towards the top end of the frequency range and at a quarter wavelength the common mode impedance presented by the EUT will be transformed into its opposite a high impedance will appear as a low impedance at the transducer and vice versa This introduces problems for EUTs which have cable entries more than 3
53. ts RFIC46 signal generator and controller RF0250 Power amplifier CDNs or other injection devices The RF0250 CDNs and other devices are fully covered by the individual user manuals supplied with each RFI C46 This compact unit provides the following functions e Signal generator according to IEC61000 4 6 100KHz 250MHz 45dBm to 0dBm e Modulation as required by the standard 1KHz AM 80 depth plus pulse modulation 2Hz 20Hz amp 200Hz e RF output level control Automatic levelling using feedback from either feedback input e An RF millivoltmeter for monitoring of applied RF stress level 60dBm to 30dBm e ADC input for use with Enhanced CDNs 0 20v dc 20mvV resolution 10 bit ADC e 4 channels of analogue inputs for EUT performance monitoring O 10v single ended 100K input impedance 10mV resolution e An EUT prompt system Volt free relays contacts Safety interlock system for the power amplifier USB interface to PC USB via rear panel RFIC46 Ce SS RF to Feedback To Power From To EUT Power from Amplifier EUT Amplifier injection Figure 25 RFIC Block diagram Page 19 Laplace Instruments Ltd User Manual RFIC46 iss E The block diagram shows the main elements of the systems inside the unit Note that the level control system includes an output level monitor to ensure that the output does not exceed the 0dBm limit thus protecting the power amplifier from
54. uct It may also be defined by the customer s expectations Criteria A no significant degradation in operation or function allowed This criteria applies to any product that has safety implications Criteria B Some degradation in operation may occur but the product recovers once the stress is removed without any operator intervention No change in operating state or loss of data occurs Page 6 Laplace Instruments Ltd User Manual RFIC46 iss E Criteria C Operation of the product is affected and operator intervention is needed to recover normal operation Again no loss of data is allowed 2 Stress injection There are three techniques that can be used for the injection of the RF signal on to the cable CDN BCI and EM clamp The CDN is the preferred device according to the standard CDN Coupling Decoupling Network The function of the CDN is quite simple To couple the RF signal into the cable lt lt Coupling connected to the EUT and to Decouple RF input cepaciter block the RF signal from the external eae equipment Associated Equipment or AE This technique is the most efficient lowest Decoupling 1008 a F inductor RF power level for a given required stress level But it is intrusive it requires a break in the cable AE EUT Fig 2 shows the basic principle of the CDN Unfortunately if the cable is unscreened the stress must be applied to each of the cable cores equally whilst maintaining th
55. ws the general principles The product is effectively held in a 1500hm environment supported 10cm above a grounded reference plane with all external connections impedance matched so that the 1500hm overall impedance to ground is maintained Significant points to note are All cables are impedance matched for the duration of the test This includes any earth or grounding connections The product is physically held EUT above a ground plane on insulating I blocks or supports ne ToAE e The stress signal is applied to 150R ison one cable at a time and each cable is tested in turn v ff VU al Full details to cover the differing io types of products are given in the Ground plane standard IEC61000 4 6 Figure 1 Outline of conducted immunity test During the test the stress frequency is stepped in increments between a start frequency and an end frequency The increment is specified as a percentage of the current frequency typically 0 5 or 1 At each frequency the stress signal is injected at the relevant level V anda 1KHz 80 depth AM modulation applied The product is monitored for any degradation in performance or operation This dwell time should be long enough to ensure any change to the product can be detected Once this dwell time is completed the frequency moves on to the next step and the test is repeated Compliance Criteria The pass fail criteria depend on the purpose and function of the prod
56. y It follows from this that you should only apply the probe to short cables preferably shorter than 60cm and certainly less than 1m For cables longer than this use the EM clamp Some laboratories believe that a very long cable gt 5m between the clamp and the AE will somehow attenuate the signal applied to the AE This is nonsense all that happens is an arbitrary and unnecessary reduction of the frequency at which cable resonance effects become significant leading to even greater lack of repeatability Page 41 Laplace Instruments Ltd User Manual RFIC46 iss E Current monitoring If you are using clamp application and the AE CM impedance cannot be constrained to 150Q which is practically the case for the majority of test set ups then clause 7 4 of the new standard puts further requirements in place It states it is necessary that the common mode impedance of the AE be less than or equal to the common mode impedance of the EUT port being tested If not measures shall be taken at the AE port to satisfy this condition The applied current is then limited through the use of a secondary monitoring probe to what would occur in a true 150Q system that is double that which occurs in calibration which is a 300Q system The measures to be taken include as an example the use of a CDN M1 or 1502 resistor from the AE to ground It is unrealistic under real life conditions in test labs to verify the AE CM impedance
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