Appnote DSL Cable measurements
Contents
1. This application note explains how to measure electrical parameters of DSL Cables such as attenuation crosstalk and phase delay This is necessary to determine if a cable complies with a certain normative standard like e g IEC 62255 3 The application note was done in cooperation with AESA Cortaillod AESA Cortaillod has over 30 years experience in cable testing and quality control of telephone and LAN cabling as well as power lines or coaxial cabling The company s headquarters is located in Colombier Switzerland For more information feel free to visit www aesa cortaillod com 2 Measurement tasks During the process of selecting a cable for a specific application it is advisable to verify the electrical characteristics outlined in the cable s data sheet By analyzing one DSL Cable pair the measurement of following parameters is shown in this application note the parameters for the other pairs are measured the same way e Attenuation e Impedance e Near End Cross Talk NEXT and Far End Cross Talk FEXT e Return Loss RL e Phase delay 3 Measurement Setup amp Results 3 1 Used Equipment The following equipment is required to perform the measurements described in this application note e Vector Network Analyzer Bode 100 incl measurement accessories e DSL Cable DUT e BALUNs 3x e Connection accessories e Calibration cable The used items are explained in the following sections OMICRON E LAB Smart Measur2. ELFEXT which is calculated ELFEXT is FEXT measured with respect to the attenuated test signal see Add On ELFEXT Measurement with Bode 100 MICRON Smart Measurement Solutions LAS iw B Bode 100 Application Note DSL Cable measurements with Bode 100 Page 12 of 21 3 5 NEXT Measurement To measure NEXT of two pairs keep the same settings and calibration as used in the attenuation measurement Only change the trace1 settings as shown i Trace 1 TR Color a Measurement Gan Display Data amp Meme gt Format MagidB max 0 00 fmin E OU 00dE Data gt Memory Connect your measurement utilities as shown to measure the NEXT between Pair1 and Pair2 Bode100 BNC Cable Pair2 BALUN LOAD Smart Measurement Solutions Bode 100 Application Note DSL Cable measurements with Bode 100 Page 13 of 21 Now you can start the frequency sweep measurement TR1 dB 10 20 30 40 50 Fea a a Aw LL ee ON ek 60 ae a tial a j 80 f 90 100 5 10 15 20 25 30 35 f MHz TR1 Mag Gain TR1 Memory Mag Gain This graph shows the crosstalk NEXT between two neighbouring pairs Our measurement result shows that the signal received at the near end of Pair2 is 40dB or more below the signal sent into Pair1 3 6 FEXT Measurement The setup for the FEXT measurement is almost similar to the NEXT setup
3. Return Loss RL of DSL Cables To measure the RL of your DSL Cable configure Bode 100 like shown in 3 Impedance Measurement Note Set the reference resistance to 110 ohm Configuration Level 0 00 dEr Attenuator CH1 zog Attenuator CH2 zog l Receiver Bandwidth hoH Measurement Reference Resishance Start the frequency measurement TR1 dB f MHz TR1 Mag Reflection Result The ripple of the return loss is caused by cable deflections 3 8 Group delay The group delay represents the time which is needed by a signal to pass our DUT MICRON Smart Measurement Solutions LAS iw B Bode 100 Application Note DSL Cable measurements with Bode 100 Page 20 of 21 pair SOENE Delay Time To measure the group delay configure the Bode 100 as shown in the attenuation measurement Calibrate the Bode 100 and set Trace1 to format Tg l Trace 1 TRI Color ay Measurement Gan Display DatatMeme gt Format Ms 360 gt ma 750 00ns min oos Data gt Memory Now the measurement can be started TR1 ns 600 es ha 500 Na INI a ae oa 400 300 200 100 f MHz TR1 Tg Gain Result The group delay is around 500ns for 100m cable this is approx 5ns 1m It is also possible to calculate the propagation speed like shown in the next section 3 8 1 Propagation Speed The propagati
4. Open Start Short Start Load Start H Advanced Load Fresistor 110 00 Short Delay Time 50 00 p pEAEpEpNYEREAHEuNApRANEnuN OF Cancel Note Perform the different impedance calibration modes with an open short load connector as described in the User Manual MICRON Smart Measurement Solutions Adan tA B Bode 100 Application Note DSL Cable measurements with Bode 100 Page 17 of 21 Calibrate Bode 100 by using the Open Short and Load Bode100 Bode100 OUT CH2 OUT CH2 Opi BALUN BALUN PLL OPEN Bode100 QH CH2 0 BALUN st LOAD st SHORT To measure the cable impedance we have to connect the DSL Cable as shown Smart Measurement Solutions Bode 100 Application Note DSL Cable measurements with Bode 100 Page 18 of 21 Bode100 BALUN LOAD LOAD Now start the measurement by pressing the single measurement button TR1 Ohm 130 oe s A 120 TE wira a 7 7 R 10 v edia RY 100 f MHz TR1 Mag Impedance Result As we can see the impedance of our DSL Cable has a slight deviation from the ideal Load 110 ohm The reason is that the wave resistance of our DSL Cable which is 120 ohm The ripple is caused by variations and deflections in the cable construction MICRON Smart Measurement Solutions LAS iw B Bode 100 Application Note DSL Cable measurements with Bode 100 Page 19 of 21 3
5. Use the same configuration as in the attenuation measurement Note You can use the same calibration as in the attenuation measurement Connect the DSL Cable as shown and start the FEXT measurement Bode100 Smart Measurement Solutions Bode 100 Application Note DSL Cable measurements with Bode 100 Page 14 of 21 The diagram below shows the result of the FEXT measurement TR1 dB 10 20 _ 30 40 50 ee re air 60 a ai 70 eae 80 ra 90 100 5 10 15 20 25 30 35 MHz TR1 Mag Gain TR1 Memory Mag Gain To add an upper limit to find out if the cable passes the requirements defined in the chosen normative std export your traces data into CSV File which can be processed in software such as e g EXCEL or MATLAB Before you export the traces data set the CSV Export settings according to your requirements as shown File Measurement Configuration Calibration Tools Help 138 42 5 E a dite User Calibration GAIN OFF IMP OFF i OS Probe Calibration GAIN OFF IMP OFF Options Startup Configuration Measurement bo Export CSW Export Decimal Separator i tad Value Separator T Ok Cancel Help Now press the Export Traces Data button on the right side of the Bode Analyzer Suite Save the CSV File and open with EXCEL or MATLAB Mil Smart Measurement Solutions SS Bode 100 Application Note DS
6. Analyzer Suite select Frequency Sweep and configure Bode 100 as shown e Mode e f min e f max e Reference e Attn CH2 e Receiver Bandwidth e DUT delay e Number of points e Impedance CH2 e Source Level e Sweep mode Configuration Device Configuration Connection Setup Measurement Gain Phase SOURCE OUTPUT Frequency Sweep 10 KHz 40 MHz Internal 20 dB 300 Hz Os 401 500 0 dBm linear mpedance Reflection Receiver Bandwidth 300 Hz DUT delay 0 00 3 Measurement period 9 24 me RECEMER 2 Internal reference Cancel To minimize the influence of the BALUNs and cables used to connect the DUT to Bode 100 it is advisable to perform a THRU calibration as shown in the manual in the section Calibration in the Gain Phase mode Smart Measurement Solutions OMICRON E LAB Bode 100 Application Note DSL Cable measurements with Bode 100 Page 9 of 21 Calibrate Bode 100 and the used BALUNs with a calibration cable Bode100 Calibration xDSL Cable Pair1 gt LOAD LOAD Note Pair1 and Pair2 are in the same quad Activate Trace 1 to measure the attenuation of the DSL cable as shown below l Trace 1 TAT Color Measurement Gain ha Display DatakMeme Format MagidEl Ymax 0 0048 fmin 30 0006 Data gt Memory Smart Measurement Solutions Bode 100 Application Note DSL Cable measurements wit
7. Bode 100 Application Note DSL Cable measurements with Bode 100 Page 1 of 21 DSL Cable Measurements with Bode100 OUTPUT WV OMICRON Q Bode 100 s CILAR N a aa _ This application note was developed with strong AESA Cortaillod support of Mr Dick Gigon AESA SA by Lukas Heinzle 2010 Omicron Lab V1 3 Visit www omicron lab com for more information Contact support omicron lab com for technical support Smart Measurement Solutions Bode 100 Application Note DSL Cable measurements with Bode 100 Page 2 of 21 Table of Contents 1 Executive Summary seers peice te see teen ene eoeiees esate pen ssnacamenenenesanoianesananaeeeenaranesanateans 3 2 Measurement CAS MS encdisedacectesdneecaudssnadaudaneceiedancecnseienecsedauecdciedanedaiedecenceseseeusceabeeuageuezauts 3 3 Measurement Setup amp ReSUItS ccc ccccceceeeceeeeeeeeeeeeeeeeseneeesenseneseesoneeesensoneseesonees 3 SU CAE AE nee nn eee ee ee cr te 3 3 1 1 AIOE AIO Ce acess tuaedienedasendmodapodesntguntuenhavennsedenonsooduactaanduaniiauhasenimonanoussndasanetiatescnate 4 3 L2 ENING renees tr e aea a a e EEE EN 4 3 1 3 Connection accessories gic ccacevacunadavws svedsunwanedanaduuedanwfanwdecaiiamodenatawadauadweadeward madenete 5 3 1 4 e lelecis agers ee T 3 2 Measurement setup INSTPUCTIONS ccc cec cee ceeceeceeceeceeceeceeceeseesseseeeeeseeceeseeseeeaes 7 3 3 Attenuation of DSL Cables ooo ec cececeee ee eceeeeee
8. L Cable measurements with Bode 100 Page 15 of 21 Diagram Setup Auto f Always Two Diagrams Export Traces Data This graph shows that the FEXT is below the required limit The used DSL Cable has passed the crosstalk test The Upper limit is according to IEC 62255 3 0 4 8 12 16 20 24 28 32 36 40 TAP RET LE PLEIN TY TT PT ETAT RET TET WE ETT TET IY EE yy BERR Eee TET tA ttt TA LETT A PET A Ey dB 100m Pairl NEXT _eeeere Upper limit Smart Measurement Solutions Bode 100 Application Note DSL Cable measurements with Bode 100 Page 16 of 21 Impedance Measurement To adjust a driver unit transmitter or receiver to a DSL Cable it is necessary to know the input impedance To measure the impedance of the used cable start your Bode Analyzer Suite and configure it as shown Configuration Device Configuration Connection Setup Measurement Gain Phase Impedance Reflection SOURCE Receiver Sweep RECEIVER 1 Bandwidth 1 kHz DUT delay 0 00 Measurement period Internal F xterna 3 06 ms reference OUTPUT For the impedance measurement you have to set the load resistor to 110 ohm in the advanced settings of the calibration window User Calibration Frequency Sweep Gain Phase Replace DUT by thru cable Aftenvards press Start to perforn Calibration Impedance Connect the corresponding part and perform the calibration by pressing the start button
9. cted with WAGO 733 female plugs Pair Short name White Q1 1 Grey Orchid Q1 2 Blue Green Q2 1 Grey Orchid Q2 2 White Black Q3 1 Grey Orchid Q3 2 Red Yellow Q4 1 Grey Orchid Q4 2 Brown Color Picture Smart Measurement Solutions Bode 100 Application Note DSL Cable measurements with Bode 100 Page 7 of 21 3 1 4 Calibration cable To minimize the influence of the BALUNs BNC cables and connectors we have to calibrate our measurement setup Therefore a calibration cable with two female plugs is required The explicit use of our calibration cable will be shown in 3 3 a W r ai Picture 3 13 3 2 Measurement setup instructions e The measurement examples covered in this application note are only performed for one pair The other wire pairs are measured exactly the same way e The used DSL Cable consists of 4 quads Every quad has 2 pairs To obtain an accurate measurement result all unused pairs of every quad should be connected to a LOAD resistor at the near and far end This additional information is not mentioned at every measurement setup Smart Measurement Solutions Bode 100 Application Note DSL Cable measurements with Bode 100 3 3 Attenuation of DSL Cables Page 8 of 21 All signals are attenuated when transmitted along cables Too much attenuation can cause signals to be lost in the noise To measure the attenuation of a DSL Cable follow the steps below Start your Bode
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11. ement Solutions Bode 100 Application Note DSL Cable measurements with Bode 100 Page 4 of 21 3 1 1 DSL Cable The DSL Cable used for the measurements in this application note had following properties e Type Copper cable 4x4x0 5 vDSL CAT3 e Manufacturer Nexans Fumay France e Physical properties 4 quads 0 5mm with general braid alu foil SF UTQ QIMF e Trade mark ET 392121 e Model marking Nexans Alcatel Lucent 1 ACxx e Length 100m During the measurements the DSL Cable is wrapped on a wooden cable reel Picture 1 1 3 1 2 BALUN A BALUN as shown in the picture is used to match the output impedance of the Bode 100 50 ohm with the cable impedance of 110 ohm The used BALUN has a balanced output signal and a frequency range from 30 KHz up to 120 MHz BNC WAGO 733 for Bode100 connector 500hm 1100hm Smart Measurement Solutions Bode 100 Application Note DSL Cable measurements with Bode 100 Page 5 of 21 3 1 3 Connection accessories To connect the BALUN and the DSL Cable we use 2 pin Wago 733 connectors Ss ig 2 female plug male plug Three special connectors Open Short and Load are used for the calibration later on The load resistor has a value of 110 ohm Picture 1 5 Smart Measurement Solutions Bode 100 Application Note DSL Cable measurements with Bode 100 Page 6 of 21 Connection table The different cable pairs of the DSL Cable are conne
12. h Bode 100 Page 10 of 21 Now start the frequency sweep measurement to record the attenuation TR1 dB Pee e er erecceceedererereecerereseccecececeeseeeneccccccecevevegan OS 610 O10 CO O18 a BD OO OOS OS S C1 OO O10 OO O S O 60 00 O10 O S OBO 0010 0 00 0 e 0 8 O 0 0 e 5 10 15 20 25 30 35 f MHz TR1 Mag Gain Result The maximum attenuation at 40MHz is about 12 9dB 100m for information on setting the cursors see the Bode 100 User Manual The attenuation at 20 MHz is about 9dB 100m Frequency Trace 1 Trace 2 20 000 MHz 9 095 dE MCursor2 40 000 MHz 12891 dB delta C2 C1 20 000 MHz 3r 96 dE Smart Measurement Solutions Bode 100 Application Note DSL Cable measurements with Bode 100 Page 11 of 21 3 4 Theory about Crosstalk NEXT and FEXT 3 4 1 Crosstalk Crosstalk is signal interference between nearby cables or cable pairs It is caused by Capacitive and inductive coupling between different transmission pairs 3 4 2 NEXT Near End Crosstalk NEXT is measured by comparing the signal received at the near end of a neighboring pair Vxtalk with the Voltage Vin injected into the other pair Pair2 Vn ER Pair1 3 4 3 FEXT Far End Crosstalk FEXT is the coupling between nearby pairs at the far end of the cable pair Pair2 re oe Ne Varak 1 Sle Pair1 FEXT V STALK V in Hint Far end crosstalk can also be expressed as Equal Level Far End Crosstalk
13. on speed is the calculated velocity of a wave passing thru the DUT 100m V_ p Tg MICR Smart Measurement Solutions LAS Wits Bode 100 Application Note DSL Cable measurements with Bode 100 Page 21 of 21 To display the measurement result in a good range we calculate the velocity factor It is the propagation speed in ratio to the speed of light in vacuum 3 10 8 m s Export the measurement data like shown in 3 6 ELFEXT Measurement to software like EXCEL or MATLAB This will allow you to generate a diagram as shown below v _P C C 100 4 Conclusion In this application note it has been shown how electrical characteristics of DSL Cables like attenuation crosstalk and phase velocity can measured with Bode 100 All measurements worked out nicely and matched the cable s measurement protocol which was provided with the cable Smart Measurement Solutions OMICRON E LAB
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