User Manual for Cascade Version 4.0
Contents
1. 0 Radial No AE Radius m 0 00197485 Root 3 83171 FIGURE 43 Display of results from resonant cavity analysis From the View pulldown menu select Display Resonant Frequency and O The program generates the display shown in Figure 43 Cascade Version 4 0 September 29 2013 57 From the View pulldown menu select E Field Plot gt E azimuthal vs Z A window will be displayed asking for the axial increment of the plot and the radial location for the fields Enter 0 5 for both values and click OK The plot in Figure 44 should A EasyPlot untitled ol File Edit Add Style Options Tools Window Help xie Jalx Azimuthal Field Component at r 0 02 Etheta z 450 4 Etheta Magnitude 1504 0 4 0 8 12 Z inches i3 ETE ENSIS E FIGURE 44 Display of the azimuthal component of the electric field for the TEO01 Cavity example be displayed The complete output from CASCADE is stored in the binary files in the case directory A description of the contents of these files and the data format is described in the Appendix entitled CASCADE Engine and Auxiliary Codes These files can be used in other plotting programs such as MathCAD to create custom Cascade Version 4 0 September 29 2013 58 graphical presentations or perform additional mathematical manipulation of the computational results Cascade Version 4 0 September 29 2013 59 9 0 Troubleshooting TABLE 2 Proble2. 8 Upon completion examine the results using options in the View pulldown Under the View menu select S71 then Primary Mode Figure 29 shows a plot of the initial configuration and the optimized configuration 9 From the Optimize pulldown menu save the optimized parameters to a file You may then close the initial case file and open the optimized case with the new parameters Increase the number of frequency points in the Run Time Parame ters window to obtain additional points for more pleasing plots Optimization With Length Constraint Sometimes it is necessary to design a waveguide component to fit into and existing system where the overall length is restricted Cascade allows the user to optimize performance by varying multiple parameters within the device while placing restrictions on the overall length The user can implement the length constraint by selecting the radio button for Use Sum of Length Constraints in the middle of the Optimization Parameters window activated in the Optimize pulldown menu Selection of the associated Specify Length Constraint Parameters button brings up the dialog shown in Figure 30 Note that the current length of each section is pre loaded into the left most column and that there are three columns containing radio buttons associated with each section This allows the user to specify up to three sets of length constraints for various combinations of sections At the bottom of the each column is an imput w
3. No specify the parameters tapers involving higher order modes the desired input and Multimode output modes will need to be Input Excitation Mode 1 specified Selection of Multi Pa A Weight Value 1 Mode as the optimization type will bring up an additional input section to specify the input mode and the output mode as FIGURE 25 Mode selection window shown in Figure 25 The weight for multimode optimization value changes the minimization from equal weighting of mode purity and reflection in calculation If the weight value gt 1 the emphasis is on mode purity Three optimization models are supported The most efficient routines are a Quasi Newton method with a finite difference gradient to minimize a single function of many variables and a modified Levenberg Marquardt algorithm Least Squares with a finite difference Jacobian to minimize several functions of many variables note that for the Least Squares optimization the number of frequency points must be greater than or equal to the number of optimization variables These methods work well for functions that are relatively smooth For functions where these Cascade Version 4 0 September 29 2013 38 methods fail to achieve a minimum a third optimization routine using a direct search complex algorithm is supported Von Smooth Optimization is initiated from the p cric De A pd Optimize pulldown menu shown in File Run view Tolerance Settings Help J Figur
4. plots of the scattering parameters or VSWR for modes used in the calcula tion that were selected in the Mode Specification window The primary mode is typically selected since it is the lowest order mode When a parameter is selected for plotting a r ee er EB Case BLOCKWINDOWTOLERANCE EN GNE GNy n a File Run Optimize Tolerance Settings Help f ly s1 a o g 5 gl Ld Mi s2 gt tb PS New 9 t e RunTime Mode s luy 522 gt sect T B in J liie VSWR vs Frequency Primary Mode Ctrl M 4 lili Smith Chart mE o 2 Display Refl and Trans Power 0 1345 d Display Mode Content S11 S12 F d isplay Mode Content m f Display Mode Content S21 S22 E Field Plot j Frequ In Aatrix s Freq lili Tolerance Histogram 2 Display Input Parameters Ctrl I g 4 D 2 as os FIGURE 38 View Pulldown Menu window appears for the user to select either the primary mode or an alternate mode If the alternate mode is selected an additional window appears for the user to select the specific mode from a list of available modes The mode plotted is indicated in the title of the plot A similar situation occurs for viewing printouts of reflected and transmitted power and mode content For resonant frequency calculations a different set of post processing options are enabled These include plots of resonant frequency and Q versus iteration number Cascade Version 4 0 Septe
5. the GUI automatically converts tapered and radiused sections into stepped sections based on algorithms described later A capability is included to input scattering parameters from other sources and include them in problem analysis and design Cascade Version 4 0 September 29 2013 11 Geometrical information is added in the GUI beginning at the extreme left of the device or structure and new sections are added to the right of the previous section As new sections are added a new line is appended to the spreadsheet on the main GUI screen The ID number of each section is shown in the first column of the spreadsheet The following columns indicate the waveguide type shape dimen sions relative position and medium of each section Buttons along the bottom of the screen allow the user to ADD EDIT DELETE or INSERT waveguide sections INSERT locations and sections to be edited or deleted are identified using the radio buttons in the first column At anytime the user can see a plot of the sections entered by selecting the DRAW GEOMETRY button ADDING NEW SECTIONS Selection of the Add Section button activates the pem Loa waveguide type selection window shown in Available Geometries Figure 7 Selection of a waveguide type activates LE E R Circular Waveguide Straight the appropriate input window for that waveguide Circular Waveguide Tapered G s Circular Waveguide Radius type Figure 8 shows the input wind
6. A CYLINDER STRAIGHT 0442 T f O IS ca Ts fem aa FIGURE 3 Settings Pulldown Menu Cascade Version 4 0 September 29 2013 8 The Preferences selection opens the dialog shown in Figure 4 The dialog allows the user to select the units used in the design and the maximum number of modes allowed for an analysis The default values are inches and 1000 respectively The next entry controls how many modes are coupled between adjacent transi tions Modes whose amplitude have dropped below this entry are not used in the cascading of adjacent scatter ing matrices thereby speeding the computation The default values pro vided should give a good balance between accuracy and computation speed for most cases On the next entry the user can select the editor viewer used for displaying text out put data The following two entries allow a user to substitute a minimiza A Preferences ESA Units 9 Inches Meters Centimeters Milimeters Restrictions Maximun Number of Modes to use in Field Expansion 1000 Minimum Amplitude to Define an Accessible Mode 20 Db Paths Executable paths C Users Valerie Cascade Distr Browse Optimization executable C UserslValerie Cascade Distr Optimize exe Min function executable FXi C Users Valerie Cascade Distr FXi exe Spline Fit executable C Users Valerie Cascade Distr SplineFit exe Cascade executable C Users Valerie Cascade Distr Cascade exe Scattout executable C User
7. Tod 5 cs venspicatededi ZU salio A0 Prosram e TTT EM A Problem SS SUID si 5 0 Run Setup and Execution e sese eee 6 0 Optimization aa 7 0 STL TTT A A DAD Tro blesh tin ida 10 0 Appendix A Examples 11 0 Appendix B Engine and Auxilliary Codes 12 0 Appendix C External Scattering Matrix File Lexam Research 10 Black Fox Way Redwood City CA 94062 650 488 8323 Email jeff LexamResearch com Copyright 1999 2003 Cascade Version 4 0 September 29 2013 1 0 Introduction CASCADE is a computer code for rapid and user friendly analysis of waveguide components such as filters microwave cavities and windows It calculates scatter ing parameters transmission reflection coefficients for general waveguide struc tures composed from cylindrical rectangular or coaxial waveguides Transitions between waveguide types are also allowed The program includes the dielectric properties of ceramics and finite conductivity of metal surfaces The program will also solve for resonant frequencies and Qs of cavity structures The program includes an optimizer that dramatically reduces design time by selec tively modifying design parameters specified by the user to achieve specified per formance The program can also input scattering matrices from other computer programs such as HFSS or measured data and incorporate that information into the total system scattering matrix calculation 2 0 Installation There are t
8. ceramic and the waveguide wall 13 Tab twice to B Input Height and enter 0 1345 14 Tab twice to Section Length and enter 0 0707 15 Click on OK Section 3 16 Select Add Section 17 Select Rectangular Waveguide Straight 18 Left click the mouse in the 4 Input Width text box 19 Enter 0 28 for the waveguide width 20 Tab twice to B Input Height and enter 0 14 21 Tab to Section Length and enter 1 0 22 Click on OK Cascade Version 4 0 September 29 2013 16 Verify that main Cascade window is the same as shown in Figure 9 E Case BLOCKWNDW genre File Run View Optimize Tolerance Settings Help EIE CERES TI ILJU 9 E x C gt ln lh New Open Save Execute Exec Opt Exec Tol Optimize Tolerance RunTime Mode Steps Sil Sil Prim SECTION W G TYPE GEOMETRY A cm B cm C cm D cm L cm Offset X Offset Y MEDIUM 1 RECTANG STRAIGHT 0 28 014 o o 1 o o Vacuum 2 RECTANG STRAIGHT 0 274 0 1345 0 0 0 0707 0 0 Custom 3 RECTANG STRAIGHT 0 28 014 o o 1 o o Vacuum Add Section 4 Edit Section Delete Section Insert Section E Draw Geometry FIGURE 9 Main Cascade window for BlockWndw example Viewing the Geometry MS k v gw 23 Select Draw Geometry and confirm that the geometry is as shown in Figure 10 There are two geometry plots shown one for the top wave guide width dimension A in the table and the side view which is the wave guid
9. cylindrical or coaxial sections If the azimuthal mode number is zero the user must further specify if TE or TM modes are to be used Cascade Version 4 0 September 29 2013 24 If the geometry consists of a mix of rectangular and cylin drical sections there are four orthogonal mode sets which can be selected The default Standard Mode Set selects usage of a mode set with sym metry of the TE 9 mode in the rectangular guide and the TE in the circular guide The alter nate mode sets are typically used in determinant sweeps to check for trapped or ghost modes To be complete the determinant sweep analysis r ED C ere uem L e Use modes up to X times cutoff 2 Azimuthal Mode Number cylinder coaxial geometries only 0 Specify TE or TM modes if azimuthal mode 0 TE modes Matrix Calculation 9 TM TEM modes Matrix Calculation Mode Set Type for structures having both rectangular and cylindrical coax section EJ FIGURE 16 Input screen for Mode Parameters should be performed with all sets A complete description of the mode sets used for the four options is described in Appendix C Cascade Engine Number of Steps in Tapered Sections Cascade Version 4 0 September 29 2013 25 Recall that CASCADE analyzes 3 Number Steps Specification O lisa systems by calculating the coupling AAA coefficients between geometries of 0 Use Internal Algorithm Calculation constant radial dimensions or x y Over
10. design Bounds of Optimization mm 5 0 6 0 15 0 16 0 1 5 2 5 16 0 17 0 1 5 2 5 16 0 17 0 1 5 2 5 15 0 16 0 5 0 6 0 1 In the Preferences section of the Settings pulldown menu set the Units to Milli meters Cascade Version 4 0 September 29 2013 40 2 Use the 4dd Section button to enter the sections as indicated in Table 1 When completed the main screen spreadsheet should appear as in Figure 27 Note that values for all parameters with optimization bounds appear with an asterisk In the Run Time Parameters screen select Scattering Matrix Calculation set the Start Frequency to 11 9 GHz and the Stop Frequency to 12 1 and the Number of frequencies to 61 The GUI automatically calculates Frequency Step in this case 0 3333 GHz Note that when Frequency Step is set instead then the Num ber of frequencies calculates automatically 4 In the Mode Parameters window set the number of modes to 80 times cutoff This case requires a large number of modes to achieve a correct solution One should always increase the number of modes until the solution stops changing to insure that sufficient modes are included in the analysis EB Case BANDPASSFILTER py lo ES File Run View Optimize Tolerance Settings Help d e 3 eb amp Y ih ll New Open Save Execute Exec Opt Exec Tol Optimize Tolerance RunTime Mode Steps S11 S11 Prim SECTION W G TYPE GEOMETRY A mm B mm C mm D mm L mm Of
11. equal weighting to both the performance requirement and the length constraint For weighting factors above 1 0 the routine will sacrifice performance in a more con certed attempt to achieve the goal of the length constraint Reduction of the Cascade Version 4 0 September 29 2013 45 weighting below 1 0 will place increased emphasis on performance at the sacrifice of the length constraint The weighting factor must always be greater than 0 0 In Appendix A there is an example problem called Optimization with Length Con straint for Helix TWT Input Window This example demonstrates optimization using measured scattering data with a constraint on the total length 7 0 Tolerance Analysis CASCADE can estimate the impact of machining tolerances on the performance of components This involves performing a Monte Carlo analysis of the perfor mance as parametric values are varied within tolerance ranges specified by the user Because of the high analysis speed of CASCADE several hundred execu tions can be performed in a reasonable period of time to provide meaningful statis tics This allows the user to determine the least restrictive tolerance ranges for critical parameters while still achieving the required yield for the device This can provide significant cost reduction on production components The first step 1s to input tolerances for critical parameters of the device These are parameters that can significantly impact performance if allowe
12. side view of cylindrical and circular geometries A cen terline is inserted for coaxial and circular sections Cascade Version 4 0 September 29 2013 7 4 0 Problem Setup This section describes the elements required for initializing a case and inputting the geometry of the waveguide or circuit components Following sections will describe analysis execution and post processing 4 0 1 File Pulldown Menu E Case CASC_TEST Run View Optimize Tolerance gt The File pulldown menu is shown in Figure 2 FIT GG E d Open Ctrl 0 The menu items allow the user to Open existing um EE files clear the spreadsheet to begin a New Bl Sacs geometry Save the current case with the same case name or use Save As to save the case under a different name Browse windows with appro priate filters are activated for user input where 1 casc test cscd Exit Ctrl Q Abr M 7 LM necessary The Exit function terminates the pro A l mss gram A verification screen appears if informa FIGURE 2 File Pulldown tion in the program has been changed since the Menu last Save operation 4 0 2 File Pulldown Menu The Settings pulldown menu is shown in Figure 3 m EH Case TEOLCAVITY File Run View Optimize Tolerance Settings Help a 1 amp Preferences Ctrl S o s Lal amp P e Ye l New Open Save Execute Exec Opt Configure toolbars me Mode Step SECTION W GTYPE GEOMETRY A in B in
13. CASCADE User Manual Version 4 0 E m EE Case TEOICAVITY E m E ae arai LU E Fle Run View Optimize Tolerance S Sy Im Tii Select Type of Calculation E E fete rer Opm Tolerance Runtime Mode Steps SI slum SECTION WGTYPE GEOMETRY AG 96 Cm Din Lin Offset X Offset v Me Scattering Matrix Calculation i cuo auen oin o o o 02 o o 0 Resonant Frequency Calculation 2 nen maen cass o o B aces o o 3 E vret 0 78 03 o o 075 o o Scattering Matrix Determinant Sweep Section to look for resonance 1 T Coaxial Tapered Window au a IET VT Cat cdi Coca y VSWR RF Medium Vacuum Spedfy Conductivity Perfect Conductor Specify C 225 Smith Chart S11 put Mode TE 1 0 Output Mode TE 1 0 A 114 pres l Ontinize 37 Cases Beera Tazen oc nde Tlence UN e Fon TG E Te Pope EasyPlot untitled Tolerance Analysis of VSWR Edi Add Style Options Tools Window Help le E Azimuthal Field Component at r 0 02 15 0 750 A n 125 Etheta z g 600 J 5 100 zs E i 4604 3 Z E 50 H z i 300 25 iu 00 1804 amo 1039 10502 10 9 10 0 1125 1135 1159 188 1202 12282 VSWR 0 T T T Lexam Research 10 Black Fox Way Redwood City CA 94062 Cascade Version 4 0 September 29 2013 1 Table of Contents 1 0
14. Cylindrical and coaxial sections are delineated from rectangular sections by the presence of a centerline drawn in those sections SAVING THE CASE The user should save information periodically using the File pulldown menu on the main screen or the Save function button shown on the Main window The name provided will be used for storage of all subsequent input and output files generated by the GUI or CASCADE engine with appropriate suffixes for identification EXAMPLE 1 RECTANGULAR BLOCK WINDOW Begin a new case by selecting the NEW option from the File pulldown menu if the main screen spreadsheet is not blank Proceed as follows Section 1 Select Add Section Select Rectangular Waveguide Straight Left click the mouse in the A nput Width text box Enter 0 28 for the waveguide width Tab twice to B Input Height and enter 0 14 Tab twice to Section Length and enter 1 0 Click on OK ND WW A U Dn Section 2 8 Select 4dd Section 9 Select Rectangular Waveguide Straight Cascade Version 4 0 September 29 2013 15 10 Select the Rf Medium Specify button Select the Custom radio button and in the text boxes enter 0 9323 as the dielectric constant and 0 0 for the loss tan gent The loss tangent is not currently used by the program Click OK to close the window 11 Left click the mouse in the A nput Width text box 12 Enter 0 274 for the waveguide width The reduced dimension provides for braze material between the
15. E Eg 50 4 3 L z T 25 57 0 0 1 0101 1 0299 1 0502 1 0709 1 0920 1 1135 1 1355 1 1579 1 1808 1 2042 1 2282 VSWR FIGURE 37 Performance histogram for 001 inch tolerance for ceramic thickness and 100 iterations 12 To get better statistics one can modify the number of iterations in the Tolerance Parameters window and resume execution from the Tolerance pulldown menu Change the number of iterations to 400 and reexecute The new histogram should now indicate that a total of 500 iterations were performed and the distri bution of occurrences should be more uniform across the range of VSWR Cascade Version 4 0 September 29 2013 52 8 0 Post Processing The post processing routines currently generate plot files using a built in plotting package called CasPlot or an external program called EasyPlot for graphical pre sentations and text files for text data A demo version of EasyPlot is included with the Cascade distribution The user can select between EasyPlot or CasPlot in the Preferences window in the File pulldown menu The user can also select which text editor will be used for text data The default is write exe Post processing features are accessed from the View pulldown menu on the main GUI screen shown in Figure 38 Various options are enabled depending on the type of analysis selected in the Run Time Parameters window and the plotting package selected For scattering matrix calculations the user can view
16. Ride With User Specification dimensions in rectangular geome E tries Tapered and radiused sections Modify Number Steps Internal Algorithm Scale Factor R lt Number of Steps Scale Factor 4 default 4 are analyzed by breaking them into a series of steps The GUI performs Number of Steps per RADIUS Section Specification this function automatically depend CEDE h 1 th f th t Over Ride With User Specification Ing on t e wave eng o es op Fixed Number of Steps per RADIUS Section 5 frequency enter ed in the Run Time Modify Number Steps Internal Algorithm Scale Factor Parameters window and the slope of Number of Steps Scale Factor 4 default 4 tapers The user can override the default values by specifying a fixed number of steps for all tapers radii or by changing the algorithm scale factor Figure 17 Note that dou bling the algorithm scale factor will FIGURE 17 Input window for setting approximately double the computa number of steps in tapers tion time Convergence of the results should be checked by increasing the scale factor to ensure adequate modeling of the geometry with steps Initiating Program Execution Analysis of the system is initiated by selecting Execute CASCADE from the Run pulldown menu or clicking the Execute function button at the top of the main screen All diagnostic and status messages from the CASCADE compute engine are written to the Program Status Window first opened by the start
17. accessed View lil VSWR vs Frequency Primary Mo Execute Cascade Display Resonant Frequency anc Pv Execute Optimization functions for easy access lil Inverse Scattering Matrix Deterrr 2 Execute Tolerancing Display Input Parameters Exit fel Save As EL Dreferenrer z 4 w j LA FIGURE 5 Configure Toolbars Cascade Version 4 0 September 29 2013 10 4 0 3 Geometrical Input Input of geometrical data is performed from the main CASCADE screen shown in Figure 6 A spreadsheet on the main screen provides information on each section of the device being analyzed rw EE Case TEDICAVITY 58 e c a s File Run View Optimize Tolerance Settings Help NY LZ E E fe y mam i L eh O h k New Open Save Execute Exec Opt Exec Tol Optimize Tolerance RunTme Mode Steps Sii S11 Prm SECTION W GTYPE GEOMETRY A in 8 n C in D in Lin Offset X Offset Y MEDIUM 1 CIUNDER STRAIGHT 012 0 0 D 02 D 0 Vacuum 2 CIUNDER STRAIGHT 01555 0 0 D 0345 0 0 Vacuum 3 CHLINDER TAPER 0 78 03 0 D 0754 0 0 Vacuum m add Section 1 Edt Secon E Delete Secton T Insert Secon Doren Geometry c 4 FIGURE 6 Main CASCADE screen showing geometry spreadsheet A device or system is modeled by segmenting the geometry into straight tapered or radiused sections of cylindrical rectangular or coaxial waveguide The compu tational engine of CASCADE models only straight waveguide sections however
18. al or inconvenient to model the entire device or system with these codes Using the facility in CASCADE the user can model the complex structure in the mesh code and save the scattering parameters to an disk file The user can then read in this file and treat this information as a Black Box section of the device whose scattering parameters are now known The remaining sections can be added using the Add facility in Cascade and the entire system modeled as a sin gle entity The Optimizer can be invoked to modify the standard elements in the geometry to obtain the desired performance characteristics of the entire device or system In Appendix A is an example where matching elements are used to match a TEo circular to TE q rectangular mode converter to standard rectangular and circular waveguide The second obvious application is in designing matching elements for hardware whose scattering parameters have been experimentally measured One could for example measure the complex reflection coefficient at the input of a helix travel ing wave circuit The measured scattering matrix data would be used as the last section in a CASCADE model to design matching elements including the input window In this way the output waveguide and window would be precisely designed to provide the optimal match to the input helix The user selects External Scattering File at the bottom of the Available Geome tries window shown in Figure 7 This will result in the
19. appearance of the External Scattering Matrix File window shown in Figure 14 Note that it is necessary to specify the input and output geometry type for the device so that the imported scat tering matrix is normalized to the appropriate impedance From this point on the Cascade Version 4 0 September 29 2013 21 file appears as any other section in the geometry except that it is labeled differ ently on the main CASCADE GUI spreadsheet File External Scattering Matrix File Browse Start Frequency End Frequency Number of Frequencies V Input waveguide Geometry 9 Circular Rectangular Coaxial Input extra parameters RF Medium Vacuum Specify Input diameter centimeters Outer diameter inches Output waveguide Geometry 9 None Circular Rectangular Coaxial e Lea d 1 I Ii I I I I i i x FIGURE 14 Input window for inputting external scattering matrix file Two examples using external scattering files are provided in Appendix A The first uses scattering parameters from HFSS and the second uses measured data to match an input window to a helix traveling wave tube 5 0 Run Setup and Execution Execution control is performed using input windows accessed from the Run pull down on the main GUI screen or the Function Buttons at the top of the main GUI window Input data determines what type of analysis is performed Scattering matrix calculation resonant frequency calculation or
20. ascade exe and S parameter postprocessor scattout exe are designed to run directly from the com mand line for custom usage by the user for example a Matlab script file The command line arguments and input output file format are described in the appen dendices The first time the Cascade GUI is called the locations of the various Cas cade executable must be defined for execution by the GUI This is performed by selection of Settings gt Preferences from the pulldown menu In the Paths block click on the Executable paths dialog browse button and select the folder where the Cascade executables are stored If all the required executables are there the list of executables names will be followed by the full path name highlighted in green Figure 4 3 0 Program Execution Start the program by executing the cascade GULexe in your Cascade binary exe cutable files directory or shortcut link The program opens up windows as shown in Figure 1 Cascade Version 4 0 September 29 2013 4 3 1 Main CASCADE Screen The main CASCADE screen is shown in Figure 1 This window is the main work ing location for setup of the geometry runtime parameters and post processing View Pulldown Menu Run Pulldown Menu Tolerancing Pulldown Menu Optimization Pulldown Menu a a Settings Pulldown Menu Help Pulldown Menu Ip lb gt a 0 t File Pulldown Menu X ri Run view Optimize Tolerance Settings Help La Customizabl
21. d 3 O The results should appear as Caladating coupling cnefficents for gude 31 32 x e Finding resonant frequency shown in Figure 18 Freg Q Det 9 4235e 010 200 0 65796 9 3765e 010 200 0 326983 9 4e 010 200 0 250548 9 38933e 010 159 513 0 0108329 e e 9 38949e 010 161 911 0 000163925 6 0 Optimization 9 38949e4010 161 878 7 87182e 008 Calculating eigenmode of cavity resonance Calculating modal amplitudes Section no 1 CASCADE includes the capability to automatically optimize performance riii dur ntes bin 7 by modifying dimensional parame as ters The performance requirements are established by the user who also defines which surfaces can be modi fied and the allowable ranges of modification DI FIGURE 18 Results of TE01 Cavity analysis The program includes three optimization routines selectable by the user These are e Quasi Newton Non Smooth Least Squares Cascade Version 4 0 September 29 2013 29 Alternative user provided optimization routines can be specified in the Prefer ences option in the File pulldown menu The format for these routines is specified in the Appendix There are also three optimization functions Minimize Reflection over Frequency Range this is useful for matching wave guide components and windows so that the reflection is minimized over a fre quency range specified by the user e Minimize Maximize Reflection over Frequency Range this i
22. d to vary far from the nominal value Input for tolerance values is located on the edit screen for each section of the device similar to the input for Optimization To input a tolerance for a parameter activate the checkbox for the parameter and an input window will appear as shown in Figure 31 The two text widgets allow the user to specify a positive and negative tolerance around the nominal value entered in the edit screen text box The user must click on OK to accept the values entered or on Cancel to cancel the operation Note that an symbol appears next to the parameter on Cascade Version 4 0 September 29 2013 46 the main GUI screen to indicate that a tolerance was specified Tolerances can be E Straight Cylindrical Waveguide 2 2 RF Medium Vacuum Conductivity Perfect Conductor _ specify As q A Input Diameter 0 1555 Upper Tolerance 0 1755 Lower Tolerance 0 1355 A Input Diameter 0 1559 E EZ Tolerance L Section Length 0 3425 inches E Optimize E Tolerance b FIGURE 31 Input screen for specifying tolerance values Both a positive and negative tolerance must be specified The nominal value is shown above the input boxes specified for more than one parameter of the device Parameters for tolerance analysis are mA UU specified in the Tolerance pulldown Optimize Tolerance Settings Help menu shown in Figure 32 The 3 QA f opti
23. determinant sweep to check for resonant modes Frequency values modal input and other parameters required for program execution are entered here Where appropriate default val ues are provided For most situations these will be adequate but the user always has the option of selecting alternative values Cascade Version 4 0 September 29 2013 22 RUNTIME PARAMETERS Input data provided in this window determines what type calculation is performed and the appropriate values r n S Run Time Parameters 0000000 ENS Select Type of Calculation Scattering Matrix Calculation for RF frequency and Q for resonant resonantrrequency Calculation frequency calculations The type cal ee ee ee culation is set by selecting the appro ERA priate radio button for Scattering Resonant frequency estimate 0 Matrix Calculation Resonant Fre QEstimate 10000 quency Calculation or Scattering eee ees aes Matrix Determinant Sweep Depend Request Mode Dump ves No art and Stop section of di ing on the selection corresponding inputs are displayed in the window Figure 15 For scattering matrix cal cancel culations the scattering parameters are stored at each frequency for post FIGURE 15 Run Time Parameters dialog Resonant Frequency Calculation processing The frequencies used are is selected selected by the user in the second sec tion of the Run Time Parameters window T
24. e om Function Buttons SECTION 1 Section aT Selector Section Type eK Ox 5 lli Execute xec Opt Exec Tol Optm e Tolerance RunTme Mode Steps SII SIPrim W G TYPE GEOMETRY A in B in C im CYUNDER STRAIGHT 0122 o CULINDER STRAIGHT 0 1555 0 0 0 CHUNDER TAPER 0 178 03 d Section Dimensions Section Media Add Section A Ed Section Delete Section de Insert Section C Dran Geometry Vacuum Vacuum FIGURE 1 Main CASCADE Window The elements of the window have the following functionality File Pulldown Menu activate the file pulldown menu by clicking and holding the left mouse button and dragging the cursor to the desired operation Cascade Version 4 0 September 29 2013 Run Pulldown Menu activate the runtime parameters menu by clicking and holding the left mouse button and dragging the cursor to the desired operation View Pulldown Menu activate the post processing features by clicking and holding the left mouse button and dragging the cursor to the desired operation Help Pulldown Menu displays information on software version and con tact information for the software developer Function Buttons provides quick access to commonly used functions and access to runtime and setup screens WG Type displays the waveguide type used for each section This can be rectangular coaxial circular or external Section Shape specified whether the section is st
25. e 26 Clicking on Execute Piai ES ey Optimization begins the optimiza New Open Sal Execute Optimization E pnis E KE Resume Optimization Execution tion process Progress can be moni senon oa y P iew imization ecution Log File 9 tored with the Program Status 1 e A b Update Case with Optimized Parameters g Window The program initiates a B b Save Optimized Parameters to Case CASCADE solve process evalu 3 C oumpes aper oara d ates the result nerates input for F es the results generates input for H O A OQ the next iteration and reexecutes a solution The process continues until convergence is achieved or FIGURE 26 Optimization Pulldown s Menu the maximum allowed iterations are performed The results of the process can be viewed using the post processor options described in the next sec tion Note that the values in the Main GUI spreadsheet are not automatically updated with the optimized values To see the optimized parameters use the Update Case with Optimized Parameters option in the Optimize pulldown win dow This will overwrite the original values Alternatively one can use the Save Optimized Parameters to File option Then close save the current file and open the optimized file using the Open option in the File pulldown menu The Optimize pulldown menu also includes options to view the optimization log file and to resume optimization if desired The Quasi Newton and LSQ optimization methods
26. e height FERE M Saving the Case FIGURE 10 Top view waveguide width for Rectangular Block Window Cascade Version 4 0 September 29 2013 17 24 From the File pulldown select Save As and save the case with the name Block Wndw Example 2 TE01 Gyrotron Cavity Begin a new case by clicking the NEW button at the top of the CASCADE main window if the main screen spreadsheet is not blank Proceed as follows Section 1 1 Select Add Section 2 Select Circular Waveguide Straight then OK 3 Enter 0 122 in the A Input Diameter text box 4 Tab twice to Section Length and enter 0 2 5 Select OK Section 2 6 Select Add Section 7 Select Circular Waveguide Straight then OK 8 In the A Input Diameter text box enter 0 1555 9 Tab twice to Section Length and enter 0 3425 10 Select OK Section 3 11 Select Add Section 12 Select Circular Waveguide Tapered then OK 13 In the A Input Diameter text box enter 0 178 14 In the B Output Diameter text box enter 0 30 Cascade Version 4 0 September 29 2013 18 15 Set Section Length to 0 754 16 Select OK Verify that Main Screen information is same as shown in Figure 11 Ee Case TEOLCAVITY File Run View Optimize Tolerance r3 Help New Open Save Execute Exec Opt amp Tol Optimize rA RunTime Mode Steps SI SiiPrim SECTION W G TYPE GEOMETRY A cm B cm C cm D c
27. ep the user specifies the start and stop frequencies and the frequency step The user also specifies a Q value which has a slight impact on the resolution of the search Mode Parameters Input for the mode parameters is done from the dialog window selected by the Run gt Mode Parameters pull down menu or the This window Figure 16 pro vides information on what modes are to be used during program execution The first input Use modes up to X times cutoff sets the number of modes to be used in the scattering matrix calculations The number of modes used in each section is determined by selecting all modes up to those whose cutoff frequency is X times the upper analysis frequency The total computational time increases quadratically with this input however failure to use a sufficient number of modes may result in an inaccurate solution A simple technique for determining the appropriate value is to incrementally increase the input value until the simulation results converge The number of modes required depends on the dimensions of the geometry and the frequency Waveguide geometries with large reactive components such as irises can require large numbers of modes The filter example described in the optimiza tion section below requires use of modes with cutoff frequency up to 80 times the upper analysis frequency for accurate analysis The middle section of the window specifies the azimuthal mode number when the entire geometry consists of only
28. fset X Offset Y MEDIUM 1 RECTANG STRAIGHT 19 05 9 53 0 0 15 0 0 Vacuum 2 RECTANG STRAIGHT 54 9 53 0 0 0 1 0 0 Vacuum 3 RECTANG STRAIGHT 19 05 9 53 0 0 15 8 0 0 Vacuum 4 RECTANG STRAIGHT 2 9 53 0 0 01 0 0 Vacuum 5 RECTANG STRAIGHT 19 05 9 53 0 0 164 0 0 Vacuum 6 RECTANG STRAIGHT Ly 9 53 0 0 0 1 0 0 Vacuum 7 RECTANG STRAIGHT 19 05 9 53 0 0 164 0 0 Vacuum 8 RECTANG STRAIGHT 2 9 53 0 0 01 0 0 Vacuum 9 RECTANG STRAIGHT 19 05 9 53 0 0 15 8 0 0 Vacuum 10 RECTANG STRAIGHT 54 9 53 0 0 0 1 0 0 Vacuum 11 RECTANG STRAIGHT 19 05 9 53 0 0 15 0 0 Vacuum C Add Section 2 Edt section Delete Section 7 Insert Section LBS Geometry f Execute Optimization FIGURE 27 Main GUI for initial band pass filter MAYBE MOVE TO START OF EXAMPLE Cascade Version 4 0 September 29 2013 41 5 In the Optimization Parameter window set the input as shown in Figure 28 The Least Squares algorithm is chosen because it is more efficient when the number of frequency steps exceeds the number of optimized variables r E Rar BT E Maximum Number of Iterations 300 Optimization Function Optimization Type O Minimize Reflection over Frequency Range Fundamental Mode 9 Minimize Maximize Reflection over Frequency Range B B GAR Multi Mode Over Moded Waveguide Optimization Optimization Algorithm Model Quasi Newton Non Smooth Q9 Least Squares Use Sum of Length Constraints Yes No Specif
29. he user can input the Number of Fre quencies or the Frequency Step and the GUI will calculate the alternate value If a resonant frequency calculation is selected additional entries in the RunTime Parameters window are displayed Figure 15 The user first designates which section of the structure is to be analyzed as a resonant cavity The user is next required to input an estimate for the resonant frequency and Q The program uses a search algorithm that requires a starting point for the search routine The number of iterations the program is allowed to perform is the next input in the window During program execution the code writes information to the Program Status Window on the status of the search This information is useful for refining the ini tial estimate if the program fails to converge within the allowable number of itera tions Cascade Version 4 0 September 29 2013 23 Following successful execution the program can write the field information to a file for input to other codes The inputs at the bottom of the Run Time Parameters window allow the user to select this option and specify the axial extent of the field information written to file The format of the output file is described in the Appen dix The Scattering Matrix Determinant Sweep allows the user to search the geometry for trapped modes and ghost modes The family of modes used in the search are described in the Mode Parameters section below For the determinant swe
30. idget for specifying the goal value for each con straint The button to the left of each input widget is a selection button that allows the user to specify whether the optimization routine is to strive for equality or for a length sum that is equal to or greater than the specified goal value If for example if the user wants the optimum value of the device to be greater than 0 5 inches and less than 1 0 then the appropriate sections would be selected in col umn one and the constraint set to gt 0 5 The appropriate sections would be selected Cascade Version 4 0 September 29 2013 44 in column 2 and the constraint set to lt 1 0 The optimization routines will attempt to satisfy both constraints HJ E Optimization Length Constraint Worksheet I EN LENGTH CONSTRAINTS Section Length 1 2 3 zi 15 01 2 158 F 3 01 4 164 5 01 6 164 7 0 1 Sum per column x 7 0 0 i l 0 I Desired Value 0 0 B 0 Weight Factor 1 1 1 i Cx FIGURE 30 Optimization Parameters setup screen for Length Constraints At the bottom of the worksheet is an input for Weight Factor When the optimiza tion routine is invoked it will attempt to optimize on the performance criteria selected in the Optimization Parameters window for example Minimize Reflec tion over Frequency Range and on the length constraints specified in the work sheet For a weighting factor of 1 0 the routine will give approximately
31. m L cm Offset X Offset Y MEDIUM 1 CYUNDER STRAIGHT 0422 o o o 02 o o Vacuum 2 CYLINDER STRAIGHT 0 1555 0 0 0 0 3425 0 0 Vacuum 3 CYUNDER TAPER 0478 03 o o 0754 o o Vacuum E Add Section 22 Edit section Delete Section 8 insert Section e FIGURE 11 Main Cascade window for TE 9 cavity example Viewing the Geometry Cascade Version 4 0 September 29 2013 19 17 Select Draw Geometry and confirm that the geometry is as shown in Figure 12 Saving the case 18 From the File pulldown select Save As and save the case with the name TEO1 cavity 4 1 Use of External Scattering Matrix Files CASCADE allows the user to input external scattering matrix files as sections in the device being modeled This has two a F3 Side View FIGURE 12 Geometry plot for TE01 Cavity obvious applications Consider a situation where a complex 3 D structure is mounted between standard 2 D coaxial rectangular or circular structures as shown in Figure 13 Typically it is necessary to use an advance mesh code such Input bns Matching Elements 3 D Structure xc Black Box P sd Output FIGURE 13 Example of using external scattering matrix files to model complex structures as HFSS and MAFIA to model 3 D structures however it may be computation Cascade Version 4 0 September 29 2013 20 ally impractic
32. m Description Window does not respond Program hangs for res onant frequency calcu lation Program Prompts for license file Cascade Version 4 0 Possible Cause A window requesting user input is hidden behind other windows Insufficient number of modes speci fied for solu tion No license file or path set incor rectly Corrective action Rearrange or iconize windows and look for active windows requesting user input If found enter a response or cancel the window Activate the DOS window and enter Ctrl C Return to main GUI window access Run pulldown menu then Mode Specification Increase the number of modes above cutoff used for the calculation and retry The program looks for the license file Lexam lic in the directory where cascade exe is installed Ifno license file is found contact the software developer to receive a license file Follow the instructions in the instal lation section of this manual to install the license If your installation uses a network license please contact the system administrator for the name of the license server Have the administra tor verify that the network license is installed and operational September 29 2013 60 Cascade Version 4 0 September 29 2013 61 Cascade Version 4 0 September 29 2013 62
33. m ms x FIGURE 19 Input window for specifying bounds of optimization variation optimization routine When the user selects OK the window closes and the radio button changes to a red color to alert the user that this parameter is selected for optimization An asterisk will appear on the main GUI screen next to the corre sponding parameter The user next selects the optimization parameters The Optimization Parameters screen is activated by clicking on the Optimize button on the main GUI screen or Cascade Version 4 0 September 29 2013 32 from the Optimize pulldown menu The Optimization Parameters window is shown in Figure 20 P y Maximum Number of Iterations 100 Optimization Function Optimization Type gt Minimize Reflection over Frequency Range 8 Fundamental Mode Minimize Maximize Reflection over Frequency Range S Multi Mode gt Over Moded Waveguide Optimization p es Optimization Algorithm Model Quasi Newton Non Smooth Least Squares Use Sum of Length Constraints Yes 9 No Specify the parameters Frequency Band Specification in GHz fio f20 f30 fa 0 Target Reflection Coefficients in Bandpass Regions Regioni 7 0 Region2 lt 0 Region 3 Y gt 0 Relative Weigting for each Bandpass Region Region 1 1 Region 2 1 Region 3 1 FIGURE 20 Optimization Parameters input screen The initial entry is for the maximum number of function evaluations iterations t
34. mary S E Blanes P 27 150000 0 081568 0 909108 Mode The program will start the zz so ss 27 240002 0 068859 0 921668 default editor and display the S sapne o reflected and transmitted power 21 360001 Ga 0 99692 27 390001 0 049853 0 940444 versus frequency as shown in 7402 oa a 27 480001 0 039829 0 950344 Figure 41 27 510000 0 036726 0 953407 27 540001 0 033744 0 956351 ou w dee Many other plotting options are available from the View pull FIGURE 41 Display of Reflected and down Figure 42 shows a Smith Transmitted Power for Block Window Chart for the block window example example Cascade Version 4 0 September 29 2013 55 Smith Chart S11 Input Mode TE 1 0 Output Mode TE 1 0 FIGURE 42 Smith Chart for Block Window example 56 September 29 2013 Cascade Version 4 0 Example TE Cavity From the File pulldown menu open the case TEOI cavity saved earlier If you have not done so execute the case to generate the output files Once a problem has been solved the output files remain in the direc tory until removed by the user or overwritten with a new execution r y E Res Freq mode file TEO1cavity op 2 jm SUCCESS Resonance calculation converged Eigenvalue 1 Resonant Freq 9 389490961le 010 Resonant Q 161 878 Maximum mode EH Mode Type TE Geometry Type Cylindrical Azimuthal No
35. mber 29 2013 53 If a Mode Dump was requested in the Run Time Parameters window the options for plotting Ep Eg and E versus axial position are displayed Example Block Window From the File pulldown menu open the BlockWndw case saved in previous exam ples If you have not previously executed the case do it now Once a problem has been solved the output files remain in the directory until removed by the user or overwritten with a new execution From the View pulldown select VSWR vs Fre quency Primary Mode The program starts EasyPlot or CasPlot and presents the display shown in Figure 39 CasPlot BlockWndw CascadeResults BlockWndw ka S L eye File Plot Type e VSWR 2 25 2 00 1 75 x L z L o C 1 50 1 25 1 00 HR 1 i LI l I i i L1 i i 1 i i i L1 i i i 27 0 27 5 28 0 28 5 29 0 29 5 30 0 Hu Frequency GHz FIGURE 39 CasPlot display of VSWR for Block Window example JEFF THIS USED TO SHOW an EASYPLOT but currently not working Cascade Version 4 0 September 29 2013 54 Exit from EasyP lot or CasPlot E SMC file C Users Valerie Cascade Original 3 0 Examples BlockWndw _ CascadeResults 81 9 5 and return to the main CAS Incident Mode No TE 1 0 CADE screen From the View Huc M ices pulldown menu select Display SS ase Lanne Refl and Trans Power Pri
36. mization function Minimize Maximize Reflection over Fre quency Range activates an additional input section This section facilitates the Cascade Version 4 0 September 29 2013 34 design of notch or bandpass filters The setup for designing a bandpass filter is Reflection Coefficient 0 HA fstart A f2 B f jena Freq GHz FIGURE 21 Configuration for design of a bandpass filter illustrated in Figure 21 Assume it is desired that the reflection coefficient below 4 0 GHz and above 7 5 GHz be greater than 0 9 In the passband between 5 0 GHz and 6 5 GHz the reflection coefficient is to be less than 0 4 The frequencies F1 F4 define three regions as shown in Figure 21 The associated input into the Optimi Cascade Version 4 0 September 29 2013 35 zation Parameters screen is shown in Figure 22 The relative weighting values are ede n e P rer AS ll DES r7 ne e AD har ine A C E Frequency Band Specification in GHz fi 4 0 f2 5 0 f3 6 5 Target Reflection Coefficients in Bandpass Regions Region 1 Y gt 0 9 Regon2 lt 0 4 Regon3 Y gt 0 9 Relative Weigting for each Bandpass Region Region 1 1 Region 2 1 FIGURE 22 Parametric input for bandpass of Figure 21 included to change the values of the minimization functions of the frequency bands Cascade Version 4 0 September 29 2013 36 Similarly A notch filter can be designed by changing the input in the Target Reflection C
37. o allow during optimization The optimizer will continue to iterate on the solution until it detects convergence or until the maximum number of function evaluations is reached The number of function evaluations required depends on the problem and the number of variables that are being optimized Typical problems achieved Cascade Version 4 0 September 29 2013 33 convergence within 100 function evaluations but larger problems may require 500 or more There is a restart option in the Optimize pulldown menu so it is not nec essary to start optimization at the beginning again if more iterations are required The next sections lists the available optimization functions optimization type and available optimization algorithms The Optimization Type selections are disabled unless the Over Moded Waveguide Optimization is selected For Minimize Reflec tion over Frequency Range the program attempts to minimize the reflection over the frequency range specified in the RunTime Parameters window Hint It is not necessary to use many frequency points when using the optimizer It is recommended that the number of frequency steps be minimized to reduce the optimization time Typically only 10 20 frequency points are required depending on how rapidly the scattering parameters vary Once an optimized solution is found the performance can be further increased by reducing the frequency range or increasing the number of frequency steps Selection of the opti
38. oefficients in Bandpass Region Figure 23 shows the configuration mm Reflection Coefficient 0 fstart fl f2 D fend Freq GHz FIGURE 23 Configuration for Notch Filter for a notch filter and Figure 24 shows the corresponding optimization parameters t Ze Hte LPS a ia pw T e Use Sum of Beriath Constraints Yes No Frequency Band Specification in GHz fl 4 0 f2 5 0 f3 6 5 fa 75 Target Reflection Coefficients in Bandpass Regions Region 3 03 Region 1 0 3 Region2 0 8 Relative Weigting for each Bandpass Region Region 1 1 Draw Region 2 1 Region 3 1 FIGURE 24 Optimization parameters for a notch filter Cascade Version 4 0 September 29 2013 37 The third optimization function 23 Optimization Parameters EN is Over Moded Waveguide Opti Maximum Number of Iterations 100 mization and is used for design Optimization Function Optimization Type ing C omponents where more Minimize Reflection over Frequency Range MERE Minimize Maximize Reflection over Frequency Range than one mode can propagate ne Over Moded Waveguide Optimization For designing components where the input and output modes are the fundamental mode in the waveguide the Optimization Type should be set to Fundamental Mode For opti Optimization Algorithm Model 9 Quasi Newton Non Smooth Least Squares mization of mode converters Or Use Sum of Length Constraints Yes
39. ons allow the user to number of ve pean G Execute Tolerancing ce Run Time tolerance iterations or view the i ml bat conical P E W GTYPE GEOMETRY A mm B mmp results in a histogram plot of the per 5 ns MIR Mem sad formance results The user can plot E E S ont S11 S12 or VSWR The histogram A Lm ar aan gps msi indicates how many simulations achieved the performance levels indicated FIGURE 32 Tolerance pull down menu Cascade Version 4 0 September 29 2013 47 The tolerance analysis parameters are shown in Figure 33 The first parameter H3 Case BLOCKWNDW l Fi r3 amp A E a A eme qme d dane E x C amp amp Y ih lit New Open Save Execute Exec Opt Exec Tol Optimize Tolerance RunTime Mode Steps S11 S 4 SECTION W G TYPE GEOMETRY A in B in C in DE 1 5 Tolerance Parameters Maximum Number of Iterations 100 Frequency to Calculate Tolerance 13 4 Number of Histogram Intervals 10 N ans aat aem P eem at T as aoa M PPS fn FIGURE 33 Tolerance Parameters input screen indicates how many iterations are to be executed with variation of the toleranced parameters The more iterations the better the statistics however the longer the analysis will require Keep in mind that the user can resume the analysis without starting over if additional iterations are indicated after viewing the results The performance of the device is specified at a single frequency
40. ow for a Gre Wende hides Tapered Coax Section The last geometry type Coaxial Waveguide Straight B Coaxial Wi ide Te d shown in the Available Geometries window is Comial Waveguide Adblrary External Scattering Matrix File This allows the Rectangular Waveguide Straight 3 A Rectangular Waveguide Tapered user to input S parameters obtained from experi Batesqin Waveguide Radas mental measurement or from other programs Se eta d External Scattering Matrix File such as Ansoft s High Frequency Structure Sim Mirror Boundary Condition ulator This feature will be described later e ewe FIGURE 7 Waveguide Type selection window Cascade Version 4 0 September 29 2013 12 All geometry input SCreens T coaxial Tapered Window ad A a are functionally similar At the top of each screen is a section for selecting the medium inside the wave guide section and the con ductivity of the metal surfaces The default media value is Vacuum and RF Medium Vacuum Specify Conductivity Perfect Conductor Specify on the Specify button and selecting materials using the radio buttons Selection of a listed material auto matically loads the appro priate values into the text boxes to the right Selection of the Custom radio button allows the user to manually enter alternative values using the keyboard After selection of the Custom radio button left click the mouse in the appropriate text bo
41. pered Sections 8 Since there are no tapers in this example no input is necessary Execute Cascade 9 Arrange windows on screen so lower portion of DOS window is visible 10 Select Execute Cascade EXAMPLE TE01 CAVITY From the File pulldown menu on the main screen open the previously saved file called TE01 cavity 1 From the Run pulldown menu select Run Time Parameters 2 Select Resonant Frequency Calculation 3 In the third section of the window enter 2 as the section to analyze for reso nance 4 Enter 94 0 as the Resonant Frequency Estimate 5 Enter 200 as the O Estimate 6 For Request Mode Dump select No 7 Select OK Mode Specification 8 Change the number of modes above cutoff to 3 9 Azimuthal Mode Number should be 0 10 TE modes should be selected Number of Steps in Tapered Sections 11 Select to Over Ride With User Specification Cascade Version 4 0 September 29 2013 28 12 Set Fixed Number of Steps per TAPERED Section to 30 13 Select OK 14 Save the case information using the File pulldown menu or Save function but ton Execute Cascade 15 Arrange windows on screen so lower portion of DOS window is visible 16 Select Execute function button at the top of the main screen 17 When execution completes go to T lt executable output EN the View p ulldown menu and select Calculating coupling coefficients for guide 27 28 A Display Resonant Frequency and Errani coping sto to rar Calcul i n r gui
42. point For a broadband device the user may want to rerun the analysis at the band edges to insure yield will be adequate throughout the operating range The final text box indicates the number of divisions on the horizontal axis of the histogram Example Block Window 1 From the file pulldown menu open the case BlockWindow in the Examples sub directory of the CASCADE install directory 2 Highlight section 2 and click on the Edit button at the bottom of the main GUI screen Cascade Version 4 0 September 29 2013 48 3 Select the Tolerance check box for the section length We will determine what tolerance is acceptable for the ceramic window thickness 4 As shown in Figure 34 enter 002 for both the positive and negative tolerance ranges E Straight Rectangular Waveguide I X RF Medium Custom specify Conductivity Perfect Conductor specify y L Section Length 0 0707 Upper Tolerance 0 002 inches Lower Tolerance 0 002 inches A Input Width 0 274 E ca To B InputHeight 0 1345 sms Tole L Section Length 0 0707 inches Optimize 7 Tolerance Centerline Offset From Previous Section DeltaX 0 inches Delta Y 0 inches ok Cancel d FIGURE 34 Ceramic thickness tolerances for block window example 5 Click on OK twice to return to the main GUI window 6 From the Tolerance pulldown menu at the top of the main GUI screen select the Tolerance Parameters op
43. raight or tapered Section Dimension displays the dimensions of each section The headings represent different things depending on the type waveguide and are defined in the section edit screens described later In all cases L represents the length of the section Offsets are only applicable to rectangular waveguides Media Type displays the medium representing the active region of the waveguide or circuit section Help Information Display provides descriptive information on the screen element located beneath the mouse cursor Section Selector radial buttons used by the Edit Delete and Insert but tons at the bottom of the screen Cascade Version 4 0 September 29 2013 6 Add Section Button activates section selection browse window for adding additional sections to the bottom of the spreadsheet right end of the geometry Edit Section Button activates the section input screen for the section indi cated by the Section Selector radial buttons This allows the user to modify the information for a particular section Delete Section Button deletes the section indicated by the Section Selec tor radial buttons Verification is required by the user before the function is performed Insert Section Button inserts a section before the section indicated by the Section Selector radial buttons This activates the Section Type Selection window Draw Geometry draws a side and top view image of rectangular geome tries and a
44. reater than 1 2 1 are considered unacceptable The histogram in Figure 36 indicates that almost half of the windows manufactured with this tolerance will exceed a VSWR of 1 2 Te CasPiot BlockWindowTolerance CascadeResuits BlockWindowTolerance wv 7 ES Se File Plot Type Tolerance Analysis of VSWR Case C Users V alerie Cascade Original 3 0 Examples BlockWindowTolerance_CascadeResultsBlockWindowTolerance Frequency 28 2000 GHz Iterations 100 12 5 10 0 o L g L o L 7 L 5 75 3 L Q L Q L S E E a 2 L L z L 2 5 0 0 1 0111 1 0509 1 0924 1 1355 1 1805 1 2274 1 2764 1 3276 1 3811 1 4372 1 4959 VSWR FIGURE 36 Performance histogram for 0 002 inch tolerance for ceramic thickness 10 Edit the ceramic thickness tolerances to 001 and reexecute the analysis Cascade Version 4 0 September 29 2013 51 11 The histogram plot should be similar to that shown in Figure 37 and indicate that approximately 95 of the iterations will meet the 1 2 1 VSWR require ment E casplot BlockWindowTolerance_CascadeResults BlockWindowTolerance wm De o lew File Plot Type Tolerance Analysis of VSWR Case C Users V alerie Cascade Original 3 0 Examples BlockWindowTolerance_CascadeResultsBlockWindowTolerance Frequency 28 2000 GHz Iterations 100 15 0 12 5 5 C n G E 5 100 T 3 FP o H 16 L 7 5 E C o L la g
45. red correctly EDIT SECTION Use the mouse to select the radio button corresponding to the section to be modi fied Clicking the left mouse button on the Edit Section button will result in dis play of the input window for that section with current values for all parameters Use the left mouse button and keyboard to modify the entries Selection ofthe OK button will close the window and update the spreadsheet INSERTING SECTIONS To insert a section use the mouse to activate the radio button of the section in the spreadsheet that will follow the new section The waveguide type selection win dow will appear and the user selects the appropriate type This will activate the input window for the new section and the user proceeds as described above Selection of the OK button will result in insertion of the new section in the spread sheet and renumbering of the following sections DELETING SECTIONS To delete a section use the left mouse button to activate the appropriate radio but ton in the first column of the spreadsheet Selection of the Delete Section button will activate a confirmation window for the user to verify the delete request Fol lowing verification the information will be removed from the spreadsheet and the following sections will be renumbered Cascade Version 4 0 September 29 2013 14 VIEWING THE GEOMETRY At any time the user can display a schematic plot of the data entered by selecting the Draw Geometry button
46. require that the initial geome try be close enough to the desired performance for the convergence algorithm to converge to a correct solution If the optimized performance does not meet the requirements the Non Smooth algorithm can sometimes locate the desired mini mum maximum when the others can not however it is less efficient and typically requires significantly longer to converge Cascade Version 4 0 September 29 2013 39 If all algorithms fail to converge to the proper solution it will be necessary to revise the initial configuration or increase the bounds on the optimized parameters Example H plane filter This example uses a series of thin irises to design a bandpass filter between 11 975 GHz and 12 025 GHz in rectangular waveguide The dimensions of the sections are provided in Table 1 CASCADE parameters for this case are included in the Cascade examples folder as BandPassFilter TABLE 1 Initial input parameters for Band Pass Filter Broad Wall Sect Width mm 19 05 5 4 19 05 2 0 19 05 Le 19 05 2 0 19 05 5 4 11 19 05 VD WAN 0 tA FW Nel h o Narrow Wall Width Length mm mm 9 53 15 0 9 53 0 1 9 53 15 8 9 53 0 1 9 53 16 4 9 53 0 1 9 53 16 4 9 53 0 1 9 53 15 8 9 53 0 1 9 53 15 0 Optimized Parameter None Broad Wall A Length L Broad Wall A Length L Broad Wall A Length L Broad Wall A Length L Broad Wall A None Follow the step below to optimize this
47. s Valerie Cascade Distr ScattOut exe EvsZGen executable C Users Valerie Cascade Distr EvsZGen exe CasPlot executable C Users Valerie Cascade Distr CasPlot exe Misc Plotting Method 9 CasPlot EasyPlot V Plot S Parameters in Db Suppress Diagnostic Output Co coca FIGURE 4 Preferences dialog for selecting units maximum number of modes and text editor viewer tion function or optimization algorithm in place of the ones provided by Cascade The interfaces for those routines are documented in the appendix An alternate routine can also be used for the interpolation of arbitrary wall profile points The final entry allows selection of the graphics program invoked for displaying plots and graphical output CasPlot is included with CASCADE and EasyPlot is a com mercial plotting program provided as demo version Cascade Version 4 0 September 29 2013 9 The Configure Toolbars selection e IA opens the dialog shown in HAZ Figure 5 The dialog allows the Editing the toolbar Man tobar z user to set the most commonly Drag the actions to the toolbar ist to add them to the toolbar v Drag them from toolbar list to remove them from the toolbar accessed functions in the pull pp Toolbar actions down menus as one click options 2 SIS ner 2 S w iode Specification 3 separator It is particularly useful for setting duel e Generate Input Data Set Only e the most commonly
48. s useful for band pass and notch filters and designing broadband waveguide components and windows Over Moded Waveguide Optimization this is used for designing mode convert ers and overmoded waveguide tapers To use the optimizer the user must define which dimensional parameters can be varied and the allowable range for that variation The input window of each sec tion contains radio buttons for selecting parameters for optimization as shown in Cascade Version 4 0 September 29 2013 30 Figure 19 Clicking the left mouse button on the radio button for a parameter 23 Straight Rectangular Waveguide Lo esl RF Medium Vacuum Specify Conductivity Perfect Conductor seedfy A Input Width 0 28 B Input Height 0 14 L Section Length 1 Centerline Offset From Previous Section DeltaX 0 inches opens up an input window for inputting the allowable range of modification as Cascade Version 4 0 September 29 2013 31 shown in Figure 19 The user must provide both a lower and an upper bound for the E 7 g ES at ww L Ut a K 7 4 J 2 B L gt E Optimization parameters e 4 A InputWidth 0 28 mee C L B t Height 0 14 B InputHeight 0 14 eaten Tolerance ka di Lower Bound for Parameter pt 4 L SectionLength 1 Tolerance e 3 Upper Bound for Parameter 0 a xL Centerline Offset From P 1 2 J Deltax 0 inches f 4 y E Cancel es ati t
49. tion The window shown in Figure 35 should appear Leave the number of iterations at the default value of 100 The center Cascade Version 4 0 September 29 2013 49 frequency of the device is approximately 28 2 GHz so we will analyze the per formance at this frequency The Tolerance Parameters window should appear as shown in Figure 35 T J TD Case BLOCKWNDW 4 dod 9j K k 9 l ln 7 New Open Save Execute Exec Opt Exec Tol Optimize Tolerance Run Time Mode Steps S11 11 Prim SECTION W G TYPE GEOMETRY A in B in C in D Gn pN 1 3 Tolerance Parameters eS 0 f 2 0 P Maximum Number of Iterations 100 3 0 e Frequency to Calculate Tolerance 28 2 d Number of Histogram Intervals 10 2 e 2 Lee Mmmm atat s US N i FIGURE 35 Tolerance parameters for Block Window example 7 From the File Pulldown menu select Save As and save the case as BlockWin dowTolerance 8 From the Tolerance pulldown menu select Execute Tolerancing Progress can be followed in the diagnostics window The analysis should take approximately 1 minute 9 When execution is completed plot the VSWR histogram by using the View pull down menu and selecting Tolerance Histogram and then VSWR The plot should be similar to that shown in Figure 36 Because of the random nature of the variation of parameters each simulation will be different Cascade Version 4 0 September 29 2013 50 Typically VSWR values g
50. up batch file It is strongly recommended that the windows on the computer screen be arranged so that the lower portion of this window is visible Cascade Version 4 0 September 29 2013 26 At the completion of execution a diagnostic information window appears if a prob lem occurred Generate Input Data Set Only The final option in the Run pulldown menu allows the user to generate only the input file for the CASCADE engine without initiating program execution This is a ASCII file with an extension of cas Advanced users can directly modify this file with a text editor and manually execute the CASCADE engine from the MSDOS prompt The format of this file is included in the Appendix EXAMPLE BLOCK WINDOW From the File pulldown menu or the Open button on the main screen open the previously saved file called BlockWndw Run Time Parameters 1 Select Run Time Parameters at the top of the main GUI screen Select the Scattering Matrix Calculation radio button default For start frequency enter 27 0 For stop frequency enter 30 0 a A vc N For Number of Frequencies enter 101 Hit the return key and note that the Fre quency Step size is automatically calculated and entered in the next text box 6 Select OK Mode Specification 7 Verify that the number of modes are 2 times cutoff The mode set is automati cally selected and requires no further input Cascade Version 4 0 September 29 2013 27 Number of Steps in Ta
51. wo steps required the install the Cascade software The first is down loading the Cascade distribution from the link provided to you by email The sec ond step is obtaining the MAC address of your PC which is to be sent to Lexam for generation of the license file Begin by extracting the contents of the zip file to a folder of your choice for example C Program Files Cascade on the computer Create a link to the Cascade_gui exe file located in the folder containing the binary executable files and move the link to your desktop for easy access to the program Then complete the following steps 1 Obtain MAC address Open a command prompt window Start gt Programs gt Accessories gt Command Prompt and type ipconfig all Find the Ethernet adapter Local Area Connec Cascade Version 4 0 September 29 2013 3 tion section ofthe output from the command Under this section there is an entry for Physical Address which has a 12 digit value This is the MAC address value to be sent to Lexam for generation of your license file 2 License File Installation After receipt of the license file for your software from Lexam copy the file to the folder where the Cascade binary executable files were stored There is no particu lar name required for the folder 3 Define executable locations The various components that provide the functionality for the Cascade GUI Cascade GUl exe such as the main computational engine C
52. x and enter the desired value the default conductivity is A Input Inner Diameter 1 143 inches Perfect Conductor how ae X x 5 C Output Inner Diameter 1 500 inches ever alternative materials R son A C P can be selected by clicking O vde C9 es FIGURE 8 Input window for tapered coax section The center region of the input screen contains a diagram of the waveguide type with all dimensions labeled with capital letters These dimensions are described below and correspond to the appropriate columns in the main window spreadsheet The TAB key will sequentially advance the user through the text boxes Alterna tively specific text boxes can be activated using the left mouse button The input window for rectangular sections contains additional inputs for waveguide offsets These can be used for stepped waveguide asymmetrical irises and similar struc tures Cascade Version 4 0 September 29 2013 13 Each parameter contains a radio button for selecting this parameter for optimiza tion Selection of the radio button activates a window for input of allowed ranges of the parameter Use of the optimizer will be described below When the OK button is selected the window is closed and the information trans ferred to the main window spreadsheet The OK button will not function if any text box contains incomplete or illegal data In this situation the user should carefully check that all appropriate inputs are ente
53. y the parameters Frequency Band Specification in GHz fi 11 92 f2 11 975 f3 12 025 f4 12 08 Target Reflection Coefficients in Bandpass Regions Regioni V gt 0 999 Regon2 lt 0 1 Region3 Y gt 0 999 Relative Weigting for each Bandpass Region Region 1 1 ann Y aD Cms Region 2 1 FIGURE 28 Optimization parameters for band pass filter Cascade Version 4 0 September 29 2013 42 6 For instructional purposes click on Execute on the main GUI screen to perform an analysis of the original input file Use the View pulldown to see the perfor mance using the initial parameters Under the View menu select S then Pri mary Mode The bandpass should resemble the blue curve in Figure 29 though somewhat more jagged due to the reduced number of frequency steps 10 L a T kad 1 N o T N ai T Return Loss dB Start Objective Optimized o o T e Ln T A o T 45 L i L L L L L L L 119 1192 1194 1196 11 98 12 1202 12 04 1206 1208 12 1 Frequency GHz FIGURE 29 Bandpass characteristics of filter before and after optimization 7 From the Optimize pulldown menu click on Execute Optimization Follow the progress in the Program Status Window The problem should converge in approximately 116 iterations which will take a few minutes depending on the computer performance Cascade Version 4 0 September 29 2013 43
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