CONCEPT-II
Contents
1. pure metallic structure EFIE e Load s on patch edges Bodies i Material parameter E Setup monitoring Field probes i Current probes o Current probes on generator wire Current probes on patch edges Current distributions e Current distr on generatorwire Voltage probes li CONCEPT II Frequency Interval GE tangential probes o E tangential probes on generatorwire Frequency loop for a special interval B rQ Print selection oo pe Print currents l l an Print wire currents into an ASCII File Frequency unit MHz Used frequencies Print red y matrix into an ASCII File Print red y matrix into a Touchstone file Presentation Linear 10 Log data Cad tools Post processing po ie Print red y matrix into a binary file _ 20 E 8 Setup simulation Minimum value 10 30 G3 Frequencies ESS 40 Frequency loop for a s Maximum value 300 50 E Port s on generator wire Interval type By step 70 opo de Port 1 on Port s on patch edges step 10 90 lt Frequency depending port scaling 100 z f Solver 110 LU decomposition with row pivoting Generate values list 120 Single precision 130 Galerkin matching 140 W OK OQ cancel Fig 2 In the display area we see the discretized structure according to Fig 1 Note that only the symmetric parts need to be considered setting up the numerical model A structure according t2. CONCEPT II CONCEPT II is a frequency domain method of moment MoM code under development at the Institute of Electromagnetic Theory at the Technische Universitat Hamburg Harburg www tet tuhh de Overview of demo examples The following demonstration examples for CONCEPT II will be discussed in detail 6CONCEPT home directory of the package 1 Wire loop directory CONCEPT demo example1 wire loop 2 Cylindrical monopole antenna radiating over a finite ground plate directory CONCEPT demo example2 monopole on plate 3 Box with aperture and internal radiator directory S CONCEPT demo example3 box with aperture 4 Dielectric sphere in a plane wave field directory SCONCEPT demo example4 dielectric sphere In order to find out how CONCEPT II works it is recommended to start with the example 1 wire loop Important file names should never contain blanks Shortcuts Help gt Navigation Example 2 Cylindrical monopole antenna radiating over a finite ground plate It is assumed that the user is already familiar with example 1 It is recommended to start from an empty directory and set up the simulation according to Fig 2 CONCEPT demo example2 monopole on plate Let us consider a thick monopole antenna on a square ground plate in free space All dimensions can be taken from Fig 1 Z CET b A h 0 5 m R 50 mm 0 8 m a a Wire between cylinder and gt finite plate Eas generator a
3. a while for the back end to finish Note that a linear system of equations has to be set up and solved for each frequency step If unsure how the MoM works refer to Section 4 of the User s manual Sometimes it is advantageous to proceed as follows before starting the simulation Simulation see menu bar gt Run simulation front end Notice the output in the message section under the display area number of unknowns size of system matrix etc Post processing gt Show complete structure a Generally all wires are combined into wire O and all surfaces into surf 0 Note that by hovering the mouse pointer over a node or a patch all available information is printed ina special line under the display area Displaying the surface current distribution For displaying the current distribution Go to Post processing see Fig 10 Click on FA Enter the values according to Fig 10 the current distribution at 300 MHz has been selected for representation a File Simulation View Options Cadoptions Post options Color Misc Help AAA AAS BIB Sar T Be MReS m Project View o CONCEPT II Post Processing Cannive Rewilis Current charge distribution on structure Simulation AJN Ei E i TE 77 ee X 4 Totalnumber of Frequencies 30 Number of bodies 0 Free space a q Select Freq no 30 Freq in MHz 300 o 7 i 7 i
4. elete Split Centre Now select two nodes as illustrated in Fig 7 by right clicking on the respective nodes Notice that a node is picked once the mouse is turned into a cross Fig 7 Two patch nodes have been selected be right mouse clicks for introducing a wire Clicking on amp or typing e gives the following sub window me CONCEPT II Add Wires Ps et hl ae x Name of wire output File generatorwire No of wires between the dots pR Wire radius in mm 0 5 Number of basis Functions on each wire 3 g os Fig 8 Change the default entries to the ones shown here OK creates the file generator wire Load the structure into the simulation Activate the Simulation tab right click on the top entry gt select Load all files from CAD Activate the check marks Magn symmetry XZ plane and Magn symmetry YZ plane Frequency sampling How to do this is indicated in Fig 2 Right click on the the entry Frequency loop for a special interval Set frequencies The shown sub window opens One can change for example the maximum frequency the minimum frequency the sampling the unit etc Do not forget to press Generate values list Only frequencies appearing in the list are considered in the simulation Excitation Right click on Excitation see Fig 9 Ports power input voltage input gt Port s on genrator wire gt Set ports enter wire number 1 and 1 W amp Current distributions Curr
5. ency case imagine a grid on a unit sphere the field is computed at each intersecting point Click the Log data tab gt 3D rad Diagram This displays the output of the diagram computation in the display area Example values computation by the power flow in the far field Poynting vector 10 MHZ radiated power 0 9945 W 300 MHz radiated power 0 9935 W A deviation of 5 between input power and radiated power can be tolerated for a loss less structure in practical situations Note that Field values are always given in V Divide by the distance in the far field and get the E field strength in the chosen direction Hint to quickly get back to the already computed surface current distribution at this stage of post processing click on the following entry of the post processing tree View results Ea Current charge distribution a 3D rad diagram pon amp 2D rad diagram The input impedance as a function of frequency Go to Post processing 11 A CONCEPT II lt 3 gt File Simulation View Options Cad options Post options Color Misc Help PieBist v Erreten Project View a TE b CONCEPT II Post Processing v G x 2 Comput RAin System responses as a function of frequency f i X 8 7 e 7 Has ot SB gt fst _ _1 ge ye Bs input impedance 1 Total number of ports 1 e numba C E Output file F
6. ent distr on generator wire Voltage probes E3 NCEPT II Port E tangential probes E tangential probes on generator wire Print selection Print currents Ports for generator wire number of wires 1 Print wire currents into an ASCII File Select a port by right click Print red y matrix into an ASCII File Print red y matrix into a Touchstone file Print red y matrix into a binary file Setup simulation n A FA Frequencies Wire number Wire position Power input in Watts Power input in Watt Frequency loop for a special interval Port 1 1 middle segment 1 B Excitation Port s on generator wire Port s on patch edges Frequency depending port scalini Delete all port s J Solver LU decomposition with row pivoti Set color Single precision lt Show port s Galerkin matching Show port number s Label size color Append gt Total ports 1 Fig 9 Right clicking on the Excitation line provides the possibility to switch to a voltage generator for example The wire where to place the port can be selected by a right click In general ports can be placed at the end center or at the beginning of a wire The same statement applies to lumped loads voltage generators or current probes on wires Checking geometry starting of the simulation Once we are sure that all data is right we can immediately start the simulation o As a frequency loop has been specified it may take
7. n Fig 12 shall be computed In our case we have chosen All frequencies Hence a 3D pattern will be computed for e CONCEPT II lt 3 gt File Simulation View Options Cadoptions Postoptions Color Misc Help q A IIRO Bim Sar Project View 3D Radiation diagrams Electric Far Field Electric near Field Magnetic near field File For complex E Far Field 3DEthetaEphi asc Distance Maximum magnitude THETA component PHI component Angles Spherical coordinate system angles in degrees THETA angle with z axis 0 lt THETA lt 180 PHI angle with x axis 0 lt PHI lt 360 Start angle THETA o End angle THETA 180 View results Start angle PHI 0 End angle PHI Logdata Cadtools Post processing Simulation amp Network B Surfaces i iv E rad Wires contour Points Info files Unload all Elements in THETA dir 20 a v a Y Symmetry Total no of freq 0 Frequency no Frequency value Delete row 1 10 Delete Delete Delete 3 4 d Delete ALl frequencies Port number WV OK OQ cancel Fig 12 The electric far field shall be computed each frequency step providing a movie showing the frequency dependence of the pattern development Choosing a sufficient number of elements in theta and phi direction is important to resolve minor lobes that may appear in the general high frequ
8. nd the imaginary part of the antenna input impedance shall be plotted columns 2 and 3 of the ASCII data file port zinl asc column 1 is the frequency The following curves are displayed 13 Input impedance 200 Real part 100 Imag part 100 200 300 Z Ohm 400 500 600 00 800 O 50 100 150 200 250 300 Frequency in MHz Fig 15 The complex input impedance as a function of frequency As could be expected we have a large negative imaginary part and a very small positive real part at the low frequency end 14
9. o Fig 2 shall be set up Discretizing the finite ground plate Activate CAD tools gt Cad tools 2 Click on H The plate tool window opens Fig 1 as CONCEPT I CAD Dw ia amp Discretization of quadrangular plates nonuniform mesh possible Output file plate surf Number of parts iS Copy Fram part a OK Current part 1 Delete current part Z OK Comer 0 yi 0 E z 0 EE Comer xi od y 0 zi 0 Comer3 x 04 y 04 z 0 Corner4 x o y 0 4 z 0 yoe e E Corpue meshes 600 Meshes 1 2 7 e aa 7 i 34 7 i 1 4 7 a Compr 1 2 E S 23 fi i 34 1 I 1 4 fi Save Read ee Apply W OK A cancel Fig 3 Creating the mesh of a 0 4 m x 0 4 m plate at 600 MHz with amp basis functions per wavelength Using 8 to 10 basis functions per wavelength is a well known rule of thumb for electrically large structure parts Frequency in MHz dF dF It is assumed that the highest frequency is 600 MHz and that the mesh involves 8 basis functions per wavelength This is far higher than the max applied frequency By setting an appropriate combination of frequency and number of patches per wavelength the grid can be adjusted to the needs Compute meshes results in a 7 by 7 element mesh Clicking on OK provides the surface patch file plate surf Output file In the general case a plate does not need to be flat or rectangular Arbitrary quadrangles can be subdi
10. or ascii data Show complete structure Total Number of curves 4 Port No View results pene Current charge distribution 8 3D rad diagram 2 2D rad diagram HH 2D EM Field rectangular Log data Cad tools Post processing f 1D EM field line Ma EM Fields ine Freq domain responses Time domain responses Current wire distr 5 Scattering parameters 7 Powerflow through surface For comparison of curves J Line integral EH Tree View results right click Freq domain responses F Network Load curves choose components Surfaces j shih contour Apply W OK OQ cancel Points Info Files Unload all 100 O O 50 100 Fig 13 Window for the selection of system responses to be displayed as a function of frequency Click on hel A sub window as shown in Fig 13 opens The only available data in this example up to this point is the input impedance which is automatically stored in case of generator excitation OK provides the magnitude in the display area as a function of frequency For an enhanced representation click Freq domain responses show results in the post processing tree This open the CONCEPT II Gnuplot front end Change the default entries to the entries as shown in Fig 14 and click Run gnuplot 12 input impedance Frequency in MHz Sm Real part A E fImag part Fig 14 The real a
11. reating the cylinder Activate CAD tools then click on W The following window opens CONCEPT II Cad a i wa ws Discretize a circular cylinder disk cone Radius bottom 0 05 Radius top 0 05 Height 10 5 Centre x 0 Centre y 0 Centre z 0 02 E Inclination angle 0 00 Rotation angle 0 00 5B Close cylinder at bottom Close cylinder at top No compression Comp Factor 1 e Frequency MHz 600 Patches per wawe length 12 5 Magn symmetry Symmetry with respect to Yz and XZ plane Set all patches to triangles v O O Fig 6 Only a quarter of a full cylinder will be discretized when clicking on OK or Apply In order to get a sufficient mesh from a geometrical point of view the Number of patches per wavelength has been set to 12 and the frequency to 600 MHz although the max applied frequency is only 300 MHZ At this frequency the mesh would be not good enough Magnetic symmetry with respect to the y z plane and the x z plane has been specified Hence only a quarter of a cylinder is generated when pressing OK Creating the wire The wire could be easily introduced as has been described in example 1 simply be entering the coordinates 0 0 0 0 0 0 02 under Simulation gt Wires Edit a new wire file There is another way of generating wires Click on the Wires button in the Cad tools 1 section The Add button will be activated automatically Wires New node Add D
12. t the plate side of the 7 q wire 0 8 m Fig 1 Geometry of the structure under investigation The antenna is formed by a cylinder of 0 5 m height A wire length 2 cm R 0 5 mm serves as connection between cylinder and plate A power generator at the lower end of the wire is feeding the structure with 1 W A frequency loop shall be considered from 10 300 MHz As we have electrical and geometrical symmetry only a quarter of the structure needs to be discretized The x z plane and the y z plane are planes of magnetic symmetry Two surface patch files need to be generated which are called plate surf and antenna surf in our example The rod connecting the bottom of the cylinder with the plate is contained in the file generator wire Notice the corresponding file names in the project tree see left side of Fig 2 section Project View Se CONCEPT II File Simulation View Options Cadoptions Post options Color Misc Help Oenul Fx AAD HSA sS EF n Aar H T Project View x home tebr action demo v2 example2 monopole on plate example2 monopole on plate Project description p ie Text at Setup structure Scaling mode 2i beq Structure in meter radii in millimeter B Symmetry o Hi Magn symmetry XZ plane Magn symmetry YZ plane Son Ideal ground a Wires Pode l W generator wire tf Check wires a Surfaces Y i teM antenna surf i W IB plate surf X Simulation A
13. ui 1b e Y a 9 ge ops Draw port position a Port number 1 Show complete structure 2 B Representation Current at phase s k E ad Number of phase intervals 16 8 p view results in degrees a D i Current charge distributio g 6 3D rad diagram o s 2i 2D rad diagram cancel 35 2D EM field rectangular t 1D EM field line BE EM fields Fig 10 Window for controlling the current distribution to be displayed It is recommended to enter 16 phase intervals for a movie Pressing OK provides the structure including its current distribution at 0 in the display area Of course a certain scaling is necessary in order to obtain a view according to Fig 11 Vector and arrow scaling has already been explained in example 1 for the case of a 2D field distribution Fig 11 Current distribution at 300 MHz In order to validate the result the power budget shall be investigated Since lumped loads resistors have not been introduced and the whole structure under investigation includes only perfect conductors the input power should be radiated completely In other words the depicted surface current distribution should be able to radiate the input power of 1W This can be achieved numerically only up to a certain degree For the computation it is necessary to establish a 3D radiation diagram Creating a 3D radiation diagram Got to Post processing see Fig 12 Click on es A sub window as depicted i
14. vided Near the feed region which is close to 0m Om Om we have to expect a rapid variation of the antenna near field and of the surface current distribution Hence we should refine the grid in this region which can conveniently be carried out as follows Select a preview pattern in the Mesh refinement section of the Cad tools 1 card Cadtools1 Cadtools2 i Geometry from simulation Surfaces jo bee v E plate surf a Wires aux lines I Points Info files Unload all Mesh refinement oHA CHIM ONA OKA O AAA O amp CAAA Group select C Visible patches Fig 4 Local mesh refinement close to the antenna feed point see Fig 2 Activating H means that quadrangles our case can be selected by right click to be subdivided into 4 smaller quadrangles Move the mouse pointer over a quadrangle near the left lower corner of the plate and right click A preview pattern marks the selected patch It is suggested that four patches near the bottom left corner i e near the antenna feed point should be marked as illustrated in Fig 4 Clicking on or typing e results in the mesh according to Fig 5 Note that triangles are generated in the transition region Each node of a patch has to be connected to the nodes of all adjacent patches In other words the grid must be closed e Fig 5 Mesh refinement at the bottom left corner near Om 0m Om C
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