PEEC Based Electromagnetic Simulator for Manhattan Shaped Geometries

Presented By,

Gaul Swapnil Narhari,

[11EC63R05],

RF & Microwave Engineering,

Indian Institute of Technology , Kharagpur.

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Outline -Introduction-PEEC-MatLab-Work Flow-Inside PEEC Package-Features of Package-Factors leading to Inaccuracies-Structure file generation-Simulating Geometries -Validation of Tool-Future Work -Conclusion

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Introduction:

A PEEC based partial-3D analysis package for rectangular shaped geometries have been developed. (2D in sense only surface (not volume) currents are evaluated & 3D in sense currents in all three dimensions is evaluated). Due to skin effect (current flows only through surface of filament) at higher frequencies analysis appears to be complete 3D.

It only needs a Matlab software & a Notepad to solve geometry. This method is efficient, accurate and faster than Hspice and other.

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PEEC:

EFIEs are interpreted in terms of the capacitive and inductive interactions between the elemental currents and charges in the discretized structure .

The IE-based partial, global rather than DE-based finite, local coupling can be taken one step further, by introducing circuit elements to construct a complete distributed equivalent circuit description of the discrete electromagnetic problem. The resulting circuits are called partial element equivalent circuits (PEEC).

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MatLab:

Matlab is a well known trademark of Mathwork, having all ingredients needed to generate interactive EM analysis,1.Efficient matrix manipulations , plotting figures with rotation, zoom & scroll option in addition to GUI.2.Built in 2D & 3D mesh generator tool. ‘Delaunay’ function to apply triangulation.3.Fourier analysis tool. 4.Optimizers :Neural network, GA, PSO algorithm can be employed very effectively thus, synthesis of EM structure for desired goal can be accomplished.

‘Use of Simulators does NOT make thinking & understanding of radio engineering , electromagnetic,

circuit theory “unnecessary” ! ’

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Work Flow :

Partial Element Computation

Formulation of Circuit Equations

Solution in time and/or Frequency

Domain

Pre ProcessingGUI

Structure File (.tng) from user

Post Processing

Report Generation

The structures are described by text-file (.tng) in a Notepad.

Analysis done in Matlab.

Generated output file can be given to enable further post processing.

.fig

.pdf

.sp

.SnP

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Inside PEEC:

Lets have a Demo.

It will be good practice to have look on flow of problem’s solutions & get idea of different functional blocks in order to know the power of analysis .

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Features:

Allows design (synthesis) by means of analysis combined with optimization say, PSO, GA.Code generates S Parameter file (.SnP for ‘n’ port) in EEsof format & thus the geometry can be exported to other tools having S Parameter calculator such as PUFF, SPEX etc .Cascading of multiple structures can be done by getting S-Parameters file of separately analysed structures and running simple cascade algorithm. So complex problems can be subdivided & solved effectively.A HSpice Netlist file comprising of all equivalent circuit connection data can also generated. For more detailed analysis say, connecting external active elements (Varactor , PIN diodes etc) user can make modification as per requirement. Generates Report file as per user request in pdf, doc, ppt & html format.

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 Factors causing impact on solution accuracy:

1. Physical modelling error: 2. Discretization error: 3. Numerical modelling Error: 4. Matrix Inversion:

However the instabilities can be avoided by many ways say, by Doubleprecision.

‘If you give garbage into the simulator, it throws garbage back to you!’

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Creating Meshed Geometries:

In order to achieve continuity in the charges and current elements and to have hold on equations solved by applying Galerkin’s approach. Few rules are set for performing meshing.

The descritized Rectangles should be non-overlaping.

Corner of one rectangle should not touch to the edge of another rectangle. Corner to corner connection is possible in order to form a orthogonal mesh of connection

Mesh must be orthogonal as formulation for same is employed.

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A Unit Cell:

A rectangular shaped unit cell is a building Block of all structures to be analyzed.

Each Rectangular unit cell has a unique rectangle identity (RectID) and nine local nodes.

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Creating Structure (.tng) files:

Various notations :First field or letter of command and associated meaning is as, Star ‘* ‘ denotes the field as titleDollar ‘$’ denotes the field as commentsDot ’.’ represents (meaningful ) commands

 Material Parameters: (Declared as a command line)

.muR 1.000000

.epsR 1.000000

.sigma 57000000.000000

This file is a notepad file in which geometry is entered using predefined commands. First element (keyword) of each command line have a meaning associated to it is as depicted below section,

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Characteristic Impedance (Z0):

.CharacImpedance 50.000000

Defining Rectangular Cells:

$ RectID X_Shift Y_Shift Z_Shift X_Exersion Y_Exersion Z_Exersion RECT1 0.0 0.0 0.0 1.525000e-3 1.343000e-3 0.050000e-3

Start entry as letter ‘R’ denotes Rectangle cell.

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Pin Connection:

In SIW application the pins / post discontinuities can be inserted by defining this parameter .Cross section of pin it can be ‘cyllindrical’ or ‘rectangular’.First field of command should start with letter ‘P’. Second and Third field represents the location ( NodeID & RectID respectively) Seventh field describes the diameter of cylinder (meter).

PIN1 6 84 6 168 cyllindrical 0.000775

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Circuit Components:

Components external to PEEC:

Loading Elements: First field of command should start with letter ‘L’.

Meaning of below command line is, Capacitor of value 10 picofarad is connected between point1 (field1,2) & point2(field3,4)

LaodPointValue 6 5 4 6 3 10e-12

Excitation: Current or Voltage excitation are applicable in our application.

I_Excitation1 7 29 7 113 1.000000

Components inside PEEC: Situation when accuracy is not main concern model reduction can be applicable internal elements can be modified

.AntennaAnalysis n

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Simulation options in PEEC:

Currently following options are available for simulation. The second field need to be yes ‘y’ or no ‘n’. It is advised to specify option in small letter, however it is case insensitive. It is MUST to declare all the below fields else it can lead to error.

.SParameters y

.RadiationPattern n

.Pattern@Resonance y

.IncludeLoading y

.SIW n

.AntennaAnalysis y

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Specifying frequency range:

.FreqRange 20.0000e9 0.10000e9 30.0000e9

.FreqObserve 27.500000e9

Cascading: Different (separately analyzed) structures can be cascaded by specifying their corresponding title of geometries,

.cascade(title1,title2)

An Example of structure (.tng) file is as given in APPENDIX A.

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.tng Assistant:

It’s set of Matlab codes that assists to create structure file (.tng). Codes are user friendly and a basic knowledge about for loop, matrices is needed to form bigger geometries even comprising of multihundreds of rectangles. After running code output returned will be a structure file (.tng) through Matlab itself . Only the rules of Mesh formation rules need to be followed.

 ‘Trade off Triangle: Trade off Simulation time,

Accuracy, size of simulation domain.’

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PEEC Matlab codes are written in a folder ‘Finalised Code’ open the Folder in Matlab using browse button at top right side in Matlab window. Make sure that the (.tng) file which is to be simulated is exist in same folder. To ensure it just type ‘dir’ command in Matlab command window & press ENTER. Check whether desired structure file name appears in window or not.

Now type ‘PEECRUN’ command in command window & press enter. A GUI will appear with to buttons in figure window named ‘Browse PEEC’ to select the structure file which is to be simulate. Select the desired file. After ‘opening’ file click on ‘Run PEEC ’ button to start the simulation

Simulating Geometries:

Report File:

Parameters that are evaluated: Return Loss, Transmission coefficient, Input Impedance, VSWR, Voltage & current distribution, Antenna far field, Time domain characteristics.

Report File consists of date & timings, error/ warning occurred while simulation process. Values of different parameters when important (events) noticeable changes occur such as resonances, peaking, zero-crossing etc. Also the result figures in .jpg format are reported at the end.

A Report file is given in APPENDIX B.

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Validation of PEEC:

For validating the codes the results of PEEC simulation are compared with MOM (Method of Moments) computation. A resistive 2X100 ohm loaded dipole is taken to analyse , Load is at centre on both side of gap. Excitation is at centre point of gap. The results are plotted.

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0 0 .5 1 1 .5 2 2 .5 3 3 .5 4 4 .5 5

x 1 08

0

1 0 0

2 0 0

3 0 0

4 0 0

5 0 0

6 0 0

7 0 0

8 0 0

9 0 0R e a l in p u t im p e d a n c e R e Z in in o h m

F re q u e n c y (H z )

Rin

(ohm

)

R e (Z in M O M )R e (Z in P E E C )

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0 0 .5 1 1 .5 2 2 .5 3 3 .5 4 4 .5 5

x 1 0 8

-1 0 0 0

-8 0 0

-6 0 0

-4 0 0

-2 0 0

0

2 0 0Im a g in a ry in p u t im p e d a n c e Im Z in in o h m

F re q u e n c y (H z )

imag

Zin

(ohm

)

im a g (Z in M O M )im a g (Z in P E E C )

The analysis (modelling) method can be applied to arbitrary shaped geometries with employs fast matrix formulation and the overall tool can be used to synthesis of problem by running neural network, optimizer algorithm.

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Future work:

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Conclusion: 1. Geometries including Folded Dipole, CPW antennas , Transmission line (with & without Bend) SIW (with & without Post Discontinuities) have been analysed. 2. Finally we come to know that simulation tool is the heart of Microwave Computer Aided Design. An integral-equation (IE) computer-solution technique (PEEC) is presented, which provides accurate results. The solution technique minimizes computer storage requirements, while maintaining calculating efficiency and simulation time.

APPENDIX A.

Structure NetList (.tng) file

Click here

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APPENDIX B. REPORT:

Click here

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Thank you...!!

You miss 100 percent of the shots you never take.—Wayne Gretzky

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