1. Modeling Printed Antennas Using The Matlab Antenna Toolbox
Wajih Iqbal
Clemson University
Advisor: Dr. Martin

2. Outline Background Integral equations and method of moments overview
Formulating the antenna model
LP patch antenna
Future work

3. Background
Graduate students usually use Ansoft HFSS for antenna modeling
Too complicated and expensive for undergrads
A much easier and user-friendly code has been developed by Makarov (Worcester Polytechnic Institute) called the Matlab Antenna Toolbox (MAT)

4. Background (cont’d)
The code is based on method of moments and is limited to about 7000 unknowns
The code is reasonably precise for simple printed antennas
I have modeled and studied 15 different antenna structures

5. Integral Equations and Method of Moments Overview
Statement of an Electromagnetic Boundary Condition
Consider an incident wave (with no z variation i.e. 2D problem) 5

6. Formulation of an Integral Equation

7. The Electric Field Integral Equation
The current on the strip is the unknown to be determined. The unknown quantity is under the integral sign.

8. Solution of Integral Equations (MoM)
Three Major Steps
Step 1: Approximate unknown (surface current) by means of a finite sum of N known functions each with an unknown coefficient.

9. Solution of Integral Equations (MoM)
Step 2: Substitute the approximation (Step 1) into the IE and establish a well-conditioned system of linear equations by enforcing the resulting equations over N subintervals which are within the interval where a solution is desired
(substitute and apply testing function)

10. Solution of Integral Equations (MoM)
Step 3: Solve the N by N linear system of equations from step 2 and thereby obtain values for the coefficients.
Once we have found J(r) we can find all the radiation properties of the antenna

11. Why Printed Antennas?
Printed antennas are low-profile planar structures that utilize printed circuit board (PCB) technology
They are compact, low cost, easy to manufacture and suitable for integration with electronic systems
Multi-band operation can also be achieved by integrating several coupled printed antenna elements of different lengths and geometries on the same PCB
Dimension can be smaller with higher dielectric
GPS, Radar, Satellite communication, Military, cell phones, and wireless laptops

12. Execution Flow Chart Create 2D geometry Create 3D geometry and feed
Input impedance/
Return loss
Near field and far
field properties
Create 2D geometry
MoM Calculations
Create 3D geometry
and feed
Patch
Ground Plane
Feeding Probe

13. Formulating the Antenna Model
Feeding Probe
Design:
Linearly polarized patch antenna
Patch is 30x40mm
Ground plane is 50x60mm
Substrate has εr = 2.55
Patch
Ground Plane
View without Dielectric
Dielectric
Patch
Feeding Probe
Ground Plane
Side View
View with Dielectric

14. 2-D Mesh Projection
Patch
Feed point
Ground plane

15. Volume Mesh Generation
Substrate structure
Layer(s) properties
Ground plane
Vertical metal faces
Feeding points
Patch
3D model ready!

16. Properties of the Patch Antenna
Input Impedance
4800 unknowns took 1.5 hours for 50 frequency points (65sec for each point)
Solid line – Matlab
Dotted line – Ansoft HFSS
Resonance

17. Properties of the Patch Antenna
Return Loss
2.99 GHz
2.93 GHz
2.96 GHz

18. Far Field Properties Directivity (xz-plane) At 2.96GHz
Co-polar dominates
At 2.96GHz
Front to back ratio is about 10dB

19. Far Field Properties Total Directivity (dB) 3D Directivity
The maximum directivity is approximately 7.4 dB at zenith

20. Near Field Properties y-Directed Electric Field
x-Directed Electric Field
z-Directed Electric Field y x

21. Near Field Properties Surface Current Distribution (z-directed)
Surface Current Distribution (x-directed)
Surface Current Distribution (y-directed)

22. Future Work
Simulate more multiband antennas accordingly with future wireless communication needs
Incorporate the genetic algorithm with the code for antenna optimization
After convergence studies construct and test a multiband antenna in the spherical near field chamber

23. Acknowledgements Dr. Anthony Martin Dr. Daniel Noneaker
Dr. Xiao-Bang Xu
Michael Frye

24. Questions ?