wiqbal presentation

8/2/2019 Wiqbal Presentation

1/24

Modeling Printed Antennas UsingThe Matlab Antenna Toolbox

Wajih Iqbal

Clemson University

Advisor: Dr. Martin


2/24

Outline

Background

Integral equations and method of

moments overview Formulating the antenna model

LP patch antenna

Future work


3/24

Background

Graduate students usually useAnsoft HFSS for antenna modeling

Too complicated and expensive forundergrads

A much easier and user-friendlycode has been developed by

Makarov (Worcester PolytechnicInstitute) called the Matlab AntennaToolbox (MAT)


4/24

Background (contd)

The code is based on method ofmoments and is limited to about7000 unknowns

The code is reasonably precise forsimple printed antennas

I have modeled and studied 15

different antenna structures


5/24

Integral Equations and Method of

Moments Overview

Statement of an

ElectromagneticBoundary Condition

Consider an incident

wave (with no z

variation i.e. 2D

problem)

5

E Ex

s

x

i+ = 0 on strip

Perfectlyconductingthinstrip

-w

i

x

w

y

Ei

90- i

i


6/24

Formulation of an Integral Equation

E xk

d

dxk J x H k x x dxx

s

w

w

bg bg c hbg= +FHG IKJ z4

2

22

02

E Ex

s

x

i+ = 0 on strip

E E ex

i i i jk xi

=0

sincos

e j

( ),s ix xE E x w w =


7/24

The Electric Field Integral Equation

4

2

0

2

kk J x H k x x dx

w

w

RST zbg c hbg

+

UVW= zd

dx

d

dxJ x H k x x dx E x x w w

w

w

x

ibg c h bg bbg02 ,

The current on the strip is the unknown to be determined. The unknown

quantity is under the integral sign.

J w J w

= =b g bg0


8/24

Solution of Integral Equations (MoM)

Step 1: Approximate unknown (surface current) by meansof a finite sum of N known functions each with an

unknown coefficient.

( )1

( )

N

n n

n

I=

J r f r

Three Major Steps


9/24

+

U

VW=

zd

dx

d

dx

J x H k x x dx E xw

w

x

i

bg c h bbg0

2


Step 2: Substitute the approximation (Step 1) into the IEand establish a well-conditioned system of linear equationsby enforcing the resulting equations over N subintervalswhich are within the interval where a solution is desired

( )1

( )

N

n n

nI

= J r f r

4

2

0

2

k

k J x H k x x dxw

w

R

ST

zbg c hbg

(substitute and apply testing function)

1 11 2 12 3 13 4 14 1

1 21 2 22 3 23 4 24 2

1 31 2 32 3 33 4 34 3

1 41 2 42 3 43 4 44 4

for subinterval 1

for subinterval 2

for subinterval 3

for subinterval 4

i

i

i

i

J Z J Z J Z J Z E

J Z J Z J Z J Z E

J Z J Z J Z J Z E

J Z J Z J Z J Z E

+ + + =+ + + =

+ + + =

+ + + =

J Z E m Nn mn mi

n

N

= =

=

, , , ,1 21


10/24


Step 3: Solve the N by N linear system of equations fromstep 2 and thereby obtain values for the coefficients.

11 12 13 14 1 1

21 22 23 24 2 2

31 32 33 44 3 3

41 42 43 44 4 4

i

i

i

i

Z Z Z Z J E

Z Z Z Z J E

Z Z Z Z J E

Z Z Z Z J E

=

Z J Emn n m

i=

1

11 12 13 141 1

21 22 23 242 2

31 32 33 443 3

41 42 43 444 4

i

i

i

i

Z Z Z ZJ E

Z Z Z ZJ E

Z Z Z ZJ E

Z Z Z ZJ E

=

[ ] [ ]1 i

n mn mJ Z E

=

Once we have found J(r) we can find all the radiation

properties of the antenna


11/24

Why Printed Antennas?

Printed antennas are low-profile planar structuresthat utilize printed circuit board (PCB) technology

They are compact, low cost, easy to manufactureand suitable for integration with electronic systems

Multi-band operation can also be achieved byintegrating several coupled printed antennaelements of different lengths and geometries onthe same PCB

Dimension can be smaller with higher dielectric

GPS, Radar, Satellite communication, Military, cellphones, and wireless laptops
http://www.wneweb.com/jpn/products/img/e_dualpifa.jpg


12/24

Execution Flow Chart

Create 2Dgeometry

Create 3D geometry

and feed

Patch Ground

Plane

Feeding

Probe

MoM Calculations

4

2

0

2

kk J x H k x x dx

w

w

RST zbg c hbg

+ UVW= zd

dx

d

dxJ x H k x x dx E x x w w

w

w

x

i

bg c h bg bbg02 ,

J Z E m Nn mn m

i

n

N

= ==

, , , ,1 21

( )1

( )N

n n

n

I

=

J r f r

Z J Emn n m

i=

Input impedance/Return loss

Near field and far

field properties


13/24

-0.02

-0.01

0

0.01

0.02

-0.03

-0.02

-0.01

0

0.01

0.02

0.0300.511.5

x 10-3

xy

z

Patch Ground Plane

Feeding Probe

Formulating the Antenna Model

Design:

Dielectric

View with Dielectric

View without Dielectric

Linearly polarized patchantenna

Patch is 30x40mm

Ground plane is 50x60mmSubstrate has r = 2.55

Side View

Patch

Ground Plane

Feeding Probe


14/24

2-D Mesh Projection

Feed point

Patch

Ground plane


15/24

Volume Mesh Generation

Layer(s) properties

Substrate structure

Ground plane

Vertical metal faces

Feeding points

Patch

3D model ready!


16/24

Properties of the Patch Antenna

4800 unknowns took 1.5 hours for 50

frequency points (65sec for each point)

Input Impedance

Solid line Matlab

Dotted line Ansoft HFSS

Resonance


17/24

Properties of the Patch Antenna

Return Loss

2.93 GHz 2.99 GHz

2.96 GHz

2.99 2.93

2%2.96Bandwidth

= =


18/24

Far Field Properties

Directivity (xz-plane)

Co-polardominates

At 2.96GHz

Front to back ratio is about 10dB


19/24

Far Field Properties

Total Directivity (dB) 3D Directivity

The maximum directivity is approximately 7.4 dB at zenith


20/24

Near Field Properties

z-Directed Electric Fieldx-Directed Electric Field

xy

y-Directed Electric Field


21/24

Near Field Properties

Surface Current Distribution (x-directed)Surface Current Distribution (y-directed)Surface Current Distribution (z-directed)


22/24

Future Work

Simulate more multiband antennasaccordingly with future wirelesscommunication needs

Incorporate the genetic algorithmwith the code for antennaoptimization

After convergence studies constructand test a multiband antenna in thespherical near field chamber


23/24

Acknowledgements

Dr. Anthony Martin

Dr. Daniel Noneaker

Dr. Xiao-Bang Xu

Michael Frye


24/24

Questions

? ? ? ? ? ? ? ?

wiqbal presentation

Documents