o The MAT codes obtain a solution by solving surface and volume integral equations via the method of moments (MOM)

o In MOM, the current on metals and the fields in dielectrics are approximated by special functions (basis functions) defined over sub-domains or sub-regions on/near the antenna

o The currents are approximated over triangular sub-domains defined on metal surfaces while the fields are approximated in tetrahedrons defined in the dielectric around the antenna

o These triangles & tetrahedrons define a mesh or grid which represents an electromagnetic/numerical model of the antenna

o Meshes with many triangles and tetrahedrons result in large memory and computer-time requirements

o One must be careful to ensure a representative and sufficiently refined mesh to get useful numerical solutions that can be used to accurately predict characteristics of real-world antennas

Ground Plane

Shorting Strip

Probe feedL-shaped slit

BACKGROUNDBACKGROUND

o Graduate students usually use Ansoft HFSS for antenna modeling

o Too complicated and expensive for undergradso A much easier and user-friendly code has been

developed by Makarov (Worcester Polytechnic Institute) called the Matlab Antenna Toolbox (MAT)

o The code is reasonably precise for simple printed antennas

PRINTED ANTENNASPRINTED ANTENNAS

NUMERICAL SOLUTION VIA INTEGRAL EQUATION AND MOMNUMERICAL SOLUTION VIA INTEGRAL EQUATION AND MOM

ANTENNA IANTENNA I

Designo This is a Planar Inverted-F Antenna (PIFA)o Rectangular patch = 36x16 mm2

o L-Shaped slit width = 1 mm o Shorting strip width = 2.5 mmo Ground plane = 18x80 mm2

o Air substrate present between the patch and ground plane

Matlab 3D modelAerial View

Return Loss Convergence Studyo The return loss was plotted for 70 frequency points

with a frequency range of 1.4-2.6 GHzo A finer mesh was used each time

Input Impedanceo Found with 3292 triangle mesh o Resonant frequencies are approx. 1.9 and 2.3 GHz

o Printed antennas are low-profile planar structures that utilize printed circuit board (PCB) technology

o They are compact, low cost, easy to manufacture and suitable for integration with electronic systems

o Multi-band operation can also be achieved by integrating several coupled printed antenna elements of different lengths and geometries on the same PCB

o Dimension can be smaller with higher dielectrico Uses: GPS, Radar, Satellite communication, Military,

cell phones, and wireless laptops

Triangular mesh Tetrahedron grid

Directivityo At 1.9 GHz the max. directivity is approx. 3.5 dBo At 2.3 GHz the max. directivity is approx. 1.2 dB

Return Loss Convergence Studyo The return loss was plotted for 50 frequency points o A finer mesh was used each time o Computation times ranged from 40 to 180 mins

Surface Currentso The magnitude of surface currents are calculated at

1.9 and 2.3 GHz

Patch

1.9 GHz

Patch

2.3 GHz

ANTENNA IIANTENNA II

Designo This is a microstrip-fed wide-slot antennao Square patch = 110x110 mm2

o Wide slot = 53.7x53.7 mm2

o Microstrip = 31.5x1.5 mm2

o Ground plane = 110x110 mm2

o 0.8 mm thin FR4 substrate (εr=4.4) present between the patch and ground plane

1.9 GHz 2.3 GHz

Patch

Dielectric

Microstrip

Matlab 3D modelAerial View

Directivityo At 1.67 GHz the max. directivity is approx. 4.5 dB

Input Impedanceo Resonant frequency is approx. 1.67 GHz

FUTURE WORKFUTURE WORK

o Simulate more multiband antennas accordingly with future wireless communication needs

o Incorporate the genetic algorithm with the code for antenna optimization

o After convergence studies construct and test a multiband antenna in the spherical near field chamber

Patch