## Microstrip Patch Antenna Design Principles

Page Contents

### Introduction

For consumer devices, wireless is everywhere! –

LTE 700 MHz,

GSM (850MHz/1.9GHz),

Wi-Fi (2.4 GHz),

Bluetooth (2.4 GHz),

GPS (1.575 GHz)

• Apple’s iPhone 4 is popular science for use of patch Antenna– But illustrates sizes and importance of good antenna design

### Why microstrip patch antenna?

How is radiation achieved? • Wavelength is key: ?/2 ,

?ℎ??? ? = ?? /??(??)^1/2

## Microstrip Patch Antenna

With the microstrip antenna, l/2 is a bit too big for consumer mobile devices

• Typically for space and military applications

• Easy to design/manufacture, yet very capable – Good value, great for antenna arrays

• Scale is better for millimeter wave RF (60+ GHz)

### Design Methodology

• Find a “comfortable” model

– Transmission Line

– easiest, can be done in Excel

– Cavity

– higher accuracy, higher complexity

– Full Wave

• Using specifications, generate initial design – Resonance frequency, gain, substrate, footprint, etc.

• Compare with an EM solver – Tune parameters such as ereff and DL (more details soon)

• Re-iterate design, prototype, measure

• Finalize design for manufacturing

For microstrip antennas, a good 1st step is to assume a standard substrate

– like Rogers RT/duroid 5880

• Importance of er, h

• To avoid cross polarization, keep 1 < W/L <1.5

• Rule of l/2 versus ~0.48l

### Footprint-Generating Equations

Also Check out other Microwave posts

End Fire Array Antenna Using CAD FEKO software

3 & 4 Port Circulator in Microwave

Gyrator in Microwave Engineering

### Quick Example patch antenna

• Rogers RT/duroid 5880 chosen:

– h=0.508mm, 100mm x 100mm board, er=2.2

• Want an antenna for GSM, fr=1.9GHz

• Use equations in Microsoft Excel

– W=6.24cm, L=5.30cm, Zin=151.8W

– Feed set to be 50W (standard): Wo=1.6mm

• Confirm antenna using an EM solver

– Sonnet yields Zin=209.7W at 1.88GHz

### Future Efforts

• Gain full theoretical control of the patch antenna

– Change bandwidth, fr, E field/directivity at will

– Use a range of IMPATT locations and values