2.4 Ghz Wi-Fi Patch Antenna

EE533 Antenna Theory

Design Project

David Racek

Fall 2010

Andy Olson

Design Overview

Rectangular patch with circular reflector disc

Designed for Wi-Fi,  IEEE 802.11 Standard

Frequency: 2.4 GHz – 2.5 GHz

Wavelength: ~12cm

Antenna Construction

Materials:

 0.016 inch copper

 SMA connector 

-Both reflector disc and rectangular patch were cut from 16 mill copper sheeting

-SMA backfeed

*dimensions are from commercial antenna. Ask me about it.

ADS Simulation

Simulation Control:

    Sweep Type: Adaptive

    Start frequency: 2.4 GHz

    End frequency: 2.5 GHz

 

Substrate model:

    Thickness: 16mm

    Permittivity (Er): 1 (air)

    
*current distribution shown in green

Simulation Pattern Results

ADS was used to simulate the antenna pattern

3D top view:                                3D side view:

Simulation Results

*max gain of about 8db

Measured Performance

VSWR and Gain were measured using a network analyzer

The following steps were used to measure gain:

1) Choose a reference dipole with a known gain of 2.15dB

2) Plot the gain on the Network Analyzer, gain will be measured in relation to this

3)Attach antenna to be tested and again plot the gain

3dB beamwidth estimated to be about 60 degrees – orientation matters!

Antenna Gain

Center Frequency:

                2.45 GHz

Scale:   5 dB/division 

Marker: 2.45 GHz

Span:   1GHz

Gain:   6.007dB

VSWR

Center Frequency:

                2.45 GHz

Scale:   250 MHz/division

Marker: 2.45 GHz

Span:   1GHz

SWR:   1:1.3204

Center Frequency:

                2.45 GHz

Marker: 2.45 GHz

Span:   1GHz

Front to Back Gain & Cross Polarization

Front to back gain is about   -16dB

Cross polarization is about 7db

This trace shows the  gain when the antenna is oriented with the ground plane towards the radiating source.

The front to back gain is the difference from when the antenna is oriented with the patch facing the radiating source versus the ground plane facing the radiating source.

Wi-Fi Testing

Antenna tested using  PCI wireless 

     LAN card

Soldered 50ohm coax directly to board

Huge improvement over standard 

      Wi-Fi antenna when patch is pointed 

      at wireless access point

Improvements & Ideas

Reduce inductance by shortening gap between SMA signal pin and feed solder point.

 Try different thicknesses of copper to improve performance 

 Try coaxial feed (in commercial design coax is soldered directly    to patch)

Conclusion

PROS:

Low cost Wi-Fi patch antenna can easily be constructed out of copper sheet

 Patch antenna provides better performance and increased range when compared to standard Wi-Fi dipole

Measured gain of 6dB and SWR of 1:1.3

CONS:

Patch antenna is highly directional and therefore must be pointed at wireless access point

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