Microstrip Patch Antenna

EEC 133 Final Project

Microstrip patch antennas are a class of low-profile antennas which are conducive to applications where size and weight are critical for performance (e.g.  in aircraft, spacecraft, and missiles)

• These antennas offer considerable flexibility in design parameters such as operating frequency, polarization, radiation pattern, and input impedance [1, p. 783].

• However, the use of patch antennas comes with several trade-offs. They typically exhibit poor efficiency, power, scan performance, polarization purity, and a notoriously narrow bandwidth [1, p. 783].

The final step that remained after fabrication was to measure the input port voltage reflection coefficient, S(1,1). This can be used to evaluate the input return loss.

Note: Disregard S(2,1) graph. Nothing was connected to port 2 so noise is being displayed.

In conclusion, the project can be considered successful. Both the simulated and measured return losses at the resonant frequency of 2.44 GHz were below the commonly accepted threshold of -10 dB, with values of -10.14 dB and -15.92 dB, respectively.

Nonetheless, there are areas where performance could be improved:

• The radiation efficiency at resonance was calculated to be 39.5% (-4.03 dB). While this falls within the typical range for consumer-grade antennas (20–70%), it lies toward the lower end of that spectrum and may be suboptimal for applications where efficiency is critical.

• Impedance matching is another aspect requiring further refinement. The antenna was designed to interface with a 50 Ω transmission line. However, the simulated input impedance was 49.55 – j32.61 Ω. The presence of ~30 ohms of capacitive reactance leads to a non-negligible mismatch, resulting in increased reflections and reduced power transfer efficiency.