Air gap tuning of patch antenna resonance

An adjustable air gap was proposed in 1984 to tune the resonant frequency of patch antennas. This method was investigated theoretically and experimentally for the case of coaxially fed patch only. The main disadvantage of applying this method to tune the frequency of coaxially fed patches is that the center conductor has to be de-soldered and re-soldered every time the width of the air gap is changed. In this paper, we investigate the air gap tuning of a rectangular patch resonance frequency. The patch is fed using aperture coupling or by a stripline. In both cases, changing the air gap width requires no de-soldering and re-soldering. It is found that for the same ratio of air gap width to substrate thickness, the resonant frequency is changed by similar percentage for all these feeding methods.