Variation of Input Impedance with Feeding Position in Probe and inset-Fed Microstrip Patch Antenna

Abstract

Proper impedance matching of a microstrip patch antenna to the feed line is paramount for efficient radiation. However, impedance matching in such a system is not easy and consequently most systems suffer from return losses. The variation of the input impedance of a probe-fed and inset-fed rectangular microstrip patch antennas along the longitudinal and transverse lengths is investigated on probe-fed and microstrip-fed antenna operating at 2.4GHz and 2.0GHz respectively. FEKO simulation software is used to evaluate and characterize the behaviour of the input resistance for varying values of feeding position. It is observed that the transverse variation in the input resistance is very minimal. The conclusion drawn here is that a cosine squared and shifted cosine squared function can be used to exactly locate the feed point in a probe and inset fed antennas respectively for an impedance matched antenna system.

Keywords: Longitudinal feeding position, FEKO, probe feeding, inset feeding, input impedance, return loss.