Analysis of Hammerhead Probes in a Rectangular Waveguide

Abstract

We present the analysis of hammerhead probes with different geometrical sizes in a rectangular waveguide. In order to investigate coupling efficiency, we vary the widths and thicknesses of the head and its handle. The results show that the probe gives higher return loss when the widths of the structure are relatively smaller, i.e. the head is of the same size and the handle is smaller than the core of the coaxial cable. Experimental measurements show that the impedance of the probe increases in corresponds to the width of the head. The poor performance found in the probe with a larger size can therefore be attributed to the impedance mismatch between the probe and the cable. It can also be observed that the probe with a thicker head and thinner handle exhibits the highest return loss and largest bandwidth. Indeed, by carefully adjusting the geometry of the hammerhead probe, the coupling efficiency is found to be better than conventional rectangular microstrip and coaxial probes. The thick head hammerhead probe gives about 22.72 dB and 31.36 dB higher peak return loss than those of the rectangular microstrip and coaxial probes. Although the bandwidths of the thick head hammerhead probe and the rectangular microstrip probe are similar, i.e. approximately 22.18 GHz, its bandwidth is about 5.88 GHz wider than the conventional coaxial probe.