Performance comparison of microstrip patch antenna for 94 GHz imaging applications

This paper presents comparative performance analysis of quarter wave transformer-fed rectangular patch antenna for W-band (75 GHz to 110 GHz). The antenna has been designed to radiate at millimetre wave imaging frequency 94 GHz. Two substrates with relative permittivity ε_r=2.2(Teflon) and ε_r = 11.7(Silicon) are used for comparison. The bulk micromachining concept has been investigated to reduce the effect of surface waves due to high permittivity substrates. The measured return loss is 38 dB at 94 GHz with a 10 dB bandwidth of 8.5% and maximum gain of 8.6 dB for ε_r=2.2 substrate. For Micromachined Si substrate 10 dB bandwidth of 12.8% and maximum gain of 7.25 dB have been achieved. The respective E and H plane radiation patterns and the 3-D polar plots have been compared. The micromachined microstrip antenna provides an efficient solution to the integration of antenna to the MMIC for imaging applications.