Design guidelines for proximity coupled U-slot microstrip antennas

The frequency bandwidth of microstrip patch antennas can be increased using both of U-slot and proximity feeding. Although some design rules have been already explained for the probe-fed U-slot antenna the proximity coupling causes to consider a lot of parameters for design procedure; consequently, to deal with all of them seems confusing. In this paper after investigating the effect of various parameters on the multiple resonant frequencies of the antenna and recognizing the most effective factors, some guidelines to design a proximity coupled U-slot microstrip antenna are proposed. In addition, an antenna element with 16% impedance bandwidth is designed at center frequency of 16.7GHz, and its broadband impedance and radiation characteristics are vastly considered. Also, 1×2 and 2×2 arrays of the antenna element are designed to use as subarrays for designing large arrays. The measurement results of return loss and radiation pattern, show good agreement with simulation results.