All-Metal Monopulse Antenna Array in the Ka-Band With a Comparator Network Combining Ridge and Groove Gap Waveguides

This letter presents an all-metal three-layer monopulse antenna based on gap waveguide technology operating in Ka-band. (specifically from 29 to 31 GHz) for direction-finding applications. This contribution stands out mainly for the simplicity of its single-layer comparator network (layer 1) composed of a combination of ridge and groove gap waveguides. Also, the compactness of the feed network (layer 2) allows for a low-profile monopulse antenna comprising only three aluminum pieces. The antenna is bottom-fed through three ports connected, two of them to the comparator network, and one directly to the corporate-feed network, to achieve one sum (S) and two difference patterns (?(H), ?(E)). Experimental results validate the concept, showing a close agreement with simulations. The measured null depth is close to -30 dB in both difference patterns, and the sum pattern achieves 26.9 dBi directivity with a realized radiation efficiency greater than 80%.