All-Metal Monopulse Antenna Array in the <i>Ka</i>-Band With a Comparator Network Combining Ridge and Groove Gap Waveguides
Miguel Ferrando‐Rocher, José I. Herranz-Herruzo, Alejandro Valero‐Nogueira, Bernardo Bernardo-Clemente
Abstract
This letter presents an all-metal three-layer monopulse antenna based on gap waveguide technology operating in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</i> -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 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Sigma$</tex-math></inline-formula> ) and two difference patterns ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta _{H}$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta _{E}$</tex-math></inline-formula> ). Experimental results validate the concept, showing a close agreement with simulations. The measured null depth is close to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 30 dB in both difference patterns, and the sum pattern achieves 26.9 dBi directivity with a realized radiation efficiency greater than 80 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> .