High-gain $2\times 2$ Millimeter-Wave SIW Cavity-backed Patch Filtenna Subarray Without Extra Filtering Circuits

Abstract

A high-gain <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2\times 2$</tex> millimeter-wave filtenna subarray without any extra filtering circuits is presented by employing a novel high-order substrate integrated waveguide (SIW) cavity. By locating particular vias on the center lines, the SIW cavity is equally divided into four sub-cavities. Exciting by a coupling slot along one side wall, TE210 mode can be excited in each sub-cavity, and quasi-TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">410</inf> mode can be produced by the left/right half sub-cavity, simultaneously. A radiating aperture with an embedded patch is loaded on each sub-cavity to form a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2\times 2$</tex> subarray. Three resonances introduced by the TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">210</inf> and quasi-TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">410</inf> SIW cavity modes and the TM <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</inf> patch mode are operated to obtain a wide impedance bandwidth. Meanwhile, quasi-TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">310</inf> and quasi-TE <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">330</inf> SIW cavity modes are excited at the lower and upper band edges, respectively, to produce radiation nulls. Another radiation null at upper band edge can be produced by the mixed electric and magnetic coupling between the patches and the SIW cavity. Hence, a bandpass filtering response can be successfully formed by these three radiation nulls. As a result, without external filtering circuits and power divider, a peak gain of 13.8 dBi can be realized by the proposed <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2\times 2$</tex> filtenna subarray. The compact and multi-functional design can be a good candidate for implementing millimeter-wave filtenna array with large scale and high performance.