Mm-Wave Wide-/Dual-Band Filtering Antennas Based on Multinull Resonator

Millimeter-wave wideband/dual-band filtering antennas are presented based on a multinull resonator, which comprises of a substrate integrated waveguide (SIW) cavity- backed slot. In wideband design, the multinull resonator provides three radiation nulls, resulting in high frequency selectivity with a rectangular coefficient K = 1.16 at bandedges (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{K}=\Delta \mathrm{f}_{-20\text{dB}}/\Delta \mathrm{f}_{-3\text{dB}}$</tex>). Four resonate modes including TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">120</inf>, a slot mode, a patch mode, and a strip mode are merged together, obtaining a wide bandwidth of 31%, a high gain of 10.4 dBi, and stable radiation patterns. A prototype of the wideband design was fabricated and measured. The multinull resonator can also be used in dual-band design. It provides two resonant modes and three radiation nulls. With a modified patch radiator, a dual- bandfiltering response with two modes and two radiation nulls for each band is realized.