A Simple Single‐Layer Wideband Filtenna With Multiple Controllable Radiation Nulls

ABSTRACT In this letter, a single‐layer wideband filtenna with multiple controllable radiation nulls is presented. The developed filtenna has a very simple structure and is composed with a square substrate integrated waveguide (SIW) cavity, a square patch, and a pair of U‐shaped slots. Notably, the filtenna possesses three radiation nulls that can be tuned by adjusting specific geometrical parameters. To achieve a wide bandwidth and better frequency selectivity, the TM 10 mode of the square patch is utilized to couple with the TE 210 mode of the square SIW cavity. And a radiation null at upper and lower edge of the passband can be simultaneously obtained because of the effective multipath coupling and the impact of TE 110 mode in SIW cavity. An extra in‐band resonance and out‐of‐band radiation null are concurrently introduced by etching a pair of U‐shaped slots at the metal ground plane so as to further expand the bandwidth and enhance the frequency selectivity. To validate the design method, a prototype of the filtenna operating at center frequency of 4.76 GHz was fabricated and measured. The measurement results show an impedance fractional bandwidth of 15.8% (4.38‐5.13 GHz) and a peak realized gain of 6.1dBi.