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 TM₁₀ mode of the square patch is utilized to couple with the TE₂₁₀ 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 TE₁₁₀ 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.