| Summary: | In this paper, a novel substrate integrated waveguide (SIW) filtenna with two controllable radiation nulls is proposed, which has the advantage of good radiation characteristics. Radiation nulls are generated by electric and magnetic mixed coupling structure and fundamental mode, respectively. And a quasi-elliptic characteristic can be obtained at the boresight gain direction. By changing the length of perturbation slot and the strength of electric coupling and magnetic coupling, the position of radiation nulls can be controlled independetly. Compared to conventional filtenna, the proposed SIW filtenna has no extra filtering circuit to increase the dimension and complexity. Two resonant modes in the passband can be excited through loading electric and magnetic mixed coupling structure in one SIW cavity. The measured results are in good agreement with simulated results. The good frequency selectivity and out-of-band rejection are achieved. The proposed antenna exhibits a maximum realized gain of 5.8 dBi at the operating bandwidth. The measured impedance bandwidth is from 9.44 GHz to 9.68 GHz and the cross-polarization levels are lower than -20 dB in both planes.
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