A Single-Layer Dual Circularly Polarized SIW Cavity-Backed Patch Filtenna With Wide Axial Ratio Bandwidth

A single-layer dual circularly polarized cavity backed patch filtenna (filtering-antenna) with wide axial ratio (AR) bandwidth is presented in this paper. The degenerated SIW cavity modes TE120/TE210 cooperating with the patch modes TM01/TM10 are utilized to achieve a wide AR bandwidth. Simultaneously, two radiation nulls, which are inherently introduced by the SIW cavity mode TE110 and mixed electromagnetic coupling between the cavity and patch, respectively, are realized at both band edges to achieve a bandpass filtering response. For demonstration, a sample was fabricated and tested. The measured results show that the proposed filtenna achieves an operating bandwidth of 12% (defined by rigorous specifications of |S11| < -10 dB, AR < 3 dB, and |S21| < -10 dB) with the center frequency of 10 GHz, a peak gain of 7.4 dBic, an in-band average gain of 6.7 dBic, and an out-of-band rejection level over -13 dB.