Wideband Circularly-Polarized Planar Slotted Substrate-Integrated Double Line Array Antenna with High-Selectivity Self-Filtering Response for Satellite Communication Application

We introduce a circularly-polarized (CP) substrate-integrated double line (SIDL) slot array antenna with self-filtering response, aimed at expanding the operating bandwidth of CP slotted arrays and enhancing the Tx-to-Rx channel isolation in Ku-band satellite communication systems. At the element level, the design retains the SIDL radiating slot while innovatively integrating stacked inclined dipoles with counterrotating orientations optimally positioned above the radiating aperture. This configuration facilitates wideband CP radiation and simultaneously generates a radiation null, thereby markedly enhancing suppression levels within the lower stopband. By introducing a cavity-backed-SIW-to-SIDL transition structure, enhanced selectivity in the gain passband is achieved while substantially extending the operational bandwidth. Further augmented through integration with a unique SIDL collinear array configuration, the proposed array attains deep out-of-band suppression and superior frequency selectivity. Experimental results demonstrate a 3-dB AR bandwidth of 28.6%, and an effective overlapped bandwidth of 23.4% with the 3-dB gain bandwidth. Furthermore, the antenna exhibits suppression levels of 23–37 dB across the Tx frequency band.