Circularly Polarized Shared-Aperture Microstrip Antenna for S-/X-Band Satellite Communications

In this paper, a dual-band circularly polarized (CP) shared-aperture microstrip patch antenna with a high frequency ratio of 4.1 is presented for S-/X-band satellite communications. The unit cell of the designed antenna is composed of a single perforated S-band trimmed patch and four X-band trimmed patches configured in a 2 × 2 array. The S- and X-band patches are interlaced, thus sharing their apertures within the same layer, which enhances isolation between the two bands and prevents the degradation of CP characteristics. The antenna was designed and optimized for the S-band frequency range of 1.9–2.05 GHz and the X-band frequency range of 7.8–9 GHz. To verify feasibility, the performance of the proposed antenna was measured in a full anechoic chamber. The measured results showed good agreement with the simulated results. The −10 dB impedance bandwidths of the S- and X-band antennas were 7.8% and 13.5%, respectively, while their measured 3-dB axial ratio bandwidths were 2% and 3.9%, respectively. Furthermore, the unit cell antenna achieved left-handed circularly polarized peak gains of 5.7 dBic at 2.02 GHz and 11.6 dBic at 8.28 GHz.