Compact self-diplexing dual-band dual-sense circularly polarized array antenna with closely spaced operating frequencies

A novel self-diplexing aperture-shared dual-band dual-sense circularly polarized (CP) antenna array is proposed for transmitting/receiving (Tx/Rx) applications in X-band satellite communication systems. The antenna is capable of receiving the left-handed CP (LHCP) signals in the low band while transmitting the right-handed CP (RHCP) signals in the high band. First, a dual-port cavity-fed linearly polarized (LP) patch antenna with high isolation is developed as the element of the array. The element is composed of a slotted patch, a U-slot loaded substrate integrated cavity (SIC), and two groups of split-ring resonators (SRRs). The LHCP and RHCP operations are achieved by employing two sequentially rotated feeding networks which are isolated by a ground plane. To reduce the mutual coupling between the radiators, narrow slots are etched out in the center of the patches. Importantly, the sharing of patches at different bands (i.e., common aperture) enables a compact footprint to be achieved for the array, which is beneficial for suppressing undesirable grating lobes due to the reduced interelement spacing. The measured results of a fabricated prototype agree well with the simulations, showing an impedance bandwidth of 7.2-7.75 GHz (7.85-8.4 GHz), 3 dB axial ratio (AR) bandwidth of 7.4-7.7 GHz (7.95-8.32 GHz), and gain of 14 dBic (14.2 dBic) at the low band (high band). The channel isolation is over 27 dB and the sidelobe levels are below-15 dB in both bands. The demonstrated low-profile dual-band, dual-sense CP antenna array can be a good candidate for satellite communication.