K/Ka Dual-Band Dual-Circular-Polarized Coplanar Phased Array Antenna with High Isolation for Satellite Communication

A K/Ka dual-band dual-circular-polarized coplanar phased array antenna with high isolation is presented in this paper. The antenna is capable of receiving the right-handed circularly polarized (RHCP) signal at K-band while transmitting the left-handed circularly polarized (LHCP) signal at Ka-band. The circularly polarized (CP) radiation is realized by loading a linear-to-circular polarizer on the K/Ka dual-band dual-linear-polarized array antenna. The K- and Ka-band arrays are arranged with separate radiating apertures in a coplanar support. Each array is composed of 8×4 elements. Simulated results show the K-band array operating from 19.7 GHz to 21 GHz with the scanning angle of ±40°, and the Ka-band array operating from 29.5 GHz to 31 GHz with the scanning angle of ±40°. Then, by use of a one-to-eight microstrip power divider with the desired phase shifting, the K/Ka-band antenna loaded with the circular polarizer can scan to ±40° with the axial ratio (AR) below 3 dB. Since the K/Ka-band array antennas are separately placed and have orthogonal linear polarizations, the inter-band isolation between the transmit (Tx) and receive (Rx) arrays can be effectively improved. The simulated results show the inter-band isolation is better than 45 dB in K-band and 32 dB in Ka-band.