Design of a Dual-Circularly Polarized X-Band Active Phased Array Based on a Balanced-Diplexer

Abstract

A low-profile X-band phased array aperture is evaluated for possible use on geostationary satellites. A unit cell of this array is a 4 × 4 dual-circularly polarized subarray of magneto-electric dipoles. When used as standalone dual-linearly polarized antenna, the subarray unit cell has reflection coefficient < -10 dB and cross-polarization isolation> 30 dB over the operating band. A balanced-diplexer consisting of two 90° hybrids and two compact diplexers is fully integrated with each subarray to enable dual-circularly polarized frequency division duplex operation. It is demonstrated that the proposed system has high rejection between transmit and receive bands without the need for highly complex and large diplexers. Scan analysis does not reveal any degradation of isolation; instead, it linearly scales with array size. Radiation patterns of the proposed phased array are grating lobes-free for scanning through the edge of the Earth's field of view.