S-band phased patch array design for satellite applications

Abstract

An S-band phased array was designed for communication between a satellite in geostationary orbit and a spacecraft in lower Earth orbit (LEO). A unique aspect of the design is the simulation of all models using Ansoft HFSS software. The array was designed for left-hand circular polarization (LHCP). It was also desired to develop an array with a minimum operational bandwidth of 4% to allow for fabrication and substrate tolerances. Multiple circularly polarized patch designs were considered, including nearly square and stacked nearly square patches with a single feed. However, since single feed patches have narrow axial ratio bandwidths of less than 1% for a 3 dB axial ratio, a dual feed square patch was chosen. A microstrip Wilkinson splitter followed by a quarter wave transformer was designed and integrated with the dual feed square patch in HFSS to provide LHCP centered at 2.2875 GHz resulting in an 8.7% bandwidth. Using the dual feed square patch antenna, a six by six element uniformly spaced planar array was modeled and simulated in HFSS. The array used tapered amplitude excitation to reduce sidelobes and a progressive phase shift to steer the main beam from the geostationary satellite toward the spacecraft in LEO.