Contents I. Introduction
Satellite communications have relied on geosynchronous (GEO) satellites for many years. Covering a large area on the Earth’s surface, consumers have accessed them through parabolic dishes and mechanically steered antenna systems [1]–[9]. Although the demand for global internet connectivity has been soaring day by day, low-earth-orbit (LEO) and medium-earth-orbit (MEO) satellites could not take the place of the traditional systems due to the high user-terminal cost. Deploying thousands of rapidly moving satellites in the lower orbits requires inexpensive ground terminals which can electronically track the satellites without moving parts. With the deployment of 5G, the cost of phased-array antennas (PAAs) has dropped drastically, and low-cost silicon beamformer chips have enabled the commercial use of silicon beamformers in SATCOM and 5G systems [10]–[28]. Multi-satellite reception has also become a requirement for some LEO constellations for make-before-break systems.
