Although phased array is a 100-year-old concept, the research and development efforts have been driven by the defense industry and radio astronomy for many decades. An active electronically scanned array (AESA) has also been getting popular in commercial satellite communications (SATCOM) and 5G cellular applications. With the recent advances in the silicon technologies, the cost barrier for commercial products has been broken down especially after the deployment of 5G wireless technologies. This dissertation focuses on building cost-efficient, all-silicon, planar, SATCOM phased arrays with agile beam steering for SATCOM ground and SATCOM on-the-move (SOTM) terminals, as well as emerging non-geosynchronous-orbit (NGSO) communication systems. It presents a 1024-element transmit (TX) and receive (RX) planar phased array pair and a 256-element scalable phased array tile with multi-satellite reception capability for Ku-band SATCOM terminals. All the three planar arrays employ silicon beamformer chips mounted on an affordable printed circuit boards, dual-polarized antennas to synthesize rotated linear polarization with high cross polarization rejection for Ku-band SATCOM applications and Wilkinson network with surface mount technology (SMT) resistors. The RX arrays also comprise silicon low-noise amplifiers (LNA) placed at the antenna terminals to increase antenna gain-to-noise temperature (G/T) without enlarging the array size. Record results in EIRP and G/T are demonstrated for the transmit and receive arrays, together with the first affordable two-beam phased-array for satellite and consumer terminal applications.