This paper presents 256-element transmitter (TX) and receiver (RX) phased arrays for satellite fixed communication at the Q and V bands, which integrate the phased-array antennas with eight-channel beamforming ICs. Wideband vector-modulated phase shifters (VGPS) and combinations of variable gain amplifier (VGA) and attenuators (ATT) are applied in the TX/RX beamforming ICs to achieve phase and gain tunings with large range and high precision. Based on the proposed beamforming ICs, the TX/RX phased arrays are realized with stacked aperture-coupled microstrip antennas on a cost-effective multi-layer PCB. Each array contains 32 TX/RX beamforming ICs, 256 antennas, and a 1-to-32 Wilkinson power divider/combiner networks. Fabricated in 65-nm CMOS technology, the packaged TX IC achieves an RMS gain error of 0.58 dB and an RMS phase error of 4.5° with 78.5-mW dc power per channel, while the$\text {OP}_{\text {1dB}}$is 9.6 dBm at 50.5 GHz. The packaged RX IC realizes a 5.3-dB NF, 0.47-dB RMS gain error, and 1.7° RMS phase error with 24.2-mW dc power per channel. The Q/V-band phased arrays are capable of scanning ±60°, while the 256-element TX phased array achieves an EIRP of 63.5 dBm. Modulated signal measurements with 200- and 400-MHz QPSK, 16-QAM and 64-QAM are also provided.