A High-Linearity K-Band 4-Beam 4-Channel Beamforming Transmitter IC for LEO SATCOM in 65nm CMOS

This paper presents a 4-beam, 4-channel fully-connected beamforming transmitter IC implemented in 65nm CMOS for K/Ka-band low Earth orbit (LEO) satellite communication downlinks. To reduce beamformer complexity and power consumption, a wideband low-loss two-stage I/Q generator directly drives a variable-gain amplifier array, enabling look-up table-free phase control. To enhance linear output power, an analog linearization technique is applied to a two-stacked power amplifier. Measurement results demonstrate a peak small-signal gain of 26 dB with a 3-dB gain bandwidth of 17–20 GHz, less than 1.3° RMS phase error, and 0.2 dB RMS amplitude error with 7-bit phase steps. The transmitter achieves 19.7 dBm OP1dB and 20.2 dBm Psat with peak drain efficiency/power-added efficiency (PAE) of 35.9%/23.0% at 19 GHz. Using a 64-QAM OFDM signal, the measured average output power reaches 13.6 dBm at −25 dB EVM with 8.5% transmitter PAE.