A Ka-Band CMOS 4-Element Beamforming Transmitter for LEO SATCOM using PA with Negative-Feedback-Based Interstage Matching Network and Asymmetric Wilkinson Power Divider

A Ka-Band four-element beamforming integrated circuit for low Earth orbit satellite communication ground terminals is presented. By employing a proposed negative-feedback-based interstage matching network in the power amplifier, the proposed BFIC achieves high output power and high gain while maintaining sufficient stability margin and efficiency. In addition, the proposed matching network improves S22 and offer robustness against VSWR variations. To address the bandwidth limitation in high-gain transmitter, wideband asymmetric Wilkinson power divider is also proposed. The divider with asymmetric in/out impedance eliminates matching networks, reduces insertion loss, and extends bandwidth. The proposed BFIC is fabricated using 65-nm CMOS process with chip area of 2.07 mm × 3.58 mm. The BFIC delivers a saturated output power of 21 dBm and a gain of 41.8 dB with a TX total efficiency of 28.9 % and -18.5 dB of S22. It also achieves RMS gain and phase errors below 0.18 dB and 1.31°.