A Compact Ka-Band Four-Antenna Four-Simultaneous Beams Transmitter for Phased Array Applications in 55-nm CMOS

This letter presents a Ka-band four-antenna transmitter supporting four simultaneous beams for phased array applications. To alleviate the design challenge of large chip area caused by the multibeam splitting and to facilitate array design, the architecture of the transmitter features a compact passive multibeam splitting network (MBSN) combined with a modified gm-based phase shifter (PS) array. Implemented in a 55-nm CMOS process, the transmitter consumes a current of 760 mA with a 1.2-V supply. From 27 to 31 GHz, the transmitter achieves a 360° phase shifting range with a 6-bit resolution, and the root mean square (rms) phase and gain errors are less than 3° and 0.5 dB, respectively. The full transmit path achieves a gain of 21 dB with less than ±1-dB variation and an output-referred 1-dB gain compression point (OP $_{1\,\text {dB}}$ ) of >2 dBm. The chip size, including pads, is only $2.7\times 3.6$ mm2.