An Ultra-Compact Ka-Band Folded Phased-Array Transceiver Front-End With Bidirectional 20-dB Gain Control

This brief presents an ultra-compact Ka-band phased-array transceiver front-end implemented in 65-nm CMOS technology. The proposed design integrates a folded variable gain front-end and a passive variable gain phase shifter. The variable gain front-end achieves a merged receive and transmit channel layout design with stacked 8-shaped transformers. The passive variable gain phase shifter accomplishes bidirectional gain and phase control using the attenuable matching transformer with coupling lines. The transceiver achieves a 20 dB bidirectional gain range, 360° phase control, 0.5 dB gain steps, and 5.625° phase steps, meeting the stringent requirements of phased-array systems. Measurements demonstrate a maximum RMS phase error of 3.6° and an RMS gain error of 0.41 dB over the 32.3-37.7 GHz frequency range. The core occupies just 0.345 mm2, representing a more than 50% reduction in area compared to prior designs, making it highly suitable for large-scale phased-array applications.