Ka-Band SiGe HBT Low Phase Imbalance Differential 3-Bit Variable Gain LNA

This letter presents the design and implementation of a differential Ka-band variable gain low noise amplifier (VG-LNA) with low insertion phase imbalance. The VG-LNA is based on a 0.12 μm SiGe heterojunction bipolar transistor process, and the gain variation is achieved using bias current steering. The measured VG-LNA gain at 32–34 GHz is 9–20 dB with eight different linear-in-magnitude gain states, and with a noise figure of 3.4–4.3 dB. The measured rms phase imbalance is2without pads.