Wideband VGA in 0.13-µm CMOS with phase reversal for 360° vector-sum phase shifters

A wideband phase-reversible variable gain amplifier (VGA) for application in full-360° vector-sum phase shifters is presented. The proposed VGA exhibits a continuously tunable gain with reversible phase, while only requiring a single-ended input. To realize the fully single-ended topology, a differential-to-single-ended converter with common-mode suppression at the output port is proposed. A modified three-stage Cherry-Hooper amplifier with inductive peaking is also adopted for gain flattening and output matching. To the best of our knowledge, it is the first time that the phase-reversible concept is proposed and realized in VGAs. As an example, a CMOS prototype exhibiting a phase-reversible and linear-in-magnitude controlled gain range of 18 dB, is demonstrated with only one control voltage. The measured 5-dB gain bandwidth is from 0.6 to 6.8 GHz, together with the input return loss better than 10 dB. Operating at 1.2 V, the chip consumes 12 mW and occupies 0.83 mm
²
, including test pads.