Fully integrated active CMOS vector modulator for 802.11a compliant diversity transceivers

In this paper, a CMOS vector modulator designed for smart antenna arrays at 5.5 GHz is presented. A quadrature all pass filter and sign select switches yield two orthogonal signal paths. Two variable gain amplifiers with strongly reduced phase shift of only ±6 ° are used to weight these paths. It has a phase control range of 360 ° and a gain range of -20 dB to 2.8 dB. The input-referred IP3 is -7 dBm at maximum gain. The current drawn from a 1.5 V supply amounts 12 mA. Using a 180 nm technology, the chip core area amounts 1.2×0.8 mm².