CMOS dual-band variable-gain amplifier for 3G-WCDMA and WLAN dual-mode RF receivers

A dual-band variable-gain amplifier (DBVGA) is presented for integrated 2.2 GHz 3G-WCDMA and 5.2 GHz WLAN transceivers. DBVGA employs a DC-and-RF current steering technique for gain control, which can minimise variations of the noise, 1 dB gain compression point, and input/output impedance when the gain is tuned. The appropriate frequency operation band of DBVGA is jointly controlled by the switched-resonator load and the input stage gate bias, resulting in high cross-band isolation and out-of-band interference rejection. All circuits except the input stages are reused for both bands to have high component reuse. A fully-integrated 0.18 mum CMOS DBVGA has been implemented to verify the proposed design