Gain calibration and feedforward automatic gain control for CMOS radio-frequency ICs

Abstract

Two circuits for improving the performance of a Bluetooth CMOS RFIC are described. A RF amplifier gain calibration circuit uses a dummy amplifier to calibrate voltage gain and output voltage swing. The dummy amplifier's and a target RF amplifier share the bias circuit, thereby allowing accurate RF gain control against temperature, bias and process variations. A 0.18 /spl mu/m CMOS calibration circuit achieved gain control within +/-0.5 dB. The second circuit, an interleafed multi-stage filter and IF amplifier for use in a low-IF receiver, has an AGC circuit with a novel feedforward control that allows rapid convergence of the amplifier gain. When applied to a Bluetooth signal, convergence was achieved within 5 /spl mu/s even in the worst case blocking signal condition.