IP2 calibrator using common mode feedback circuitry

Abstract

An IP2 calibration technique is developed using the common mode feedback circuitry in a direct-conversion receiver for wireless CDMA/PCS/GPS/FM applications. The IP2 calibrator is capable of providing a different CMFB gain to tune its common mode output impedance for each of the positive and negative mixer outputs. The method performs a 20-dB improvement in IIP2. The CDMA mixer achieves an uncalibrated IIP2 of 44 dBm, an IIP3 of 4 dBm, a noise figure of 6.5 dB and a voltage gain of 42.2 dB. The receiver RFIC is implemented in a 0.5 /spl mu/m SiGe BiCMOS process, and it operates from a 2.7 to 3.1 V single power supply. It exceeds all CDMA requirements when tested individually or on a handset.