A direct conversion receiver with an IP2 calibrator for CDMA/PCS/GPS/AMPS applications

A second-order intercept point (IP2) calibration technique is developed using common-mode feedback (CMFB) circuitry in a direct-conversion receiver for wireless CDMA/PCS/GPS/AMPS applications. The IP2 calibrator is capable of providing different CMFB gain to tune its common-mode output impedance for each of the positive and negative mixer outputs. The CDMA mixer applying this method achieved a second-order input intercept point (IIP2) of 64 dBm, a third-order input intercept point (IIP3) of 4 dBm, a noise figure of 6.5 dB and a voltage gain of 42.2 dB. This result shows a 20 dB improvement from an uncalibrated IIP2 of 44 dBm. 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.