Fully Configurable Capacitor-Less Oversampling DC Offset Cancellation for Direct Conversion Receivers

This brief presents a fully integrated dc offset cancellation (DCOC) scheme with configurable cut-off frequency and settling time. The proposed digitally assisted real-time DCOC scheme prevents the high gain baseband circuitry from saturation in direct conversion receivers. The proposed DCOC is designed and implemented in a 0.18 μm CMOS process. It occupies an area of 0.042 mm² and consumes a current of 0.58 mA for I and Q paths under 1.8 V supply. The residual output dc offset voltage (DCOV) is less than 5 mV under the maximum baseband gain of 62 dB. The 3-dB high-pass cut-off frequency can be configured from 100 Hz to 1 kHz and settling time varying from 5.7 ms to 0.7 ms when the receiver operates under the maximum baseband gain.