This paper presents a DC offset calibration (DCOC) method combined with analog and digital circuits for direct conversion receivers. To work effectively, the LNA is shut off for better isolation and replaced by an equivalent resistance to keep the same transfer function of DC offset between calibration and operation. This method adopts DACs to compensate DC offset, then averages and eliminates the residual DC offset in the digital domain. Measurements show that this DCOC method achieves 0.44 mV DC offset and improves IM2 by 10 dB. The DCOC circuits occupy 0.23 mm 2 in 40 nm CMOS and consume 124 µA at 1.3 V supply.
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