A Sine-LO Square-Law Harmonic-Rejection Mixer—Theory, Implementation, and Application

A square-law harmonic-rejection mixer (SL-HRM) driven by a sine local oscillator (LO) is proposed for wideband and tunable rejection of all LO harmonics. The key performances including the gain, noise figure (NF), input-referred third-order intercept point (IIP3), and harmonic rejection ratio (HRR) with respect to the amplitude and purity of the sine-LO are analyzed. In the circuit level, the SL-HRM incorporates a voltage-boosted technique to surmount the gain and NF penalties of square-law mixing, while guaranteeing the device reliability via introducing a supply startup circuit and a node-voltage protection circuit. The entailed high-purity sine-LO is achieved via a digital-intensive square-to-sine LO generator plus a passivelow-pass filter. Fabricated in 65-nm CMOS, the VHF-/UHF-band SL-HRM has a tunable gain of 1–13 dB, associated with an NF of 27–15 dB, under an LO amplitude of 50–200 mV . The IIP3 is stable within from 6.5 to 7.6 dBm, as expected. The tunable and are 13–40 dB and 17–45 dB, respectively. The mixer core consumes 7.5 mW at 2.5 V, while the LO generator draws 3–6 mW at 1.2 V. The total active area is just 0.042 mm .