A 4.8-mW 4-GHz CMOS Class-B-Like Down-Converter for Harmonic Mixing Rejection

In a wideband receiver, higher frequency channels may be converted to the frequency of a desired signal by a harmonic mixing mechanism. To alleviate this issue, this paper proposes a topology, called the classBlike converter, to achieve high harmonic mixing rejection in frequency translation without any filtering. The converter is based on a linear commutation with a sinusoidal local oscillator for a small harmonic mixing, while its gain and noise performances are comparable to that of a switching-type converter. Most important, the circuitry of the proposed converter is simple and can be incorporated with other harmonic rejection techniques. The circuit is implemented with a 0.18-μm 1.8-V CMOS technology and the power consumption is 4.8 mW. Measurement results indicate that the third- to ninth-order harmonic rejections are more than 45 dB in average within a 4-GHz frequency range. A polyphase prototype with the proposed converter achieves higher than 70-dB third-order harmonic rejection even under a 2^° phase and 2% gain mismatch.