A 5-6 GHz 1-v CMOS direct-conversion receiver with an integrated quadrature coupler

This paper describes a novel monolithic low voltage (I -V) CMOS RF front-end architecture with an integrated quadrature coupler (QC) and two subharmonic mixers for direct-down conversion. The LC-folded-cascode technique is adopted to achieve low-voltage operation while the subharmonic mixers in conjunction with the QC are used to eliminate LO self-mixing. In addition, the inherent bandpass characteristic of the LC tanks helps suppression of LO leakage at RF port. The circuit was fabricated in a standard 0. 18-mu m CMOS process for 5-6 GHz applications. At 5.4 GHz, the RF front-end exhibits a voltage gain of 26.2 dB and a noise figure of 5.2 dB while dissipating 45.5 mW from a 1.0-V supply. The achieved input-referred DC-offset due to LO self-mixing is below - 110.7 dBm.