A 24-GHz Receiver Frontend With an LO Signal Generator in 0.18- $\mu$ m CMOS

Utilizing a standard 0.18-mum CMOS process, a receiver frontend and a local oscillator (LO) module are implemented for RF applications at the 24-GHz industrial, scientific, medical band. The proposed frontend is composed of a three-stage low-noise amplifier, a down-conversion mixer, and IF amplifiers. With an IF frequency of 4.82 GHz, the fabricated circuit demonstrates a conversion gain of 28.4 dB and a noise figure of 6.0 dB while maintaining an input return loss better than 14 dB. The measured P _{in - 1dB} and IIP₃ of the receiver frontend are -23.2 and -13.0 dBm, respectively. In addition, a circuit module, which generates the required dual down-conversion LO signals, is also included in this study. The proposed LO generator consists of a 19-GHz low-phase-noise voltage-controlled oscillator (VCO), a 4 : 1 frequency divider, and a quadrature phase-tuning circuit. From the measurement results, the VCO exhibits a tuning range of 850 MHz and a phase noise of -110 dBc/Hz at 1-MHz offset frequency. Operated at a supply voltage of 1.8 V, the current consumptions for the receiver frontend and the LO generator are both 30 mA.