Design and Analysis of Low Flicker-Noise CMOS Mixers for Direct-Conversion Receivers

Abstract

This paper presents the design and analysis of low flicker-noise RF mixers in a 0.18-mum CMOS process for C-band direct-conversion receivers. The low flicker-noise mixers are implemented by incorporating a double-balanced Gilbert-type configuration, the RF leakageless current bleeding technique, and the resonating technique for the tail capacitance. First, a double-balanced Gilbert-type mixer using the current bleeding technique has been fabricated and measured for lowering flicker corner frequency. Second, a double-balanced Gilbert-type mixer using the current bleeding technique with one resonating inductor has been designed to improve conversion gain and flicker-noise performance. Third, by using two separate inductors at the node between the current bleeding device and local oscillator switches, conversion gain and flicker-noise performance are significantly improved. A conventional Gilbert-type mixer without any technique has also been fabricated and measured for comparative purposes. The Gilbert-type mixer using the current bleeding technique with two resonating inductors has a measured conversion gain of 16.1 dB, a measured input third-order intercept point of -5 dBm, a measured noise figure of 9.8 dB at 1 MHz, and a flicker corner frequency of 125 kHz while consuming only 7 mW of dc power. To the best of our knowledge, the proposed mixer shows the lowest flicker corner frequency (125 kHz) with more than 15 dB of conversion gain in the CMOS process