Design and analysis of a mixer for WLAN direct-conversion receiver

Abstract

In this thesis, double-balanced down-mixer for IEEE 802.11a direct-conversion receiver is designed, measured, and analyzed by focusing in flicker noise. Designed mixer is fabricated by using 0.25um a single poly five metal (1P5M) of TSMC. In direct-conversion receiver, flicker noise significantly reduces the signal-to-noise ratio (SNR) of whole receiver system. This thesis propose that flicker noise caused by indirect mechanism is able be to reduced by using bonding-wire inductance, which make the parallel resonance at LO frequency. Thus the effective tail-capacitance is reduced at LO frequency. These causes of NF degradation are analyzed by modeling the parasitic tail-capacitance of common source node. As a measurement result, designed mixer performs at 5.8GHz as follows: 12.3dB voltage gain, -0.5dBm P1dB, -5.8dBm IIP2, and 12.3dB noise figure averaged in the 155kHz~10MHz with 9mA current consumption from 3.0V supply. Proposed noise reduction technique leads to improvement of noise performance and voltage gain, which is about 4.5dB NF falling and 2dB gain rising, respectively.