An analysis of voltage-driven passive-mixer based SAW-less transmitters

摘要

An Analysis based on time domain simulation of a transmitter based on voltage-driven passive mixer is described here. SAW-less multi-mode (2G/3G) transmitter requires very low noise at RX band frequency to not desensitize the receiver for 3G mode and also meet -164dBc/Hz at 20MHz offset to meet the modulation mask in 2G mode. As compared to conventional Gilbert cell mixer based designs, the voltage driven passive-mixer operates from a lower power supply voltage, has zero power consumption, and lower noise. The key to achieving SAW-less operation is the low-noise passive mixer and a baseband (BB) anti-alias filter. The analysis here describes the detail of different loading on the passive-mixer and the base-band filter and the effect of different designs on the output power, linearity and required base-band current.