|This thesis presents an RF receiver frontend with a 4-path passive mixer for software defined radio (SDR) applications. By utilizing frequency translation property of the passive mixer, the out of band interference experiences minor amplification while target band signal acquires a much larger gain with relatively large load impedance. This frequency dependent loading at low noise amplifier output is transferred to the receiver input with voltage feedback to achieve optimized matching only at the target band. The design was implemented in 0.18um SiGe BiCMOS technology. Simulation results show a noise figure of 4.3 dB and a filtering attenuation of 10dB for out of band interferences for the proposed RF front-end.