A software-defined radio receiver architecture robust to out-of-band interference

In a software-defined radio (SDR) receiver it is desirable to minimize RF band-filtering for flexibility, size and cost reasons, but this leads to increased out- of-band interference (OBI). Besides harmonic and intermodulation distortion (HD/IMD), OBI can also lead to blocking and harmonic mixing. A wideband LNA amplifies signal and interference with equal gain. Even a low gain of 6dB can clip OdBm OBI to a 1.2V supply, blocking the receiver. Hard-switching mixers not only translate the wanted signal to baseband but also the interference around LO harmonics. Harmonic rejection (HR) mixers have been used, but are sensitive to phase and gain mismatch. Indeed the HR in shows a large spread, whereas other work only shows results from one chip. This paper describes techniques to relax blocking and HD/IMD, and make HR robust to mismatch.