Architectural solution for second-order intermodulation intercept point improvement in direct down-conversion receivers

Second-order intermodulation is a great drawback in zero-intermediate frequency (IF) receivers. Many complex techniques for distortion cancelling have been proposed in the literature. In this study, the authors propose a simple architectural solution for second-order intermodulation intercept point (IIP2) improvement and also theoretically and experimentally demonstrate the high rejection level abilities. To determine its performance, a classical in-phase and quadrature (IQ) demodulator was also designed and used as a reference. In order to compare their non-linear behaviour in the presence of interfering signals, two types of zero-IF demodulators were tested in this work in terms of error vector magnitude and bit error rate. This study shows that by using the three-phase architecture it is possible to gain 20 dB in blocking effect rejection in comparison to the classical IQ architecture.