Synthetic Diversity for Artifact Suppression and Simultaneous Multi-Band Down-Conversion in Widely-Tunable Receivers

This paper presents a novel system architecture to suppress in-band artifacts (IBAs) generated from out-of-band (OOB) interferers, including reciprocal mixing by the local oscillator’s (LO) spurs and phase noise (PN), third-order intermodulation (IM3) artifacts, and harmonic down-conversion (HDC) artifacts. Theory and design procedure are explained, and measurement results from a prototype taped out in 45 nm RF SOI process are presented. The receiver was designed for the frequency range of 1.2 GHz–2.4 GHz and achieved a noise figure (NF) of 3.1 dB–6.2 dB, blocker -1 dB compression point (B1dB) of -10.3 dBm, and OOB third-order input-referred intercept point (IIP3) of 9.3 dBm on average, before artifact suppression. Measurements were performed on 16-quadrature amplitude modulated (16QAM) signals with modulated and unmodulated OOB interferers to show artifact suppression for various kinds of IBA. For each IBA, artifact suppression performance was assessed across frequency and interferer power. Interference tolerance improvement of up to 38 dB was achieved. Additionally, reconstruction of the artifacts for the cases of spur and HDC was demonstrated, showing simultaneous recovery of two signals, providing a form of carrier aggregation.