IIP2 Improvement by Radiated LO-to-RF Leakage Mitigation in Radio Receivers for Low Power Wireless Communication Systems

This paper presents a second-order distortion improvement technique based on the mitigation of radiated local-oscillator (LO) to radio-frequency (RF) leakage. This leakage might become one of the major sources for IIP2 degradation due to massive floorplanning and placement proximity constraints between high-power and sensitive RF blocks in modern multiband and large-scale integrated radio receivers. IIP2 performance is also constrained by low power requirements in multiple-interference wireless applications such as the internet-of-things (IoT) and wireless sensor networks. The proposed technique employs 8-shaped coils in both down-converter mixer and LO generation circuits while presenting an area-effective solution with normal coils being directly replaced by 8-shaped coils within the same area. The presented solution involves zero extra power consumption and negligible noise degradation due to slight decrease in the coils quality-factor. The relative advantages have been demonstrated on a zero-IF CDMA receiver operating in the PCS 1960-MHz band with measured 20 to 25 dB improvement on both LO-to-RF leakage and IIP2 parameters.