5.2 0.25-to-4GHz Harmonic-Resilient Receiver with Built-In HR at Antenna and BB Achieving +14/+16.5dBm 3rd/5th IB Harmonic B1dB

Widely tunable and reconfigurable receivers are heavily in demand both for high-performance and low-power applications such as 5G New Radio and IoT. One of the crucial features required for a widely tunable RX is the ability to suppress harmonic blockers efficiently and at the earliest opportunity. Methods to achieve harmonic rejection (HR) can be categorized into two groups of active and passive HR (Fig. 5.2.1). Many active approaches have been introduced based on weighted recombination at the baseband (BB) [1] or at a preliminary stage employing multi-input multi-output HR-TIAs [2] to prevent harmonic blockers from undergoing any voltage amplification for improved linearity. However, active methods can only tolerate small blocker voltage swings at their input, leading to the desensitization of the entire receiver in the presence of strong harmonic blockers. In the past year, passive approaches to achieve HR have been reported in [3, 4]. The HR N-path transformixer in [3] passively suppresses harmonic blockers before they reach BB LNAs, offering a higher linearity. Yet, this method suffers from limited $3 ^{rd}/ 5 ^{th}$ HR of 25dB and exhibits poor performance against even harmonic blockers. The fully passive N-path-based HR mixer described in [4], effectively rejects harmonic blockers before they reach the BB amplifiers, by simultaneously utilizing capacitor stacking and charge sharing in the HR mixer cell. Although this approach ensures harmonic blockers are eliminated at the mixer output, the terminals of the mixer switches in each path are still exposed to the harmonic blockers.