3.9 An RF-to-BB current-reuse wideband receiver with parallel N-path active/passive mixers and a single-MOS pole-zero LPF

The latest passive-mixer-first wideband receiver (RX) [1] has managed to squeeze the power (10 to 12mW) via resonant multi-phase LO and current-reuse harmonic rejection BB, but the removals of RF gain and virtual ground severely penalize its NF (10.5±2.5dB), while devaluing its original IIP3 benefits (+10dBm). The described wideband RX exploits an RF-to-BB current-reuse topology, with parallel N-path active/passive mixers, to leverage such power-performance tradeoffs. Specifically, the RX features: 1) a current-reuse RF front-end with an N-path active mixer to realize most RF-to-BB functions in the current domain, resulting in better power efficiency and linearity; 2) a feedforward N-path passive mixer to enable LO-defined input matching with zero external components, while offering frequency-translated band-pass filtering and noise cancelling; 3) a single-MOS pole-zero LPF to perform current-mode BB filtering while alleviating the tradeoff between the in-/out-of-band linearity, and 4) a BB-only two-stage harmonic-recombination (HR) amplifier to boost the 3^rd and 5^th harmonic rejection ratios (HRR_3,5) with low hardware intricacy. Targeting the TV-band (0.15 to 0.85GHz) cognitive radios for IEEE 802.22/802.11af, the RX manifests favorable NF (4.6±0.9dB) and out-of-band IIP2/IIP3 (+61/+17.4dBm) under low power dissipation (10.6 to 16.2mW).