A 0.5-3GHz Receiver with a Parallel Preselect Filter Achieving 120dB/dec Channel Selectivity and +28dBm Out-of-Band IIP3

Abstract

Recent sub-6GHz receivers (RXs) attempted to realize RF channel selection at the RX input for suppressing large close-in blockers. Although mixer-first RXs can achieve sharp RF filtering and good out-of-band (OOB) linearity, they suffer from large noise figure (NF) and high LO leakage [1] [2]. Alternatively, [3]–[5] exploited an N-path notch filter around an LNTA to simultaneously achieve low NF and a moderate channel selection at the RX input. However, their OOB IIP3 and blocker 1dB compression point (B1dS) are at least 10dB worse than the mixer-first RXs. This paper proposes an LNTA-based RX that shows a similar OOB linearity as prior art mixer-first RXs without sacrificing NF. This is achieved by (1) adding a parallel preselect filter at the RX input to improve the RF selectivity and achieve +6dBm B1dB; (2) proposing third-order RF and baseband filters to attenuate close-in blockers by a 120dB/dec roll-off; (3) introducing a feedback network to reduce the in-band (IB) gain fluctuations to <0.5dB.