2.1 A highly linear inductorless wideband receiver with phase- and thermal-noise cancellation

Abstract

As there is no off-chip RF filtering available in a true Software-Defined-Radio (SDR), SDR receivers typically sufferfrom two fundamental issues when subject to large out-of-band blockers: gain compression and reciprocal mixing. Recently developed techniques based on passive mixers [1,3,4] addressed the first issue, with [1] notably achieving 0dBm blocker-tolerance and low-noise (Fig. 2.1.1 top left), yet they are still susceptible to reciprocal mixing (RM). Meanwhile, another recent work [2] showed a technique to cancel the RM by exploiting the symmetry of the phase noise (Fig. 2.1.1 top right). However, it is only capable of cancelling the RM caused by a moderate CW blocker (up to −10dBm), and lacks a front-end that is wideband, highly linear, and low-noise. In this work, we report a new architecture with phase- and thermal-noise cancellation to tackle the aforementioned challenges. The resulting design achieves 2dB small-signal NF and tolerates 0dBm blockers, yet incorporates no inductors even in the RF VCO. A low-cost wideband ring oscillator is integrated on-chip, and the phase-noise cancellation is capable of rejecting the RM when either a CW or a modulated blocker is present. This inductorless receiver achieves competitive performance compared with the state-of-the-art, breaking the traditional trade-off between LOGEN's power, phase noise, and cost commonly seen in all receivers.