A 2.4-GHz Super-Regenerative Transceiver With Selectivity-Improving Dual Q-Enhancement Architecture and 102- $\mu \text{W}$ All-Digital FLL

Abstract

A multichannel super-regenerative transceiver with a selectivity-improving dual Q-enhancement architecture and a 102- $\mu \text{W}$ all-digital frequency-locked loop (FLL) is presented for bio-signal sensor nodes covering the 2.36–2.4-GHz medical band and 2.4-GHz industrial-scientic-medical (ISM) band. The conventional super-regenerative receiver suffers from the weak selectivity, and its performance is deteriorated in proportion to an increase of the data rate. The proposed receiver implements dual Q-enhancement operation of the low-noise amplifier (LNA) and super-regenerative oscillator (SRO) and improves the interferer rejection without data rate dependence. For channel frequency synthesis, an all-digital FLL is integrated. The digital fine-tuning method obviates the control voltage discharging issue of oscillator in analog phase locked loop (PLL) during SRO quenching operation, and the simplified all-digital frequency loop reduces the frequency synthesizer power in the ultralow-power sensor nodes. Implemented in 90-nm CMOS technology, the proposed transceiver occupies an effective die size of 1.81 mm2 and achieves an sensitivity of −82 dBm at 1-Mb/s/ $10^{-3}$ bit error rate (BER) and interference selectivity of 32 dB at a 1-Mb/s/10-MHz offset while consumping $102~\mu \text{W}$ at the all-digital FLL and 0.93/2.37 nJ/b at receiver/transmitter, respectively.