A Delta-Sigma Pulse-Width Digitization Technique for Super-Regenerative Receivers

摘要

This paper presents a delta-sigma pulse-width digitizer ( $Delta Sigma$-PWD) architecture designed for a super-regenerative receiver (SR-RX) operated at the 400-MHz Medical Implantable Communications Service (MICS) band. The $Delta Sigma$-PWD employs the operation principle of a $Delta Sigma$ modulator to convert the pulse-width (PW) value into digital domain and achieve fine resolution, which allows the SR-RX to support the 2-ASK/4-ASK modulations. It can be considered as the PW domain counterpart of a conventional $Delta Sigma$ modulator. The proposed architecture is capable of suppressing the PW quantization error over the direct-sampling-type PW detector by 23 dB. A linear model for the $Delta Sigma$-PWD is devised in this paper for system analysis and design optimization. Fabricated in a 0.18-$mu{hbox {m}}$ CMOS process, the whole receiver draws 700 $mu{hbox {A}}$ from a 1.3-V supply, while the $Delta Sigma$ -PWD consumes only 100 $mu{hbox {A}}$. When operated on the 4-ASK modulation signal with 312-kbps data rate, the receiver achieves an energy efficiency of 2.9 $~$nJ/bit and ${-}hbox{76-dBm}$ sensitivity.