A 2.4 GHz low power wireless transceiver analog front-end for endoscopy capsule system

Abstract

This work presents the design and implementation of a 2.4 GHz low power wireless transceiver analog front-end for the endoscopy capsule system in 0.25 lm CMOS. The prototype integrates a low-IF receiver analog front-end (low noise amplifier, double-balanced downconverter, band-pass-filtered AGC loop, and ASK demodulator) and a direct-conversion transmitter analog front-end (20 MHz IF PLL with well-defined amplitude control circuit, ASK modulator, up-converter, and output buffer) on a single chip together with one integrated RF oscillator and two LO buffers. Trade-off has been made over the design boundaries of the different building blocks to optimize the overall system performance. All building blocks feature the circuit topologies that enable comfortable operation at low power consumption. As a result, the IC works at a 2.5 V power supply, while only consuming 15 mW in receiver (RX) mode and 14 mW in transmitter (TX) mode. To build a complete transceiver for the endoscopy capsule system, only an antenna, a duplexer, and a digital controller are needed besides the presented analog front-end chip.

A high-speed differential CMOS Schmitt trigger with regenerative current feedback and adjustable hysteresis

“…They play a critical role in a number of emerging applications including frequency doublers [2], retinal focal-plane sensors [3], sub-threshold SRAM [4], image sensors [5], and wireless transponders and sensors [6,7]. Schmitt triggers are traditionally implemented using operational amplifiers with a resistive positive feedback [8].…”

“…Schmitt trigger with variable hysteresis proposed by Katyal et al [18] uses two two-input inverters to construct the needed hysteresis. The differential Schmitt trigger evolved from the comparator proposed by Allstot in [19] appeared in wireless transponders and sensors [6,7]. The hysteresis of this Schmitt trigger, however, is fixed.…”

Differential CMOS Schmitt trigger with tunable hysteresis

“…They play a critical role in a number of emerging applications including retinal focal-plane sensors [2], sub-threshold SRAM [3], and wireless transponders and sensors [4,5]. Schmitt triggers are traditionally implemented using operational amplifiers with a resistivebased positive feedback.…”

“…The preceding Schmitt triggers with variable hysteresis are all single-ended. Differential Schmitt triggers evolved from Allstot's comparator [14] appeared in wireless transponders and sensors [4,5]. The hysteresis of these Schmitt triggers, however, cannot be tuned.…”

Design techniques for ASK demodulators of passive wireless microsystems: a state-of-the-art review

“…The limited power resources available to passive wireless microsystems limit the demodulation scheme of passive microsystems to ASK-based typically as they offer the advantages of simple baseband circuits subsequently low power consumption. ASK demodulators have been widely used in passive wireless microsystems, such as smart cards [1], neural recording microprobes [2,3], retinal prosthetic devices [4], microstimulators [5], wireless local-area sensor networks [6], RFID transponders [7,8], wireless environmental monitoring systems [9], wireless implantable electronics [10], wireless endoscopy [11,12], and hearing-aid devices [13,14]. Table 1 compiles some of the recent work on ASK demodulators of passive wireless microsystems.…”