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This paper presents an RF-powered transceiver for wireless sensor network applications. The circuit is composed of an RF energy harvesting system, implemented by means of a threshold-compensated multistage rectifier, power management unit, and phase-locked loop (PLL)-based RF front end. Initially, the PLL in closed-loop condition locks the voltage-controlled oscillator (VCO) to a multiple of the RF input frequency and allows frequency-shift keying (FSK) data recovery. Then, the PLL feedback loop is opened and the VCO signal is used to generate the uplink carrier, thus enabling active transmission without requiring external quartz for frequency reference. This approach overcomes the reader self-jamming drawback that greatly limits the operating range of backscattering-based RF-powered devices. Moreover, uplink and downlink operations are performed by exploiting a single carrier frequency according to a half-duplex communication scheme, which results in a low-complexity and low-cost wireless solution. The circuit was fabricated in a 130-nm CMOS technology and operates with a minimum input power as low as −18.8 dBm. It supports the FSK and ASK demodulation and OOK data transmission in the industrial scientific and medical band at 915 MHz. [ABSTRACT FROM PUBLISHER]

This paper presents a 90-nm CMOS batteryless transceiver for RF-powered wireless sensor networks. The circuit is made up of a RF energy harvesting module that is implemented through a multi-stage rectifier, a power management unit, and a PLL-based RF front-end that enables TX carrier synthesis by exploiting the RF input signal as a reference frequency. This avoids the use of a local crystal oscillator, thus implementing a highly integrated low-cost wireless transceiver. An active narrowband transmission scheme is adopted with the aim of overcoming the reader self-jamming that limits the operating range of backscattering-based RF-powered devices. The circuit supports a 915-MHz FSK downlink and a 2.45-GHz OOK uplink, while achieving a data rate up to 5 Mbps. It operates with an RF input power as low as –17.1 dBm. [ABSTRACT FROM PUBLISHER]