A 2.2 \mu\text{W} $12 dBm RF Powered Wireless Current Sensing Readout Interface IC With Injection Locking Clock Generation
This paper presents a wireless powering current sensing readout system on a CMOS platform for portable electrochemical measurement. The wireless sensing system includes energy efficient power management circuitry, a sensor readout interface, and a backscattering wireless communication scheme. For power and area constrained bio sensing applications, the proposed readout circuitry incorporates an ultra low power potentiostatic system that generates a current according to the electrochemical reaction, as well as an oscillator based time to digital converter instead of a voltage domain analog to digital converter. To avoid a bulky battery and power hungry clock reference, the chip is wirelessly powered and injection locked by the modulated radio waves, which includes a 918 MHz carrier signal mixed with a 3.2 MHz modulated signal. The chip, implemented using a 0.18 mm CMOS process, occupies a silicon area of 1 mm2. The proposed design achieves a sensitivity of 289 Hz/nA and an R2 linearity of 0.997 over a current range of 200 nA while consuming 2.2 mW at a supply voltage of 0.8 V. The chip, integrated with a PCB antenna, has minimum sensitivities of 12 dBm and 25 dBm for RF powering and injection locking mechanisms, respectively.
IEEE Transactions on Circuits and Systems I: Regular Papers