An Ultralow-Power Crystal-Free Batteryless TDD Radio for Medical Implantable Applications

This article presents an event-driven ultralowpower radio intended for miniaturized biomedical implants. In its powerlink, the system employs an RF-to-dc converter to scavenge energy from the electromagnetic waves in the 2.4-GHz unlicensed industrial, scientific, and medical (ISM) band. The bidirectional time-division datalink is realized by exploiting the 915-MHz ISM band, and its operation is coordinated by a smart control module, where the cyclic redundancy check is conducted to switch the system between monitoring and interrogation modes. A proof-of-concept radio is fabricated in a 0.13-μm CMOS process with the chip area of 1.4 mm2. Without employing any external components, the radio is robust to process, supply voltage, and body temperature variations, leading to a low-cost and highly integrated wireless solution. During the monitoring mode, the downlink data reception and demodulation are realized by a receiver that consumes 27.5 μW while achieving a sensitivity of -69 and -59 dBm at the data rates of 1 and 100 kb/s, respectively. Dissipating peak power of 49.5 μW in the interrogation mode, the data transmitter delivers an output power of -30.6 dBm with a data rate of 2.5 Mb/s.