A Ultra-low-power Wake-up Wireless Transmitter for Bio-luminescence Detection in Ingestible Capsules

This paper presents a wake-up transmitter (WuTX) for bio-luminescence detection in ingestible capsules. The WuTX achieves long-term standby operation through sleep and work modes, with dual-mode switching implemented by a wake-up timer (WuTIM). In sleep mode, only the always-on LDO (L D O_A o B), reference circuits, and WuTIM are activated, the system operates at 0.4 V through L D OA o B, leading to a power consumption of just 10 nW. In work mode, all modules are enabled by WuTIM, the system operates at 1.1 V through L D O_T X. A chirp injection is adopted to shorten the start-up time of the crystal oscillator (XCO), providing a 26 MHz reference frequency within 1.8 ms while consuming only 25.8 μ ∼W. Then, a narrow pulse injection signal drives the injection-locked ring oscillator (ILRO) to produce a 130 MHz signal. This signal further generates a 910 MHz carrier frequency by an edge combiner (EC). Finally, a switched capacitor power amplifier (SCPA) is adopted to provide a wide output power range. Fabricated in a 40 nm CMOS process, the WuTX can achieve - 1 6 d B m output power with a power consumption of 830 μ W, leading to an energy efficiency up to 15.9 pJ / bit.