Abstract
This article presents an ultrasound (US) transceiver IC including a highly power-efficient US receiver (RX) and a high-voltage (HV) US transmitter (TX) for US capsule endoscopy (USCE) systems for the first time. The proposed USCE system employs the developed IC, a single-element piezoelectric trans- ducer (PZT), and a mechanically rotating reflector to obtain 360 ◦ transmural scans while traveling through the gastrointestinal (GI) tract. Since the USCE system operates with a tiny battery, power efficiency is greatly important. To reduce power consumption by decreasing the required operating speed of the analog-to-digital converter (ADC), we propose a new RX structure employing synchronized analog envelope detection. It is unlike conventional US RX ICs that necessitate power-hungry high-speed ADCs to acquire the US signal residing at a high center frequency with wide bandwidth. Instead, the proposed work employs an analog envelope detector based on a quadrature demodulation method. As a result, it uses only a single circuit path rather than two (I and Q) paths by using a demodulation carrier whose phase is synchronized with the incoming US signal. A ping-pong noise-shaping (NS) SAR ADC is adopted to improve resolution while maintaining low power consumption. Besides, the TX IC, including an on-chip charge pump, is designed to generate HV pulses to drive the PZT. The prototype IC is fabricated in a 0.18 µm bipolar-CMOS-DMOS (BCD) process. The RX consumes 2.3 mW, and the ADC ach