A compact and energy-efficient ultrasound receiver using PTAT reference circuit

Abstract

Portable and embedded ultrasound applications require energy-efficient receivers that can operate over a wide range of incident ultrasonic energy. In this paper we show that by directly injecting the ultrasonic signal into a proportional-to-absolute-temperature (PTAT) reference circuit, the pre-amplification and rectification stages used in a conventional ultrasonic receiver can be eliminated which leads to a significant improvement in the system energy-efficiency. The PTAT circuit self-biases itself in accordance to the magnitude of the incident ultrasound pressure signal and is also configured to function as an active diode (with threshold voltage of ≈25 mV) to achieve signal rectification. In this paper we present measurement results obtained from a PTAT-based ultrasound receiver that has been prototyped in a 0.5 μm CMOS process, and we compare the performance to a standard transconductance amplifier (TCA) based design that has also been prototyped in the same process. The improvement in input dynamic range was measured to be 25 dB and sensitivity of the PTAT-based receiver was measured to be 21 Hz/mV when the biasing current is 16.67 nA. We also present the bit-error-rate (BER) performance when the receiver circuit is used for a substrate communications application where ultrasound is used for transmitting and receiving data through an Aircraft grade Aluminum plate.