An Element-Matched Electromechanical $\Delta\Sigma$ ADC for Ultrasound Imaging

This paper presents a power- and area-efficient approach to digitizing the echo signals received by piezoelectric transducer elements, commonly used for ultrasound imaging. This technique utilizes such elements not only as sensors but also as the loop filter of an element-level
$\Delta \Sigma $
analog to digital converter (ADC). The receiver chain is thus greatly simplified, yielding savings in area and power. Every ADC becomes small enough to fit underneath a
$150\,\,\mu \mathrm {m} \times 150\,\,\mu \mathrm {m}$
transducer element, enabling simultaneous acquisition and digitization from all the elements in a 2-D array. This is especially valuable for miniature 3-D probes. Experimental results are reported for a prototype receiver chip with an array of
$5 \times 4$
element-matched ADCs and a transducer array fabricated on top of the chip. Each ADC consumes 800
$\mu \mathrm {W}$
from a 1.8 V supply and achieves a SNR of 47 dB in a 75% bandwidth around a center frequency of 5 MHz.