An Element-Matched Electromechanical <tex-math notation="LaTeX">ΔΣ </tex-math> 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-levelΔ Σanalog 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 a150\,\,μ m × 150\,\,μ mtransducer 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 of5 × 4element-matched ADCs and a transducer array fabricated on top of the chip. Each ADC consumes 800μ Wfrom a 1.8 V supply and achieves a SNR of 47 dB in a 75% bandwidth around a center frequency of 5 MHz.