An Element-Matched Electromechanical ΔΣ ADC for Ultrasound Imaging.

This work presents a powerand 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 ΔΣ ADC. The receive chain is thus greatly simplified, yielding savings in area and power. Every ADC becomes small enough to fit underneath a 150 μm × 150 μm transducer element, enabling simultaneous acquisition and digitization from all the elements in a 2D array. This is especially valuable for miniature 3D probes. Experimental results are reported for a prototype receiver chip with an array of 5 × 4 element-matched ADCs and a transducer array fabricated on top of the chip. Each ADC consumes 800 μW from a 1.8 V supply and achieves a SNR of 47dB in a 75% bandwidth around a center frequency of 5MHz.