A Multi-Channel Bipolar Programmable CMOS Pulser With PMUT Array for Synthetic Aperture Ultrasound Imaging

The development of wearable PMUTs ultrasound platforms is currently bottlenecked by the reliance on unipolar excitation, which limits bandwidth, degrades power efficiency, and introduces DC-bias artifacts. To overcome these limitations, this paper proposes a hardware co-design methodology integrating a custom bipolar multi-channel programmable Complementary Metal-Oxide-Semiconductor (CMOS) pulser with a 32-channel wideband piezoelectric micromachined ultrasonic transducer (PMUT) array.

Fabricated using a 0.18 μ m BCD process, the transmit circuit generates flexible 2-level to 5-level bipolar stepped waveforms with adjustable frequencies (1–5 MHz) and an 7.4 Vpp amplitude. This multi-level bipolar excitation strictly suppresses high-order harmonic distortion, eliminates baseline DC stress, and drastically reduces dynamic power consumption. Driven by a 2-cycle 7.4 Vpp CMOS pulser, the co-designed PMUT channel on an SOI substrate achieves a remarkably wide fractional bandwidth of 64% at a 5 MHz center frequency and delivers a robust transmitted acoustic pressure of 63.4 kPa at a 5 mm distance.