Probe development of CMUT and PZT row-column-addressed 2-D arrays

This paper presents the characterization of two prototyped fully integrated 62 + 62 row-column-addressed (RCA) 2-D transducer array probes, which are based on capacitive micromachined ultrasonic transducer (CMUT) and on piezoelectric transducer (PZT) technology, respectively. Both transducers have integrated apodization to reduce ghost echoes and were designed with similar acoustical features i.e. 3 MHz center frequency, λ/2-pitch and 24.8 mm²  × 24.8 mm² active footprint. The transducer arrays were assembled in a 3-D printed probe handle with electromagnetic shield and integrated electronics for driving the 128-channel coaxial cable to the scanner. The electronics were designed to allow all elements, both rows and columns, to be used interchangeably as either transmitters or receivers. The transducer characterization i.e. bandwidth, phase delay, surface pressure, sensitivity, insertion loss, and acoustical crosstalk, were based on several single element measurements, including pressure and pulse-echo, and were evaluated quantitatively and comparatively. The weighted center frequency was 3.0 MHz for both probes and the measured -6 dB fractional bandwidth was 109 ± 4% and 80 ± 3% for the CMUT and the PZT probe, respectively. The surface pressures of the CMUT and PZT were 0.55 ± 0.06 MPa and 1.68 ± 0.09 MPa, respectively, and the receive sensitivities of the rows (receiving elements) were 12.9 ± 0.7 μV/Pa and 13.7 ± 2.1 μV/Pa.