This paper presents the design, fabrication, and experimental evaluation of a prototype lead zirconium titanate (PZT) matrix transducer with an integrated receive ASIC, as a proof of concept for a miniature three-dimensional (3-D) transesophageal echocardiography (TEE) probe. It consists of an array of 9 ×12 piezoelectric elements mounted on the ASIC via an integration scheme that involves direct electrical connections between a bond-pad array on the ASIC and the transducer elements. The ASIC addresses the critical challenge of reducing cable count, and includes front-end amplifiers with adjustable gains and micro-beamformer circuits that locally process and combine echo signals received by the elements of each 3 ×3 subarray. Thus, an order-of-magnitude reduction in the number of receive channels is achieved. Dedicated circuit techniques are employed to meet the strict space and power constraints of TEE probes. The ASIC has been fabricated in a standard 0.18-μm CMOS process and consumes only 0.44 mW/channel. The prototype has been acoustically characterized in a water tank. The ASIC allows the array to be presteered across ±37° while achieving an overall dynamic range of 77 dB. Both the measured characteristics of the individual transducer elements and the performance of the ASIC are in good agreement with expectations, demonstrating the effectiveness of the proposed techniques.

This paper describes the design of a transesophageal probe using a matrix (2D array) ultrasonic transducer for 3D echocardiography. To obtain images with sufficient resolution, several thousand elements are required. To reduce the channel count from the transducer to the imaging system, it is necessary to include electronics close to the transducer and use smart signal processing for data reduction. A micro-beamforming method called pre-steering is proposed. All the groups have the same delay configuration, which will simplify the required electronics. For a correct design, delay steps and the maximum delay are of importance. Furthermore, the delay should be programmable for each direction. Simulations are performed to investigate the effect of pre-steering on the received field. The delay and sum operations are realized by an integrated circuit. Simulations show that, for the micro-beamformer of a matrix transducer, the pre-steering approach is an effective method to reduce the complexity of the electronics and the channel count, while maintaining an adequate receive field.

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