Design of Digital Delayed Transmitting and Data Acquisition Circuit in Ultrasonic Phased Array System

摘要

In ultrasonic phased array, each of all array elements should transmit the ultrasonic signal with proper delay sequence to synthesize the ultrasonic beam and corresponding to the proper time delays the ultrasonic echoes received will be used to achieve the echo signal synthesized. Therefore, how to control the delay time accurately is one of the keyt techniques. The conventional method is to use analog delay lines to implement the delay time, however, the delay lines as delay elements are extremely complicated for transmitting and receiving the ultrasonic signals. Moreover, the accuracy of the delay time is not able to be controlled easily. This paper presents a novel digital circuit of transmitting delay and data acquisition for ultrasonic phased array. The controls of impulse counting and impulse phase are combined to accomplish accurate delay time. Analog delay lines are not needed, so that we can simplify the design of the system and improve the accuracy of the delay time. That is, when the system clock frequency is 100MHz the accuracy will be up to 2.5ns. The delay time and data acquisition are both controlled by a high-speed FPGA chip. In the article the design of this circuit is described in detail.