Patent ID: 6839303

Claim:
A matched filter which selects an arc-shaped part of ultrasonic transducer elements from a plurality of ultrasonic transducer elements arranged in a circular form and forms a receiving beam oriented in a central direction of said arc-shaped part, said matched filter comprising: a shift register which has as many stages as a number given by (the number of said ultrasonic transducer elements arranged in the circular form)×(n−1)+(the number of said ultrasonic transducer elements of the arc-shaped part), where n is an integer, and stores signal trains obtained from said ultrasonic transducer elements of the arc-shaped part among signal trains of multiple scanning cycles sequentially entered from said ultrasonic transducer elements arranged in the circular form in the order of a signal train of the nth scanning cycle, a signal train of the (n−1)th scanning cycle, . . . , a signal train of the second scanning cycle and a signal train of the first scanning cycle; a plurality of multipliers which divide said ultrasonic transducer elements of the arc-shaped part into n blocks according to the direction in which the receiving beam is formed, selects signals of the ultrasonic transducer elements of a block closest to the beam direction from the signal train of the nth scanning cycle, selects signals of the ultrasonic transducer element of a block next to the block closest to the beam direction from the signal train of the (n−1)th scanning cycle, . . . , selects signals of the ultrasonic transducer elements of a block next to block most distant from the beam direction from the signal train of the second scanning cycle, selects signals of the ultrasonic transducer elements of the block most distant from the beam direction from the signal train of the first scanning cycle, and multiplies the individual signals by corresponding coefficients; and an adder which adds up results of multiplications performed by the individual multipliers and outputs the sum as correlation data.