Abstract: An ultrasonic detecting apparatus which includes a sequence generating means and a transmission signal generating means for generating a transmission signal corresponding to the sequence. The detecting apparatus also includes a transmitting means to transmit waves, which may be ultrasonic waves, to an object and a receiving means for receiving an echo corresponding to the transmission signal. A correlation operation means performs a correlation operation with respect to the echo. In another general aspect, the sequence generating means may generate more than one sequence, some of whose auto-correlation functions produce substantially zero sidelobe in the summed result. In a further general aspect, the sequence generating means generates two or more sequences, with each of the sequences being different from the others and having substantially the same auto-correlation function as the others.

Abstract: An ultrasonic detecting apparatus which includes a generator which generates more than three transmission signals. The detecting apparatus also includes a transmitter/receiver which transmits waves, which may be ultrasonic waves, to an object and receives echoes corresponding to the transmission signal. A correlator performs correlation operations with respect to the echoes. The results of the correlation operations are processed to obtain a signal with substantially zero side lobes.

Abstract: An inspection apparatus utilizing a pulse compression technique is described which comprises a signal generator, a transmission/reception probe; first and second correlators and an adder. The signal generator generates a composite transmission signal consisting of signals Sap(t), Saq(t), Sbp(t) and Sbq(t) respectively based on a basic unit signal ga(t) and a sequence {p}, the signal ga(t) and a sequence {q}, a basic unit signal gb(t) and the sequence {p}, and the signal gb(t) and the sequence {q}, to the probe to transmit the composite transmission signal to a target. The first correlator performs a correlation operation of echo signals Rap(t), Raq(t), Rbp(t) and Rbq(t) corresponding to the signal Sap(t), Saq(t) and Sbq(t) by utilizing reference signals Ua(t) and Ub(t) based on the sequences to provide results Caap(t), Caaq(t), Cbbp(t) and Cbbq(t).

Abstract: An ultrasonic non-destructive inspecting apparatus is constructed to comprise a transmission signal generator, an ultrasonic probe, a correlator and an adder wherein a transmission signal based on a sequence is generated and transmitted to a specimen, its echo is correlation processed with an appropriate reference signal, and the results of the correlation processes are summed to judge a reflection matter within the specimen.

Abstract: A filter bank constituted in such a manner that an interdigital transducer on the input side of a plurality of each of surface acoustic wave filters having different pass bands is used as a shunt element and the shunt element is connected to a series element composed of reactance elements to form a ladder-type circuit, and a circuit composed of an inductor and a capacitor connected in parallel with each other is used as one part of the series element to form a pole near the cut-off frequency, to increase an amount of attenuation of a T-type circuit near the cut-off frequency, and to largely reduce transmitted electric power of spurious components even in a surface acoustic wave filter in a section near a signal source.