Increasing the rate of recording ultrasonic echo signals in the double-scanning mode

Abstract

To reduce the time of recording echo signals by an antenna array that operates in the double-scanning mode, it was proposed to use a set of pseudo-orthogonal coding signals. As the coding signals, it is possible to use frequency-modulated signals or phase-manipulated signals according to the Kasami code by analogy to the FDMA or CDMA techniques for multichannel communication. The use of the maximum-entropy method for decoding echo signals made it possible to reduce the noise level and increase the longitudinal resolution of reflector images in comparison to the case of using matched filtering. If an image is formed as the coherent sum of several partial images that are reconstructed using the C-SAFT method for various positions of the antenna array, it is proposed to use several sets of Kasami codes in order to additionally reduce the noise level by more than 6 dB. Numerical experiments show the efficiency of the proposed approach.