Ultrasonic Imaging Research Based On Pseudo-random Code Combined With LFM Wave And Sparse Linear Array

Ultrasonic imaging technology has been widely used in the medical detection and industrial production detection, with its characteristics of nondestructive, intuitive and simple principle. The technology provides a great convenience for disease diagnosis and industrial products detection. At present, the transmit mode of the most of the ultrasonic imaging system is multilaunching and multiple reception. But the circuit design is more complex and the cost will increase. So this paper launches a study to reduce the cost of ultrasonic imaging system and improve the quality of ultrasonic imaging.This paper first introduces and analyses the composition of ultrasonic imaging system, summarized from the disposal way of transducer arrays, the choice of the emission signal, the signal processing methods and imaging methods. A new adaptive beamforming ultrasonic point amplitude imaging method is proposed based on pseudorandom code phase modulation linear frequency modulation signal and sparse linear array.In allusion to the multilaunching and multiple reception mode of the traditional ultrasonic imaging system, this paper adopts a new mode, that is, the transmitting array launch at the same time and only launch once. Transducer array is set as sparse array, and is composed of 4 array element and 8 receiving array element. The 12 array elements can be used to build a virtual array has 32 evenly spaced virtual array elements with the virtual array technology. Because of using the transmit mode, the four emission signal need to have good orthogonality when use the virtual array technology. On the basis of analyzing some common emission signal, propose a kind of signal meets the requirements, pseudorandom code phase modulation linear frequency modulation signal. Pseudorandom code choose the Gold code sequence which has good orthogonality and numerous. After operating for Gold code phase modulation and linear frequency modulation, the new signal has good orthogonality and pulse compression properties.In order to further improve the quality of ultrasonic imaging, especially improve the lateral resolution ability of imaging, on the basis of the pulse compression performance of the emission signal, improvement the Capon adaptive beamforming method. Calculate the adaptive weighted according to the pulse compression signal. To weighted delay superposition for the pulse compression signal and realize imaging.At last, according to the setting of each tache, a comprehensive simulation is performed. The experimental results show that the new adaptive beamforming ultrasonic point amplitude imaging method based on pseudorandom code phase modulation linear frequency modulation signal and sparse linear array can achieve high contrast and good spatial resolution of ultrasonic imaging. In addition, in this paper, the front-end ultrasonic imaging system has been designed and developed. It can realize the emission signal constructed in this paper, and the received signal can be processed offline for completing image.