Ultrasonic transmitting, receiving and amplifying circuits are designed. Thereceived signals are sampled with the high speed ADC (analog-to-digital converter), and dealt withthe DSP (digital signal processing). A forw...Ultrasonic transmitting, receiving and amplifying circuits are designed. Thereceived signals are sampled with the high speed ADC (analog-to-digital converter), and dealt withthe DSP (digital signal processing). A forward-backward IIR (infinitive impulse response) filterwith no delay is designed to filter the sampled data, and series A and B are achieved by narrow andwide band filtering, respectively. In series A, the start point of the cycle first exceeding thethreshold is calculated accuratelyby interpolation, and the start cycle is detected by fittingcycles in series A and its inversion A' to cycles in B with variance analysis. Therefore, the startpoint of the start cycle is calculated precisely. By deriving the relationships between the traveltime in the opposite directions of three axes and the airflow velocities, the wind velocity anddirection are calculated. Experiments show that the reliability and the precision are improved, andthe circuits are simplified.展开更多
Speckle noise has long been known as a limiting factor for the quality of an ultrasound B-mode image.In this study,anisotropic diffusion filtering is proposed as an effective method for ultrasound speckle reduction.Th...Speckle noise has long been known as a limiting factor for the quality of an ultrasound B-mode image.In this study,anisotropic diffusion filtering is proposed as an effective method for ultrasound speckle reduction.This article provides a brief description of anisotropic diffusion filtering proposed by Perona and Malik,and compares its speckle filtering effects with other filtering methods including median,moving average,and frequency domain Gaussian low-pass.In this study,multiple filters are implemented in Matlab.For each filter,three different types of noisy images with speckle noise are tested.The results show that anisotropic filter can reduce the noise more effectively and meanwhile preserve the boundaries of the objects.In addition,this filter has more controllable filtering parameters and is independent on the information of the noise.展开更多
The increase of frame rate,though with the potential in a coded ultrasound system,is generally concomitant with the simultaneous transmission of a number of apertures,and in consequence leads to increased cross-talks ...The increase of frame rate,though with the potential in a coded ultrasound system,is generally concomitant with the simultaneous transmission of a number of apertures,and in consequence leads to increased cross-talks between different apertures.In view of this,a new coding scheme using staggering repetition interval was proposed.The transmitting signals were constructed by repeating the two(or more) modulated codes using staggering repetition interval,and then allocated to and transmitted simultaneously among different apertures.The decoding process was based on the subsection-matched filter under the assistance of different matched filters for different apertures.At last the outputs of subsection-matched filtering were added together.Staggering changed the positions of cross-correlation(CC) peaks from coinciding,which resulted in an effective reduction of CC.Our theoretical analysis and simulations showed that,the coding scheme can be used to reduce cross-talk,and a good cross-talk reduction will be achieved if the staggering delay is kept in an appropriate range.展开更多
文摘Ultrasonic transmitting, receiving and amplifying circuits are designed. Thereceived signals are sampled with the high speed ADC (analog-to-digital converter), and dealt withthe DSP (digital signal processing). A forward-backward IIR (infinitive impulse response) filterwith no delay is designed to filter the sampled data, and series A and B are achieved by narrow andwide band filtering, respectively. In series A, the start point of the cycle first exceeding thethreshold is calculated accuratelyby interpolation, and the start cycle is detected by fittingcycles in series A and its inversion A' to cycles in B with variance analysis. Therefore, the startpoint of the start cycle is calculated precisely. By deriving the relationships between the traveltime in the opposite directions of three axes and the airflow velocities, the wind velocity anddirection are calculated. Experiments show that the reliability and the precision are improved, andthe circuits are simplified.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.NS2014060)
文摘Speckle noise has long been known as a limiting factor for the quality of an ultrasound B-mode image.In this study,anisotropic diffusion filtering is proposed as an effective method for ultrasound speckle reduction.This article provides a brief description of anisotropic diffusion filtering proposed by Perona and Malik,and compares its speckle filtering effects with other filtering methods including median,moving average,and frequency domain Gaussian low-pass.In this study,multiple filters are implemented in Matlab.For each filter,three different types of noisy images with speckle noise are tested.The results show that anisotropic filter can reduce the noise more effectively and meanwhile preserve the boundaries of the objects.In addition,this filter has more controllable filtering parameters and is independent on the information of the noise.
基金Project (Nos.60772147 and 60871060) supported by the National Natural Science Foundation of China
文摘The increase of frame rate,though with the potential in a coded ultrasound system,is generally concomitant with the simultaneous transmission of a number of apertures,and in consequence leads to increased cross-talks between different apertures.In view of this,a new coding scheme using staggering repetition interval was proposed.The transmitting signals were constructed by repeating the two(or more) modulated codes using staggering repetition interval,and then allocated to and transmitted simultaneously among different apertures.The decoding process was based on the subsection-matched filter under the assistance of different matched filters for different apertures.At last the outputs of subsection-matched filtering were added together.Staggering changed the positions of cross-correlation(CC) peaks from coinciding,which resulted in an effective reduction of CC.Our theoretical analysis and simulations showed that,the coding scheme can be used to reduce cross-talk,and a good cross-talk reduction will be achieved if the staggering delay is kept in an appropriate range.
