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首页> 外文期刊>IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control >Frequency division transmission imaging and synthetic aperture reconstruction
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Frequency division transmission imaging and synthetic aperture reconstruction

机译：频分透射成像和合成孔径重建

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摘要

In synthetic transmit aperture imaging only a few transducer elements are used in every transmission, which limits the signal-to-noise ratio (SNR). The penetration depth can be increased by using all transmitters in every transmission. In this paper, a method for exciting all transmitters in every transmission and separating them at the receiver is proposed. The coding is done by designing narrow-band linearly frequency modulated signals, which are approximately disjointed in the frequency domain and assigning one waveform to each transmitter. By designing a filterbank consisting of the matched filters corresponding to the excitation waveforms, the different transmitters can be decoded at the receiver. The matched filter of a specific waveform will allow information only from this waveform to pass through, thereby separating it from the other waveforms. This means that all transmitters can be used in every transmission, and the information from the different transmitters can be separated instantaneously. Compared to traditional synthetic transmit aperture (STA) imaging, in which the different transmitters are excited sequentially, more energy is transmitted in every transmission, and a better signal-to-noise-ratio is attained. The method has been tested in simulation, in which the resolution arid contrast was compared to a standard synthetic transmit aperture system with a single sinusoid excitation. The resolution and contrast was comparable for the two systems. The method also has been tested using the experimental ultrasound scanner RASMUS. The resolution was evaluated using a string phantom. The method was compared to a conventional STA using both sinusoidal excitation and linear frequency modulated (FM) signals as excitation. The system using the FM signals and the frequency division approach yielded the same performance concerning both axial (of /spl ap/ 3 /spl lambda/) and lateral resolution (of /spl ap/ 4.5 /spl lambda/). A SNR measurement showed an increase in SNR of 6.5 dB compared to the system using the conventional STA method and FM signal excitation.
机译：在合成传输孔径成像中，每次传输仅使用几个换能器元件，这限制了信噪比（SNR）。可以通过在每个传输中使用所有发射机来增加穿透深度。在本文中，提出了一种在每次传输中激励所有发送器并在接收器处将它们分离的方法。通过设计窄带线性调频信号来完成编码，该窄带线性调频信号在频域中大约不相交，并为每个发射机分配一个波形。通过设计一个由与激励波形相对应的匹配滤波器组成的滤波器组，可以在接收机处对不同的发射机进行解码。特定波形的匹配滤波器将仅允许该波形中的信息通过，从而将其与其他波形分开。这意味着所有发射器都可以在每次传输中使用，并且来自不同发射器的信息可以立即分离。与传统的合成发射孔径（STA）成像相比，在传统的合成发射孔径（STA）成像中依次激发不同的发射器，每次发射中发射的能量更多，并且获得了更好的信噪比。该方法已在仿真中进行了测试，其中将分辨率和对比度与具有单正弦激励的标准合成发射孔径系统进行了比较。两种系统的分辨率和对比度相当。该方法也已使用实验性超声波扫描仪RASMUS进行了测试。使用字符串体模评估分辨率。该方法与使用正弦激励和线性调频（FM）信号作为激励的常规STA进行了比较。使用FM信号和分频方法的系统在轴向（/ spl ap / 3 / spl lambda /）和横向分辨率（/ spl ap / 4.5 / spl lambda /）方面产生了相同的性能。与使用常规STA方法和FM信号激励的系统相比，SNR测量显示出SNR的提高了6.5 dB。

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