基于FPGA的两种高速高阶FIR滤波器的设计与比较

目的 设计满足全数字眼科超声系统高速高性能信号处理需要的数字滤波器.方法 用加入流水线级的并行乘累加方式和基于分割表的并行分布式算法设计基于现场可编程门阵列(FPGA)的32阶高速FIR低通滤波器,并在Quartus Ⅱ开发平台及Modelsim仿真平台上进行仿真验证.结果 2种方式设计的FIR滤波器经仿真验证,均满足设计要求.结论 通过对设计结果的分析比较,基于分割表的并行分布式算法设计的滤波器能在灵活配置资源占用的情况下,实现高速数据处理,为全数字眼科超声系统中滤波器的实现方法提供了选择的依据.     

全数字超声成像中采用双脉冲激励时动态滤波器的设计

目的分析数字超声成像中采用双脉冲单极性激励时,超声回波的频谱及其随深度的变化趋势。方法根据在不同深度利用回波的不同频率的分量进行成像的滤波器匹配思想,设计了一组动态滤波器。既保证了近场图像分辨力又能兼顾远场图像的灵敏度。结果此滤波器在现场可编程门阵列（FPGA）芯片中实现。结论研究证明在全数字超声成像设备中,使用此滤波器得到的超声图像比使用常值滤波器得到的超声图像质量有所提高。     

基于FPGA的眼科超声数字化中CIC内插滤波器的改进与实现

目的眼科高频超声数字化成像中使用内插滤波器可等效地提高采样率以节约资源。方法在研究分析了级联积分梳状（CIC）滤波器的基础上,结合运用余弦（COSINE）滤波器和内插二阶多项式（1SOP）滤波器对其进行改进。结果通过硬件描述语言描述改进后的高效结构,并在现场可编程门阵列（FPGA）中实现,最后通过实验仿真验证该内插变频算法的有效性。结论改进后的CIC滤波器基本保留了效率和资源节约方面的优势,同时也改善了其通带宽度和阻带衰减特性,能够适用于10MHz的高频眼科超声信号处理的要求。     

基于FPGA的眼科超声数字化成像中内插变频技术与实现

眼科高频超声数字化成像中使用内插滤波器可等效地提高采样率以节约资源。在研究分析了有限脉冲响应（FIR）内插滤波器的两种常见结构以及半带滤波器、级联积分梳状（CIC）滤波器两种特殊结构等四种内插滤波器的基础上,设计了四种高效结构。通过Verilog硬件描述语言描述以上四种高效结构,并在现场可编程门阵列（FPGA）中实现,最后通过实验仿真验证各内插变频算法的有效性。以有限脉冲响应（FIR）内插滤波器的两种常见结构以及半带滤波器为基础改进的高效结构均能达到变频的效果,同时可节约资源且效率更高。而CIC滤波器高效结构在效率和资源节约方面虽更具优势,但未能达到眼科超声变频信号处理所要求的性能,尚不适用。     

一种新型自适应动态滤波器在超声成像中的应用

目的 为使动态滤波器的中心频率可实时匹配回波信号中心频率,本文设计了一种新型的自适应动态滤波器.方法 本文自适应机制是以快速傅里叶变换（fast Fourier transform,FFT）算法实时分析真实回波信号的频率特性,根据频率编号自适应匹配动态滤波器的系数.该滤波器的所有模块基于现场可编程门阵列（field programmable gate array,FPGA）硬件实现,最后将加入白噪声的正弦信号使用Modelsim时序仿真工具进行仿真.结果 仿真结果表明,这种滤波器能良好匹配回波信号中心频率,消除噪声.结论 本文提出的自适应动态滤波器满足高速实时系统的要求,为超声系统中滤波器的设计提供了可靠依据.     

基于FPGA的全数字眼科超声诊断仪信号处理设计与实现

目的研制基于FPGA(field programming gate array,可编程逻辑门陈列)的全数字眼科超声回波信号处理系统.方法信号处理技术主要采用内插、动态滤波、TGC、包络检波和对数放大.在FPGA中采用以原理图设计为顶层模块.硬件描述语言VHDL作为底层模块的设计方法.结果通过构建实验模型验证了系统各阶段信号处理的有效性.对正常人体眼球和眼眶进行检测,获得了很好的回波信号.结论本设计对眼科高频超声回波信号具有良好的实时处理能力,达到了设计要求,具有良好的应用前景.     

全数字B超的信号处理

全数字B超是超声医疗仪器的发展方向,它的基本技术特点是用数字硬件电路来实现数据量极其庞大的超声信号的实时处理。概述了全数字B超的发展方向及主要的信号处理技术,包括动态滤波、对数放大、包络检波和二次采样,并详细介绍了国内外信号处理各阶段采用的方法。     

基于FPGA的超声射频信号自适应滤波器

目的 医学超声的射频回波信号具有明显的时变特性,传统滤波器难以获得理想的滤波效果,本文提出一种基于现场可编程门阵列（field programmable gate array,FPGA）的实时自适应滤波器以解决这一问题.方法 根据双通道自适应滤波器原理,设计双脉冲激励以获得双通道输入,滤波器集成在一个Altera Cyclone II FPGA上,采用延时最小均方误差（delayed least-mean-square,DLMS）控制算法以提高速度.结果 对超声体模和人体组织回波进行的仿真及硬件滤波实验表明,该滤波器具有明显的信号增强作用,对不同深度信号的处理效果没有明显的差别,并且可以达到50MS/s的数据吞吐量,满足实时处理要求.结论 FPGA速度快,体积小,耗电低,在超声扫描仪中应用广泛,本文提出的基于FPGA超声射频信号的自适应滤波方案滤波效果明显,具有很强的实用性.     

全数字B超动态滤波器的设计与实现

为在全探测深度内获取最佳分辨力的超声回波图像,本研究基于现场可编程门阵列(FPGA)设计了一种动态滤波器,将全数字B超的探测深度平均分为64段,采用64个32阶带通滤波器与之对应,完成人体超声回波信号的动态滤波处理。所设计滤波器应用于128阵元、3.5MHz的全数字B超设备中,并与使用常值滤波器的图像进行了分析比较。通过对仿组织超声体模的检测显示,在图像的探测深度、远场分辨力和噪声滤除等方面都有了较为明显的提高。     

血管内超声弹性成像中的数据采集系统设计

基于射频信号处理的血管内超声弹性成像技术对于动脉粥样硬化易损斑块的识别具有重要意义。为验证超声弹性重建算法的准确性,设计了一种血管内超声射频信号采集系统,系统利用线同步信号为触发源,同步采集超声射频信号、心电和血压信号;引入基于单片机的控制模块,解决多块采集卡同步和超声射频信号帧间旋转不一致性矫正问题;将采集卡和控制模块等集成到同一控制平台下,实现各硬件块之间的协同工作;利用ini配置文件和MATLAB计算引擎调用技术,简化采集卡配置过程,实现采集结果的可视化。     

Microprocessor based digital signal processing system.

A microprocessor based digital signal processing system is presented in this paper. The software developed for this system enables the user to easily specify any kind of a digital filter for realtime operation. As demonstrated by a sample hardware design and implementation, low-cost dedicated applications are now feasible.     

表面肌电检测中消除工频干扰的方法

从硬件和软件数字信号处理方面介绍了表面肌电检测中消除工频干扰的方法,硬件上采用了共模屏蔽驱动电路,模拟陷波器;数字信号处理方面应用自适应数字陷波器和谱内插的方法.模拟陷波器和数字陷波器由于消除工频干扰的同时也去除了信号成分,一般只在简单生物反馈中使用.谱内插的方法是在假设真实信号的50Hz成分可以通过内插法由相邻的频率成分估计出,这样就可以消除工频干扰,而且即使工频干扰的相位发生变化也可很好的消除其影响.     

Palm print image recovery and de-noising via multi-channel wavelet filter bank

In this paper, a 3-channel wavelet transform method is introduced to recover palm print images following serious deformation. The deformation processing is actually a kind of digital re-sampling. A filter bank consisting of three filters is implemented for wavelet decomposition of the palm print image, and then a procedure of binary interpolation is performed after the image is reconstructed by another filter bank consisting of another three filters. The design of multi-channel wavelet filter bank is based on the Quadrature Mirror Filter (QMF) method. Because the noise is caused by the Morie stripe, the images are further de-noised after the geometry deformation is addressed. Acceptable results have been obtained.     

Palm print image recovery and de-noising via multi-channel wavelet filter bank

In this paper, a 3-channel wavelet transform method is introduced to recover palm print images following serious deformation. The deformation processing is actually a kind of digital re-sampling. A filter bank consisting of three filters is implemented for wavelet decomposition of the palm print image, and then a procedure of binary interpolation is performed after the image is reconstructed by another filter bank consisting of another three filters. The design of multi-channel wavelet filter bank is based on the Quadrature Mirror Filter (QMF) method. Because the noise is caused by the Morie stripe, the images are further de-noised after the geometry deformation is addressed. Acceptable results have been obtained.     

Methods of filtering the heart-beat artefact from the breathing waveform of infants obtained by impedance pneumography

A major problem with impedance pneumography is the artefact on the respiratory waveform caused by the beating of the heart. Three filters are described for reducing the amplitude of this artefact; (i) signal averaging, (ii) analogue filtering, and (iii) digital filtering. A comparison of the three filters suggested that the digital filter was most appropriate for use with a computerised data analysis system. The digital filter gave a 7dB reduction in the amplitude of the artefact. The number of breaths correctly detected by the computerised data analysis system from the respiratory waveform was slightly greater than the number of breaths correctly detected from the unfiltered respiratory waveform. The small improvement in the number of breaths correctly detected did not justify the inclusion of the filter in the automatic data analysis system.     

A method for digital signal processing based laser-Doppler flowmetry.

Non-invasive measuring of blood perfusion of tissue is important for establishing the influence of vascular diseases on microcirculation. A signal processing method for laser-Doppler flowmetry is presented in this article. The method is based on the digital filtering. A couple of filters are suggested. One of them is a digital passband filter, second - a digital filter transforming spectrum P(f) of the input signal to fP(f) spectrum. Performance of the suggested method is investigated in comparison with behaviour of the PERIMED instrument as well as with applications based on DFT.     

New algorithmic-based digital filter processing system for real-time continuous blood pressure measurement and analysis in conscious rats

A new algorithmic-based digital filter processing system for real-time continuous blood pressure (BP) measurement and analysis in freely-moving conscious rats has been developed. Real-time recognition of BP waveforms, real-time noise rejection and determination of representative waveform indexes (WIs) at indicated time points using digital filters and Smirnov's rejection test were realized with this system. Digital filters were applied for two different purposes: waveform segmentation and smoothing the calculations of representative WIs. Smirnov's rejection test was used for real-time noise rejection and yielded an accurate rejection rate of 99.99%. The result was that the digital filter processing and Smirnov's rejection test realized accurate real-time BP measurement and analysis in freely-moving conscious rats using a personal computer.     

Enhancing obstetric and gynecology ultrasound images by adaptation of the speckle reducing anisotropic diffusion filter

OBJECTIVE: So far there is no ideal speckle reduction filtering technique that is capable of enhancing and reducing the level of noise in medical ultrasound (US) images, while efficiently responding to medical experts' validation criteria which quite often include a subjective component. This paper presents an interactive tool called evolutionary speckle reducing anisotropic diffusion filter (EVOSRAD) that performs adaptive speckle filtering on ultrasound B-mode still images. The medical expert runs the algorithm interactively, having a permanent control over the output, and guiding the filtering process towards obtaining enhanced images that agree to his/her subjective quality criteria. METHODS AND MATERIAL: We employ an interactive evolutionary algorithm (IGA) to adapt on-line the parameters of a speckle reducing anisotropic diffusion (SRAD) filter. For a given input US image, the algorithm evolves the parameters of the SRAD filter according to subjective criteria of the medical expert who runs the interactive algorithm. The method and its validation are applied to a test bed comprising both real and simulated obstetrics and gynecology (OB/GYN) ultrasound images. RESULTS: The potential of the method is analyzed in comparison to other speckle reduction filters: the original SRAD filter, the anisotropic diffusion, offset and median filters. Results obtained show the good potential of the method on several classes of OB/GYN ultrasound images, as well as on a synthetic image simulating a real fetal US image. Quality criteria for the evaluation and validation of the method include subjective scoring given by the medical expert who runs the interactive method, as well as objective global and local quality criteria. CONCLUSIONS: The method presented allows the medical expert to design its own filters according to the degree of medical expertise as well as to particular and often subjective assessment criteria. A filter is designed for a given class of ultrasound images and for a given medical expert who will later use the respective filter in clinical practice. The process of designing a filter is simple and employs an interactive visualization and scoring stage that does not require image processing knowledge. Results show that filters tailored using the presented method achieve better quality scores than other more generic speckle filtering techniques.