A simple odd-symmetric filter for digital broadcasting

A new odd-symmetric filter for ISI suppression and VSB transmission is proposed. The frequency response of the proposed filter is similar to that of an ideal raised-cosine filter, but in contrast to raised-cosine the new filter is realizable, e.g. using simple active filters. Simulation results show that concerning ISI suppression the new filter is significantly more efficient than the classical Butterworth or Chebyshev filters. The proposed filter can be also used as a VSB filter for TV modulators and demodulators.     

A Compact Channel-Dropping Filter for Stripline and Microwave Integrated Circuits

A compact channel-dropping filter geometry is described that is particularly suited for stripline and microwave integrated circuits (MIC). The channel-dropping filter is comprised of a hairpin bandpass filter and a new bandstop filter, referred to herein as a folded-line bandstop filter. Design parameters for the latter filter for a range of bandwidths are tabulated. Analytical and experimental data for a trial channel-dropping filter are presented and discussed.     

基于总体变差模型的数字滤波器设计及其性能研究

根据经典总体变差恢复模型,设计了一种新型的应用于图像去噪的数字TV滤波器的一种算法。该新型滤波器是绝对稳定的低通滤波器,在抑制噪声的同时能够很好的保留图像的细节信息。与一般的统计滤波器不同,该滤波器充分利用了局部数据的梯度信息精确计算滤波器系数,滤波过程是图像自适应的。文中直接给出了新型滤波器固定的模板形式,使滤波过程简单易行。最后将新型滤波器与中值滤波器、均值滤波器、高斯滤波器等进行性能比较,效果更好。     

Oversampled filter banks from extended perfect reconstruction filter banks

Oversampled filter banks are currently being proposed for robust transmission applications. In this paper, we completely characterize multidimensional doubly finite-impulse-response (FIR) filter banks, that is, oversampled filter banks whose dual is FIR. Then, we consider the problem of extending perfect reconstruction critically sampled multidimensional filter banks in order to obtain doubly FIR (DFIR) filter banks. As a result, very simple criteria for constructing DFIR filter banks as extensions of orthogonal filter banks are obtained. This paper also analyzes the problem of constructing totally FIR filter banks, i.e., DFIR filter banks that remain DFIR even when some channels are removed. It is shown that any totally FIR filter bank can be implemented as the cascade of a critically sampled DFIR filter bank whose number of channels is equal to the subsampling factor, a redundant finite-dimensional transform, and a suitable set of delays.     

Modified RHKF Filter for Improved DR/GPS Navigation against Uncertain Model Dynamics

In this paper, an error compensation technique for a dead reckoning (DR) system using a magnetic compass module is proposed. The magnetic compass‐based azimuth may include a bias that varies with location due to the surrounding magnetic sources. In this paper, the DR system is integrated with a Global Positioning System (GPS) receiver using a finite impulse response (FIR) filter to reduce errors. This filter can estimate the varying bias more effectively than the conventional Kalman filter, which has an infinite impulse response structure. Moreover, the conventional receding horizon Kalman FIR (RHKF) filter is modified for application in nonlinear systems and to compensate the drawbacks of the RHKF filter. The modified RHKF filter is a novel RHKF filter scheme for nonlinear dynamics. The inverse covariance form of the linearized Kalman filter is combined with a receding horizon FIR strategy. This filter is then combined with an extended Kalman filter to enhance the convergence characteristics of the FIR filter. Also, the receding interval is extended to reduce the computational burden. The performance of the proposed DR/GPS integrated system using the modified RHKF filter is evaluated through simulation.     

Image detail-preserving filter for impulsive noise attenuation

A new nonlinear filter is proposed for attenuating impulsive noise while preserving image details. The filter truncates the grey value of a pixel to the maximal or minimal value of its enclosed surrounding band. Impulsive noise inside the band is thus attenuated while image details are preserved as long as they stretch to the band. The recursive form of the proposed filter leads to a simple architecture for fast implementation. Theoretical analysis and experimental results demonstrate the effectiveness of this new filter for both noise attenuation and detail preservation. For moderately contaminated images, as shown in the experiments, the proposed filter outperforms the standard median filter, the centre-weighted median filter and the unidirectional multistage median filter in terms of mean absolute error and filtering speed.     

新型毫米波微带带通滤波器

介绍了一种新型的加载电容型毫米波微带带通滤波器。对这种滤波器进行了分析,推导出了滤波器中所用谐振单元间的耦合系数。该滤波器通过加载电容而出现慢波效应,使得在不改变电路性能的情况下,减小了电路尺寸。同时由于电路中加载电容形成的慢波效应而出现了带阻效应,因此对谐波有很好的抑制作用。利用高频分析软件CST仿真分析并设计了这种新型的加载电容型毫米波微带带通滤波器,实验结果与设计曲线结果相符。     

Waveguide Bandpass Filters for Millimeter-Wave Radiometers

A fundamental requirement for most mm-wave heterodyne receivers is the rejection of the input image signal which is located close to the local oscillator frequency. For this purpose we use a bandpass filter, which for heterodyne receivers is also called an image rejection filter. In this paper we present a systematic approach to the design of a waveguide bandpass filter with a passband from 100 to 110 GHz and upper rejection bandwidth in the range from 113 to 145 GHz. We consider two non-tunable filter configurations: the first one is relatively selective with 11 sections (poles) whereas the second one is simpler with 5 sections. We used established design equations to propose an initial guess for the geometries of the filters, optimized the geometries, constructed the filters using two different milling methods, measured their transmission and reflection characteristics, and compared the measurements with numerical simulations. Measurements of both filters agree well with simulations in frequency response and rejection bandwidth. The insertion loss of the 11-pole filter is better than 10 dB and that of the 5-pole filter is better than 5 dB. The 11-pole filter has a sharper attenuation roll-off compared with the 5-pole filter. The upper out-of-band rejection is better than 40 dB up to 145 GHz for the 11-pole filter and up to 155 GHz for the 5-pole filter.     

Micromachined 22 GHz PI filter by CMOS compatible ICP deep trench technology

A K-band second-order bandpass filter with planar inductive pi-network using CMOS technology is demonstrated for the first time. To reduce the substrate loss of the filter, the CMOS process compatible backside inductively-coupled-plasma (ICP) deep trench technology is used to selectively remove the silicon underneath the filter. After the ICP etching, a 55.5-92.2% improvement in quality factor is achieved for the inductors in the filter. In addition, a 1.1 dB improvement in maximum available power gain (G_Amax) in K-band is achieved for the filter after the ICP etching. These results show that the micromachined pi (PI) filter is very promising for microwave/millimetre-wave RFIC applications     

A hybrid active filter for damping of harmonic resonance inindustrial power systems

This paper proposes a hybrid active filter for the damping of harmonic resonance in industrial power systems. The hybrid filter consists of a small-rated active filter and a 5th-tuned passive filter. The active filter is characterized by detecting the 5th-harmonic current flowing into the passive filter. It is controlled in such a way as to behave as a negative or positive resistor by adjusting a feedback gain from a negative to positive value, and vice versa. The negative resistor presented by the active filter cancels a positive resistor inherent in the passive filter, so that the hybrid filter acts as an ideal passive filter with infinite quality factor. This significantly improves damping the harmonic resonance, compared with the passive filter used alone. Moreover, the active filter acts as a positive resistor to prevent an excessive harmonic current from flowing into the passive filter. Experimental results obtained from a 20-kW laboratory model verify the viability and effectiveness of the hybrid active filter proposed in this paper     

矩形波导E面金属插片滤波器的CAD技术

矩形波导E面金属插片滤波器是毫米波波段的一种重要滤波器形式。利用计算机辅助技术设计矩形波导E面金属插片滤波器,解决了传统矩形波导E面金属插片滤波器设计过程中自动化程度低,需要大量查表的问题,为这种类型滤波器的研制和生产打下了坚实的基础。采用编写的CAD程序完成一个滤波器设计实例,结果表明了用该程序设计E面滤波器的可行性。 更多还原     

A 6.6-kV transformerless shunt hybrid active filter for installation on a power distribution system

This paper presents a fully-digital-controlled shunt hybrid filter for damping of harmonic propagation in power distribution systems. The harmonic propagation is caused by resonance between line inductances and power capacitors installed for power factor correction. A possible solution to damping out harmonic propagation is based on installation of a shunt pure active filter at the end of a feeder. This paper proposes a shunt hybrid active filter characterized by series connection of a seventh-tuned LC filter per phase and a small-rated three-phase active filter. Like the pure filter, the hybrid filter is connected to the end bus of a feeder. The capacitor of the LC filter imposes a high impedance to the fundamental frequency, so that the fundamental voltage appears across the capacitor. This unique feature allows us to directly connect the hybrid filter to the 6.6-kV power line without step-down transformers. Furthermore, the capacitor used in this hybrid filter is lighter, cheaper and smaller than the transformer used in the pure filter. Theoretical analysis, along with experimental results obtained from a 200-V, 20-kW laboratory system, verifies the viability and effectiveness of the proposed hybrid filter.     

开关电源中直流输出滤波电感的设计

针对开关电源中直流输出滤波电感设计难的问题,分析了滤波电感铁芯的工作状态和特点,由直流输出滤波电感的作用及其铁芯工作的状态,提出设计滤波电感的限制条件,得到了滤波电感的设计步骤,以便从事这方面的设计人员更方便、有效地进行设计。     

结合图像分割的改进导引滤波

为了更好地对图像进行平滑同时保持边缘不模糊,设计一种新的滤波方法。对基于该方法的图像滤波、细节增强等算法进行研究。首先,根据图像的亮度和颜色对图像进行分割,将图像分成不同的区域。接着,在不同的区域进行导引滤波,得到互不交叠的多个滤波子图像。然后,将这些子图融合,得到基于分割的改进导引滤波结果。最后,利用提出的改进导引滤波方法提出一种多尺度的细节增强方法。实验结果表明,在图像光滑和细节增强方面,提出的方法都要好于传统的导引滤波:提出的方法不仅能较好的光滑图像,同时保持边缘清晰,减少了传统滤波方法在边缘处的光晕现象。     

基于CPFDE的目标跟踪算法研究

在目标跟踪中,为了克服粒子滤波的粒子退化和贫化问题,提高滤波精度,文中将差分演化算法与容积粒子滤波相结合,形成了差分演化容积粒子滤波算法。在粒子进行先验更新时, 使用容积卡尔曼滤波算法融入当前时刻的量测信息并用其来产生重要性密度函数,并且在重采样阶段,用差分演化算法对根据重要性密度函数抽取的采样粒子做优化操作,从而克服粒子滤波存在的粒子退化及贫化问题,提高滤波性能。实验结果表明,和粒子滤波、无迹粒子滤波、容积粒子滤波相比,该算法有着更高的滤波精度和更好的稳定性,并且能够提高雷达机动目标跟踪的精确性。     

宽带LC带通滤波器优化设计及其Matlab仿真

宽带滤波器是宽带通信系统中基本的电路单元,因此对宽带滤波器的设计及其优化有着非常重要的意义。在宽带滤波器原理的基础上提出一种宽带滤波器的优化设计方法,即采用影像参数法的定K式和m导出式进行组合优化设计LC带通滤波器,并用Matlab仿真进行参数的调整,最终达到获得滤波性能良好的宽带LC带通滤波器。该方法在实际应用中获得了很好的效果。     

TV-VGA视频转换中的降噪措施及硬件实现

为了满足图像实时处理时对速度的要求,以及适应能够同时抑制高斯噪声和脉冲噪声的需要,提出了一种简单有效的滤波方法一混合滤波。MATLAB上的算法仿真表明：通过将中值滤波器与均值滤波器级联,可以有效的滤除视频图像中的混合噪声（脉冲噪声和高斯噪声）。采用Verilog HDL对电路进行设计,并在Xilinx公司的Spartan-IIE系列芯片上实现了混合滤波器。此滤波器算法简单,便于硬件实现,可以应用于实时图像处理中。     

基于H∞滤波器的红外小目标运动预测和跟踪方法

根据H∞滤波理论,提出了基于H∞滤波预测技术的红外图像小目标运动预测和跟踪方法,为了降低模型阶数以加快图像处理速度,滤波过程被分解在水平和垂直两个方向上分别进行,即将滤波器分解为x、y方向上两个子滤波器．H∞滤波器是一种基于最优化最坏情况下的滤波技术,它对噪声源的要求不高,能较好地应用在复杂场景下的目标运动预测与跟踪．实验证实了在噪声源不能确定或是未知的情况下,它比Kalman滤波器对红外小目标的运动预测更加准确并具有更好抗扰动性．     

一类非线性时滞系统的鲁棒H∞滤波器设计

 研究了满足下列条件的时滞系统的鲁棒H_∞滤波问题:假设系统的参数矩阵带有不确定性,且不确定参数是时变且范数有界的.在系统的状态与输出中同时都含有非线性无穷分布时滞与离散时滞.在设计滤波器的过程中,引入了一个新的Lyapunov-Krasovskii泛函.通过线性矩阵不等式技术,提出了参数不确定时滞系统的鲁棒H_∞滤波器存在的时滞依赖条件.鲁棒H_∞滤波器可以保证带有参数不确定性的滤波误差系统是渐近稳定的,并且满足给定的H_∞性能指标.通过仿真的研究证明了该方法的有效性.     

一种Farrow结构数字延时滤波器的设计

普通数字延时滤波器虽然结构简单,但系数计算过程复杂,在延时参数快速变化时,系数更新速度无法满足实时性要求,在工程应用上受限制。采用Farrow结构数字延时滤波器能够更加灵活高效地进行分数延时滤波,延时参数改变时,无需重新计算滤波器系数,更容易在现场可编程门阵列(FPGA)上实现。介绍了一种Farrow结构数字延时滤波器,提出采用基于对称结构的滤波器系数求解方法,并经过加权优化,获得最终Farrow滤波器的系数。系数计算过程中,通过对设计所得Farrow滤波器延时精度和误差的分析,调整加权因子的取值和滤波器阶数,进而提高延时精度。计算机仿真结果证明了加权对称系数求解Farrow滤波器系数方法的有效性和实用性。