Exact design of stray-insensitive switched-capacitor lowpass ladder filters from unit-element prototypes

A new technique is described in which stray-insensitive SC lowpass ladder filters of the LDI type are designed without the need for network synthesis. These filters exactly simulate the response of a unit element cascade prototype filter and may be designed with a usable frequency range up to one half the sampling frequency. This design procedure requires no more than simple hand calculation.     

基于Matlab的巴特沃斯滤波器设计

为了得到较纯净的真实信号,对巴特沃斯模拟滤波器的幅频特性、设计方法及设计步骤进行了研究,利用Matlab程序,设计了巴特沃斯模拟滤波器,给出了Matlab设计程序,并分析了巴特沃斯模拟滤波器的幅频特性.利用Matlab程序绘制了巴特沃斯模拟滤波器的幅频特性曲线,并利用Matlab实现了模拟滤波器原型到模拟低通、高通、带通、带阻滤波器的转换.由模拟滤波器原型设计模拟高通滤波器的实例说明了滤波器频率转换效果.     

低功耗、低灵敏度有源带通滤波器设计的新方法

提出运用低通到带通的频率变换法与阻容细化法相结合的思想,直接利用2阶的低通(LP)滤波器原型电路实现4阶低功耗、低灵敏度的带通(BP)滤波电路的设计新方法。具体而言,通过对低通原型滤波电路进行阻抗变换以及时其对应的RC电路实现所谓“有损的LP-BP变换”,就可以实现带通(BP)滤波电路的设计。选用2阶切比雪夫(Chebyshev)低通滤波器电路为原型,给出4阶带通滤波器的具体设计过程,并通过PSpice软件来验证此种方法的可行性和实用性。     

Design of Linear Phase Selective Comb-Line Filter

A multiwire approach has been used to develop design equations for linear phase selective comb-line filter. The filter under consideration consists of two rows of inductive resonators separated by a slotted coupling surface. Through the development process a multipath prototype network has been considered. A frequency transformation has been formulated to relate the multipath prototype network and the multiwire comb-line structure. Hence, once the element-values of the prototype network are chosen to meet prescribed requirements, the corresponding comb-line filter element values can be computed through the developed explicit formulas. To illustrate the design procedure a brief design example is presented.     

Control Design Guidelines for Single-Phase Grid-Connected Photovoltaic Inverters With Damped Resonant Harmonic Compensators

The injection of low-harmonic current to the electrical grid is nowadays regulated by international standards. In order to accomplish these standards, selective harmonic compensation is carried out in grid-connected photovoltaic inverters by means of resonant harmonic compensators. This paper gives a systematic design procedure for selecting the gains and parameters of these harmonic compensators. Other factors considered in the design process include frequency deviation, grid synchronization, and transient response. Both a design example meeting the requirements of grid interconnection and selected experimental results from a digital-signal-processor-based laboratory prototype are also reported.     

任意阶开关电流低通滤波器的系统设计

提出了任意阶开关电流低通滤波器的一种系统设计方法,该方法遵循从RLC滤波器到有源RC滤波器,再到开关电容滤波器,最后到开关电流滤波器的顺序进行设计,方法简单易行.给出了3阶开关电流低通滤波器的设计实例,ASIZ仿真频率响应满足所需要的频率技术要求.     

基于频率响应掩蔽法的宽带滤波器的设计

针对FIR滤波器设计中锐截止宽带滤波器阶数较高、计算复杂的问题,提出用频率掩蔽法,先设计一个过渡带为目标过渡带的L倍的原型滤波器,其实现复杂度远小于所要求的滤波器,依据L倍内插滤波器的过渡带宽是原型滤波器的1/L的原理,利用一对互补滤波器和掩蔽滤波器,得到了较低计算复杂度的锐截止宽带滤波器。     

Frequency transform synthesis method for cross-coupled resonator bandpass filters

In this letter, an improved synthesis method for equal-ripple cross-coupled resonator bandpass filter is proposed based on the frequency transform method and Atia's method. In this method, the conventional lowpass prototype method is revised by replacing the low pass prototype with the frequency transform method. The detailed element extraction procedure in z-domain is given. Also the coupling matrix reduction implemented by optimization algorithm is described. This method is powerful for filter synthesis with asymmetric frequency response and complex transmission zeros. The design examples are presented and the experimental results validate its effectiveness.     

Current-fed three-phase and voltage-fed three-phase activeconverters with optimum PWM pattern scheme and their performanceevaluations

This paper describes a new approach to select the optimum sinewave pulsewidth modulation (PWM) patterns suitable for a large-capacity current-fed active PWM power converter and a practical design procedure to determine circuit constants of a low-pass filter connected to suppress higher line current harmonics flowing into the utility-grid AC power source. A feasible test is implemented by building a prototype 500 kW three-phase current-fed PWM power converter which is designed and controlled on the basis of the proposed considerations. It is verified from a practical point of view that these new conceptual considerations are more effective and acceptable to minimize higher harmonic current components flowing into the utility-grid AC power source. This experimental setup provides highly efficient steady-state characteristics of the current-fed three-phase PWM power converter under the operating condition of a unity power factor correction and sinewave line current shaping schemes. Furthermore, this unique optimum PWM pattern derived from the theoretical method proposed here is conveniently applicable to a voltage-fed three-phase PWM converter. It is verified that this optimum PWM pattern provides excellent switching performance with a lower switching frequency mode than the conventional carrier-based PWM scheme     

Minimax design of two-channel IIR QMF banks with arbitrary groupdelay

The paper deals with the minimax design of two-channel infinite impulse response (IIR) QMF banks with arbitrary group delay, for which the IIR analysis filters and the resulting filter bank possess the frequency response optimal in the minimax (L_∞) sense. Utilising a lattice structure for the denominators of the IIR analysis filters, a design technique is presented based on an approximation scheme and a weighted least-squares (WLS) algorithm, previously developed by one of the authors for solving the resulting design problem that is basically a nonlinear optimisation problem. During the design process, this technique finds the tap coefficients for the numerator and the reflection coefficients for the denominator of the prototype IIR analysis filter simultaneously. The stability of the designed prototype IIR analysis filter is ensured by incorporating an efficient stabilisation procedure to make all of the reflection coefficient values fall between -1 and +1. Computer simulations show the effectiveness of the proposed design technique     

An Analytic Design Method for Microstrip Tunable Filters

This paper describes an analytic design procedure for microstrip tunable filters. Step-impedance resonators are employed and loaded with varactors for achieving agility in the filter response. Fixed lumped capacitors are utilized as admittance inverters in order to minimize the number of varactors in the filter. An analytic approach for filter design makes it possible to achieve a tunable filter showing the same frequency response when the center frequency is adjusted. A two-pole microstrip tunable filter whose center frequency can be adjusted from 1.1 to 1.5 GHz is designed to demonstrate the validity of design theory. A prototype tunable filter operating from 2.1 to 2.7 GHz is also designed and measured. A good agreement between the measured and simulated results is shown. Finally, three- and four-pole tunable filters are designed to show straightforward application of the presented design method to higher order tunable filter design.      

Filtering of quaternion signals

Filtering of quaternion signals that specify group point objects and images in the form of polyhedrons in a 3D space is considered. It is shown that the main difference between a quaternion filter and filters for real and complex-valued signals is that, in a quaternion filter, each mth harmonic of the input signal is split into two harmonics: the reference harmonic with frequency m and the image harmonic with the frequency s-m. This behavior of the filter results from the noncommutativity of the multiplication operation for quaternions, a circumstance that necessitates the calculation of two scalar products with nonzero values at frequencies m and s-m, respectively, rather than one scalar product.     

A three-phase active power filter operating with fixed switchingfrequency for reactive power and current harmonic compensation

The performance and dynamic characteristics of a three-phase active power filter operating with fixed switching frequency is presented and analyzed in this paper. The proposed scheme employs a PWM voltage-source inverter and has two important characteristics. First, it operates with fixed switching frequency, and second, it can compensate the reactive power and the current harmonic components of nonlinear loads. Reactive power compensation is achieved without sensing and computing the reactive component of the load current, thus simplifying the control system. Current harmonic compensation is done in time domain. The principles of operation of the proposed active power filter along with the design criteria of the power and control circuit components are discussed in detail. Finally, experimental results obtained from a 5 kVA prototype confirm the feasibility and the features of the proposed system     

An Investigation of Open- and Short-Ended Resonators and Their Applications to Bandpass Filters

In this paper, we investigate both open- and short-ended half-wavelength microstrip resonators and their applications to bandpass filter designs. Using voltage-wave analyses, we examine the resonance and coupling properties of these resonators at their fundamental and harmonic frequencies. Loading them with a lumped-circuit element at the locations of zero-voltage point of the second harmonic allows control of fundamental frequency response without altering that of the second harmonic. A resistive loading can suppress the second harmonic while a p-i-n diode loading yield a switchable bandpass filter. The coupling regions between an open-ended resonator and a short-ended resonator of higher order bandpass filters can be chosen such that second-, third-, and fourth-harmonic suppression, as well as dual passband, can be achieved. Simulation and experimental results agree well, validating the proposed bandpass filter design methodology.     

Entwurf modulierter digitaler Filterbänke

In this paper, we present an improved design method for multirate modulated filter banks with uniform or nouniform frequency spacing. Compared to other design techniques, our method converges very rapidly and allows for the design of excellent prototype filters, especially for audio signal processing applications. The optimization procedure avoids nonlinear function minimization and requires linear equation solving only. We demonstrate our method by a design example of filter banks for critical-band analysis/synthesis.     

An original approach to the design of bandpass cavity filters withmultiple couplings

A novel approach to the design of general cavity filters with each cavity coupled to an arbitrary number of other cavities is presented. This approach is based on a suitable characterization of the filter structure which does not require one to model separately the cavities (resonators) and the coupling elements. Suitably defined equivalent admittances are associated with each cavity allowing one to design the filter structure once the parameters of a suitable low-pass prototype are given; an efficient procedure for the synthesis of such a prototype with equiripple passband response is also presented which allows one to arbitrarily prescribe transmission zeros placed in the complex plane (even asymmetrically). The described design approach is particularly convenient when the filter structure does not allow a simple modeling of the resonators and coupling elements separately. This is the case of slot-coupled cavity filters and of filter structures based on arrays of coupled transmission lines. It is also shown that the simplified design approach often adopted in the past, where only two coupled cavities at a time are considered, can produce large errors even in the case of filters with all attenuation poles at infinity (i.e., two couplings per cavity)     

Discrete Frequency Tuning Active Filter for Power System Harmonics

Severe voltage distortion, due to power system harmonic resonance, has been reported in recent years. This issue becomes more significant in high penetration of a photovoltaic (PV) network. A conventional voltage detection active filter operates as similar conductance for all harmonic frequencies to resolve this problem whether in a fixed conductance command or in an automatic gain adjustment control. However, its filtering capability is impeded by the mismatch between the active filter and the radial line, and the voltage distortion may still be significant. This paper proposes a discrete frequency tuning active filter to suppress power system harmonics. The active filter operates as variable conductance for each individual harmonic frequency. Each harmonic conductance is dynamically adjusted according to the corresponding harmonic voltage distortion of the active filter installation point in response to increase or decrease of nonlinear loads, or variation of resonant frequency in the power system. The mismatching problem between the feeder impedance and the active filter can be avoided effectively. Therefore, harmonic voltage distortion can be maintained at an allowable level throughout the feeder with lower peak current and lower rms current of the active filter, and loads installed at various locations of the power system receive more uniform voltage waveform.     

LCL滤波器在并联型有源电力滤波器中的设计

在满足相同的高频滤波效果的情况下,LCL滤波器所需的总电感值比L滤波器小,因此更适于在大功率、开关频率较低的电流源控制型并网设备上应用。然而针对该类型滤波器的参数设计不仅关系到开关频率处纹波抑制效果,同时也会影响电流控制器的性能。随着高频谐波抑制效果明显的LCL滤波器在并联型有源滤波器中应用,基于谐波电流跟踪控制器的LCL参数设计需要进一步研究,因此文中基于并联型有源电力滤波器给出一套LCL滤波器设计方法,并通过仿真验证该LCL滤波器的有源电力滤波器的有效性。     

一类冗余比为2的二维DFT调制滤波器组的设计

本文构建了一类冗余比为2的二维线性相位的双原型离散傅立叶变换（DFT）调制滤波器组。利用原型滤波器的多相位分解,推导出了该滤波器组的完全重构(PR)条件。基于该PR条件,我们将滤波器组的设计归结为一个关于原型滤波器的多相位分量的无约束优化问题。由于原型滤波器是线性相位的,多相位分量之间具有一定的关系,因此我们可以简化该优化问题。仿真结果验证了滤波器组PR条件的正确性。同时,仿真表明了优化算法的有效性,设计所得的滤波器组重构误差很小、频率特性较好,基本满足实际应用的需要。      

The Design of Broad-Band Frequency Doublers Using Charge-Storage Diodes

Many frequency multipliers can be viewed as consisting of an impedance inverter which couples together impedances at two different frequencies. Using this point of view, the design, construction, and evaluation of a five-resonator, broad-band frequency doubler employing charge-storage diodes is discussed. The doubler is a balanced design, employing two diodes and a balun. Design procedures which relate a low-pass filter prototype to the doubler circuit are presented. Good agreement between theory and experiment has been demonstrated; the experimental doubler exhibits approximately an octave bandwidth at 50 percent efficiency with an input frequency range of 1 to 2 GHz.