带DGS结构的宽带微带线准椭圆函数滤波器设计

准椭圆滤波器体积小，重量轻，结构紧凑，比契比雪夫滤波器有更好的过渡特性，更高的带外抑制，在卫星通信和移动通信中有广泛的应用前景。但在用准椭圆滤波器实现宽带滤波器时，有时会遇到耦合间隙过小难以加工的问题。在准椭圆滤波器的谐振器底板加入缺陷接地结构（DGS），可以增强谐振器之间的耦合。应用DGS结构，用较宽的耦合间隙实现较强的耦合，从而使宽带滤波器物理上更容易实现。应用三维电磁场仿真软件，设计了一种带DGS结构的宽带微带线准椭圆函数滤波器。     

Compact Ultra-Wideband Bandpass Filters Using Composite Microstrip–Coplanar-Waveguide Structure

Compact ultra-wideband bandpass filters are proposed based on the composite microstrip–coplanar-waveguide (CPW) structure. In this study, the microstrip–CPW transitions and the CPW shorted stubs are adopted as quasi-lumped-circuit elements for realizing a three-pole high-pass filter prototype. By introducing a cross-coupled capacitance between input and output ports of this high-pass filter and suitably designing the transition stretch stubs, a compact three-pole ultra-wideband bandpass filter is implemented with two transmission zeros located close to the passband edges. To further improve the selectivity, two microstrip shorted stubs are added to implement a five-pole ultra-wideband bandpass filter with good out-of-band response. Being developed from the quasi-lumped elements, and not from the transmission lines, the proposed ultra-wideband filters have sizes more compact than those of the published wideband filters. The proposed ultra-wideband filters have the merits of compact size, flat group delay, good insertion/return loss, and good selectivity. Agreement between simulated and measured responses of these filters is demonstrated.     

Nonidealities in traveling wave and transversal FIR filters operating at microwave frequencies

We examine the effects of transmission-line nonidealities like series loss, terminal impedance mismatch, circuit noise, and transconductor input and output capacitances on the performance of traveling-wave (TWA) and transversal finite-impulse response (FIR) filters. A general framework is presented for the analysis and simulation of such filters in the context of a real communication channel. Simulation results for adaptive equalizers operating at a data rate of 10 Gbps are given. Intuition is derived for the vastly superior performance of TWA-FIR filters. We also show that the effects of series losses can be counteracted in some measure by deliberately misterminating the transmission lines with a resistance lower than their characteristic impedance.     

Calculation of narrowband lowpass filters with finite impulse response

This study provides a review of digital filters known under the name “interpolated finite impulse response filters” (IFIR filters) that make it possible to create narrowband lowpass filters (LPF) with substantially reduced computational load and, consequently, a simpler design as compared with the conventional finite impulse response filters (FIR filters).     

Quasi-equiripple approximation of minimum phase FIR filters by updating desired response

The authors present a numerical method for the Chebyshev approximation of minimum phase FIR digital filters. This method is based on solving a least squares (LS) problem iteratively. At each iteration, the desired response is transformed so as to have an equiripple magnitude error. This method makes it possible to design minimum phase FIR filters whose magnitude error is quasi-equiripple. Using this method, a quasi-equiripple solution is obtained very quickly. Since the proposed methods do not require any time-consuming optimisation procedure, they require less computational complexity than conventional methods. Finally, some examples to illustrate the advantage of the proposed methods are shown.     

RAPID PROTOTYPING - Area efficient FIR filters for high speed FPGA implementation

A new algorithm that synthesises multiplier blocks with low hardware requirement suitable for implementation as part of full-parallel finite impulse response (FIR) filters is presented. Although the techniques in use are applicable to implementation on application-specific integrated circuit (ASIC) and Structured ASIC technologies, analysis is performed using field programmable gate array (FPGA) hardware. Fully pipelined, full-parallel transposed-form FIR filters with multiplier block were generated using the new and previous algorithms, implemented on an FPGA target and the results compared. Previous research in this field has concentrated on minimising multiplier block adder cost but the results presented here demonstrate that this optimisation goal does not minimise FPGA hardware. Minimising multiplier block logic depth and pipeline registers is shown to have the greatest influence in reducing FPGA area cost. In addition to providing lower area solutions than existing algorithms, comparisons with equivalent filters generated using the distributed arithmetic technique demonstrate further area advantages of the new algorithm     

Performance comparisons for nonrecursive digital filters with nonlinear phase characteristics

This letter presents a comparison between the performance, in terms of ripple and transition bandwidth, of nonrecursive digital filters with arbitrary phase characteristics and those with a linear phase response. Results are given which show that filters can be designed to have an arbitrary phase response, yet give as good a gain response as filters with linear phase.     

A new structure and design method for variable fractional-delay 2-D FIR digital filters

In this paper, a new structure and design method are proposed for variable fractional-delay (VFD) 2-D FIR digital filters. Basing on the Taylor series expansion of the desired frequency response, a prefilter–subfilter cascaded structure can be derived. For the 1-D differentiating prefilters and the 2-D quadrantally symmetric subfilters, they can be designed simply by the least-squares method. Design examples show that the required number of independent coefficients of the proposed system is much less than that of the existing structure while the performance of the designed VFD 2-D filters is still better under the cost of larger delays.     

On the design of a multiplexer with a common junction

Two sets of formulas for scattering parameters are presented for multiplexers having parallel and series configurations with a common junction. A new general design approach is developed for multiplexers having any response types and any number of channel filters of arbitrary degree, bandwidth, and interchannel spacing. By using these formulas and computer optimization techniques for all the element values in the channel filters, the design process results in a good match at the common input port over the transmission frequency band. Several examples including a contiguous multiplexer are given to demonstrate the design procedure.This work was supported by Air Force Systems Command under Contract F33615-84-K-1556.     

Explicit Design Formulas for Waveguide Single-Sided Filters

Explicit formulas are given for the design of optimum single-sided waveguide filters. Using a uniform waveguide with iris-coupled series stubs irregularly spaced along the waveguide, this class of filter results in a significant reduction in the number of resonators required to meet single-passband and single-stopband specifications over conventional techniques. Design information is given for both the Chebyshev and elliptic function cases from which the required structure may be obtained without recourse to synthesis procedures. Computer simulations of the response characteristics of both the quarter- and modified three-quarter-wave coupled quasi low-pass and the quasi high-pass designs are given. Experimental results on fifth-degree Chebyshev filters operating in X band for the former case are presented showing close agreement with theory.     

Filter digitization based on polynomial interpolation

Describes a polynomial interpolation based filter digitization technique which aims to preserve an analog system's frequency response. It is shown that the procedure is capable of digitizing non-bandlimited, including highpass, analog filters. In most cases considered, it results in digital filters whose frequency response is closer to the frequency response of the analog filter than that of filters designed using impulse invariance or the bilinear transformation     

Turbocharging Interpolated FIR Filters [DSP Tips & Tricks]

Interpolated finite impulse response (IFIR) filters drastically improve the computational efficiency of low-pass finite impulse response (FIR) filters designed using the traditional Parks-McClellan design method. This article presents a trick to further improve the computational efficiency of traditional IFIR filters.     

Digital linear filters with finite pulse response. Brief collected results

It is represented brief review investigations, related to development and enhancement of digital linear filters with finite pulse response (FPR-filters). It is proposed high-quality low-pass filters and filters, approximating definite digital filters with infinite pulse response (IPR-filters). The basis of all proposed filters is Fourier transformation of polynomial trigonometrical kernels of Jackson type.     

General IIR optical filter design for WDM applications usingall-pass filters

A general design algorithm is presented for infinite impulse response (IIR) bandpass and arbitrary magnitude response filters that use optical all-pass filters as building blocks. Examples are given for an IIR multichannel frequency selector, an amplifier gain equalizer, a linear square-magnitude response, and a multi-level response. Major advantages are the efficiency of the IIR filter compared to finite impulse response (FIR) filters, the simplicity of the optical architecture, and its tolerance for loss. A reduced set of unique operating states is discussed for implementing a reconfigurable multichannel selection filter     

Optimum masking levels and coefficient sparseness for Hilbert transformers and half-band filters designed using the frequency-response masking technique

Hilbert transformers and half-band filters are two very important special classes of finite-impulse response filters often used in signal processing applications. Furthermore, there exists a very close relationship between these two special classes of filters in such a way that a half-band filter can be derived from a Hilbert transformer in a straightforward manner and vice versa. It has been shown that these two classes of filters may be synthesized using the frequency-response masking (FRM) technique resulting in very efficient implementation when the filters are very sharp. While filters synthesized using the FRM technique has been characterized for the general low-pass case, Hilbert transformers and half-band filters synthesized using the FRM technique have not been characterized. The characterization of the two classes of filter is a focus of this paper. In this paper, we re-develop the FRM structure for the synthesis of Hilbert transformer from a new perspective. This new approach uses a frequency response correction term produced by masking the frequency response of a sparse coefficient filter, whose frequency response is periodic, to sharpen the bandedge of a low-order Hilbert transformer. Optimum masking levels and coefficient sparseness for the Hilbert transformers are derived; corresponding quantities for the half-band filters are obtained via the close relationship between these two classes of filters.     

Radar m.t.i.: a comparison of 2nd-order digital-filter realisations when the stopband is very narrow

Design of recursive digital m.t.i. filters becomes difficult when the cutoff frequency is as low as 1/100 p.r.f., because the filter may have large internal gain, generate high noise levels and have a response which is sensitive to parameter errors. The results of a study of 2nd-order sections are described and two realisations which minimise the word length are presented.     

Applications of Directional Filters for Multiplexing Systems

The design of microwave multiplexing systems for frequency channelization of a broad-band microwave spectrum is complicated by problems such as off-resonance mismatch and mutual interaction between adjacent filters. By employing directional filters as basic building blocks, it is possible to construct multiplexing filters with a perfect input match since the input VSWR of a directional filter is theoretically unity both at resonance and off-resonance. Less insertion loss of a manifold may be obtained by the use of directional filters than with conventional band-pass filters. Curves giving the predicted response of a manifold containing n elements are presented for single-tuned and double-tuned directional filters. An asymmetrical response shape is obtained which has a midband insertion loss related to the separation of adjacent channels. An experimental model consisting of a five-channel multiplexer has been constructed utilizing double-tuned-circular-waveguide directional filters.     

时变级联滤波器的两种设计方法

本文针对雷达杂波抑制中常用的时变级联滤波器,提出了两种实用的设计方法。第一种方法通过时变级联滤波器与时变非级联滤波器的等效来设计时变级联滤波器。该方法可以使时变级联滤波器具有最佳杂波滤波器的效果。第二种方法通过对总的等效滤波器的设计来得到级联滤波器第二级的权系数。分析表明,时变级联滤波器第二级的频率响应很难写出,但可以通过总的等效频率响应来体现。     

Fixed-point design of generalised comb filters: a statistical approach

This study is concerned with the problem of designing computationally efficient generalised comb (GC) filters. Basically, GC filters are anti-aliasing filters that guarantee superior performance in terms of selectivity and quantisation noise rejection compared to classical comb filters, when used as decimation filters in multistage architectures. Upon employing a partial polyphase (PP) architecture proposed in a companion study, the authors develop a sensitivity analysis in order to investigate the effects of the coefficients' quantisation on the frequency response of the designed filters. The authors show that the sensitivity of the filter response to errors in the coefficients is dependent on the particular split of the decimation factor between the two sub-filters constituting the PP architecture. The sensitivity analysis is then used for developing a fixed-point implementation of a sample filter from the class of GC filters, used as reference filter throughout the study. Finally, the authors present computer simulations in order to evaluate the performance of the designed fixed-point filters.     

Two-dimensional FlR filter design using matrix dilation approach

This paper develops an approach for the optimal design of two-dimensional (2-D) finite impulse response (FIR) filters based on the minimization of a new performance index. The approach gives analytical expressions for the optimal solution and offers a two-parameter family of suboptimal filters. It is shown that the conventional least square solutions is a member of this family. The approach is based on a result in linear algebra, and used in robust control theory, known as the dilation equation. An efficient numerical algorithm for solving the filter design problem using the dilation equation is proposed, and some techniques for choosing the design parameters are discussed. Finally, some examples are shown illustrating the flexibility of the design using the new approach