Design and implementation of filters using transfer functions inthe Z domain

In this paper, a novel approach composed of digital signal-processing techniques and optimization algorithms is developed to design and implement filters at microwave frequencies. The design phase begins with the adoption of digital filter prototypes and the implementation phase is facilitated by using both parametric modeling techniques and optimization algorithms. All the zeros of digital filter prototypes are removed first; the remaining part of the prototypes is then transformed to an autoregressive (AR) process by parametric modeling techniques. The values of characteristic impedances of transmission lines synthesizing the filters are adjusted according to the AR process by optimization algorithms. Both low-pass and bandpass filters are designed and then implemented in the form of a microstrip line, and their frequency responses are measured to validate the novel approach     

Image Parameter Design of Noncommensurate Distributed Structures: An Application to Microstrip Low-Pass Filters

The direct application of the image parameter method (IPM) to distributed structures is suggested in order to overcome some limitations of classical design methods for microwave filters. Several advantages are pointed out: 1) Wider degrees of freedom are obtained using noncommensurate structures. 2) The IPM can be applied directly to a microwave structure without any use of lumped prototypes. 3) Possible technological constraints can be easily incorporated in the design procedure. 4) Filters designed according to the IPM can be cascaded together in order to improve their characteristics. An application to the design of a class of microstrip low-pass filters, which have been previously designed on a low-frequency approximation basis, is illustrated in detail. The IPM is shown to provide an effective control of both the passband and stopband, leading to filters with improved characteristics, as demonstrated by the experimental results.     

Quasi-static design technique for MM-wave micromachined filterswith lumped elements and series stubs

This paper describes micromachined, membrane-supported low-pass and bandpass filters which are suitable for microwave and millimeter-wave (MM-wave) application. The designs are realized in coplanar-waveguide (CPW) form using short- and open-end series stubs with integrated metal-insulator-metal (MIM) capacitors, and are compact in lateral and longitudinal dimensions. A computationally efficient analysis has been developed for the design and characterization of the filters. The technique is based on a quasi-static coupled-line (CL) treatment of the series stubs, and uses normal mode impedance parameters, which are calculated with the spectral-domain approach (SDA). Due to the broad TEM-bandwidth of the membrane-supported transmission lines, the method can accurately predict filter responses well into the rejection band. To demonstrate the above claims, the measured and simulated S-parameters of a 0.3 mm ×2.2 mm low-pass filter with a cutoff frequency at 17 GHz, and a second passband at 115 GHz, are presented. The new approach is also used in the design of bandpass filters which exhibit 1.5-2-dB insertion loss and bandwidths around 10%     

高阶全极点CCII低通滤波器的设计

提出了一种利用第二代电流传送器CCII（Second Generation Current Conveyor）和多端输出电流传送器MOCC（Multiple Outputs Current Conveyor）实现的高阶全极点电流模式低通滤波器。给出了系统的设计公式,并举例设计了一个五阶Butterworth低通滤波器,通过PSPICE仿真,得出的结论与理论分析完全吻合。此低通滤波器不仅电路结构简单,而且用的元器件数目较少。     

Stepped-Impedance Transformers and Filter Prototypes

Quarter-wave transformers are widely used to obtain an impedance match within a specified tolerance between two lines of different characteristic impedances over a specified frequency band. This paper gives design formulas and extensive tables of designs, most of which were especially derived so that an integrated account could be presented for the first time. Numerous examples are given. Only homogeneous, synchronous transformers and filters are included in this paper, but a short bibliography on related topics is appended. The theory is also applied to band-pass filters, by showing how to convert quarter-wave transformers into half-wave filter prototypes. The theoretical and numerical results presented are applicable to the design of impedance transformers, direct-coupled cavity filters, short-line low-pass filters, optical antireflection coatings and interference filters, acoustical transformers, branch-guide directional couplers, TEM-mode coupled-transmission-line directional couplers, and other circuits. These applications have been or will be dealt with in separate papers; this paper gives the basic theory and some of the numerical data required for these applications.     

The Design of Evanescent Mode Waveguide Bandpass Filters for a Prescribed Insertion Loss Characteristic

A design theory for evanescent dominant mode waveguide filters is presented. The cutoff guide is represented by its equivalent /spl pi/-section network, the elements of which closely approximate lumped inductances. Resonators may be formed by introducing appropriate capacitive obstacles at suitable intervals along the guide. The filter that results is a microwave analog of lumped inductance filters with series inductance coupling, the magnitude of the series "inductance" being controlled by the separation between capacitive obstacles. The theory derives the equivalent ladder network from the low-pass prototype and is accurate up to at least 20 percent band-widths. Filters may be designed to couple into other cutoff waveguide components using the same basic principles, a propagating guide, and coaxial terminations. The filters are normally constructed in standard production waveguide and are simple and cheap to manufacture. A considerable size and weight reduction, compared with orthodox waveguide filters, is possible at the cost of a small increase in insertion loss.     

Microwave Filters--1965

A review of recent and current work on microwave filters is presented, and an extensive bibliography of recent articles is appended. The review is largely qualitative and pictorial, rather than mathematical. Among the microwave filter topics discussed are band-pass filters with cascaded lifes or cavities; band-pass and band-stop filters with stubs and parallel-line coupling; low-pass and high-pass filters; the connection between dissipation loss, group delay, and power-handling capacity; delay equalizers; diplexers; directional filters; tunable filters, especially magnetically tunable filters; dielectric-resonator filters; filter techniques applied to semiconductor devices; the connection between filters and directional couplers; filters with open walls; and filters for millimeter waves and higher frequencies.     

电压模式n阶CFA低通滤波器的设计

提出了一种仅用电流反馈放大器(current feedback amplifier,CFA)实现的高阶电压模式低通滤波器,给出了系统的设计公式.给出了4阶Butterworth低通滤波器应用示例,经Pspice仿真分析,结果表明,所提出的设计方法可行.该设计方法具有电路结构简单、元器件数目少等优点.     

A Generalized Chebyshev Suspended Substrate Stripline Bandpass Filter

A design method for narrow-band suspended substrate strip-line filters having a true bandpass structure is presented. A generalized Chebyshev low-pass prototype is used, resulting in a convenient form of realization in suspended substrate stripline. A prototype device, designed with the aid of a computer program, is given as an example. Results from this device show that the method of realizing such a filter is viable for many applications and maybe suitable to replace more conventional types of microwave filter realized using TEM-mode resonators.     

SWITCHED-CURRENT FILTER DESIGN USING CASCADED SECTIONS

A new analogue sampled-data active device, named as a switched-current operationalamplifier (SIOA), is presented. The use of active circuit elements may simplify drawing the circuitdiagram significantly greatly and may permit easier analysis and synthesis of SI networks. Anumber of all pole and elliptic (second-or third-order) switched-current (SI) filters are derivedfrom the switched capacitor prototypes. These can be used as simple self-contained filters or asfilter sections in the cascaded realizations of a higher order transfer functions. To illustrate theapproach, a fifth-order low-pass filter is designed.     

一种新颖的电压模式N阶CFA低通滤波器的系统设计

提出了一种基于电流反馈放大器(CFA)的n阶电压模式多环反馈(multiple-loop feedback,简称MF)低通滤波器的系统设计方法,推导了系统的设计公式,利用该方法可导出n阶不同结构的低通滤波器,所产生的滤波器由n个CFA、n个电容、n个电阻构成。以三阶Butterworth低通滤波器为例阐述了设计过程,并用pspice进行仿真分析,设计和仿真结果表明,系统设计理论是正确的,设计方法是可行的。     

基于Matlab的模拟滤波器设计与仿真

巴特沃思、切比雪夫模拟低通滤波器通常是设计模拟高通、带通和带阻滤波器的原型,先按给定频率响应巴特沃思、切比雪夫低通Ha（s）逼近,然后由选定Ha（s）实现二端口网络的电路结构和参数值。在此对达林顿T型和П型电路结构的滤波器元件参数进行了编程计算,并对其系统函数的幅频特性进行仿真。仿真结果符合设计要求,该方法便捷,程序具有可扩展性。     

A Technique for the Design of Multiplexers Having Contiguous Channels

A general procedure for the design of multiplexer having contiguous channel frequency bands is presented. Using this procedure, the individual channel band-pass filters are designed from low-pass prototype filters having a resistive termination at one end only. The use of parallel-connected band-pass filters designed in this fashion, along with a susceptance-annulling network, is shown to be capable of giving a nearly constant input conductance across the operating band of a multiplexer. A three-channel design example using comb-line band-pass filters was worked out and its input admittance and attenuation characteristics were computed. This design was also constructed and tested. The computer and experimental results demonstrated the validity of the theory.     

A general-purpose computer program for the design of two-dimensional recursive filters — 2DFil

A general-purpose interactive computer program for the design of linear causal shift-invariant two-dimensional recursive filters is presented in terms of its organization and operation. Narrow-band fan filters and circularly symmetric low-pass and high-pass filters for many useful image-processing applications can be designed using this program. The design is by numerical optimization of a guaranteedstable analog transfer function which is derived from a general two-dimensional passive prototype network. Corresponding discrete transfer functions are obtained by the double bilinear transformation. In using the program, selection of one code from a menu of predefined design codes provides the designer with various design features; these include the use of a doubly-terminated network to eliminate erroneous gain spikes, the use of a network particularly suited to circularly symmetric functions, and a facility for designing filters potentially useful for high-speed parallel processing. Design examples of a low-order highly selective fan filter and a circularly symmetric low-pass filter are included.     

Design of microwave filters

A survey of the major techniques used in the design of microwave filters is presented in this paper. It is shown that the basis for much fundamental microwave filter theory lies in the realm of lumped-element filters, which indeed are actually used directly for many applications at microwave frequencies as high as 18 GHz. Many types of microwave filters are discussed with the object of pointing out the most useful references, especially for a newcomer to the field     

Design of Wide-Band (and Narrow-Band) Band-Pass Microwave Filters on the Insertion Loss Basis

A method for design of band-pass microwave filters is described that combines the image and insertion-loss points of view to give an approximate design method having simplicity, but also high precision. This method is applicable for filter designs ranging from narrow to very wide bandwidths (2 to 1 or more). The desired insertion loss characteristic is obtained by use of a lumped-element, Tchebycheff, or maximally flat (or other) low-pass prototype. With the aid of the concept of impedance inverters, the prototype is converted into a cascade of symmetrical (but differing) sections. The image properties of symmetrical sections of the band-pass microwave filter structure are then related to those of corresponding sections of the prototype. Straightforward design equations are given for filters using short-circuited or open-circuited stubs, and also for filters using parallel-coupled lines. Mapping functions are derived that permit accurate prediction of the microwave filter cutoff characteristic from that of the prototype. The responses of a number of filter designs were computed, and a Tchebycheff filter with a 2.2 to 1 band-width was built and tested. The reponses of all of the filter designs were in close agreement with the prescribed characteristics, and the accuracy of the mapping functions was verified.     

A New Class of Distributed Prototype Filters with Applications to Mixed Lumped/Distributed Component Design

The distributed prototype filter consists of a cascade of shunt stubs of equal length alternating with uniform transmission lines, each of twice the stub length. If the stubs are open circuited, they may be replaced by lumped capacitors to synthesize a mixed lumped/distributed (L/D) filter having near optimum Chebyshev or Zolotarev characteristics. The rate of cutoff and the general character of the stopband region is predictable. The use of Zolotarev prototypes enables the impedance level within the filter to be controlled and gives greater selectivity. Designs suitable for either transverse electromagnetic (TEM) line or waveguide low-pass filters are presented. If the stubs are short-circuited, the prototype may be used to design quasi-high-pass or bandpass filters of very large bandwidth. An example is given of an inductive-iris-type filter of approximately 100-percent bandwidth for which previous theories have been unsuitable. The theory is capable of extension to more complicated mixed L/D structures containing both series and shunt elements.     

Tables of Element Values for the Distributed Low-Pass Prototype Filter

An exact general synthesis for the distributed stepped-impedance low-pass prototype filter is presented here. Tables of values of the step impedances of filters having Chebyshev equal-ripple characteristics are given for up to 21 elements over a wide range of bandwidths and ripple levels. The tables are usefuf for the design of short-line low-pass filters, direct-coupled cavity filters, stepped-impedance acoustic or optical filters, impedance transformers, and branched guide directional couplers, as described in the papers of L. Young.     

Filters with Single Transmission Zeros at Real or Imaginary Frequencies

A new unified theory is presented for the synthesis of exactly equiripple low-pass prototypes having: a) one simple pole of attenuation at a real frequency; or b) a single pair of real-axis transmission zeros (giving linear-phase performance). These types of filters may be regarded as representing the least possible degree of complication over the conventional Chebyshev filter, and are usually realized with one extra cross coupling in the structure. It is demonstrated that this gives much improved skirt selectivity in the case of a finite frequency pole, making it a viable intermediate case between the Chebyshev and elliptic function filters, while in the case of real-frequency zeros, very flat group delay over 50 percent of the passband is achieved with minimal cost in insertion loss and skirt rejection. Approximate and exact synthesis techniques are described, including results for the previously neglected odd-degree case. Experimental results demonstrate agreement with theory.     

一种新颖的高阶全极点OTA—C低通滤波器设计方法

本文提出一种高阶全极点OTA-C低通滤波器设计方法.用该方法对二～七阶Butterworth最平坦型低通滤波器进行了设计和SPICE模拟分析。同时证明了所提方法具有理论上严谨、工程上实用的特点。