Network synthesis was originally intended to produce filters ofthe kind formerly described as "wave filters" but now usually justcalled filters. That is, filters whose purpose is to pass waves ofcertain while rejecting waves of other wavelengths. Network synthesisstarts out with a specification for the transfer function of thefilter, H(s), as a function of , s. This is used togenerate an expression for the input impedance of the filter (thedriving point impedance) which then, by a process of or expansions results inthe required values of the filter components. In a digitalimpementation of a filter, H(s) can be implemented directly.
The method can be viewed as the inverse problem of . Network analysis starts with a network and byapplying the various electric circuit theorems predicts theresponse of the network. Network synthesis on the other hand,starts with a desired response and its methods produce a networkthat outputs, or approximates to, that response.
Cauer filters have equal maximum ripple in the passband and thestopband. The Cauer filter has a faster transition from thepassband to the stopband than any other class of network synthesisfilter. The term Cauer filter can be used interchangeably withelliptical filter, but the general case of elliptical filters canhave unequal ripples in the passband and stopband. An ellipticalfilter in the limit of zero ripple in the passband is identical toa Chebyshev Type 1 filter. An elliptical filter in the limit ofzero ripple in the stopband is identical to a Chebyshev Type 2filter. An elliptical filter in the limit of zero ripple in bothpassbands is identical to a Butterworth filter. The filter is namedafter and the transfer function is based on .
In general, the sections of a network synthesis filter areidentical topology (usually the simplest ladder type) but differentcomponent values are used in each section. By contrast, thestructure of an image filter has identical values at each section -this is a consequence of the infinite chain approach - but may varythe topology from section to section to achieve various desirablecharacteristics. Both methods make use of low-pass followed by frequency transformations and impedancescaling to arrive at the final desired filter.
The driving point is a mathematicalrepresentation of the input impedance of a filter in the frequencydomain using one of a number of notations such as (s-domain) or (). Treating it as a one-portnetwork, the expression is expanded using or expansions. Theresulting expansion is transformed into a network (usually a laddernetwork) of electrical elements. Taking an output from the end ofthis network, so realised, will transform it into a filter with the desired transfer function.
The advantages of the method are best understood by comparing itto the methodology that was used before it, the .The image method considers the characteristics of an individual in an infinitechain () of identical sections. The by this method suffer frominnaccuracies due to the theoretical termination impedance, the , not generally being equal to the actual terminationimpedance. This is not the case with network synthesis filters, theterminations are included in the design from the start. The imagemethod also requires a certain amount of experience on the part ofthe designer. The designer must first decide how many sections andof what type should be used, and then after calculation, willobtain the transfer function of the filter. This may not be what isrequired and there can be a number of iterations. The networksynthesis method, on the other hand, starts out with the requiredfunction and outputs the sections needed to build the correspondingfilter.
Description :Market_Desc: · University of PuneCourse Code 304183, (Course Name: Network Synthesis and Filter Design): BE (Electronics and Telecommunication)Course Code 304203, (Course Name: Network Synthesis and ...
Network synthesis is a method of designing .It has produced several important classes of filter including the, the and the . It was originallyintended to be applied to the design of passive linear but its results can alsobe applied to implementations in and .The essence of the method is to obtain the component values of thefilter from a given mathematical ratio expression representing thedesired transfer function.
Her main areas of interest include Networks and Lines, Network Synthesis and Filter Design, Digital Signal Processing and Electromagnetic Engineering.
Kaduskar has also authored Network Fundamentals and Analysis, Principles of Electromagnetics and Network Synthesis and Filter Design (with Wiley India).