Frequency filters are widely used in communicationsudsystems today. Historically they have been constructedudfrom inductors, capacitors and resistors and suchudcircuits are well understood. However they suffer fromudthe disadvantages of large physical size and high cost.udA monolithic realisation of frequency filters wouldudgreatly reduce the cost of systems in which filters areudused and would increase their reliability in hostileudenvironments.udIn this thesis a novel approach to the realisationudof sampled-data monolithic frequency filters isudpresented. The method is based on the use of sampledudanalogue signals and is related to the wave digitaludfilter in its design techniques. The eventualudmonolithic realisation in NMOS technology is in theudform of a switched-capacitor structure.udWhile the main body of the research is concernedudwith the implementation of filters which are based onuddistributed prototype networks, some work onudintegratable filters which are based on lumped elementudprototypes is also presented. For either type theuddesign model is exact and the resulting filter isudoptimally insensitive to parameter variations. Theudfilters are implemented using a technique which ensuresudthat performance is limited by capacitor ratios, whichudare moderate as compared with alternative publishedudapproaches.udA prototype integrated circuit suitable for use inudthe audio frequency band has been designed touddemonstrate the validity of the approach for theudfilters based on distributed prototypes and contains.udfilters of third, fifth and seventh order. Results areudpresented for these filters and also for a pseudobandpassudfilter which uses the periodicity of theudprototype distributed network. The seventh orderudfilter had a cut-off frequency of one eighth of theudfilter sample rate and achieved a stop band attenuationudof well over 70dBudAn implemetation of a wave filter based on a lumpedudelement prototype is also described and results areudpresented. This work is expected to form the basis ofuda novel implemetation of bandpass filters.udThe responses achieved for all the wave filtersudconstructed show excellent agreement with the theory.
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