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The design of high frequency and ultra-narrow-band switched-capacitor filters

Betts, Andrew Keith; (1991) The design of high frequency and ultra-narrow-band switched-capacitor filters. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

This thesis is concerned with the design of Switched-Capacitor (SC) circuits for applications in the MHz range, and for applications requiring bandpass filters with relative bandwidths of much less than 1% (ie. Q100). Both of these design goals are presently beyond the capability of standard, commercial SC circuits, which all use CMOS processes. In the first case, the limitations of the CMOS FET's make it extremely difficult to design circuits with sufficiently small settling times for accurate processing of signals in the MHz range. In the second, large capacitor spreads and high sensitivity to nonideal circuit phenomena make it impractical to build conventionally designed filters with relative bandwidths less than about 1%. The high-frequency goal has been approached using GaAs MESFET technology, combined with new circuit design and optimisation techniques. Novel integrator circuits with low sensitivity to amplifier gain and immunity to amplifier input offset are presented (these phenomena are far more significant in GaAs than Si technologies). The circuits are used in the design of a demonstrator GaAs SC filter, which has been carefully optimised using automated symbolic analysis techniques. In the work on narrow-band filters, the limitations of advanced multipath SC filter architectures are analysed using Monte-Carlo techniques based on a high-level abstraction of the filter architecture. This analysis highlights the large influence of unwanted 'mirror components' on filter responses, resulting from the mismatch of passband centre frequencies of the individual filters in the multi-path system. To alleviate these problems, a new 'N*M' multi-path architecture is proposed, which uses 'pseudo-N-path' techniques to advantage. Finally, novel pseudo-N-path circuits with very low sensitivity to amplifier gain are presented.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: The design of high frequency and ultra-narrow-band switched-capacitor filters
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
Keywords: Applied sciences; Bandpass filters
URI: https://discovery.ucl.ac.uk/id/eprint/10113093
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