Naslov
Projektiranje aktivnih RC filtara postupkom skaliranja impedancija
(Active RC filter design using impedance tapering)

Autori
Jurišić, Dražen

Vrsta, podvrsta i kategorija rada
Ocjenski radovi, doktorska disertacija

Fakultet
Fakultet elektrotehnike i računarstva

Mjesto
Zagreb

Datum
17.04

Godina
2002

Stranica
267

Mentor
Mijat, Neven

Ključne riječi
low-sensitivity; low-power; low-noise; allpole filters; active-RC filters; impedance tapering

Sažetak
The design procedure of low-sensitivity, low-pass (LP) 2nd- and 3rd-order class-4 Sallen and Key active resistance-capacitance (RC) allpole filters, using impedance tapering, has already been published. There a ladder structure in the positive feedback loop of an operational amplifier was used. In this work, desensitisation using impedance tapering is applied to LP, HP and BP filters up to 6th-order, with single operational amplifier. Realizability constraints are also given. It was shown that the filters up to 3rd-order are analytically solvable, while the higher-than-3rd-order filters can be solved only numerically. It was shown that HP filters have dual properties to LP filters with respect to sensitivity. Among various topologies of BP filters, the best topology is proposed. The sensitivity of a filter's transfer function to component tolerances is examined using Schoeffler's sensitivity measure as a basis for comparison. Monte Carlo runs are performed as a double-check. The improvement comes free of charge ; component count and topology remain unchanged, whereas the component values, selected for impedance tapering, account for the considerable decrease in sensitivities to component tolerances for the LP as well as for the HP and BP filters. The design of even-order single-amplifier band-pass (BP) active-RC filters using a modified low-pass to band-pass (LP-BP) frequency transformation, applied to a half-order low-pass (LP) filter as a prototype, is also presented. It is shown that a BP filter can be realized by substitution of resistors and capacitors of the ladder in the low-pass prototype filter, by serial and parallel RC circuits in the resulting BP structure. Such a substitution results from a so-called, "lossy" LP-BP transformation. The design procedure is simple, and the closed-form design equations, starting from the specifications of the BP filter, are presented. A complete step-by-step design procedure is verified using filter examples, and double-checked using PSPICE. Low sensitivity performances are achieved by applying the "impedance-tapering" design technique. The influence of the so-called "design-frequency" parameter on the sensitivity and noise performances is investigated in detail. It was shown that, by an appropriate choice of the design frequency value, the filter's sensitivity and noise could be significantly reduced. Furthermore, desensitisation using "impedance-tapering" is applied to other filter types, for example to class-3 circuits with negative feedback. The class-3 circuit is complementary to the class-4 circuit.

Izvorni jezik
Engleski

Znanstvena područja
Elektrotehnika

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