Tunable resonator for use in active-RC continuous-time filters

Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Unwanted signal suppression

Reexamination Certificate

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C327S336000

Reexamination Certificate

active

11203579

ABSTRACT:
An integrated circuit (IC) resonator in which resonator parameters potentially affected by IC fabrication processes are correctable after fabrication. Resonance frequency tuning is effected by forming each feedback capacitor in a pair of integrator circuits to include a variable capacitance device, such as a varactor diode. A tuning signal is applied to the varactor diode to adjust the total capacitance value and, therefore, the resonance frequency. Similarly, the quality (Q) factor of the resonator is adjusted by providing a variable capacitance in an RC (resistance-capacitance) network coupling the output of one of the integrator circuits to the input of the other. The variable capacitance in the RC network permits adjustment of phase in the event that the integrator circuits do not provide a desired 180° total phase shift.

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European Search Report for corresponding EP 06 01 6324, completed Apr. 4, 2007.
Yamazaki A et al: “An Active-RC Reconfigurable Lowpass-Polyphase Tow-Thomas Biquad Filter”; Circuits and Systems, 2004. MWSCAS '04. The 2004 47thMidwest Symposium on Hiroshima, Japan Jul. 25-28, 2004, Piscataway, NJ, USA, IEEE, vol. 1, Jul. 25, 2004, pp. 157-160, XP010738961 ISBN: 0-7803-8346-X; Figs. 2, 6; Chapter 2-3.
Jurgen A E P Van Engelen et al: “A Sixth-Order Continuous-Time Bandpass Sigma-Delta Modulator for Digital Radio IF”; IEEE Journal of Solid-State Circuits, IEEE Service Center, Piscataway, NJ, US, vol. 34, No. 12, Dec. 1999 XP011061155, ISSN: 0018-9200; Fig. 6; Chapter VI.

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