Tuning filters having transconductor cells

Details Tuning filters having transconductor cells Tuning filters having transconductor cells

2006-11-14

2006-11-14

Le, Dinh T. (Department: 2816)

Miscellaneous active electrical nonlinear devices, circuits, and

Specific identifiable device, circuit, or system

Unwanted signal suppression

C327S552000

Reexamination Certificate

active

07135915

ABSTRACT:
In one embodiment, a filter with a main signal path having one or more biquadratic filter sections is tuned using a tuning circuit based on a biquadratic filter that can be configured to oscillate at the filter's cutoff frequency. In one application, a tuning circuit outside of the main signal path is used to tune each biquadratic filter section of the main signal path. In another application, each filter section along the main signal path has a biquadratic filter that can oscillate and corresponding tuning elements that enable the filter section to tune itself. According to certain embodiments of the present invention, a biquadratic filter is made to oscillate by applying a common-mode voltage signal to the inputs of the filter's third transconductor cell to make the cell's transconductance go to zero. The invention may also be implemented in the context of filters having ladder structures in their main signal path.

REFERENCES:
patent: 5625317 (1997-04-01), Deveirman
patent: 5729230 (1998-03-01), Jensen et al.
“A 1.92GHz Image-Reject Front-End with Automatic Tuning in a 0.15μm CMOS Technology”, by Mustafa H. Koroglu et al., Sep. 2003, 2003 IEEE International Solid-State Circuits Conference, Paper 15.2, 10 pages.
“Integrated Continuous-Time Filters” Principles, Design, and Applications, by Y.P. Tsividis and J.O. Voorman, Reprint vol. IEEE Circuits and Systems Society, New York, 1993, pp. 282-283.

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