The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 14, 2006
Filed:
Jan. 13, 2004
James A. Bailey, Snowflake, AZ (US);
Robert Kuo-wei Chen, North Andover, MA (US);
James A. Bailey, Snowflake, AZ (US);
Robert Kuo-Wei Chen, North Andover, MA (US);
Agere Systems Inc., Allentown, PA (US);
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.