Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – Unwanted signal suppression
Reexamination Certificate
2000-05-19
2001-07-17
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
06262624
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to electrical signal filters and, more particularly, to a temperature and process compensation circuit for an electrical signal filter.
BACKGROUND ART
There is an ever present demand for analog data signal filters. Many signal filters, such as those constructed with a differential operational amplifier, do not have stable gain-bandwidth products, or transconductance (Gm/C). The Gm/C of a signal filter varies with fluctuations in temperature and process characteristics. Process characteristics are physical and/or chemical properties resulting from the manufacturing process. If the Gm/C of the filter is allowed to fluctuate, the filter's transfer characteristic will become erratic and may drift outside acceptable operating parameters.
Some techniques for adjusting the Gm/C of filters are known. However, most of these techniques lack sufficient sensitivity to invoke a fast and accurate response to Gm/C changes of the filter. Therefore, there exists a need in the art for circuits, and associated methods, for regulating the Gm/C of data signal filters.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, the present invention is a filter compensation circuit. The filter compensating circuit having a sine wave generator, the sine wave generator generating a sine wave; a filter coupled to the sine wave generator and delaying a phase of the sine wave; a filter sine to square wave converter coupled to the filter and converting the delayed sine wave into a filter square wave signal; a reference sine to square wave converter coupled to the sine wave generator and converting the sine wave into a reference square wave signal; a comparator coupled to the filter sine to square wave converter and to the reference sine to square wave converter, the comparator comparing a phase relationship between the filter square wave signal and the reference square wave filter; and a correction signal generator coupled to the comparator, the correction signal generator generating a correction signal based on the comparison of the phase relationship, the correction signal being fed back to the filter to adjust a transconductance of the filter.
According to another aspect of the invention, the invention is a data filter for conditioning a data signal. The data filter has a compensation circuit, the compensation circuit having a proxy filter, a comparator and a compensation signal generator, the proxy filter delaying a reference signal, the comparator comparing a phase difference between the reference signal and the delayed reference signal and the compensation signal generator generating a correction signal feedback to the data filter and the proxy filter to adjust the transconductance of the data filter and the proxy filter.
According to another aspect of the invention, the invention is a method of adjusting Ai transconductance of a data filter. The method having the steps of generating a sine wave; delaying the sine wave with a proxy filter; converting the delayed sine wave to a filtered square wave signal; converting the sine wave into a reference square wave signal; comparing a phase relationship between the filter square wave signal and the reference square wave signal; and generating a correction signal based on the comparison of the phase relationship and feeding the correction signal back to the data filter and the proxy filter to adjust transconductance of the filters.
According to another aspect of the invention, the invention is a method of adjusting a data filter, the data filter used to condition a data signal. The method having the steps of: providing a proxy filter; delaying a reference signal with the proxy filter; comparing a phase difference between the reference signal and the delayed reference signal; generating a correction signal based on the phase difference; and adjusting the transconductance of the data filter and the proxy filter with the correction signal.
REFERENCES:
patent: 5192884 (1993-03-01), Kusano
patent: 5200716 (1993-04-01), Amano
patent: 5912589 (1999-06-01), Khoury et al.
patent: 5963084 (1999-10-01), Eschauzier
patent: 6107870 (2000-08-01), Kawano
Advanced Micro Devices , Inc.
Le Dinh T.
Renner, Otto, Boisselle & Otto, LLP
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