Controlling the bandwidth of an analog filter

Details Controlling the bandwidth of an analog filter Controlling the bandwidth of an analog filter

2011-05-03

2011-05-03

Le, Lana N (Department: 2614)

Telecommunications

Receiver or analog modulated signal frequency converter

Noise or interference elimination

C455S296000, C455S334000

Reexamination Certificate

active

07937058

ABSTRACT:
A digital tuning system (250) for changing a cutoff frequency of an analog filter (132) includes digital synthesizers (292and294) for producing a two-tone calibration signal (196) applied to an input of the filter after a quality factor of the filter is increased. The filter includes at least one R/C circuit with two resistors (304and306) for changing the quality factor and arrays (308and310) of capacitors for changing the cutoff frequency. The amplitude of the magnitude responses (409and411) of the filter to each tone (405and407) is measured by a two discrete Fourier transform single-frequency bin power detection circuits (253and254) while the filter is sequenced through a plurality of capacitance settings. An optimal capacitance for the R/C circuit is selected by comparing, to a pre-selected value, a difference between the responses of the filter to each tone, for each capacitance setting.

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