Digital filter and oversampling analog to digital converter employing the same

• US 5,506,798 A
• Filed: 09/26/1994
• Issued: 04/09/1996
• Est. Priority Date: 12/28/1993
• Status: Expired due to Fees

• Current Assignee: Fujifacom Corporation
• Original Assignee: Fujifacom Corporation
• Inventors: Shimada, Katsuyoshi, Kikuchi, Takeshi
• Primary Examiner(s): Mai, Tan V.
• Application Number:
  US08/312,195
• Time in Patent Office: 561 Days
• Field of Search: 364/724.1, 364/724.12, 364/724.13
• US Class Current: 708/315
• CPC Class Codes: H03H 17/0266 Filter banks
• CPC Class Codes: H03H 17/0294 Variable filters; Programmable filters

Abstract

A digital filter has a cut-off frequency which can be varied by a simple control circuit. The digital filter includes a tap coefficient setting section and a convolution calculation section. The convolution calculation section is constructed so as to repetitively perform the processing of first performing repetitive convolution calculation wherein a same convolution calculation operation is performed once or successively by a plurality of times using same tap coefficients or same input data and then varying the tap coefficient or the input data to allow the repetitive convolution calculation to be repeated subsequently. The digital filter can be applied to an oversampling analog to digital converter.

Claims

1. A digital filter, comprising:

tap coefficient setting means for setting a single set of tap coefficients; and

convolution calculation means for performing convolution calculation using the single set of tap coefficients from said tap coefficient setting means and input data;

said convolution calculation means being constructed, in order to allow variation of the cut-off frequency of said digital filter, to repetitively perform the processing of first performing repetitive convolution calculation wherein a same convolution calculation operation is performed once or successively by a plurality of times using same tap coefficients of the single set of tap coefficients or same input data and then varying the tap coefficient or the input data to allow the repetitive convolution calculation to be repeated.

2. A digital filter as claimed in claim 1, further comprising pointer means for controlling so that elements of the single set of tap coefficients are supplied successively or while being thinned out to said convolution calculation means.

3. A digital filter as claimed in claim 1, wherein said tap coefficient setting means has a single set of tap coefficients set in advance therein with which a selectable lowest cut-off frequency is realized.

4. A digital filter for use with an apparatus which requires correction of a gain error caused by analog to digital conversion, comprising:

tap coefficient setting means for setting a tap coefficient;

convolution calculation means for performing convolution calculation using the tap coefficient from said tap coefficient setting means and input data; and

correction value setting means for setting a correction value with which correction of the gain error is performed;

said convolution calculation means including multiplication means by which gain correction IS o performed using the correction value received from said correction value setting means.

5. A digital filter as claimed in claim 4, wherein said convolution calculation means includes, in addition to said multiplication means which performs multiplication calculation between the tap coefficient from said tap coefficient setting means and the input data, addition means for adding a result of the multiplication by said multiplication means to accumulation information, accumulation means for accumulating a result of the addition by said addition means as the accumulation information, a first selector for selectively outputting the tap coefficient from said tap coefficient setting means or the correction value from said correction value setting means to said multiplication means, and a second selector for supplying a result of the accumulation by said accumulation means to said addition means when said first selector selects the tap coefficient but supplying zero information to said addition means when said first selector selects the correction value.

6. A digital filter, comprising:

a first digital filter section including first tap coefficient setting means for setting a first tap coefficient and first convolution calculation means for performing convolution calculation using the first tap coefficient from said first tap coefficient setting means and input data, said first convolution calculation means being constructed, in order to allow variation of the cut-off frequency of said digital filter, so as to repetitively perform the processing of first performing repetitive convolution calculation wherein a same convolution calculation operation is performed once or successively by a plurality of times using same tap coefficients or same input data and then varying the first tap coefficient or the input data to allow the repetitive convolution calculation to be repeated subsequently; and

a second digital filter section provided at a following stage to said first digital filter section and including second tap coefficient setting means for setting a second tap coefficient, second convolution calculation means for performing convolution calculation using the second tap coefficient from said second tap coefficient setting means and the input data, and correction value setting means for setting a correction value with which correction of a gain error is performed, said second convolution calculation means performing gain correction by means of multiplication means using the correction value received from said correction value setting means.

7. A digital filter, comprising:

tap coefficient setting means for setting a tap coefficient;

convolution calculation means for performing convolution calculation using the tap coefficient from said tap coefficient setting means and input data; and

correction value setting means for setting a correction value with which correction of a gain error is performed;

said convolution calculation means being constructed, in order to allow variation of the cut-off frequency of said digital filter, so as to repetitively perform the processing of first performing repetitive convolution calculation wherein a same convolution calculation operation is performed once or successively by a plurality of times using same tap coefficients or same input data and then varying the tap coefficient or the input data to allow the repetitive convolution calculation to be repeated subsequently;

said convolution calculation means performing gain correction by means of multiplication means using the correction value received from said correction value setting means.

8. An oversampling analog to digital converter employing a digital filter, comprising:

an analog to digital conversion section; and

a decimation filter provided at a following stage to said analog to digital conversion section;

said decimation filter being constructed as a digital filter which includes tap coefficient setting means for setting a single set of tap coefficients and convolution calculation means for performing convolution calculation using the single set of tap coefficients from said tap coefficient setting means and input data, said convolution calculation means being constructed, in order to allow variation of the cut-off frequency of said decimation filter, to repetitively perform the processing of first performing repetitive convolution calculation wherein a same convolution calculation operation is performed once or successively by a plurality of times using same tap coefficients of the single set of tap coefficients or same input data and then varying the tap coefficient or the input data to allow the repetitive convolution calculation to be repeated.

9. An oversampling analog to digital converter employing a digital filter, comprising:

an analog to digital conversion section; and

a decimation filter provided at a following stage to said analog to digital conversion section;

said decimation filter being constructed as a digital filter which includes tap coefficient setting means for setting a tap coefficient, convolution calculation means for performing convolution calculation using the tap coefficient from said tap coefficient setting means and input data, and correction value setting means for setting a correction value with which correction of a gain error caused by analog to digital conversion by said analog to digital conversion section should be performed, said convolution calculation means being constructed so as to perform gain correction by means of multiplication means using the correction value received from said correction value setting means.

10. An oversampling analog to digital converter, comprising:

an analog to digital conversion section; and

a decimation filter provided at a following state to said analog to digital conversion section;

said decimation filter including a plurality of decimation filter sections;

a first one of said decimation filter sections including first tap coefficient setting means for setting a first tap coefficient and first convolution calculation means for performing convolution calculation using the first tap coefficient from said first tap coefficient setting means and input data, said first convolution calculation means being constructed, in order to allow variation of the cut-off frequency of said decimation filter, to repetitively perform the processing of first performing repetitive convolution calculation wherein a same convolution calculation operation is performed once or successively by a plurality of times using same tap coefficients or same input data and then varying the first tap coefficient or the input data to allow the repetitive convolution calculation to be repeated subsequently; and

a second one of filter sections said decimation which is provided at a to said first following stage decimation filter section including second tap coefficient setting means for setting a second tap coefficient, second convolution calculation means for performing convolution calculation using the second tap coefficient from said second tap coefficient setting means and the input data, and correction value setting means for setting a correction value with which correction of a gain error caused by analog to digital conversion by said analog to digital conversion section is performed, said second convolution calculation means performing gain correction by means of multiplication means using the correction value received from said correction value setting means.

11. An oversampling analog to digital converter employing a digital filter, comprising:

an analog to digital conversion section; and

a decimation filter provided at a following stage to said analog to digital conversion section;

said decimation filter being constructed as a digital filter which includes tap coefficient setting means for setting a tap coefficient, convolution calculation means for performing convolution calculation using the tap coefficient from said tap coefficient setting means and input data, and correction value setting means for setting a correction value with which correction of a gain error is performed, said convolution calculation means being constructed, in order to allow variation of the cut-off frequency of said decimation filter, to repetitively perform the processing of first performing repetitive convolution calculation wherein a same convolution calculation operation is performed once or successively by a plurality of times using same tap coefficients or same input data and then varying the first tap coefficient or the input data to allow the repetitive convolution calculation to be repeated subsequently and to perform gain correction by means of multiplication means using the correction value received from said correction value setting means.