Pulse or digital communications – Receivers – Interference or noise reduction
Reexamination Certificate
2006-07-04
2006-07-04
Luther, William (Department: 2616)
Pulse or digital communications
Receivers
Interference or noise reduction
C708S315000, C708S420000
Reexamination Certificate
active
07072429
ABSTRACT:
A first series of filter coefficients stored in a memory itself corresponds to a given filter characteristic such as a given high cutoff frequency. A second series of filter coefficients is generated by performing an interpolation process on the first series of filter coefficients. At that time, the contents, such as interpolation coefficients, of the interpolation process are varied in correspondence to a desired filter characteristic to be achieved, so that the interpolation process generates a second series of filter coefficients according to an impulse response characteristic that is obtained as a consequence of expanding or compressing, in a time-axis direction, an impulse response characteristic represented by the given first series of the filter coefficients. Thus, by the interpolation process, there is produced such a second series of filter coefficients that achieves a different filter characteristic (e.g., different high cutoff frequency). Where the sampling frequency of a time series of digital signals is to be changed from a given first frequency to a second frequency, an aliasing noise frequency may vary depending on a value of the first or second sampling frequency, in which case it is necessary to vary the cutoff frequency of a filter for eliminating the aliasing noise. However, by performing the interpolation process in the above-noted manner, the filter characteristic for eliminating the aliasing noise can be varied as desired.
REFERENCES:
patent: 5250748 (1993-10-01), Suzuki
patent: 5365468 (1994-11-01), Kakubo et al.
patent: 5451944 (1995-09-01), Sogo
Luther William
Morrison & Foerster
Pham Chi H.
Yamaha Corporation
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