Sampling frequency converter for converting a lower sampling frequency to a higher sampling frequency and a method therefor

DETAILED DESCRIPTION An object of the present invention is to provide a low-cost sampling frequency converter having a reduced number of parts and a simple circuit configuration.
Another object of the present invention is to achieve a converter for converting a low sampling frequency to a high sampling frequency in a simple circuit configuration and at a low cost.
Still another object of the present invention is to provide a method for converting a sampling frequency.
The sampling frequency converter according to the present invention comprises time axis compression means receiving sequential digital data Q.
sub.
i formed with a sampling frequency f.
sub.
m for adding (n-m) meaningless dummy data, to the received data every time the number of the received sequential digital data Q.
sub.
i becomes m and reading out the same at the rate of a frequency f.
sub.
n (n>m, f.
sub.
m :f.
sub.
n =m:n) and interpolating means, which operate at the rate of the frequency f.
sub.
n, receiving outputs from the time axis compression means for performing predetermined interpolating filter processing.
The interpolating means comprises means for storing predetermined n kinds of tap coefficients and means for sequentially reading out different kind of tap coefficients from the storing means, and one transversal type digital filter for filtering the supplied sequential data including dummy data based on the tap coefficients.
The tap coefficients are set to nullify the added dummy data.
In the above described structure, data having the sampling frequency f.
sub.
m is converted to data having the sampling frequency f.
sub.
n by adding (n-m) dummy data thereto.
The dummy data are periodically applied to the filter.
However, the dummy data are nullified by suitably selecting tap coefficients.
In addition, n kinds of tap coefficients are sequentially and circulatingly switched at the rate of the frequency f.
sub.
n (cycle T=1/f.
sub.
n).
Thus, conversion from the sampling frequency f.
sub.
m to the sampling frequency f.
sub.
n can be made by a single digital filter