Coded data generation or conversion – Sample and hold – Having variable sampling rate
Patent
1996-07-19
1998-01-13
Williams, Howard L.
Coded data generation or conversion
Sample and hold
Having variable sampling rate
H03M 100
Patent
active
057084327
ABSTRACT:
A digitizing system coherently samples an input signal of frequency F.sub.t and generates an output data sequence representing magnitudes of N successive samples. The digitizing system generates a timing signal by frequency dividing a clock signal of frequency F.sub.MCLK by an integer factor K and supplies the timing signal to a digitizer. The digitizer coherently samples the input signal N times over M cycles of input signal to produce an N-term data sequence representing one cycle of the input signal. The timing signal frequency sets the digitizer sampling rate. The digitizing system includes a computer programmed to execute an algorithm for finding an appropriate value for K so that the system substantially achieves coherent sampling of the input signal despite limitations in allowable ranges of K, M and N. The algorithm searches a Farey series to locate terms of the form P/Q from which it may derive candidate values of K (K=Q.sub.i *J), M (M=P*J) and N (N=Q.sub.i), wherein P and Q are relatively prime integers, J is an integer greater than 0 and Q.sub.i is an integer factor of Q. The algorithm locates the particular Farey series term most closely approximating the ratio F.sub.t /F.sub.MCLK for which candidate values of K, M and N fall within their allowable ranges. The digitizing system then frequency divides the master clock signal by that candidate value of K.
REFERENCES:
patent: 5589763 (1996-12-01), Burns
Coleman, Brendan, Pat Meehan, John Reidy and Pat Weeks, "Coherent Sampling Helps When Specifying DSP A/D Converters," EDN Oct. 15, 1987, pp. 145-152.
Mielke, Frequency Domain Testing of ADCs, IEEE Design & Test of Computers, vo. 13, No. 1 pp. 64-69, Spring 1996.
Reynolds David Dean
Slizynski Roman Aureli
Credence Systems Corporation
Williams Howard L.
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