Jitter-corrected spectrum analyzer
AssigneeCredence Systems Corporation
InventorsJonathan M. Shaw, John B. Shaw
Life of this patent
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Abstract
An analog signal is digitized by an analog-to-digital (A/D) converter clocked by a periodically jittery clock signal. Elements of the digital data sequence (vector) output of the A/D converter are sorted into a set of smaller vectors according to clock signal jitter phase and each of the smaller vectors is then separately subjected to Fourier transform and time shift functions. The resulting vectors are then processed to produce an output vector representing the frequency spectrum of the analog signal.
Claims11
A method for processing an analog signal to produce an output vector representing a frequency spectrum of the analog signal, the method comprising the steps of:
- a. generating a periodically jittery clock signal of average period T seconds having N edges, wherein each Kth generated edge and every Mth generated edge thereafter has a similar timing error of JITTERK seconds, wherein K is an integer 0≦K<M, M and N/M are integers greater than 1, and wherein JITTERK is other than constant for all values of K;
- b. digitizing the analog signal in response to each of the N clock signal edges to produce a vector (A) having N elements AJ, for all integer values of J, 0≦J<N;
- c. arranging all elements AJ of vector A into M vectors BK, for all integer values of K, 0≦K<M, such that each Kth vector BK includes a Kth element AK of vector A and every Mth element of vector A thereafter;
- d. separately subjecting each vector BK to a Fourier transform function to produce a corresponding one of a set of M vectors CK, for all integer values of K, 0≦K<M, and
- e. evaluating a correction function having as parameters JITTERK and vectors CK, for all integer values of K, 0≦K<M, to generate the output vector representing the frequency spectrum of the analog signal.
Dependencies are inferred from the claim text.