Method and apparatus for computing interpolation factors in sample rate conversion systems
AssigneeTeradyne, Inc.
InventorsDaniel A. Rosenthal, Corey A. Nazarian
Life of this patent
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Abstract
The invention allows the interpolation factor, a critical parameter in sample rate conversion systems, to be computed in a real-time system where there is a complex relationship between a DSP clock and the data clocks. Typically, two or three of the clocks in such a system will have simple relationships (such as CLOCK1=2*CLOCK2). This relationship leads to degenerate cases where, in fact, there are only one or two clocks to consider rather than three. Furthermore, the invention allows for input data rates that are higher than the DSP clock rate. The invention also provides for an arbitrary time delay to be applied to the output signal.
Claims21
A method for rate-converting sampled data comprising:
- receiving input data sampled according to an input sample clock;
- receiving a value indicative of an output sample clock differing from the input sample clock by a non-integer value;
- determining respective relationships between each of the input and output sample clocks and a processor clock, wherein each of the input and output sample clocks are independent from the processor clock;
- determining an interpolation factor as a function of the input sample clock, the output sample clock, and the determined relationships between each of the input and output sample clocks and the processor clock;
- and
- generating output data as a function of the input data and the interpolation factor, wherein the output data corresponds to the input data sampled according to the output sample clock, thereby rate converting the input data from the input sample clock to the output sample clock.
An apparatus for converting sampled data from a first rate to a second rate comprising:
- a rate converter receiving input data sampled according to an input sample clock and configured to produce output data indicative of the input data sampled according to an output sample clock, the rate converter operating at a processing clock rate that is independent from either of the input sample clock and the output sample clock;
- an accumulator receiving the processing clock and configured to monitor a sate of the processor clock and to determine respective relationships of each of the input sample clock and the output sample clock to the processor clock;
- and
- an interpolation factor circuit in communication with the accumulator and the rate converter, the interpolation factor circuit receiving the respective relationships of each of the input sample clock and the output sample clock to the processor clock and configured to calculate an interpolation factor having at least an upper fractional portion and a lower fractional portion, the interpolation factor calculated as a function of the input sample clock, the output sample clock, and the processor clock, the rate converter configured to convert the input data to the output data as a function of the interpolation factor.
An apparatus for converting sampled data from a first rate to a second rate comprising:
- means for receiving input data sampled according to an input sample clock;
- means for receiving a value indicative of an output sample clock differing from the input sample clock by a non-integer value;
- means for determining respective relationships between each of the input and output sample clocks and a processor clock, wherein each of the input and output sample clocks are independent from the processor clock;
- means for determining an interpolation factor as a function of the input sample clock, the output sample clock, and the determined relationships between each of the input and output sample clocks and the processor clock;
- and
- means for generating output data as a function of the input data and the interpolation factor, wherein the output data corresponds to the input data sampled according to the output sample clock, thereby rate converting the input data from the input sample clock to the output sample clock.
Dependencies are inferred from the claim text.