Polyphase buffer for rate-conversion
Provided are, among other things, systems, apparatuses methods and techniques for changing the sampling rate of a discrete-time signal. One such apparatus includes a plurality of parallel processing paths, with each path comprising multiple storage banks and multiplexing elements that operate at a subsampling rate.
1. An apparatus for converting a discrete-time input sequence at one sampling rate, into a discrete-time output sequence at a different sampling rate, comprising:
a plurality of multi-bit input lines for accepting, in a parallel format and at an input sampling rate, different multi-bit samples of an input signal;
a plurality of data storage banks, each having an input that is coupled to one of said input lines, and also having plural outputs;
a plurality of block selection elements, each having plural inputs that are coupled to outputs of said data storage banks and also having an output;
a plurality of bank selection elements, each having plural inputs that are coupled to outputs of said block selection elements and also having an output; and
a plurality of output lines coupled to the outputs said bank selection elements and providing, in parallel format and at an output sampling rate, the multi-bit samples of an output signal,
wherein each of said data storage banks includes plural buffer cells which store samples received on current and prior intervals of the input sampling rate and provide independent access to said stored samples,
wherein each of said block selection elements determines, according to a first configuration parameter, whether a particular output sample reflects a current or a prior interval of said input sampling rate,
wherein each of said bank selection elements determines, according to a second configuration parameter, which of said data storage banks is coupled to which of said output lines, and
wherein at least one of: (1) input samples are periodically repeated to increase said output sampling rate relative to said input sampling rate, or (2) input samples are periodically skipped to reduce said output sampling rate relative to the input sampling rate, based on dynamic configuration of the block and bank selection elements.
2. An apparatus according to claim 1 , wherein each of said block selection elements and each of said bank selection elements is an independent functional component.
3. An apparatus according to claim 1 , wherein at least two of said block selection elements are integrated into a single functional component.
4. An apparatus according to claim 1 , wherein at least two of said bank selection elements are integrated into a single functional component.
5. An apparatus according to claim 1 , wherein at least one block selection element and at least one bank selection element are integrated into a single functional component.
6. An apparatus according to claim 1 , wherein the first configuration parameter for at least one block selection element is generated within said apparatus.
7. An apparatus according to claim 6 , wherein the first configuration parameter for at least one block selection element is generated from the second configuration parameter for at least one bank selection element.
8. An apparatus according to claim 1 , wherein the first configuration parameter for at least one block selection element is provided by an external input.
9. An apparatus according to claim 1 , wherein the second configuration parameter for at least one bank selection element is generated within said apparatus.
10. An apparatus according to claim 1 , wherein the second configuration parameter for at least one bank selection element is provided by an external input.
11. An apparatus according to claim 1 , wherein the ratio of said input sampling rate to the ratio of said output sampling rate is a rational number.
12. An apparatus according to claim 11 , wherein said ratio is a rational number that can be expressed with a denominator that is an integer multiple of a total number of said output lines.
13. An apparatus according to claim 1 , wherein said data storage banks provide access to samples received on at least two prior intervals of said input sampling rate.
14. An apparatus according to claim 1 , wherein said data storage banks provide access to samples received on at least three prior intervals of said input sampling rate.
15. An apparatus according to claim 1 , wherein at least one of said data storage banks incorporates at least one buffer cell for inhibiting simultaneous write and read access to a same storage location.
16. An apparatus according to claim 15 , wherein at least one of said at least one buffer cell is implemented as an elastic buffer.
17. An apparatus according to claim 15 , wherein at least one of said at least one buffer cell is implemented as a first-in first-out memory.