Programmable sample rate conversion engine for wideband systems
View Patent ↗A programmable hardware architecture and design methodology for the implementation of a sample rate conversion engine is presented. The conversion engine supports scalable filter taps and can be tuned to a range of interpolation and decimation requirements. The conversion engine can be used effectively in wideband systems to efficiently extract and process digital sequences with protocol specific sampling rate requirements. The conversion engine can also be used as a hardware accelerator for software defined radios and communication systems that require adaptive sampling rates.
1. A sample rate conversion engine for upconversion, filtering with a set of filtering coefficients applied to delayed samples and down conversion comprising:
a multiplier accumulator unit;
a sample delay line;
a bank of coefficient registers, each containing a reduced set of the set of filtering coefficients to be applied to input samples for each of successive outputs; and
control logic which for each of the successive outputs selects a reduced set of filtering coefficients from the bank of coefficient registers and a reduced set of samples from the sample delay line to be applied to the multiplier accumulator unit.
2. The sample rare conversion engine of claim 1 , wherein the reduced set of the set of filtering co-efficients is selected to include only filtering co-efficients to be applied to non-zero samples.
3. The sample raw conversion engine of claim 2 , wherein the reduced set of input samples are selected to only compute output samples.
4. The sample rate conversion engine of claim 1 , wherein the bank of coefficient registers is programmable.
5. The sample rate conversion engine of claim 1 , wherein a conversion rate is variable.
6. The sample rate conversion engine of claim 5 , wherein the conversion rate is varied by modifying the reduced sets of filtering coefficients stored in the bank of coefficient registers.
7. The sample rate conversion engine of claim 1 , wherein the number of reduced sets of filtering coefficients stored in the bank of coefficient register is dependent on a number of interpolated zero samples.
8. The sample rate conversion engine of claim 1 , wherein the number of reduced sets of samples is dependent on the output sampling rate.
9. The sample rare conversion engine of claim 1 , wherein a number of multipliers in the multiplier accumulator unit is fixed.
10. The sample rate conversion engine of claim 1 , wherein the conversion ratio is P/Q, the number of multipliers is N and the number of sets of filtering coefficients is P, to compute successive Q output samples one of the sets of filtering coefficients is applied to each of Q sets of input samples in the multiplier accumulator unit.
11. The sample rate conversion engine claim 1 , wherein the conversion ratio is P/Q, the number of multipliers is N, the reduce set of the set of filtering coefficients stored in the bank is h[rP+nQ (mod P)] and a reduced set of input samples is x(nQ
P)−r] and a successive output y[n] is the product of the reduced set of filtering coefficients and the reduced set of input samples for r=0 to N−1.
12. A method of up converting, filtering with a set of filtering coefficients applied to delayed samples and down converting comprising
storing reduced sets of the set of filtering coefficients to be applied to input samples for each of successive outputs within a programmable bank of coefficient registers; and
for each of the successive outputs, selecting a reduced set of filtering coefficients and a reduced set of samples from a sample delay line to be applied to a multiplier accumulator unit.
13. The method of claim 12 , wherein a conversion rate is variable.
14. The method of claim 13 , wherein the conversion rate is varied by modifying the reduced sets of filtering coefficients stored in the bunk of coefficient registers.
15. The method of claim 12 , wherein the number of reduced sets of filtering coefficients stored in the bank of coefficient register is dependent on a number of interpolated zero samples.
16. The method of claim 12 , wherein the number of reduced sets of samples is dependent on the output sampling rate.
17. The method of claim 12 , wherein a number of multipliers in the multiplier accumulator unit is fixed.
18. The method of claim 12 , wherein the conversion ratio is P/Q, the number of multipliers is N and the number of sets of filtering coefficients is P, to compute successive Q output samples one of the sets of filtering coefficients is applied to each of Q sets of input samples in the multiplier accumulator unit.
19. The method of claim 12 , wherein the conversion ratio is P/Q, the number of multipliers is N, the reduced set of filtering coefficients is h[rP+nQ (mod P) and a reduced set of input samples is x(nQ/P)−r] and a successive output y[n] is the product of the reduced set of filtering coefficients and the reduced set of input samples for r=0 to N−1.
20. A sample rate conversion engine for upconversion, filtering with a set of filtering coefficients applied to delayed samples and down conversion comprising:
means for storing; reduced sets of the set of filtering coefficients to be applied to input samples for each of successive outputs within a programmable bank of coefficient registers; and
for each of the successive outputs, means for selecting a reduced set of filtering coefficients and a reduced set of samples from sample delay line to be applied to a multiplier accumulator unit.