Second-Order Polynomial, Interpolation-Based, Sampling Rate Converter and Method and Transmitters Employing the Same

• US 20080309524A1
• Filed: 05/15/2008
• Published: 12/18/2008
• Est. Priority Date: 06/18/2007
• Status: Abandoned Application

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Staszewski, Robert B., Waheed, Khurram, Syllaios, Ioannis L.
• Application Number:
  US12/121,090
• Publication Number:
  US 20080309524A1
• Time in Patent Office: Days
• US Class Current: 341/61
• CPC Class Codes: H03H 17/028 Polynomial filters
• CPC Class Codes: H03H 17/0685 the ratio being rational

Abstract

A sampling rate converter, a method of performing digital sampling rate conversion and a wireless transmitter incorporating the filter or the method. In one embodiment, the sampling rate converter includes: (1) an input configured to receive digital data from a first clock domain sampled at a first sampling rate, (2) an output configured to provide digital data to a second clock domain sampled at a second sampling rate that differs from the first sampling rate and (3) a filter with a second-order, polynomial-based impulse response coupled to the input and the output and configured to apply coefficients having only one nonunitary divisor to the digital data from the first clock domain.

Claims

1. A sampling rate converter, comprising:

an input configured to receive digital data from a first clock domain sampled at a first sampling rate;

an output configured to provide digital data to a second clock domain sampled at a second sampling rate that differs from said first sampling rate; and

a filter with a second-order, polynomial-based impulse response coupled to said input and said output and configured to apply coefficients having only one nonunitary divisor to said digital data from said first clock domain.

2. The sampling rate converter as recited in claim 1 wherein said nonunitary divisor is four.

3. The sampling rate converter as recited in claim 1 wherein a single clock source is employed to establish said first sampling rate and said second sampling rate.

4. The sampling rate converter as recited in claim 1 wherein said first sampling rate is less than said second sampling rate.

5. The sampling rate converter as recited in claim 1 wherein said filter is further configured to perform:

$y<br><br>\left[k\right]=\left\{\frac{1}{4}·<br><br>x<br><br>\left[n\right]-\frac{1}{4}·<br><br>x<br><br>\left[n-1\right]-\frac{1}{4}·<br><br>x<br><br>\left[n-2\right]+\frac{1}{4}·<br><br>x<br><br>\left[n-3\right]\right\}·<br><br>{\mathrm{\mu <br><br>}}^2+\left\{-\frac{1}{4}·<br><br>x<br><br>\left[n\right]+\frac{5}{4}<br><br>x<br><br>\left[n-1\right]-\frac{3}{4}·<br><br>x<br><br>\left[n-2\right]-\frac{1}{4}·<br><br>x<br><br>\left[n-3\right]\right\}·<br><br>\mathrm{\mu <br><br>}+x<br><br>\left[n-2\right].$

6. The sampling rate converter as recited in claim 1 wherein said first sampling rate and said second sampling rate are not related by an integer multiple.

7. The sampling rate converter as recited in claim 1 wherein said sampling rate converter is employed in a wireless transmitter selected from the group consisting of:

a polar transmitter, and

a Cartesian transmitter.

8. A method of performing digital sampling rate conversion, comprising:

receiving digital data from a first clock domain sampled at a first sampling rate; and

employing a filter with a second-order, polynomial-based impulse response to apply coefficients having only one nonunitary divisor to said digital data from said first clock domain, thereby to provide digital data to a second clock domain sampled at a second sampling rate that differs from said first sampling rate.

9. The method as recited in claim 8 wherein said nonunitary divisor is four.

10. The method as recited in claim 8 further comprising employing a single clock source to establish said first sampling rate and said second sampling rate.

11. The method as recited in claim 8 wherein said first sampling rate is less than said second sampling rate.

12. The method as recited in claim 8 wherein said filter is further configured to perform:

$y<br><br>\left[k\right]=\left\{\frac{1}{4}·<br><br>x<br><br>\left[n\right]-\frac{1}{4}·<br><br>x<br><br>\left[n-1\right]-\frac{1}{4}·<br><br>x<br><br>\left[n-2\right]+\frac{1}{4}·<br><br>x<br><br>\left[n-3\right]\right\}·<br><br>{\mathrm{\mu <br><br>}}^2+\left\{-\frac{1}{4}·<br><br>x<br><br>\left[n\right]+\frac{5}{4}<br><br>x<br><br>\left[n-1\right]-\frac{3}{4}·<br><br>x<br><br>\left[n-2\right]-\frac{1}{4}·<br><br>x<br><br>\left[n-3\right]\right\}·<br><br>\mathrm{\mu <br><br>}+x<br><br>\left[n-2\right].$

13. The method as recited in claim 8 wherein said first sampling rate and said second sampling rate are not related by an integer multiple.

14. The method as recited in claim 8 wherein said method is carried out in a wireless transmitter selected from the group consisting of:

a polar transmitter, and

a Cartesian transmitter.

15. A wireless transmitter, comprising:

a digital baseband unit;

a pulse-shaping filter coupled to the digital baseband unit and configured to operate in a first clock domain to provide digital data sampled at a first sampling rate;

a sample rate converter coupled to said pulse-shaping filter and responsive to an interpolating signal to apply coefficients having only one nonunitary divisor to said digital data from said first clock domain; and

an output coupled to said sample rate converter and configured to provide digital data to a second clock domain sampled at a second sampling rate that differs from said first sampling rate.

16. The wireless transmitter as recited in claim 15 further comprising a single clock source configured to establish said first sampling rate and said second sampling rate.

17. The wireless transmitter as recited in claim 15 wherein said first sampling rate is less than said second sampling rate.

18. The wireless transmitter as recited in claim 15 wherein said first sampling rate and said second sampling rate are not related by an integer multiple.

19. The wireless transmitter as recited in claim 15 wherein said wireless transmitter is selected from the group consisting of:

a polar transmitter, and

a Cartesian transmitter.

20. The wireless transmitter as recited in claim 15 wherein the sample rate converter is a filter with a second-order, polynomial-based impulse response.

21. The wireless transmitter as recited in claim 16 wherein said first sampling rate and said second sampling rate are established through frequency division of said single clock source.

22. The wireless transmitter as recited in claim 21 wherein said interpolating signal is generated through said frequency division.