Low-splatter peak-to-average signal reduction with interpolation

• US 5,638,403 A
• Filed: 04/28/1995
• Issued: 06/10/1997
• Est. Priority Date: 04/28/1995
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Tziortzis, Alek, Birchler, Mark A., Jasper, Steven C.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Kim, Kevin
• Application Number:
  US08/430,969
• Time in Patent Office: 774 Days
• Field of Search: 375/296, 375/295, 332/107, 332/123, 332/159, 455/50.1, 455/52.1, 455/52.3, 455/63, 455/67.3, 455/114, 364/723
• US Class Current: 375/296
• CPC Class Codes: H04B 7/005 Control of transmission; Equalising
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2624 by soft clipping

Abstract

A method of low-splatter peak-to-average reduction for a linear communication system includes the step of sampling (1201) an input signal at a first rate, yielding a plurality of input samples. When at least one (1401, 1403, and 1405) of the plurality of input samples is above a first threshold, a local maximum (1401) is determined (1207) from among the plurality of input samples. At least one value (1407 and 1409) is interpolated (1207) between the local maximum and at least one sample (1405) adjacent to the local maximum. The at least one value and the local maximum are compared (1211) to determine which has the highest magnitude. The value having the highest magnitude (1407) is compared (1213) to a second threshold. When the value having the highest magnitude (1407) is above the second threshold, an attenuating window is centered (1505) at the value having the highest magnitude and applying (1507) the attenuating window to at least some of the plurality of input samples.

Claims

1. A method of low-splatter peak-to-average reduction for a linear communication system, comprising the steps of:

sampling an input signal at a first rate, yielding a plurality of input samples;

determining when at least one of the plurality of input samples is above a first threshold;

when at least one of the plurality of input samples is above a first threshold, determining which of the plurality of input samples is a local maximum;

interpolating at least one value between the local maximum and at least one sample adjacent to the local maximum, wherein the at least one sample is one of the plurality of input samples;

comparing the at least one value and the local maximum to determine which has the highest magnitude;

comparing the value having the highest magnitude to a second threshold; and

when the value having the highest magnitude is above the second threshold, centering an attenuating window at the value having the highest magnitude and applying the attenuating window to at least some of the plurality of input samples.

2. The method of claim 1, wherein the step of interpolating further comprises the steps of:

identifying a first sample of the plurality of input samples, which first sample is adjacent to the local maximum and is one sample earlier in time with respect to the local maximum;

identifying a second sample of the plurality of input samples, which second sample is adjacent to the local maximum and is one sample later in time with respect to the local maximum;

comparing the magnitude of the first sample with the magnitude of the second sample and finding which sample has a greater magnitude, yielding a higher sample; and

interpolating at least one value between the local maximum and the higher sample.

3. The method of claim 2, wherein a first value is interpolated at a first time that is half-way between the local maximum and the higher sample, and a second value is interpolated at a second time that is half-way between the local maximum and the first time.

4. The method of claim 1, wherein the at least one value is interpolated at a time evenly spaced between the local maximum and the at least one sample adjacent to the local maximum.

5. The method of claim 1, wherein at least two values are interpolated at a second rate that is four times the first rate.

6. The method of claim 1, wherein the attenuating window is an inverted Hanning window.

7. The method of claim 1, wherein each method step is performed in a radio frequency transmitter.

8. A method of low-splatter peak-to-average reduction for a linear communication system, comprising the steps of:

sampling an input signal at a first rate, yielding a plurality of input samples;

interpolating at least one value between the input samples at a second rate, yielding at least one interpolated sample;

determining at which of the plurality of input samples or the at least one interpolated sample to align an attenuating window, thereby yielding an aligning sample;

determining a set of local attenuating values separated in time by one over the first rate, yielding the attenuating window;

aligning the attenuating window with the aligning sample; and

applying the attenuating window to at least some of the plurality of input samples.

9. The method of claim 8, wherein the aligning step further comprises centering the aligning value with the center of the attenuating window.

10. The method of claim 8, wherein the attenuating window is an inverted Hanning window.

11. The method of claim 8, wherein each method step is performed in a radio frequency transmitter.

12. A method of low-splatter peak-to-average reduction for a linear communication system, comprising the steps of:

sampling an input signal at a first rate, yielding a plurality of input samples;

determining when at least one of the a plurality of input samples is above a first threshold;

when at least one of the a plurality of input samples is above a first threshold, determining which of the a plurality of input samples is a local maximum;

interpolating at a second rate at least one value between the local maximum and at least one sample adjacent to the local maximum;

comparing the at least one value and the local maximum to determine which has the highest magnitude;

comparing the value having the highest magnitude to a second threshold; and

when the value having the highest magnitude is above the second threshold;

determining a set of local attenuating values separated in time by one over the first rate, yielding an attenuating window;

aligning the attenuating window with the value having the highest magnitude; and

applying the attenuating window to at least some of the a plurality of input samples.

13. The method of claim 12, wherein the step of interpolating further comprises the steps of:

identifying a first sample of the plurality of input samples, which first sample is adjacent to the local maximum and is one sample earlier in time with respect to the local maximum;

identifying a second sample of the plurality of input samples, which second sample is adjacent to the local maximum and is one sample later in time with respect to the local maximum;

comparing the magnitude of the first sample with the magnitude of the second sample and finding which sample has a greater magnitude, yielding a higher sample; and

interpolating at least one value between the local maximum and the higher sample.

14. The method of claim 13, wherein a first value is interpolated at a first time that is half-way between the local maximum and the higher sample, and a second value is interpolated at a second time that is half-way between the local maximum and the first time.

15. The method of claim 12, wherein the at least one value is interpolated at a time evenly spaced between the local maximum and the at least one sample adjacent to the local maximum.

16. The method of claim 12, wherein at least two values are interpolated at a second rate that is four times the first rate.

17. The method of claim 12, wherein the attenuating window is an inverted Hanning window.

18. The method of claim 12, wherein the aligning step further comprises centering the aligning value with the center of the attenuating window.

19. The method of claim 12, wherein each method step is performed in a radio frequency transmitter.

20. The method of claim 12, wherein the step of interpolating further comprises the steps of:

identifying a first sample of the plurality of input samples, which first sample is adjacent to the local maximum and is one sample earlier in time with respect to the local maximum;

identifying a second sample of the plurality of input samples, which second sample is adjacent to the local maximum and is one sample later in time to with respect to the local maximum;

comparing the magnitude of the first sample with the magnitude of the second sample and finding which sample has a greater magnitude, yielding a higher sample; and

interpolating two values, a first value and a second value, between the local maximum and the higher sample, wherein the first value is interpolated at a first time that is half-way between the local maximum and the higher sample, and the second value is interpolated at a second time that is half-way between the local maximum and the first time.