Measurement of distortion in an amplifier

• US 7,592,795 B2
• Filed: 07/15/2008
• Issued: 09/22/2009
• Est. Priority Date: 06/30/2006
• Status: Expired due to Fees

• Current Assignee: Cingular Wireless II LLC (AT&T, Inc.)
• Original Assignee: Cingular Wireless II LLC (AT&T, Inc.)
• Inventors: Prather, Scott
• Primary Examiner(s): Dole; Timothy J
• Application Number:
  US12/173,575
• Publication Number:
  US 20080265868A1
• Time in Patent Office: 434 Days
• Field of Search: 324/76.19
• US Class Current: 324/76.19
• CPC Class Codes: G01R 23/20 Measurement of non-linear distortion
• CPC Class Codes: H03F 1/32 Modifications of amplifiers to reduce non-linear distortion by negative feedback H03F1/34
• CPC Class Codes: H04B 17/10 of transmitters

Abstract

Parametric measurement of first- and second-generation telecommunications equipment has been relatively straightforward. The evolution to more complex transmission schemes such as those proposed for third-generation (3G) telecommunications devices can employ the subject methods and apparatus and apply AM-PM test procedures to a multicarrier amplifier RF environment to properly characterize the parametric performance of these transmission systems, particularly those operating in a multicarrier environment.

Claims

1. A method, comprising:

inputting a stimulus signal approximating a Gaussian noise signal limited to a frequency band into an amplifier wherein said stimulus signal comprises a notch in a portion of said frequency band and wherein the stimulus signal comprises a plurality of frequency spaced tones where the number of tones is a function of the bandwidth of the frequency band; and

inputting a test signal approximately in the center of the notch and measuring amplitude and phase shifts in outer corners of the test signal.

2. The method as recited in claim 1 further comprising:

measuring amplitude and phase distortion in the notch portion of the frequency band from the output of the amplifier.

3. The method as recited in claim 1 wherein the phases of the plurality of frequency spaced tones are random.

4. The method as recited in claim 1 wherein the stimulus signal is upconverted approximately in an operating frequency range of the amplifier.

5. The method as recited in claim 1 comprising increasing the power level of the stimulus until the passband power from the amplifier is approximately the same as its rated average output power.

6. The method as recited in claim 1 comprising measuring the on channel intermodulation distortion by measuring the noise power ratio within the notch of the stimulus signal.

7. The method as recited in claim 1 wherein the amplifier is a linear power amplifier.

8. A system, comprising:

an arbitrary waveform generator that generates a stimulus signal approximating a Gaussian noise signal limited to a frequency band into an amplifier wherein said stimulus signal comprises a notch in a portion of said frequency band and wherein the stimulus signal comprises a plurality of frequency spaced tones where the number of tones is a function of the bandwidth of the frequency band;

a signal generator configured to input a test signal approximately in the center of the notch; and

a spectrum analyzer that measures amplitude and phase shifts in outer corners of the test signal.

9. The system as recited in claim 8 wherein the spectrum analyzer measures amplitude and phase distortion in the notch portion of the frequency band from the output of the amplifier.

10. The system as recited in claim 8 wherein the phases of the plurality of frequency spaced tones are random.

11. The system as recited in claim 8 comprising an upconverter for upconverting the stimulus signal approximately in an operating frequency range of the amplifier.

12. The system as recited in claim 8 comprising a mechanism for increasing the power level of the stimulus so that the passband power from the amplifier is approximately equal to its rated average output power.

13. A system, comprising:

means for generating a stimulus signal approximating a Gaussian noise signal limited to a frequency band into an amplifier wherein said stimulus signal comprises a notch in a portion of said frequency band and wherein the stimulus signal comprises a plurality of frequency spaced tones where the number of tones is a function of the bandwidth of the frequency band; and

means for inputting a test signal approximately in the center of the notch and measuring amplitude and phase shifts in outer corners of the test signal.

14. The system as recited in claim 13 comprising means for measuring amplitude and phase distortion in the notch portion of the frequency band from the output of the amplifier.

15. The system as recited in claim 13 wherein the phases of the plurality of frequency spaced tones are random.

16. The system as recited in claim 13 comprising an up converter for upconverting the stimulus signal approximately in an operating frequency range of the amplifier.

17. The system as recited in claim 13 comprising a mechanism for increasing the power level of the stimulus so that the passband power from the amplifier is approximately equal to its rated average output power.

18. The system as recited in claim 13 wherein the amplifier comprises a linear amplifier.