Equalization for traveling wave tube amplifier nonlinearity measurements

• US 20050123032A1
• Filed: 10/08/2004
• Published: 06/09/2005
• Est. Priority Date: 10/10/2003
• Status: Active Grant

• Current Assignee: DIRECTV, LLC (AT&T, Inc.)
• Original Assignee: The DIRECTV Group, Inc. (AT&T, Inc.)
• Inventors: Chen, Ernest C.
• Granted Patent: US 7,502,429 B2
• Time in Patent Office: Days
• US Class Current: 375/229
• CPC Class Codes: H04L 1/206 for modulated signals
• CPC Class Codes: H04L 25/03012 operating in the time domain H04L25/03165, H04L25/03178 take precedence
• CPC Class Codes: H04L 27/34 Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems

Abstract

A method and system provide the ability to measure a transmission performance characteristic. A signal is received and equalized. The equalized signal is demodulated and an ideal signal is generated from the demodulated equalized signal. A performance characteristic is the estimated from a difference between the ideal signal and the equalized signal.

Claims

1. A method of measuring a transmission performance characteristic, comprising:

receiving a signal;

equalizing the signal using a linear equalizer to restore nonlinearity;

demodulating the equalized signal;

generating an ideal signal from the demodulated equalized signal; and

estimating the performance characteristic from a difference between the ideal signal and the received signal.

2. The method of claim 1, further comprising coherently averaging the received signal to reduce noise.

3. The method of claim 1, wherein the step of estimating the performance characteristic includes fitting a curve of the received signal versus the ideal signal.

4. The method of claim 3, wherein the curve is an AM-AM plot.

5. The method of claim 3, wherein the curve is an AM-PM plot.

6. The method of claim 1, further comprising inverse filtering the received signal to restore nonlinearity.

7. A system for measuring a transmission performance characteristic, comprising:

(a) an equalizer for equalizing a received signal;

(b) a demodulator for demodulating the equalized signal;

(c) a signal generator for producing an ideal signal from the demodulated equalized signal; and

(d) a processor for estimating the performance characteristic from a difference between the ideal signal and the equalized signal.

8. The system of claim 7, wherein the processor is further configured to coherently average the ideal signal to reduce noise and wherein the performance characteristic is based on the difference between the coherently averaged ideal signal and coherently averaged equalized signal.

9. The system of claim 7, wherein the processor is configured to estimate the performance characteristic by fitting a curve of the received signal versus the ideal signal.

10. The system of claim 9, wherein the curve is an AM-AM plot.

11. The system of claim 9, wherein the curve is an AM-PM plot.

12. The system of claim 7, further comprising an inverse filter that is used on the received signal to restore nonlinearity.