Post-amplifier filter rejection equalization

• US 6,674,808 B1
• Filed: 12/28/1999
• Issued: 01/06/2004
• Est. Priority Date: 12/28/1999
• Status: Expired due to Fees

• Current Assignee: General Dynamics C4 Systems Incorporated (General Dynamics Corporation)
• Original Assignee: General Dynamics Decision Systems, Inc. (General Dynamics Corporation)
• Inventors: Higashi, Albert Howard, Griph, Richard Steven
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): WILLIAMS, LAWRENCE B
• Application Number:
  US09/473,349
• Time in Patent Office: 1,470 Days
• Field of Search: 375/285, 375/296, 375/297, 375/298, 375/220, 455/20
• US Class Current: 375/285
• CPC Class Codes: H03F 1/3247 using feedback acting on predistortion circuits H03F1/3264 takes precedence
• CPC Class Codes: H03F 2201/3233 Adaptive predistortion using lookup table, e.g. memory, RAM, ROM, LUT, to generate the predistortion
• CPC Class Codes: H04L 27/368 adaptive predistortion

Abstract

A post-HPA filter rejection equalizer system and method locally equalizes post-HPA filtering. A predistorter (20) uses a phase error to control the predistortion, and an equalizer (46) uses a magnitude error to control the equalization. The equalizer samples the HPA output multiple occurrences in a burst fashion. The equalized signal is then used to determine phase and magnitude errors. The phase errors (54) are used to update the predistorter (20), and the magnitude errors (52) are used to update the analytic equalizer.

Claims

1. A communication system comprising:

a modulator for modulating a data stream onto a carrier wave to generate a modulated signal, the modulator converting data on the data stream into symbols for transmission by the transmission system;

an amplifier for amplifying the modulated signal prior to transmission to generate an amplified signal, the amplifier including an amplifier filtering effect the distorts the modulated signal, wherein the modulated signal is also distorted by a pre-amplifier filtering effect;

a predistorter, the predistorter receiving the modulated signal prior to amplification by the amplifier, the predistorter generating an inverse signal of the pre-amplifier filtering effect, the inverse signal varying the modulated signal to define a predistorted signal;

an equalizer receiving a portion of the amplified signal, the equalizer removing he amplifier filtering effect and generating a equalized signal, the equalized signal being operable to vary generation of the inverse signals;

an error estimator, the error estimator receiving the equalized signal and estimating a difference between the equalized signal and the modulated signal, defined as an error signal, the error signal having a phase error component and a magnitude error component;

a predistorter tap update generator, the predistorter tap update generator generating a first signal for controlling operation of the predistorter in accordance with the phase error component output by the error estimator; and

an equalizer tap update generator, the equalizer tap update generator generating a second signal for controlling operation of the equalizer in accordance with the magnitude error component output by the error estimator.

2. The communication system of claim 1 wherein the equalizer samples the amplified signal at predetermined intervals, the predetermined intervals being defined as less than continuous.

3. The communication system of claim 1 wherein the equalizer samples the amplified signal at predetermined intervals, the predetermined intervals being defined as less than continuous.

4. The communication system of claim 1 wherein the amplifier is one of a traveling wave tube amplifier (TWTA) or a solid state power amplifier (SSPA).

5. A method for a transmission of data comprising the steps of:

modulating a digital data stream onto a carrier wave to generate a modulated signal, wherein modulating the stream of digital data includes the step of converting the digital data stream into symbols for transmission;

amplifying the modulated signal prior to transmission to generate an amplified signal, the step of amplifying introducing an amplifying filtering effect that distorts the modulated signal, wherein the modulated signal is also distorted by a pre-amplifier filtering effect occurring prior to the step of amplifying;

predistorting the modulated signal prior to amplifying the modulated signal, the step of predistorting including generating an inverse of the pre-amplifier filtering effect, the inverse varying the modulated signal to define a predistorted signal;

equalizing a portion of the amplified signal by removing the amplifying filtering effect and generating an equalized signal, the equalized signal being operable to vary generation of the inverse of the pre-amplifier filtering effect;

estimating an error between the equalized signal and the modulated signal, the error having phase error and magnitude error components;

generating a first signal for controlling the step of predistorting in accordance with the phase error component; and

generating a second signal for controlling the step equalizing in accordance with the phase error component.

6. The method of claim 5 wherein the step of equalizing further comprises sampling the amplified signal at predetermined intervals, the predetermined intervals being defined as less than continuous.

7. The method of claim 5 wherein the step of equalizing further comprises sampling a portion of the amplified signal at predetermined intervals, the predetermined intervals being defined as less than continuous.

8. A communication system comprising:

a modulator for modulating a digital data stream onto a carrier wave to generate a modulated signal, the modulator converting data on the data steam into symbols for transmission by the transmission system;

a high power amplifier (HPA) for amplifying the modulated signal prior to transmission to generate an amplified signal, the HPA including an HPA filtering effect that distorts the modulated signal, wherein the modulated signal is also distorted by a pre-HPA filtering effect prior to amplification by the HPA;

a predistorter, the predistorter receiving the modulated signal prior to amplification by the HPA, the predistorter generating an inverse signal of the pre-HPA filtering effect, the inverse signal varying the modulated signal to define a predistorted signal;

an equalizer receiving a portion of the amplified signal, the equalizer removing the HPA filtering effect and generating an equalized signal, the equalized signal being operable to vary generation of the inverse signal of the pre-HPA filtering effect;

an error estimator, the error estimator receiving the equalized signal and estimating an error signal defined as a difference between the equalized signal and the modulated signal, the error signal having a phase error component and a magnitude error component;

a predistorter tap update generator, the predistorter tap update generator generating a first signal for controlling operation of the predistorter in accordance with the phase error component; and

an equalizer tap update generator, the equalizer tap update generator generating a second signal for controlling operation of the equalizer in accordance with the magnitude error component, wherein the equalizer samples the amplifier output signal at predetermined intervals, the predetermined intervals being defined as less than continuous.