Method and apparatus for reducing the peak-to-average power in multi-carrier RF communication systems

• US 5,302,914 A
• Filed: 10/20/1992
• Issued: 04/12/1994
• Est. Priority Date: 10/20/1992
• Status: Expired due to Term

• Current Assignee: American Telephone & Telegraph Company (AT&T, Inc.)
• Original Assignee: AT&T, Inc.
• Inventors: Ocenasek, Josef, Nitz, William A., Arntz, Bernard J.
• Primary Examiner(s): Mullins, James B.
• Application Number:
  US07/964,596
• Time in Patent Office: 539 Days
• Field of Search: 330/124 R, 330/129, 330/279, 330/295, 455/103, 455/126
• US Class Current: 330/129
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03G 3/3042 in modulators, frequency-changers, transmitters or power amplifiers transmission power control in bidirectional transmission systems H04W52/04
• CPC Class Codes: H04L 27/2621 Reduction thereof using phase offsets between subcarriers
• CPC Class Codes: H04L 27/2637 with direct modulation of individual subcarriers
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Therefore a method and apparatus for controlling a linear amplifier processing a plurality of carrier signals of a multi channel carrier system alters the phases of one or more sources of the multi-channel signals in response to a detected peak envelope power or of a peak to average power ratio at regular scheduled intervals. This reduces the peak envelope power to average envelope power ratio and enables the reduction in the power rating required by the amplifiers handling the multi-channel signal.

Claims

1. In a power amplifier system in which an individual amplifier processes a plurality of signal channel carriers each assigned different frequencies and spaced from one another by frequency differentials small in magnitude as compared with the assigned different frequencies, a method of increasing the average power handling capacity of the amplifier;

comprising the steps of;

monitoring a peak power level of the combined signals processed by the amplifier;

determining if the peak power is equal to or greater than a power threshold;

altering a phase of at least one of the carriers if the peak power is equal to or greater than the power threshold;

again determining if the peak power is equal to or greater than the power threshold;

altering a phase of additional carriers if the peak power is equal to or greater than the power threshold;

ceasing alteration of phases of the carriers when the peak power drops below the threshold.

2. In a power amplifier in which an individual amplifier processes a plurality of signal channel carriers each equally spaced from one another by similar frequency differentials, a method of increasing the average power handling capacity of the amplifier;

comprising the steps of;

monitoring a peak power level of the combined signals processed by the amplifier;

determining if the peak power is equal to or greater than a power threshold;

altering a phase of at least one of the carriers if the peak power is equal to or greater than the power threshold;

again determining if the peak power is equal to or greater than the power threshold;

altering a phase of additional carriers if the peak power is equal to or greater than the power threshold;

ceasing alteration of phases of the carriers when the peak power drops below the threshold.

3. In a power amplifier system in which an individual amplifier processes a plurality of signal channel carriers each assigned different frequencies and spaced from one another by frequency differentials small in magnitude as compared with the assigned different frequencies, a method of increasing the average power handling capacity of the amplifier;

comprising the steps of;

monitoring a peak power level and an average power level of the combined signals processed by the amplifier and determining a ratio of the peak power to the average power;

altering a phase of at least one of the carriers and determining if the ratio of the peak power to the average power is reduced from an existing value;

altering a phase of additional carriers and determining if the ratio of the peak power to the average power is reduced from an existing value;

ceasing alteration of phases of the carriers when the ratio of the peak power to the average power is not further reduced.

4. A system for reducing the peak-to-average power ratio in an amplifier processing a plurality of different signal channels, each channel having a different carrier frequency, comprising:

a plurality of radio transceivers connected to receive FM modulated information signals at different carrier frequencies for each of the radio transceivers;

a plurality of phase shifters equal in number to and each connected to one of the plurality of radio transceivers;

a combiner for combining all the modulated information signals into a composite modulated signal;

an amplifier connected to amplify the composite modulated signal to a radio transmission level;

a coupling device for sensing power input to the amplifier;

a peak power detector and average power detector connected to the coupling device;

a controller connected to the peak power detector and to the average power detector for monitoring the peak to average power ratio and applying control signals to each of phase shifters for reducing the peak-to-average ratio by shifting a phase of a signal in individual channels.

5. A system for reducing the peak-to-average power ratio in an amplifier processing a plurality of different signal channels, each channel having a different carrier frequency, as claimed in claim 4, wherein:

each of the plurality of phase shifters are each connected to an input of one of the radio transceivers.

6. A system for reducing the peak-to-average power ratio in an amplifier processing a plurality of different signal channels, each channel having a different carrier frequency, as claimed in claim 4, wherein:

each of the plurality of phase shifters are each connected to an output of one of the radio transceivers.