Adaptive feed forward system

• US 3,922,617 A
• Filed: 11/18/1974
• Issued: 11/25/1975
• Est. Priority Date: 11/18/1974
• Status: Expired due to Term

• Current Assignee: Robert F. Hertz, William B. Denniston
• Original Assignee: Robert F. Hertz, William B. Denniston
• Inventors: Denniston, William B., Hertz, Robert F.
• Primary Examiner(s): Mullins, James B.
• Application Number:
  US05/524,680
• Time in Patent Office: 372 Days
• Field of Search: 330/52,149,151 328/162,163 333/16 325/65,472,474,475,476,479,481
• US Class Current: 330/149
• CPC Class Codes: H03F 1/3235 using a pilot signal
• CPC Class Codes: H03F 1/345 using hybrid or directional couplers
• CPC Class Codes: H03F 2201/3212 Using a control circuit to adjust amplitude and phase of a signal in a signal path

Abstract

A feed forward system for reducing the distortion products from a device such as an amplifier, wherein a sample of the device input signal is subtractively combined with a sample of the device output signal to produce a sample of the distortion products. The distortion sample is adjusted in phase and amplitude and subtractively combined with the device output to produce a distortion-reduced system output. First and second pilot signals, applied to the device input and output respectively, are detected in the sample of the distortion products and in the system output to produce control signals which adjust the phase and amplitude of the input signal sample and the distortion sample to provide an adaptive system which automatically compensates for uncontrolled variations in the system components. A portion of the distortion sample produced by the feed forward process is fed back to the device input by way of a negative feedback circuit to reduce the signal handling capacity required of components such as an auxiliary amplifier used in processing the distortion sample.

Claims

1. An adaptive feed forward system of the type designed to reduce the distortion from a device such as an amplifier, including means for extracting a sample of the distortion products from the output of said device, adjustable means for equalizing said sample and the products remaining in the output after extracting the sample, means for subtractively combining said equalized sample and remaining products to produce a distortion-reduced system output, and means including pilot signal generator and coherent detector means for automatically adjusting said equalizing means to compensate for uncontrolled variations in the system components, wherein the improvement comprises:

a. means for extracting a sample of the system output, and b. means for applying said sample of the system output to said coherent detector means.

2. An adaptive feed forward system as claimed in claim 1, wherein said means for extracting a sample of the distortion products includes adjustable means for equalizing a desired input signal and its replica in samples of the input and output signals of said device, means for subtractively combining said input and output samples, and second pilot signal generator and coherent detector means for automatically adjusting said means for equalizing the desired signal and its replica to automatically compensate for uncontrolled variation in the system components, wherein the improvement comprises:

a. means for extracting a portion of the distortion products sample, and b. means for applying said portion of the distortion products sample to said second coherent detector means.

3. An adaptive feed forward system as claimed in claim 2, further comprising:

a. means for feeding back a portion of said sample of the distortion products to the input of said device, and b. means for adjusting the phase and amplitude of said feedback sample to oppose and thereby reduce the distortion products in the output of said device.

4. An adaptive feed forward method of the type designed to reduce the distortion from a device such as an amplifier, including the steps of extracting a sample of the distortion products from the output of said device, equalizing said sample and the distortion products remaining in the output after extracting sample, subtractively combining said equalized sample and remaining products to produce a distortion-reduced system output, adding a pilot signal to the output of said device, detecting said pilot signal coherently, and adjusting the equalizing of said sample and said products in response to the detected pilot signal to automatically compensate for uncontrolled variation in the system components, wherein the improvement comprises the steps of:

a. extracting a sample of the system output, and b. coherently detecting the pilot signal in said sample of the system output.

5. An adaptive feed forward method as described in claim 4, further comprising the steps of:

a. feeding back a portion of said sample of the distortion products to the input of said device, and b. adjusting the phase and amplitude of said feedback sample to oppose and thereby reduce the distortion products in the output of said device.