Method and apparatus for calibrating a remote system which employs coherent signals

• US 6,384,781 B1
• Filed: 04/26/2001
• Issued: 05/07/2002
• Est. Priority Date: 04/26/2001
• Status: Expired due to Fees

• Current Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Original Assignee: Lockheed Martin Corporation (Martin Marietta Corporation)
• Inventors: Ashe, Jeffrey Michael, Kautz, Gregory Michael, Silverstein, Seth David
• Primary Examiner(s): Phan, Dao
• Application Number:
  US09/843,439
• Time in Patent Office: 376 Days
• Field of Search: 342/165, 342/174, 342/368, 342/375
• US Class Current: 342/368
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices

Abstract

A method for calibrating a remote system having a plurality of N elements, N being a positive integer number. An input signal to each of the N elements is processed according to beamforming bits to determine the output of a corresponding element. The output of the plurality of N elements is a composite signal. The method includes the steps of: (a) transmitting a calibration signal to input the plurality of N elements of the remote system; (b) selecting a first set of beamforming bits for each of the plurality of N elements based upon entries of a predetermined invertible matrix; (c) processing the calibration signal at the remote system according to the beamforming bits for each of the N plurality of elements; (d) detecting a reference signal from the remote system and the composite signal transmitted from the N plurality of elements based on the first set of beamforming bits; (e) repeating steps (b)-(d) for successive sets of beamforming bits to generate a set of signals; and (f) processing the set of signals for generating calibration data for each of the N plurality of elements of the remote system. Preferably, the remote system comprises a phased array system and wherein each of the N plurality of elements comprises an individual antenna in the phased array system.

Claims

1. A method for calibrating a remote system having a plurality of N elements, N being a positive integer number, an input signal to each of said N elements being processed according to beamforming bits to determine the output of a corresponding element, the output of the plurality of N elements being a composite signal, the method comprising the steps of:

(a) transmitting a calibration signal to input the plurality of N elements of the remote system;

(b) selecting a first set of beamforming bits for each of the plurality of N elements based upon entries of a predetermined invertible matrix;

(c) processing the calibration signal at the remote system according to the beamforming bits for each of the N plurality of elements;

(d) detecting a reference signal from the remote system and the composite signal transmitted from the N plurality of elements based on the first set of beamforming bits;

(e) repeating steps (b)-(d) for successive sets of beamforming bits to generate a set of signals; and

(f) processing the set of signals for generating calibration data for each of the N plurality of elements of the remote system.

2. The method of claim 1, wherein said remote system comprises a phased array system and wherein each of the N plurality of elements comprises an individual antenna in the phased array system.

3. The method of claim 2, wherein the beam forming bits are selected from a group consisting of 22½

degree phase shift bit, 45 degree phase shift bit, 90 degree phase shift bit, 180 degree phase shift bit, and an attenuation bit.

4. The method of claim 1, further comprising the step of splitting the calibration signal into N+1 signals, N signals being input into the corresponding N plurality of signals and the remaining signal being transmitted as the reference signal.

8. The apparatus of claim 1, further comprising a signal splitter for splitting the calibration signal into N+1 signals, N signals being input into the corresponding N plurality of signals and the remaining signal being transmitted as the reference signal.

9. The apparatus of claim 1, wherein the predetermined invertible matrix is a Hadamard matrix.

5. An apparatus for calibrating a remote system having a plurality of N elements, N being a positive integer number, an input signal to each of said N elements being processed according to beamforming bits to determine the output of a corresponding element, the output of the plurality of N elements being a composite signal, said apparatus comprising:

means for transmitting a calibration signal to input the plurality of N elements of the remote system;

means for selecting successive sets of beamforming bits for each of the plurality of N elements based upon entries of a predetermined invertible matrix;

processing the calibration signal at the remote system according each of the sets of beamforming bits for each of the N plurality of elements;

means for detecting a reference signal from the remote system and the composite signal transmitted from the N plurality of elements based on each of the sets of beamforming bits to generate a set of signals; and

means for processing the set of signals for generating calibration data for each of the N plurality of elements of the remote system.

6. The apparatus of claim 5, wherein said remote system comprises a phased array system and wherein each of the N plurality of elements comprises an individual antenna in the phased array system.

7. The apparatus of claim 6, wherein the beam forming bits are selected from a group consisting of 22½

degree phase shift bit, 45 degree phase shift bit, 90 degree phase shift bit, 180 degree phase shift bit, and an attenuation bit.