Antenna array with system for locating and adjusting phase centers of elements of the antenna array

• US 5,235,342 A
• Filed: 05/18/1992
• Issued: 08/10/1993
• Est. Priority Date: 08/30/1989
• Status: Expired due to Fees

• Current Assignee: GEC Marconi Limited (Gooding Consumer Electronics Ltd.)
• Original Assignee: GEC Marconi Limited (Gooding Consumer Electronics Ltd.)
• Inventors: Tittensor, Paul J., Orton, Richard S.
• Primary Examiner(s): Hille, Rolf
• Assistant Examiner(s): Brown, Peter T.
• Application Number:
  US07/883,904
• Time in Patent Office: 449 Days
• Field of Search: 342/173, 342/372, 343/792.5, 343/703, 343/853, 455/103-105
• US Class Current: 343/703
• CPC Class Codes: H01Q 11/10 Logperiodic antennas H01Q11/08 takes precedence
• CPC Class Codes: H01Q 21/22 Antenna units of the array energised non-uniformly in amplitude or phase, e.g. tapered array or binomial array
• CPC Class Codes: H01Q 3/26 varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture H01Q3/12, H01Q3/22, H01Q3/24 take precedence

Abstract

In an antenna array consisting of a plurality of antennas, an antenna may behave as if its transmitted radiation emanates from a position, phase center, disposed away from the actual location. Probe antennas are used with a processor to locate the phase center of respective antennas at a selected frequency of transmission and to adjust the phase center to a desired location, thereby calibrating the antenna array for the selected frequency.

Claims

1. Apparatus for calibrating a transmit antenna array having a plurality of antennas, the transmit antenna array operating at frequencies in the range of 3 to 30 megahertz, each antenna including a row of elements in a log periodic configuration, the apparatus comprising:

a plurality of probe antennas spaced apart from each other and disposed in one of a near and an intermediate field region of the antenna array for receiving signals transmitted by respective antennas of the array; and

processing means for determining the location of a phase center of a respective antenna of the array at one selected frequency of transmission by processing a received signal to determine the phase at the probe antennas of the received signal transmitted by the respective antenna of the array, the processing means containing data to indicate the selected phase shift between the respective element and each probe antenna at that selected frequency, a phase sifter being connected to the respective antennas of the array, said processing means being operative to adjust the phase shifter when transmitting at the selected frequency by an amount dependent upon the determined location of the respective phase center.

2. Calibration apparatus as claimed in claim 1, in which each antennas of the array comprises at least one dipole, and wherein the processing means compares the phase of the signal received at a probe antenna with an associated expected phase for a respective dipole of the respective antenna of the array, the associated expected phase being based on the frequency and wavelength of transmission, and the distance of the respective dipole from the probe antenna.

3. Calibration apparatus as claimed in claim 2, in which the processing means produces an error signal from the received an the expected phases and adjusts the phase shifter connected to the respective antenna of the array in dependence on the error signal.

4. Calibration apparatus as claimed in claim 1, wherein each antenna of the array is a log periodic antenna having a boresight and comprising dipoles arranged in a straight line along said boresight, the corresponding dipoles of each antenna of the array being arranged in straight lines with respective dipoles of the other antennas of the array, the bore sights of the antennas of the array being parallel to the one another.

5. Calibration apparatus as claimed in claim 1, wherein three probe antennas are provided.

6. Calibration apparatus as claimed in claim 4, wherein the probe antennas are arranged in a line broadside to the bore sights of the antennas of the array.

7. The apparatus of claim 1 wherein the elements are dipole elements.

8. The apparatus of claim 1, wherein the rows of elements are arranged side-by-side and parallel to one another.

9. The apparatus of claim 1 wherein the transit antennas array is a phased array.

10. A method of calibrating a transmit antenna array having a plurality of antennas, the transmit antennas array operating at frequencies in the range of 3 to 30 megahertz, each antenna including a row of elements in a log periodic configuration, the method comprising:

taking measurement of the phase of a signal at one selected frequency transmitted by a respective one of the antennas of the array to a plurality of positions spaced apart in one of a near and an intermediate field region of the antenna array;

determining the location of a phase center of the respective one of the antennas from the measurements utilizing data indicating the excited phase shift between the respective element and each probe antenna at that selected frequency; and

applying an off-set to the phase of the signal transmitted by the respective one of the antennas dependent on the determined location of the phase center.

11. An antenna array comprising:

13. The antenna array according to claim 11, wherein three probe antennas are provided.

12. a plurality of transmit antennas for transmitting signals, each transmit antenna being operatively connected to one of a like plurality of phase shifters, each phase shifter being connected to an associated amplifier and transmitter;

a plurality of probe antennas disposed to receive signals transmitted form the transmit antennas;

processing means connected to each of the phase shifters and connected to the probe antennas, for determining the location of a phase center of a respective transit antenna at on selected frequency of transmission by processing a received signal to determine the phase at the probe antennas of the received signal transmitted by the respective transmit antenna, and for controlling the phase shifters based on the determined location of the respective phase center, the processing means containing data to indicate the expected phase shift between the respective element and each probe antenna at that selected frequency;

wherein the transmit antennas each comprise a plurality of dipoles in a log periodic configuration.