Phased array antenna management system and calibration method

• US 5,530,449 A
• Filed: 11/18/1994
• Issued: 06/25/1996
• Est. Priority Date: 11/18/1994
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (AT&T, Inc.)
• Original Assignee: Hughes Electronics Corporation (AT&T, Inc.)
• Inventors: Thompson, James D., Berman, Arnold L., Wachs, Marvin R.
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US08/342,541
• Time in Patent Office: 585 Days
• Field of Search: 342/372, 342/173, 342/174, 342/360
• US Class Current: 342/174
• CPC Class Codes: H01Q 3/267 Phased-array testing or checking devices

Abstract

A management system and calibration method for use with a phased array antenna that increases its robustness to component changes or failures. The present invention employs a system level measurement of amplitude and phase, conducted during nodal operation, to determine on an element by element basis, the tracking performance of individual chains that for the antennas. This amplitude and phase information is employed to compensate the each chain for the measured error. The present system and method measures the amplitude and phase of individual element chains utilizing probe carriers. The required correction coefficients for each chain is determined from the measured amplitude and phase data, and each individual element chain is individually compensated to remedy the amplitude and phase errors. The present system and method generates a probe carrier that is applied to each element chain along with normal communication signal waveforms. The probe carrier is sufficiently small (narrow bandwidth, low power, or encoded) so that it does not significantly degrade system operation. The relative amplitude and phase of the probe carrier, as applied to an element chain, is measured. By switching the probe carrier in time sequence between each chain, the differential amplitude and phase characteristics of each of the chains is determined. This also serves to detect component failures in a chain. Each chain includes commandable amplitude and phase weighting networks. Once the differential amplitude and phase tracing characteristics of the antenna re characterized, the individual weighting networks are commanded to settings that compensate for the measured values.

Claims

1. A phased array antenna management system for use with a phased array communication system comprising transmit and receive phased array antennas that each include a plurality of antenna element chains, wherein each chain comprises an amplitude adjustment network, a phase adjustment network, an amplifier, a filter, and an antenna element, and wherein each chain has a desired amplitude and phase relationship with respect to the other chains of its respective antenna, said system comprising:

a probe carrier source for generating a noninterfering probe carrier signal that is processed by each antenna element chain;

means for determining the amplitude and phase produced by each chain of the transmit and receive phased array antennas in response to the probe carrier signal, for comparing the amplitude and phase produced by each chain to the desired amplitude and phase for each chain, for determining which antenna chains do not have the desired amplitude and phase relationship therebetween, and for generating corrective weighting coefficients for chains that do not have the desired amplitude and phase; and

means for applying the corrective weighting coefficients to the amplitude and phase adjustment networks of each chain of the transmit and receive phased array antennas to produce the desired amplitude and phase relationship therebetween.

2. The phased array antenna management system of claim 1 wherein the probe carrier source comprises a commutator switch for sequentially processing the probe carrier signal through each antenna element chain.

3. The phased array antenna management system of claim 1 wherein the probe carrier source comprises a signal source modulated by a code generator for generating orthogonal probe carrier signals for processing by each antenna element chain.

4. The phased array antenna management system of claim 1 wherein the means for determining the amplitude and phase produced by each chain comprises:

a calibration station remotely located from the transmit and receive phased array antennas that comprises an antenna, a receiver, and amplitude and phase determining means for detecting the amplitude and phase produced by each chain; and

a communications link coupled between the transmit and receive phased array antennas and the calibration station.

5. The phased array antenna management system of claim 1 wherein the means for determining the amplitude and phase produced by each chain comprises a local antenna, a receiver, and amplitude and phase determining means for detecting the amplitude and phase produced by each chain.

6. A method of calibrating transmit and receive phased array antennas of a phased array communication system, wherein respective antenna element chains comprising each of the antennas have a desired amplitude and phase relationship with respect to signals processed thereby, said method comprising the steps of:

processing noninterfering probe carrier signals through each antenna chain of the transmit and receive antennas;

comparing the respective phases and amplitudes of the processed probe carrier signals to provide a map of differential amplitudes and phases of each antenna chain of the respective transmit and receive antennas;

determining which antenna chains do not have the desired amplitude and phase relationship between the probe carrier signals processed thereby;

generating corrective weighting coefficients for the antenna chains that do not have the desired amplitude and phase relationship between the probe carrier signals processed thereby; and

applying the corrective weighting coefficients to each chain of the transmit and receive antennas to produce the desired amplitude and phase relationship between signals processed thereby.