System and method for widely-spaced coherent transmit arraying using a remote receiver

• US 10,270,506 B2
• Filed: 02/02/2016
• Issued: 04/23/2019
• Est. Priority Date: 10/05/2015
• Status: Active Grant

• Current Assignee: Specialized Arrays, Inc.
• Original Assignee: Specialized Arrays, Inc.
• Inventors: Martin, G. Patrick, Minear, Kathleen Marie
• Primary Examiner(s): McGue, Frank J
• Application Number:
  US15/013,283
• Publication Number:
  US 20170099091A1
• Time in Patent Office: 1,176 Days
• Field of Search: 342458
• CPC Class Codes: G01S 13/0218 Very long range radars, e.g. surface wave radar, over-the-horizon or ionospheric propagation systems for meteorological use G01S13/95
• CPC Class Codes: G01S 13/74 Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 7/006 using shared front-end circuitry, e.g. antennas G01S13/765, G01S13/825 take precedence
• CPC Class Codes: G01S 7/288 Coherent receivers
• CPC Class Codes: H04B 17/14 of the whole transmission and reception path, e.g. self-test loop-back
• CPC Class Codes: H04B 17/19 Self-testing arrangements
• CPC Class Codes: H04B 17/24 with feedback of measurements to the transmitter
• CPC Class Codes: H04B 17/309 Measuring or estimating channel quality parameters
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 7/0615 of weighted versions of same signal

Abstract

A system and method for operating a communications or radar system wherein the system is a closed-loop coherent transmit array consisting of a plurality of antenna elements that may be widely-spaced, many wavelengths apart, an array control system, and a remote receiver that can feedback a measure of the transmit performance, and is a cooperative receiver, a bent-pipe, or a reflector. The method involves generation of weights which are applied to the array transmit signals based on feed-back data from a remote receiver compensating for at least one: circuit, propagation, and polarization phase errors. The method correlates feedback performance changes with transmit weight perturbations, enabling maximization of transmitted power delivered to the remote receiver. The method further involves an optimization control process that can be coordinated, with systematic weight perturbations and adjustment, or which can be operated asynchronously and autonomously, nevertheless achieving maximization of the received signal power.

Claims

1. A closed loop method for operating a coherent transmit communications or radar system, the coherent transmit communications or radar system including a plurality of antennas, a remote receiver in communication with the plurality of antennas, an array control system in communication with the plurality of antennas, and a performance monitor in communication with the remote receiver and the array control system and configured to receive feedback information from the remote receiver relating to a measure of transmit performance from the plurality of antennas to the remote receiver, the method comprising the steps of:

providing by the array control system a plurality of communications uplinks between the antennas and the remote receiver, the communications uplinks including transmit signals generated by the plurality of antennas and received by the remote receiver;

receiving by the performance monitor a plurality of communications downlinks from the remote receiver;

generating by the array control system a plurality of weights to be applied to transmit signals from the plurality of antennas to maximize a response at the remote receiver, the weights compensating for at least one of circuit, propagation, and polarization phase errors determined from the feedback information; and

applying by the array control system the plurality of weights to the transmit signals for each of the plurality of antennas,

wherein the step of generating the plurality of weights to be applied to the plurality of transmit signals to maximize the response at the remote receiver includes a provision for calculation of complex weights, or a provision for calculation of phase shifters for aligning the carrier signal phase which comprises a weight control algorithm that correlates feedback performance changes with transmit weight perturbations, enabling maximization of transmitted power delivered to the remote receiver and an optimization control process that can be coordinated, with systematic weight perturbations and adjustment, or which can be operated asynchronously and autonomously.

2. The method of claim 1, wherein the weight control algorithm suitable for long-loop, closed-loop transmit arraying optimization includes at least one of a gradient following SNR maximization process, a direct calculation of the optimum weight, and a random search optimization method, and wherein the weights calculated are based at least on feed-back data from the remote cooperative receiver and wherein the weights calculated by the weight control algorithm compensate for phasing errors between the control system and said plurality of antenna elements.

3. The method of claim 1, wherein the step of applying the weights is performed by an apparatus that performs in-phase and quadrature multiplications or shifts the phase of the transmitted signals which results in the transmitted signals from each of the antennas arriving at the remote receiver substantially simultaneously.

4. The method of claim 1, wherein a computer model is used to pre-correct a rate of change of the weights.

5. The method of claim 1, further comprising a complex envelope methodology for transmit array beamforming in which RF phasing is independently accomplished with complex weighting and information alignment is accomplished at baseband by sample delay with no impact on phase.

6. The method of claim 1, wherein the step of generating the plurality of weights to be applied to the plurality of transmit signals includes a provision for calculation of baseband delay weights for aligning the signal information content for said plurality of antenna elements, wherein the means for aligning information content of the transmission from the several array elements comprises correlating feed-back performance information with information delay perturbations.

7. The method of claim 1, further comprising a step of correcting for latency between a change in the plurality of weights to the transmit signals and receipt of the plurality of communication downlinks from the remote receiver.

8. The method of claim 1, wherein the remote receiver is one of a cooperative receiver satellite, a bent-pipe satellite, a reflector satellite, and a non-cooperative radar target that returns a power sample as the communications downlinks.

9. The method of claim 1, wherein the remote receiver provides the feedback information relating to the transmit performance to the performance monitor via the plurality of communications downlinks.

10. The method of claim 1, wherein the performance monitor further performs a step of correlating performance changes with weight perturbations, wherein the performance changes include at least one of power changes in the receive signal, and amplitude and phase coherency changes in the information content but are specific to an individual transmitter channel.

11. A closed loop coherent transmit communications or radar system, comprising:

a plurality of antennas;

a remote receiver in communication with the plurality of antennas;

an array control system in communication with the plurality of antennas and configured to cause a plurality of communications uplinks between the plurality of antennas and the remote receiver, the communications uplinks including transmit signals generated by the plurality of antennas and received by the remote receiver, wherein the array control system further includes a component for generation of a plurality of weights to be applied to the transmit signals from the plurality of antennas to maximize a response at the remote receiver, and a component for application of the weights to the transmit signals for each of the plurality of antennas compensating for at least one of circuit, propagation, and polarization phase errors determined from feedback information, wherein the component for generation of a plurality of weights to be applied to the plurality of transmit signals to maximize the response at the remote receiver includes a component for calculation of complex weights, or a component for calculation of phase shifters for aligning the carrier signal phase which comprises a weight control algorithm that correlates feedback performance changes with transmit weight perturbations, enabling maximization of transmitted power delivered to the remote receiver and an optimization control process that can be coordinated, with systematic weight perturbations and adjustment, or which can be operated asynchronously and autonomously; and

a performance monitor in communication with the remote receiver and the array control system and configured to receive the feedback information from the remote receiver relating to a measure of transmit performance from the plurality of antennas to the remote receiver.

12. The system of claim 11, wherein the component for generation of the plurality of weights to be applied to the transmit signals from the plurality of antennas includes a computer using software algorithms that maximize the response at the remote receiver.

13. The system of claim 11, wherein the remote receiver is one of a cooperative receiver satellite, a bent-pipe satellite, a reflector satellite, and a non-cooperative radar target that returns a power sample.

14. The system of claim 11, wherein the remote receiver provides the feedback information relating to transmit performance to the performance monitor via a plurality of communication downlinks from the remote receiver.

15. The system of claim 14, wherein the performance monitor is located at one of the remote receiver and the array control system, and the remote receiver has a transmit capability in order to return feedback information to the array control system.

16. The system of claim 11, wherein the component for application of the weights to the transmit signals for each of the plurality of antennas includes an apparatus for adjusting antenna transmission weighting values with in-phase and quadrature multiplication, or for a shifting in a phase of the transmitted signals, resulting in the transmitted signals from the plurality of antennas arriving at the remote receiver substantially simultaneously.

17. The system of claim 11, further comprising a component that implements a complex envelope methodology for transmission whereby RF beamforming is accomplished with carrier phase and information alignment is accomplished at baseband by sample delay.

18. The system of claim 11, wherein the array control system further comprises a component for correcting latency between a change in the plurality of weights to the transmit signals and receipt of a plurality of communication downlinks from the remote receiver.

19. The system of claim 18, wherein the component for correcting latency uses a computer modeled rate of change to calculate adjustment to the weights due to an actual rate of change.