Adaptive steerable null antenna processor

• US 4,280,128 A
• Filed: 03/24/1980
• Issued: 07/21/1981
• Est. Priority Date: 03/24/1980
• Status: Expired due to Term

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Masak, Raymond J.
• Primary Examiner(s): Lieberman, Eli
• Application Number:
  US06/132,941
• Time in Patent Office: 484 Days
• Field of Search: 343/100 LE, 343/854, 343/100 SA
• US Class Current: 342/380
• CPC Class Codes: G01S 3/06 Means for increasing effective directivity, e.g. by combining signals having differently oriented directivity characteristics or by sharpening the envelope waveform of the signal derived from a rotating or oscillating beam antenna comparing amplitude of signals having differently oriented directivity characteristics to determine direction G01S3/16, G01S3/28
• CPC Class Codes: G01S 7/2813 Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays specially adapted to secondary radar systems G01S13/762; aerials or aerials systems H01Q21/29, H01Q25/00
• CPC Class Codes: H01Q 3/2611 Means for null steering; Adaptive interference nulling

Abstract

An adaptive signal processing system for enhancing the signal-to-interfere characteristics on both receive and transmit using an in phase-quadrature correlator to control phase and amplitude adjust circuits located in the antenna signal paths. The amplitude adjustment provides amplitude balance control with variable delay lines between a quadrature hybrid and a sum-difference hybrid. The analog outputs of the correlator are digitized to control incrementally adjustable delay lines of the phase and amplitude circuits in binary steps.

Claims

1. A steerable null antenna processor system for receiving desired wave energy signals from at least one angular region of space within the area covered by the system and for suppressing interfering signals from at least one other angular region comprising:

antenna means having at least first and second antenna elements;

antenna signal path means including combining means coupled between said antenna elements and a common port for supplying said desired wave energy signals to said common port;

nulling means comprising phase means and amplitude means forming part of said antenna signal path means, both the phase means and the amplitude means being adjustable in incremental steps and having control inputs, operative in response to digital control inputs to adjust the phase and amplitude values of the nulling means;

analog controller means having correlator means, at least one reference input and at least one feedback input from said antenna signal path means, said analog controller means being operative to generate analog phase and amplitude control signals, converter means to change the last said signals to digital control signals and to supply them to said control inputs of the nulling means, to thereby steer at least one null to interfering signals;

said correlator means comprising an in phase hybrid and a quadrature hybrid with inputs coupled to said feedback and reference inputs, two mixers connected to multiply together outputs from said hybrids, and integration means to generate said analog phase and amplitude control signals.

2. A system according to claim 1, for both receiving and transmitting, wherein said antenna signal path means including the nulling means is reciprocal for received signals and transmitted signals to and from said common port respectively with substantially the same antenna radiation pattern, so that a null direction established for received signals may be maintained during transmission.

3. A system according to claim 1 or 2, wherein said analog controller means comprises a least means square loop.

4. A system according to claim 3, wherein said amplitude means comprises an amplitude balance control network including a quadrature hybrid, a sum-difference hybrid, and additional phase means which is adjustable in incremental steps and which is coupled between said hybrids, to provide a variable ratio of signal power amplitude at said antenna elements with respect to the combined power at said common port.

5. A steerable null antenna processor system for receiving wave energy signals from at least one angular region of space within the area covered by the system and for suppressing interfering signals from at least one other angular region, using antenna elements;

said processor system comprising;

nulling means coupled between said antenna elements and a common port for supplying said desired wave energy signals to said common port, said nulling means being comprised of phase means and amplitude means, the amplitude means being a variable ratio combiner comprising a quadrature hybrid, a sum-difference hybrid, and two delay lines at least one of which is adjustable in incremental steps, each hybrid having a first, a second, a third and a fourth port, with one of said delay lines connected from the third port of a first of said hybrids to the first port of a second of said hybrids, and the other said delay line connected from the fourth port of the first hybrid to the second port of the second hybrid, said common port being the fourth port of the second hybrid;

wherein said phase means comprises two delay lines at least one of which is incrementally adjustable, one connected from the first antenna element to the first port of said first hybrid, and the other connected from the second antenna element to the second port of the first hybrid;

memory means to store digital signals for setting said delay lines to selected steps, comprising phase memory means connected to control inputs of the delay lines of said phase means, and amplitude memory means connected to control inputs of the delay lines of said amplitude means;

analog controller means with a least means square loop comprising a reference path, a feedback path, and correlation means;

the reference path and feedback paths having respective input connections from said third and fourth ports of the second hybrid;

the correlation means comprising in phase/quadrature means connected to the feedback and reference paths to derive in phase and quadrature components and means to multiply them together, the correlation means further comprising integration means coupled to the in phase-quadrature means and having an analog amplitude output and an analog phase output on which analog control signals are produced,

analog-to-digital means comprising sample-and-hold means and analog-to-digital converter means coupled between said outputs of said integration means and said memory means;

said analog controller means being operative in response to analog signals input to the feedback path and reference path to supply digital signals to said memory means to steer a null to interfering signals.

6. A system according to claim 5, for both receiving and transmitting, wherein said nulling means is reciprocal for received signals and transmitted signals to and from said common port respectively with substantially the same antenna radiation pattern, so that a null direction established for received signals may be maintained during transmission.

7. A system according to claim 5 or 6, wherein said in phase/quadrature means comprises an in phase hybrid coupled to the feedback path, a quadrature hybrid coupled to the reference path, and two mixers, each having two inputs, one from each of the last said hybrids;

and said integration means comprises two resistance-capacitance low pass filters, each followed by video amplifier means coupled respectively to said analog amplitude output and said analog phase output.

8. A system according to claim 7, wherein said analog-to digital means includes time division multiplex means arranged to time share the sample-and-hold means and the analog-to-digital converter means for alternating use for amplitude control signal and phase control signal conversion.

9. A system according to claim 8, wherein in said nulling means said first hybrid is the quadrature hybrid and said second hybrid is the sum-difference hybrid, said common port being the difference port of the second hybrid and said reference path being coupled to the sum port.