Adaptive direction of arrival antennae system
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorErnest W. Coleman
Life of this patent
Estimating the term…
Abstract
A system for adaptively determining the direction of arrival (DOA) of a larly polarized RF signal. Three antennae are positioned at fixed distances from one another in a right triangle configuration to receive the RF signal. The antennae are alternatingly switched into two orthogonally aligned pairs and each pair exhibits an antenna pattern null which is adaptively steered toward the RF signal by a computer program operatively connected to a variable phase shifter which selectively alters the phase of the received signal. An algorithm within the program calculates the direction of arrival of the signal relative to a selected one of the antenna pair axes.
Claims10
An antennae system for adaptively determining the direction of arrival angle .alpha. of a signal source, comprising, in combination:
- first, second and third antennae fixed in a right triangle configuration for receiving the signal source and for producing respective output signals indicative of said source:
- phase shifting means having a first input connected to receive the output signal from the respective one of said antennae fixed at the right angle apex of said configuration and for producing a phase shifted output signal upon receipt of a control signal at a second input;
- means connected to receive the phase shifted output signal, output signals from the respective others of said antennae and control signals for alternatingly summing said phase shifted output signal with selected ones of the other antenna output signals according to the receipt of said control signals and for producing summed output signals indicative thereof;
- detecting means connected to receive the summed output signals for detecting the levels thereof and for producing an output indicative of said levels;
- and
- processing means connected to provide said control signals to said phase shifting means second input and to said summing means and connected to receive the detecting means output for calculating the antenna pattern null angles .theta. of orthogonal pairs of said antennae according to the equation ##EQU5## wherein .psi. = the phase angle of the summed output signals having the lowest output level and the antennae in each of said pairs are separated by one quarter wavelength, and for producing the direction of arrival angle of the signal source according to the equation ##EQU6## wherein .theta..sub.1 = the null angle of one orthogonal antennae pair and .theta..sub.2 = the null angle of the other orthogonal antennae pair.
A method for calculating the direction of arrival angle .alpha. of an RF signal source comprising the steps of:
- placing three antennae in a right triangle configuration having two orthogonal pairs of antennae with a spacing of one quarter wavelength between respective antennae forming each of said pairs;
- incrementally shifting the phase angle of the signal received by the antenna placed at the apex of the right triangle;
- summing the shifted phase angle signal with only the received signal from the remaining antenna is one of the orthogonal pairs;
- selecting the phase angle .psi..sub.1 of the summed signal having the lowest energy level;
- calculating a first antenna pattern null angle .theta..sub.1 according to the equation ##EQU7## summing the shifted phase angle signal with only the received signal from the remaining antenna in the other of the orthogonal pairs;
- selecting the phase angle .psi..sub.2 of the summed signal having the lowest energy level;
- calculating a second antenna pattern null angle .theta..sub.2 according to the equation ##EQU8## calculating the direction of arrival angle according to the equation ##EQU9##
Dependencies are inferred from the claim text.