function [angleDeg angleRad]=aoaInter(phaseAngle, distance, opFreq)% AOAINTER  Interferometer based angle of arrival% %   [angleDeg angleRad]=aoaInter(phaseAngle, distance, opFreq)%   %   OUTPUTS%   angleDeg     = Calculated angle of arrival of the radar signal [degrees]%   angleRadians = Calculated angle of arrival of the radar signal [radians]% %   INPUTS%   phaseAngle = phase difference of received signal between two antennas%                [degrees]%                this can be entered as an array if more than two antennas%                eg. [193 87]%   distance   = distance between antennas [m]%                ensure this corresponds with the phase angle difference%                eg. phi 1-2 = 193, dist 1-2 = 0.5m%   opFreq     = operating frequency [Hz]% %   EXAMPLE:%   Phase angle difference between antennas%   phi 1-2 = 193%   phi 1-3 = 87%   Distance between antennas%   1-2 = 0.5m%   2-3 = 0.1m%   Operating frequency is 3 GHz%   myArrivalAngle = aoaInter([193 87],[0.5 0.6],3e9)% %   AIM:%   To determine the angle of arrival of a radar signal% %   TECHNICAL BACKGROUND:%   An interferometer is a system which determines the angle of arrival of%   a signal by comparing the phase of the signal when it arrives. The%   phase is measured over an array of irregularly spaced linearly arranged%   antenna pairs. The spacing of these antenna pairs is crucial to achieve%   an accurate system.%   In an interferometer system, a longer baseline will provide a more%   accurate angular result. However this comes at the cost of ambiguities.%   Once an antenna baseline is increased to more than half a wavelength,%   ambiguities will arise. A well designed system will result in%   ambiguities being reduced or eliminated by having several well placed%   antennas. Therefore there will only be one solution between several%   pairs.%   Adv: high accuracy from short baseline, works against pulsed and CW%   Disadv: cost, multiple antennas, receiver phase matchiing requirements % %   REFERENCE:%   Benson, Frater, Ryan, TACTIACL ELECTRONIC WARFARE, Argoss Press, 2007,%   pp.218,219.%   Adamy, INTRO TO EW MODELLING AND SIMULATION, Artech house, 2003, p.134% %   AUTHOR: Jason MOYLE%   DATE: September 2008 % %   See also ANGLESEARCH, AOAERR%% Initiate variablesanglePhi=d2r(phaseAngle);   % Convert angles to radiansl=f2l(opFreq);              % Wavelengthd=distance;                 % Distance between antennas%% Calculate possible valid anglesfor i=1:length(anglePhi)    phi=anglePhi(i);    D=d(i);%     fprintf('Results for angle %.0d',i)    clear theta;    for n=0:5        theta(n+1)=asind((n+phi/2/pi)*l/D);    end    aoa(i,:)=theta;           % possible aoa for each set of antennasend%% Search for angle of arrivalangleDeg = angleSearch(aoa);angleRad = d2r(angleDeg);