# Generation of random phase factors.

46 views (last 30 days)
Ved on 8 Dec 2013
Commented: Ved on 9 Dec 2013
How to generate a random phase vector of size MxN following these conditions:
for M=1:5
N = 4; % number of columns in output phase matrix (P_out)
theta= 1xN random values over range of [0:360] degrees
P=exp(j*theta) % Phase factor
P_out= MxN output row vector for random N values of theta
end
Conditions for choosing theta:
1. 0 <= theta <= 2*pi % Range of theta
2. Each theta is any whole number multiple of smallest non-zero theta.for e.g.,
say for N = 4: theta=[45,0,180,225]% random angles
here each value of theta is a some whole number multiple of 45: [45x0=45, 45x1=45, 45x4=180, 45x5=225]
So,
P_out=MXN matrix having all different angles in a row.
Any help is much appreciated, regards

Wayne King on 8 Dec 2013
Edited: Wayne King on 8 Dec 2013
Maybe you want something like this:
N = 4; % number you want
MaxAngle = floor(360/N)-1;
StartAng = randi([0 MaxAngle],1,1);
phaseangles = StartAng:StartAng:N*StartAng;
I've tried to make sure above that you only get angles in [0 360] but you if you really want every phase angle to be a multiple of some starting angle, the more angles you want, the greater that restricts your initial angle choice --unless you don't care about wrapping around the circle.
Ved on 9 Dec 2013
@Wayne King: thank you !

Image Analyst on 8 Dec 2013
Edited: Image Analyst on 8 Dec 2013
Try this:
numberOfAngles = 4; % or however many you need
theta = 45 * (randi(8, 1, numberOfAngles) - 1)
Of course, multiply by pi/180 if you want it in radians. Also, you can use sind(), cosd(), etc. if you want to use functions that work in degrees instead of radians.
Ved on 9 Dec 2013
@Image Analyst:Thank you

Wayne King on 8 Dec 2013
Edited: Wayne King on 8 Dec 2013
The way you have set it up, the phase angles are not random
If you really want phase angles randomly chosen to cover the interval (-pi, pi]
theta = -pi+2*pi*rand(10,1);
The above gives you 10 of them.
Ved on 8 Dec 2013
@Wayne King: Thank you but could i get non fractional theta values [0 : 360 degrees] and each theta is some whole number multiple of smallest non-zero theta.

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