how to plot the phase shift

i want this graph but this code didn't work properly after rp is 1

clear; 
clc; 

tetai = 0:0.01:89.99; 
n1 = 1.5; 
n2 = 1; 
tetac = asind(n2/n1); 
tetat = asind(n1*sind(0:0.01:tetac)/n2); 
L = length(tetat); 
L2 = length(tetai); 
tetat(L+1:1:L2) = 90; 

rp = (n2*cosd(tetai) - n1*cosd(tetat))./(n1*cosd(tetat) + n2*cosd(tetai)); 

% treating amplitude coefficients as complex
rp_complex = rp + 1i*0;

phase_rp_deg = angle(rp_complex) * (180/pi); % Calculating phase of rp in degrees

plot(tetai, phase_rp_deg);  % Plotting phase of rp as a function of incident angle
ylim([0 180]);  % Setting y-axis limit to -180 to 180 to represent phase in degrees
xlabel('Incident Angle (degrees)');
ylabel('Phase of rp (degrees)');
title('Phase of rp vs Incident Angle');

[Anton Kogios]

I have no idea about this topic, but something from your code is that you are trying to get the angel of a complex number you made. But you made it have 0 imaginary component, so the angle will just be 0.

[Voss]

... or 180 degrees, for negative real numbers.

Answer 1

[Sandeep Mishra]

Hi 학준,

While reproducing the provided code snippet in MATLAB R2024a, I noticed the following observations:

• The variable “rp” consists of all real values.
• The variable “rp_complex” is simply the sum of “rp” and 0, making "rp_complex" also a real number.
• The "phase_rp_deg" variable utilizes the MATLAB function "angle" which returns the phase angle for each element in the complex array “rp_complex”.

Based on the above observations, it is evident that the variable "rp_complex" is always a real number. Consequently, "phase_rp_deg" will yield a result of “0” for each complex number of “rp_complex”.

Additionally, to plot the complex angle graph, you can utilize the following example code:

% Adding complex variable (2i) to real value rp
rp_complex = rp + 1i*2 

Refer to the following documentation for more details on the “angle” function.

1. https://www.mathworks.com/help/releases/R2024a/matlab/ref/angle.html

I hope it helps.