# Python code using matplotlib library to generate 72 images to create a gif file that shows
# how phase change is achieved by changing I and Q signals amplitude in IQ modulators
# 
# I- inphase Q-quadrature

# Physics concept : how by only changing the magnitude of I and Q signals amplitude
# one can change the phase of I+Q wave signal

import matplotlib.pyplot as plt
import numpy as np

# t is the current phase, and phase is changed from 0° to 355° in the steps of 5°

for t in range(0,356,5):

    # I) CREATING FUNCTION FOR PLOTTING

    # creating a blue circle in PHASOR DIAGRAM using parametric equation (radius=1, theta=s)
    s=np.linspace(0, 2 * np.pi, 400)
    x1=np.cos(s)
    y1=np.sin(s)

    # creating I and Q vectors magnitude (x=I, y=Q) in PHASOR DIAGRAM
    x = 1*np.cos(0.0174533*t)
    y = 1*np.sin(0.0174533*t)

    # creating I, Q, I+Q amplitude and Phase (0° to 720°) for WAVE DIAGRAM
    x2 = np.linspace(0, 721, 400) # Pahse from 0° to 720° divided into 400 points
    y2 = 1*np.sin(0.0174533*t)*np.sin(0.0174533*x2) # Q
    z2 = 1*np.cos(0.0174533*t)*np.cos(0.0174533*x2) # I
    q2 = (y2 + z2) # (I+Q)

    # creating text to show current phase t
    text1 = "phase = " + str(t)+'°'

    # II) CREATING THE PLOT (phasor and wave diagram in one plot arranged 1 x 2)

    # ax1 = Phasor diagram subplot and ax2 = Wave diagram subplot
    fig, (ax1, ax2) = plt.subplots(1, 2, figsize=(9.5,4.1))
    ax1.title.set_text('Phasor diagram')
    ax2.title.set_text('Wave diagram')

    # Setting the position of the subplot title
    ax1.title.set_position([.5, 1.05])
    ax2.title.set_position([.5, 1.05])

    # II-A) PHASOR DIAGRAM

    # including the current phase inside the Phasor diagram subplot
    ax1.text(0.9, 0.9, text1, bbox=dict(boxstyle="square",facecolor='white', alpha=0.5))

    # setting the y axis limit
    ax1.set_ylim(-1, 1)

    # Plotting the blue outer circle of radius = 1
    ax1.plot(x1, y1, 'b')

    # Move left y-axis and bottom x-axis to centre, passing through (0,0)
    ax1.spines['left'].set_position('center')
    ax1.spines['bottom'].set_position('center')

    # Eliminate upper and right axes
    ax1.spines['right'].set_color('none')
    ax1.spines['top'].set_color('none')

    # Show ticks in the left and lower axes only
    ax1.xaxis.set_ticks_position('bottom')
    ax1.yaxis.set_ticks_position('left')

    # Setting the y axis ticks at (-1,-0.5,0,0.5,1)
    ax1.set_yticks([-1,-0.5,0,0.5,1])

    # Creating Arrows and dashed lines
    ax1.arrow(0, 0, x, y, length_includes_head='True', head_width=0.05, head_length=0.1, color='g') # I+Q
    ax1.arrow(0, 0, x, 0, length_includes_head='True', head_width=0.05, head_length=0.1, color='b') # I
    ax1.arrow(0, 0, 0, y, length_includes_head='True', head_width=0.05, head_length=0.1, color='r') # Q
    ax1.arrow(x, 0, 0, y, length_includes_head='True', head_width=0, head_length=0, ls='-.') # vertical dashed lines
    ax1.arrow(0, y, x, 0, length_includes_head='True', head_width=0, head_length=0, ls='-.') # Horizontal dashed lines

    # II-B) WAVE DIAGRAM

    # setting the y axis limit
    ax2.set_ylim(-1.5, 1.5)

    # Setting the y axis ticks at (0, 180, 360, 540, 720) degree phase
    ax2.set_xticks([0, 180, 360, 540, 720])

    # Setting the position of the x and y axis
    ax2.spines['left'].set_position(('axes', 0.045))
    ax2.spines['bottom'].set_position(('axes', 0.5))

    # Eliminate upper and right axes
    ax2.spines['right'].set_color('none')
    ax2.spines['top'].set_color('none')

    # Creating x and y axis label
    ax2.set_xlabel('Phase (degree)', labelpad=0)
    ax2.set_ylabel('Amplitude', labelpad=0)

    # Plotting I, Q and I+Q waves
    ax2.plot(x2, z2, 'b', label='I', linewidth=0.5)
    ax2.plot(x2, y2, 'r', label='Q', linewidth=0.5)
    ax2.plot(x2, q2, 'g', label='I+Q')

    # function for amplitude of I+Q green arrow
    c1=1 * np.cos(0.0174533 * t) * np.cos(0.0174533 * t)+1*np.sin(0.0174533*t)*np.sin(0.0174533*t)

    # plotting I+Q arrow that moves along to show the current phase
    ax2.arrow(t, 0, 0, c1, length_includes_head='True', head_width=10, head_length=0.07, color='g')

    # plotting I and Q amplitude arrows at position 180° and 90° respectively
    ax2.arrow(180, 0, 0, 1*np.cos(0.0174533*t)*np.cos(0.0174533*180), length_includes_head='True', head_width=10, head_length=0.07, color='b')
    ax2.arrow(90, 0, 0, 1*np.sin(0.0174533*t)*np.sin(0.0174533*90), length_includes_head='True', head_width=10, head_length=0.07, color='r')

    # Creating legend
    ax2.legend(loc='center', ncol=3, bbox_to_anchor=[0.5, 0.94])

    # Adjusting the relative position of the subplots inside the figure
    fig.subplots_adjust(left=0.07, bottom=0.15, right=None, top=None, wspace=0.3, hspace=None)

    # Saving the figure
    fig.savefig('0file%s.png' %t)

    # Clearing the figure for the next iteration
    fig.clf()