#!/usr/bin/env python
# coding: utf-8

# # Strap Reactance Frequency Fit

# The antenna straps having a given length, their reactance is non zero. Let's look to the strap reactances from the realistic antenna model in vacuum and facing the water tank (aka the "aquarium"):

# In[ ]:


import matplotlib.pyplot as plt
import numpy as np
import skrf as rf
from tqdm.notebook import tqdm

# WEST ICRH Antenna package
import sys; sys.path.append('..')
from west_ic_antenna import WestIcrhAntenna

# styling the figures 
rf.stylely()


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# HFSS simulation of the antenna front-face radiating in WEST empty chamber (vacuum)
file_vacuum = '../west_ic_antenna/data/Sparameters/front_faces/WEST_ICRH_antenna_front_face_curved_30to70MHz.s4p'
ntw_vacuum = rf.Network(file_vacuum)

# HFSS simulation of the antenna front-face direclty facing the water tank
file_aquarium = '../west_ic_antenna/data/Sparameters/front_faces/aquarium/HFSS/Epsr_55MHz/WEST_ICRH_front_face_with_aquarium_Daq00cm.s4p'
ntw_aquarium = rf.Network(file_aquarium)


# Let's plot the front-face resistance R_s ($X_s=\Im(Z)$) and reactance ($X_s=\Im(Z)$) of each port for each cases:

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fig, ax = plt.subplots(2, 1, sharex=True)
# real parts
[ntw_vacuum.plot_z_re(m=idx, n=idx, ax=ax[0], ls='--', color=f'C{idx}',
                      label=f'vacuum - port {idx}') for idx in range(4)]
[ntw_aquarium.plot_z_re(m=idx, n=idx, ax=ax[0], color=f'C{idx}',
                        label=f'aquarium - port {idx}') for idx in range(4)]
ax[0].set_title('Real part of the front-face port impedances')
# imag parts
[ntw_vacuum.plot_z_im(m=idx, n=idx, ax=ax[1], ls='--', color=f'C{idx}',
                      label=f'vacuum - port {idx}') for idx in range(4)]
[ntw_aquarium.plot_z_im(m=idx, n=idx, ax=ax[1], color=f'C{idx}',
                        label=f'aquarium - port {idx}') for idx in range(4)]
ax[1].set_title('Imaginary part of the front-face port impedances')
fig.tight_layout()
[a.legend(ncol=2) for a in ax]


# As one can see, while the resistance of the front-face's ports obviously depend of the coupling conditions, while the reactance is almost independant of the coupling conditions and only depends of the frequency. 
# 
# Hence, one can fit the strap reactance with frequency only:

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from numpy import polyfit, polyval


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# polynomial fit of the strap reactance
coeffs = polyfit(ntw_vacuum.frequency.f/1e6, 
                 ntw_vacuum.z_im[:,0,0], 
                 deg=3)
print(coeffs)


# The strap reactance can be approximated by the following formula:
# 
# $$
# X_s(f_{\mathrm{MHz}}) 
# = 
# 1.66\times 10^{-4} f_{\mathrm{MHz}}^3 
# -1.53\times 10^{-2} f_{\mathrm{MHz}}^2 
# + 1.04 f_{\mathrm{MHz}}
# -7.77
# $$

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def Xs(f_MHz):
    """
    Strap Reactance [Ohm] for a given frequency in MHz
    """
    return 1.66e-04*f_MHz**3 -1.53e-02*f_MHz**2 + 1.04*f_MHz -7.77


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fig, ax = plt.subplots()
ntw_vacuum.plot_z_im(m=0, n=0, ax=ax, lw=2, label='simulation')
ax.plot(ntw_vacuum.frequency.f, Xs(ntw_vacuum.frequency.f/1e6), 
        lw=2, ls='--', label='fit')
ax.set_xlim(30e6, 70e6)
ax.legend()
ax.grid(True)
ax.set_title('Strap Reactance $X_s$')
ax.set_ylabel('$X_s$ [$\Omega$]')


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from IPython.core.display import HTML
def _set_css_style(css_file_path):
    """
    Read the custom CSS file and load it into Jupyter
    Pass the file path to the CSS file
    """
    styles = open(css_file_path, "r").read()
    s = '<style>%s</style>' % styles
    return HTML(s)

_set_css_style('custom.css')