Using scikit-rf plotting SMith Chart with normalized to 50 Ohms

Dennis

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Apr 29, 2023, 10:36:20 AMApr 29

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Hey, I have a question regarding the SmithChart. Is it possible normilize the values to 50 Ohm and get this values in a new touchstone file?

Dennis

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Apr 29, 2023, 3:40:14 PMApr 29

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data = rf.Network(File)

idx_start = np.abs(data.f - (plot_data_s2p[0][2]*1000000)).argmin()
idx_stopp = np.abs(data.f - (plot_data_s2p[0][3]*1000000)).argmin()
freq = rf.Frequency(start=data.f[idx_start], stop=data.f[idx_stopp])
freq_new = data.frequency[idx_start:idx_stopp]

data_new = data.interpolate(freq_new)
data_new.s11.plot_s_smith(ax=ax0, label = filenames[counter_filename], linewidth=0.9, draw_labels=True)

mhuser

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Apr 29, 2023, 4:44:10 PMApr 29

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If the data are not normalized to 50 ohm, it is possible to renormalize them:

data_normalized = data.copy()

data_normalized.renormalize([50, 50])

data_normalized.write_touchstone(filename = 'example.s2p')

Network.renormalize

Network.write_touchstone

Dennis

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Apr 29, 2023, 4:57:51 PMApr 29

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The data is normalized to 50 ohm, I can convert them with data.s11.z to the impedance as that I know, but I want to draw the labels on the Smith Chart also to 50 Ohm and not normalized to 1

Message has been deleted

mhuser

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Apr 29, 2023, 6:26:42 PMApr 29

to scikit-rf

plot_z_smith(...) does not exist.

But if you want to replace the 1 with 50 you can call the plotting function manually:

import skrf as rf
from matplotlib import pyplot as plt
rf.stylely()

plt.figure()
rf.plotting.smith(draw_labels = True, ref_imm = 50.0)

rf.plotting.plot_smith(n.s[:, 0, 0], title = None, x_label = None, y_label = None, label = 's11')

mhuser

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Apr 29, 2023, 6:30:31 PMApr 29

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This should also works:

plt.figure()
rf.plotting.smith(draw_labels = True, ref_imm = 50.0)

data.plot_s_smith(0, 0)

Dennis

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Apr 30, 2023, 5:09:03 AMApr 30

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That is working for me, thanks a lot. But I got another problem in regards. If I put draw_labels = False the markers with scatter and annote are getting plottet and if I put draw_labels = True they will not beeing plotted

filenames.append(os.path.basename(os.path.splitext(File)[0]))

data = rf.Network(File)

idx_start = np.abs(data.f - (plot_data_s2p[0][2]*1000000)).argmin()
idx_stopp = np.abs(data.f - (plot_data_s2p[0][3]*1000000)).argmin()
freq = rf.Frequency(start=data.f[idx_start], stop=data.f[idx_stopp])
freq_new = data.frequency[idx_start:idx_stopp]

data_new = data.interpolate(freq_new)

rf.plotting.smith(ax=ax0, draw_labels = False, ref_imm = 50, chart_type='z')
data_new.s11.plot_s_smith(ax=ax0, label = filenames[counter_filename], linewidth=0.9)
leg1 = ax0.legend(loc="upper right", fontsize= 6)

lines = ax0.get_lines()
colors = [line.get_color() for line in lines]
new_colors = colors[3:]
table_colors = np.repeat(new_colors, 3)

if table_s11 == 1:
s11_points = []
s11_points_index = []
for i in range(len(plot_data_s2p[3])):
s11_points = np.append(s11_points, np.interp(plot_data_s2p[4][i]*10e5, data.f, np.squeeze(data.s11.s)))

print(s11_points)
# Add Marker
for i in range(len(plot_data_s2p[3])):
ax0.scatter(s11_points.real[i], s11_points.imag[i], marker = '.', s=20, color=new_colors[counter_filename])
ax0.annotate(plot_data_s2p[6][i], (s11_points.real[i], s11_points.imag[i]), xytext=(-7, 7), textcoords='offset points', color=new_colors[counter_filename])

mhuser

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Apr 30, 2023, 6:18:28 AMApr 30

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Nice plot!

Strange, this works for me:

fig, ax0 = plt.subplots()
rf.plotting.smith(ax = ax0, draw_labels = True, ref_imm = 50.0, chart_type = 'z')
n.plot_s_smith(ax = ax0)
leg0 = ax0.legend(loc="upper right", fontsize= 6)
ax0.scatter(n.s.real[1, 0, 0], n.s.imag[1, 0, 0], marker = '.', s=20, color='r')
ax0.annotate('M1', (n.s.real[1, 0, 0], n.s.imag[1, 0, 0]), xytext=(-7, 7), textcoords='offset points', color='r')

Dennis

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Apr 30, 2023, 3:43:28 PMApr 30

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I found my problem: Sadly it was the color iterate with lines = ax0.get_lines() colors = [line.get_color() for line in lines].

I don't know, but it took weird colours and every fourth colour was my line colour. I fixed it by new_colors = colors[4::5].

the first element of the array is always a white colour in regards I couldn't see any Markers on the plot beacause it was white :D.

filenames.append(os.path.basename(os.path.splitext(File)[0]))
data = rf.Network(File)

idx_start = np.abs(data.f - (plot_data_s2p[0][2]*1000000)).argmin()
idx_stopp = np.abs(data.f - (plot_data_s2p[0][3]*1000000)).argmin()
freq = rf.Frequency(start=data.f[idx_start], stop=data.f[idx_stopp])
freq_new = data.frequency[idx_start:idx_stopp]
data_new = data.interpolate(freq_new)

rf.plotting.smith(ax=ax0, draw_labels = True, ref_imm = 50, chart_type='z')

data_new.s11.plot_s_smith(ax=ax0, label = filenames[counter_filename], linewidth=0.9)
leg1 = ax0.legend(loc="upper right", fontsize= 6)

lines = ax0.get_lines()
colors = [line.get_color() for line in lines]

new_colors = colors[4::5]
table_colors = np.repeat(new_colors, 3)

print(new_colors)

if table_s11 == 1:
s11_points = []
s11_points_index = []
for i in range(len(plot_data_s2p[3])):

s11_points_index = np.append(s11_points_index, np.abs(data.f - (plot_data_s2p[3][i]*1000000)).argmin())
s11_points = np.append(s11_points, np.interp(plot_data_s2p[3][i]*10e5, data.f, np.squeeze(data.s11.s)))

# Add Marker
for i in range(len(plot_data_s2p[3])):

ax0.scatter(data.s11.s.real[int(s11_points_index[i])], data.s11.s.imag[int(s11_points_index[i])], marker = '.', s=20, color=new_colors[counter_filename])
ax0.annotate(plot_data_s2p[6][i], (data.s11.s.real[int(s11_points_index[i])], data.s11.s.imag[int(s11_points_index[i])]), xytext=(-7, 7), textcoords='offset points', color=new_colors[counter_filename])

s11_points_legend = []

for i in range(len(plot_data_s2p[3])):

s11_points_legend = np.round(np.append(s11_points_legend, np.interp(plot_data_s2p[4][i]*10e5, data.f, np.squeeze(data.s11.z[:,0,0]))),2)
legend_labels.append([plot_data_s2p[6][i], str(plot_data_s2p[3][i])+' MHz', str(np.round(s11_points_legend[i],3))])
counter_filename = counter_filename + 1

mhuser

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Apr 30, 2023, 4:06:06 PMApr 30

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I'm glad it works. The plot looks very good and the display of the marker table with colours is excellent!

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