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1 files changed, 78 insertions, 0 deletions

diff --git a/buch/papers/ellfilter/python/elliptic2.py b/buch/papers/ellfilter/python/elliptic2.py
new file mode 100644
index 0000000..92fefd9
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+++ b/buch/papers/ellfilter/python/elliptic2.py
@@ -0,0 +1,78 @@
+# %%
+
+import matplotlib.pyplot as plt
+import scipy.signal
+import numpy as np
+import matplotlib
+from matplotlib.patches import Rectangle
+
+
+def ellip_filter(N):
+
+    order = N
+    passband_ripple_db = 3
+    stopband_attenuation_db = 20
+    omega_c = 1000
+
+    a, b = scipy.signal.ellip(
+        order,
+        passband_ripple_db,
+        stopband_attenuation_db,
+        omega_c,
+        btype='low',
+        analog=True,
+        output='ba',
+        fs=None
+    )
+
+    w, mag_db, phase = scipy.signal.bode((a, b), w=np.linspace(0*omega_c,2*omega_c, 4000))
+
+    mag = 10**(mag_db/20)
+
+    passband_ripple = 10**(-passband_ripple_db/20)
+    epsilon2 = (1/passband_ripple)**2 - 1
+
+    FN2 = ((1/mag**2) - 1)
+
+    return w/omega_c, FN2 / epsilon2
+
+
+plt.figure(figsize=(4,2.5))
+
+for N in [5]:
+    w, FN2 = ellip_filter(N)
+    plt.semilogy(w, FN2, label=f"$N={N}$")
+
+plt.gca().add_patch(Rectangle(
+    (0, 0),
+    1, 1,
+    fc ='green',
+    alpha=0.2,
+    lw = 10,
+))
+plt.gca().add_patch(Rectangle(
+    (1, 1),
+    0.01, 1e2-1,
+    fc ='green',
+    alpha=0.2,
+    lw = 10,
+))
+
+plt.gca().add_patch(Rectangle(
+    (1.01, 100),
+    1, 1e6,
+    fc ='green',
+    alpha=0.2,
+    lw = 10,
+))
+plt.xlim([0,2])
+plt.ylim([1e-4,1e6])
+plt.grid()
+plt.xlabel("$w$")
+plt.ylabel("$F^2_N(w)$")
+plt.legend()
+plt.savefig("F_N_elliptic.pdf")
+plt.show()
+
+
+