From a6fed801495ec0db4114dd97b489bfdf87df68f8 Mon Sep 17 00:00:00 2001
From: Thomas Kolb <cfr34k-git@tkolb.de>
Date: Sat, 29 Jan 2022 22:03:51 +0100
Subject: [PATCH] Added script for plotting the spectrum of signal dumps

---
 impl/utils/plot_spectrum.py | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100755 impl/utils/plot_spectrum.py

diff --git a/impl/utils/plot_spectrum.py b/impl/utils/plot_spectrum.py
new file mode 100755
index 0000000..16481f6
--- /dev/null
+++ b/impl/utils/plot_spectrum.py
@@ -0,0 +1,24 @@
+#!/usr/bin/env python3
+
+import sys
+
+import numpy as np
+import matplotlib.pyplot as pp
+
+with open(sys.argv[1], 'rb') as infile:
+    header = infile.read(4)
+    if header != b'CPX_':
+        print(f"Error: not a complex signal file. Format {header} not implemented yet.")
+        exit(1)
+
+    T = np.fromfile(infile, dtype=np.float32, count=1)
+    data = np.fromfile(infile, dtype=np.complex64)
+
+    f = np.arange(-1/(2*T), 1/(2*T), 1/T/data.size)
+
+    spec = 20*np.log10(np.absolute(np.fft.fftshift(np.fft.fft(data))) / data.size)
+
+    pp.plot(f, spec, 'b-')
+    pp.legend(['Spectrum'])
+    pp.xlabel('Frequency [Hz]')
+    pp.show()