kopia lustrzana https://github.com/NanoVNA-Saver/nanovna-saver
206 wiersze
7.9 KiB
Python
206 wiersze
7.9 KiB
Python
# NanoVNASaver
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#
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# A python program to view and export Touchstone data from a NanoVNA
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# Copyright (C) 2019, 2020 Rune B. Broberg
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# Copyright (C) 2020,2021 NanoVNA-Saver Authors
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <https://www.gnu.org/licenses/>.
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import logging
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import math
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from PyQt5 import QtWidgets
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from NanoVNASaver.Analysis import Analysis
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from NanoVNASaver.Formatting import format_frequency
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logger = logging.getLogger(__name__)
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class LowPassAnalysis(Analysis):
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def __init__(self, app):
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super().__init__(app)
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self._widget = QtWidgets.QWidget()
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layout = QtWidgets.QFormLayout()
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self._widget.setLayout(layout)
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layout.addRow(QtWidgets.QLabel("Low pass filter analysis"))
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layout.addRow(
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QtWidgets.QLabel(
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f"Please place {self.app.markers[0].name}"
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f" in the filter passband."))
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self.result_label = QtWidgets.QLabel()
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self.cutoff_label = QtWidgets.QLabel()
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self.six_db_label = QtWidgets.QLabel()
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self.sixty_db_label = QtWidgets.QLabel()
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self.db_per_octave_label = QtWidgets.QLabel()
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self.db_per_decade_label = QtWidgets.QLabel()
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layout.addRow("Result:", self.result_label)
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layout.addRow("Cutoff frequency:", self.cutoff_label)
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layout.addRow("-6 dB point:", self.six_db_label)
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layout.addRow("-60 dB point:", self.sixty_db_label)
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layout.addRow("Roll-off:", self.db_per_octave_label)
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layout.addRow("Roll-off:", self.db_per_decade_label)
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def reset(self):
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self.result_label.clear()
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self.cutoff_label.clear()
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self.six_db_label.clear()
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self.sixty_db_label.clear()
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self.db_per_octave_label.clear()
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self.db_per_decade_label.clear()
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def runAnalysis(self):
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self.reset()
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pass_band_location = self.app.markers[0].location
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logger.debug("Pass band location: %d", pass_band_location)
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if len(self.app.data.s21) == 0:
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logger.debug("No data to analyse")
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self.result_label.setText("No data to analyse.")
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return
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if pass_band_location < 0:
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logger.debug("No location for %s",
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self.app.markers[0].name)
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self.result_label.setText(
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f"Please place {self.app.markers[0].name} in the passband.")
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return
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pass_band_db = self.app.data.s21[pass_band_location].gain
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logger.debug("Initial passband gain: %d", pass_band_db)
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initial_cutoff_location = -1
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for i in range(pass_band_location, len(self.app.data.s21)):
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db = self.app.data.s21[i].gain
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if (pass_band_db - db) > 3:
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# We found a cutoff location
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initial_cutoff_location = i
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break
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if initial_cutoff_location < 0:
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self.result_label.setText("Cutoff location not found.")
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return
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initial_cutoff_frequency = self.app.data.s21[initial_cutoff_location].freq
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logger.debug("Found initial cutoff frequency at %d", initial_cutoff_frequency)
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peak_location = -1
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peak_db = self.app.data.s21[initial_cutoff_location].gain
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for i in range(0, initial_cutoff_location):
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db = self.app.data.s21[i].gain
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if db > peak_db:
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peak_db = db
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peak_location = i
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logger.debug("Found peak of %f at %d", peak_db, self.app.data.s11[peak_location].freq)
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self.app.markers[0].setFrequency(str(self.app.data.s21[peak_location].freq))
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self.app.markers[0].frequencyInput.setText(str(self.app.data.s21[peak_location].freq))
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cutoff_location = -1
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pass_band_db = peak_db
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for i in range(peak_location, len(self.app.data.s21)):
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db = self.app.data.s21[i].gain
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if (pass_band_db - db) > 3:
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# We found the cutoff location
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cutoff_location = i
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break
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cutoff_frequency = self.app.data.s21[cutoff_location].freq
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cutoff_gain = self.app.data.s21[cutoff_location].gain - pass_band_db
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if cutoff_gain < -4:
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logger.debug(
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"Cutoff frequency found at %f dB"
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" - insufficient data points for true -3 dB point.",
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cutoff_gain)
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logger.debug("Found true cutoff frequency at %d", cutoff_frequency)
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self.cutoff_label.setText(
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f"{format_frequency(cutoff_frequency)}"
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f" ({round(cutoff_gain, 1)} dB)")
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self.app.markers[1].setFrequency(str(cutoff_frequency))
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self.app.markers[1].frequencyInput.setText(str(cutoff_frequency))
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six_db_location = -1
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for i in range(cutoff_location, len(self.app.data.s21)):
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db = self.app.data.s21[i].gain
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if (pass_band_db - db) > 6:
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# We found 6dB location
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six_db_location = i
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break
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if six_db_location < 0:
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self.result_label.setText("6 dB location not found.")
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return
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six_db_cutoff_frequency = self.app.data.s21[six_db_location].freq
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self.six_db_label.setText(
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format_frequency(six_db_cutoff_frequency))
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ten_db_location = -1
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for i in range(cutoff_location, len(self.app.data.s21)):
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db = self.app.data.s21[i].gain
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if (pass_band_db - db) > 10:
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# We found 6dB location
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ten_db_location = i
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break
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twenty_db_location = -1
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for i in range(cutoff_location, len(self.app.data.s21)):
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db = self.app.data.s21[i].gain
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if (pass_band_db - db) > 20:
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# We found 6dB location
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twenty_db_location = i
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break
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sixty_db_location = -1
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for i in range(six_db_location, len(self.app.data.s21)):
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db = self.app.data.s21[i].gain
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if (pass_band_db - db) > 60:
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# We found 60dB location! Wow.
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sixty_db_location = i
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break
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if sixty_db_location > 0:
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sixty_db_cutoff_frequency = self.app.data.s21[sixty_db_location].freq
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self.sixty_db_label.setText(
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format_frequency(sixty_db_cutoff_frequency))
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elif ten_db_location != -1 and twenty_db_location != -1:
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ten = self.app.data.s21[ten_db_location].freq
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twenty = self.app.data.s21[twenty_db_location].freq
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sixty_db_frequency = ten * \
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10 ** (5 * (math.log10(twenty) - math.log10(ten)))
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self.sixty_db_label.setText(
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f"{format_frequency(sixty_db_frequency)} (derived)")
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else:
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self.sixty_db_label.setText("Not calculated")
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if (ten_db_location > 0 and
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twenty_db_location > 0 and
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ten_db_location != twenty_db_location):
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octave_attenuation, decade_attenuation = self.calculateRolloff(
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ten_db_location, twenty_db_location)
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self.db_per_octave_label.setText(
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str(round(octave_attenuation, 3)) + " dB / octave")
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self.db_per_decade_label.setText(
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str(round(decade_attenuation, 3)) + " dB / decade")
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else:
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self.db_per_octave_label.setText("Not calculated")
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self.db_per_decade_label.setText("Not calculated")
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self.result_label.setText(
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"Analysis complete (" + str(len(self.app.data.s11)) + " points)")
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