nanovna-saver/src/NanoVNASaver/Windows/TDR.py

#  NanoVNASaver
#
#  A python program to view and export Touchstone data from a NanoVNA
#  Copyright (C) 2019, 2020  Rune B. Broberg
#  Copyright (C) 2020, 2021 NanoVNA-Saver Authors
#
#  This program is free software: you can redistribute it and/or modify
#  it under the terms of the GNU General Public License as published by
#  the Free Software Foundation, either version 3 of the License, or
#  (at your option) any later version.
#
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#  GNU General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program.  If not, see <https://www.gnu.org/licenses/>.
import logging
import math

import numpy as np

# pylint: disable=import-error, no-name-in-module
from scipy.signal import convolve
from scipy.constants import speed_of_light

from PyQt6 import QtWidgets, QtCore, QtGui

from NanoVNASaver.Windows.Defaults import make_scrollable

logger = logging.getLogger(__name__)

CABLE_PARAMETERS = (
    ("Jelly filled (0.64)", 0.64),
    ("Polyethylene (0.66)", 0.66),
    ("PTFE (Teflon) (0.70)", 0.70),
    ("Pulp Insulation (0.72)", 0.72),
    ("Foam or Cellular PE (0.78)", 0.78),
    ("Semi-solid PE (SSPE) (0.84)", 0.84),
    ("Air (Helical spacers) (0.94)", 0.94),
    # Lots of cable types added by Larry Goga, AE5CZ
    ("RG-6/U PE 75\N{OHM SIGN} (Belden 8215) (0.66)", 0.66),
    ("RG-6/U Foam 75\N{OHM SIGN} (Belden 9290) (0.81)", 0.81),
    ("RG-8/U PE 50\N{OHM SIGN} (Belden 8237) (0.66)", 0.66),
    ("RG-8/U Foam (Belden 8214) (0.78)", 0.78),
    ("RG-8/U (Belden 9913) (0.84)", 0.84),
    # Next one added by EKZ, KC3KZ, from measurement of actual cable
    ("RG-8/U (Shireen RFC®400 Low Loss) (0.86)", 0.86),
    ("RG-8X (Belden 9258) (0.82)", 0.82),
    # Next three added by EKZ, KC3KZ, from measurement of actual cable
    ('RG-8X (Wireman "Super 8" CQ106) (0.81)', 0.81),
    ('RG-8X (Wireman "MINI-8 Lo-Loss" CQ118) (0.82)', 0.82),
    ('RG-58 (Wireman "CQ 58 Lo-Loss Flex" CQ129FF) (0.79)', 0.79),
    ("RG-11/U 75\N{OHM SIGN} Foam HDPE (Belden 9292) (0.84)", 0.84),
    ("RG-58/U 52\N{OHM SIGN} PE (Belden 9201) (0.66)", 0.66),
    ("RG-58A/U 54\N{OHM SIGN} Foam (Belden 8219) (0.73)", 0.73),
    ("RG-59A/U PE 75\N{OHM SIGN} (Belden 8241) (0.66)", 0.66),
    ("RG-59A/U Foam 75\N{OHM SIGN} (Belden 8241F) (0.78)", 0.78),
    ("RG-174 PE (Belden 8216)(0.66)", 0.66),
    ("RG-174 Foam (Belden 7805R) (0.735)", 0.735),
    ("RG-213/U PE (Belden 8267) (0.66)", 0.66),
    ("RG316 (0.695)", 0.695),
    ("RG402 (0.695)", 0.695),
    ("LMR-240 (0.84)", 0.84),
    ("LMR-240UF (0.80)", 0.80),
    ("LMR-400 (0.85)", 0.85),
    ("LMR400UF (0.83)", 0.83),
    ("Davis Bury-FLEX (0.82)", 0.82),
)


class TDRWindow(QtWidgets.QWidget):
    updated = QtCore.pyqtSignal()

    def __init__(self, app: QtWidgets.QWidget):
        super().__init__()
        self.app = app

        self.td = []
        self.distance_axis = []
        self.step_response_Z = []

        self.setWindowTitle("TDR")
        self.setWindowIcon(self.app.icon)

        QtGui.QShortcut(QtCore.Qt.Key.Key_Escape, self, self.hide)

        layout = QtWidgets.QFormLayout()
        make_scrollable(self, layout)

        self.tdr_velocity_dropdown = QtWidgets.QComboBox()
        for cable_name, velocity in CABLE_PARAMETERS:
            self.tdr_velocity_dropdown.addItem(cable_name, velocity)
        self.tdr_velocity_dropdown.insertSeparator(
            self.tdr_velocity_dropdown.count()
        )
        self.tdr_velocity_dropdown.addItem("Custom", -1)
        self.tdr_velocity_dropdown.setCurrentIndex(1)  # Default to PE (0.66)
        self.tdr_velocity_dropdown.currentIndexChanged.connect(self.updateTDR)
        layout.addRow(self.tdr_velocity_dropdown)

        self.tdr_velocity_input = QtWidgets.QLineEdit()
        self.tdr_velocity_input.setDisabled(True)
        self.tdr_velocity_input.setText("0.66")
        self.tdr_velocity_input.textChanged.connect(self.app.dataUpdated)
        layout.addRow("Velocity factor", self.tdr_velocity_input)

        self.tdr_result_label = QtWidgets.QLabel()
        layout.addRow("Estimated cable length:", self.tdr_result_label)

        layout.addRow(self.app.tdr_chart)

    def updateTDR(self):
        # TODO: Let the user select whether to use high or low resolution TDR?
        FFT_POINTS = 2**14

        if len(self.app.data.s11) < 2:
            return

        if self.tdr_velocity_dropdown.currentData() == -1:
            self.tdr_velocity_input.setDisabled(False)
        else:
            self.tdr_velocity_input.setDisabled(True)
            self.tdr_velocity_input.setText(
                str(self.tdr_velocity_dropdown.currentData())
            )

        try:
            v = float(self.tdr_velocity_input.text())
        except ValueError:
            return

        step_size = self.app.data.s11[1].freq - self.app.data.s11[0].freq
        if step_size == 0:
            self.tdr_result_label.setText("")
            logger.info("Cannot compute cable length at 0 span")
            return

        s11 = [complex(d.re, d.im) for d in self.app.data.s11]
        window = np.blackman(len(self.app.data.s11))

        windowed_s11 = window * s11
        td = np.abs(np.fft.ifft(windowed_s11, FFT_POINTS))
        step = np.ones(FFT_POINTS)
        step_response = convolve(td, step)

        self.step_response_Z = 50 * (1 + step_response) / (1 - step_response)

        time_axis = np.linspace(0, 1 / step_size, FFT_POINTS)
        self.distance_axis = time_axis * v * speed_of_light
        # peak = np.max(td)
        # We should check that this is an actual *peak*, and not just
        # a vague maximum
        index_peak = np.argmax(td)

        cable_len = round(self.distance_axis[index_peak] / 2, 3)
        feet = math.floor(cable_len / 0.3048)
        inches = round(((cable_len / 0.3048) - feet) * 12, 1)

        self.tdr_result_label.setText(f"{cable_len}m ({feet}ft {inches}in)")
        self.app.tdr_result_label.setText(f"{cable_len}m")
        self.td = list(td)
        self.updated.emit()