vna calibration

.github/workflows/python_publish.yml

@@ -54,7 +54,13 @@ jobs:
       with:
         name: python-package-distributions
         path: dist/
+    - name: Set up Python
+      uses: actions/setup-python@v5
+      with:
+        python-version: "3.x"
     - name: Publish distribution 📦 to PyPI
       uses: pypa/gh-action-pypi-publish@release/v1
       with:
         password: ${{ secrets.PYPI_API_TOKEN }}
+        verbose: true
+        print-hash: true

README.md

@@ -1,6 +1,6 @@
 # Charon
 
-Named after [Pluto's moon](https://en.wikipedia.org/wiki/Charon_(moon)), Charon is a simple RF switch assembly for using the [ADI Pluto SDR]() as a vector network analyzer.
+Named after [Pluto's moon](https://en.wikipedia.org/wiki/Charon_(moon)), Charon uses the [ADI Pluto SDR]() as a vector network analyzer. The basic usage is as a 1 port VNA but this can be extended to arbitrarily many ports with the addition of a couple RF switches.
 
 ## Installation
 

charon_vna/pluto_example.py

@@ -0,0 +1,63 @@
+# Copyright (C) 2019 Analog Devices, Inc.
+#
+# SPDX short identifier: ADIBSD
+
+
+# I'm not sure why but sometimes I need to run this once to make the rest of my scripts work.
+# Probably just me running things manually out of order or something but I'm throwing this in here until I verify.
+
+import time
+
+import adi
+import matplotlib.pyplot as plt
+import numpy as np
+from scipy import signal
+
+# Create radio
+sdr = adi.Pluto(uri="ip:192.168.3.1")
+
+# Configure properties
+sdr.rx_rf_bandwidth = 4000000
+sdr.rx_lo = 2000000000
+sdr.tx_lo = 2000000000
+sdr.tx_cyclic_buffer = True
+sdr.tx_hardwaregain_chan0 = -30
+sdr.gain_control_mode_chan0 = "slow_attack"
+
+# Read properties
+print("RX LO %s" % (sdr.rx_lo))
+
+# Create a sinewave waveform
+fs = int(sdr.sample_rate)
+print(fs)
+N = 1024
+fc = int(-3000000 / (fs / N)) * (fs / N)
+ts = 1 / float(fs)
+t = np.arange(0, N * ts, ts)
+i = np.cos(2 * np.pi * t * fc) * 2**14
+q = np.sin(2 * np.pi * t * fc) * 2**14
+iq = i + 1j * q
+
+# Send data
+sdr.tx(iq)
+
+# Collect data
+for r in range(20):
+    x = sdr.rx()
+    f, Pxx_den = signal.periodogram(x, fs, return_onesided=False)
+    plt.clf()
+    plt.semilogy(f, Pxx_den)
+    plt.ylim([1e-7, 1e2])
+    plt.xlabel("frequency [Hz]")
+    plt.ylabel("PSD [V**2/Hz]")
+    plt.grid(True)
+    plt.draw()
+    plt.pause(0.05)
+    time.sleep(0.1)
+
+plt.show()
+
+
+plt.plot(np.real(x))
+plt.plot(np.imag(x))
+plt.show()

charon_vna/vna.py

@@ -0,0 +1,332 @@
+# %% imports
+import copy
+import time
+from pathlib import Path
+from typing import Optional
+
+import adi
+import iio
+import matplotlib as mpl
+import numpy as np
+import skrf as rf
+import xarray as xr
+from matplotlib import pyplot as plt
+from matplotlib.gridspec import GridSpec
+from matplotlib.patches import Circle
+from matplotlib.ticker import EngFormatter
+from numpy import typing as npt
+from scipy import signal
+
+dir_ = Path(__file__).parent
+
+
+# https://wiki.analog.com/resources/tools-software/linux-drivers/iio-transceiver/ad9361-customization
+
+
+# %% helper functions
+def get_config(sdr: adi.ad9361):
+    config = dict()
+    config["rx_lo"] = sdr.rx_lo
+    config["rx_rf_bandwidth"] = sdr.rx_rf_bandwidth
+    config["rx_enabled_channels"] = sdr.rx_enabled_channels
+    for chan in config["rx_enabled_channels"]:
+        config[f"rx_hardwaregain_chan{chan}"] = getattr(sdr, f"rx_hardwaregain_chan{chan}")
+        config[f"gain_control_mode_chan{chan}"] = getattr(sdr, f"gain_control_mode_chan{chan}")
+
+    config["tx_lo"] = sdr.tx_lo
+    config["tx_rf_bandwidth"] = sdr.tx_rf_bandwidth
+    config["tx_cyclic_buffer"] = sdr.tx_cyclic_buffer
+    config["tx_enabled_channels"] = sdr.tx_enabled_channels
+    for chan in config["tx_enabled_channels"]:
+        config[f"tx_hardwaregain_chan{chan}"] = getattr(sdr, f"tx_hardwaregain_chan{chan}")
+
+    config["filter"] = sdr.filter
+    config["sample_rate"] = sdr.sample_rate
+    config["loopback"] = sdr.loopback
+
+    return config
+
+
+def db10(p):
+    return 10 * np.log10(np.abs(p))
+
+
+def db20(p):
+    return 20 * np.log10(np.abs(p))
+
+
+def minmax(x):
+    return (np.min(x), np.max(x))
+
+
+def generate_tone(f: float, N: int = 1024, fs: Optional[float] = None):
+    if fs is None:
+        fs = sdr.sample_rate
+    fs = int(fs)
+    fc = int(f / (fs / N)) * (fs / N)
+    ts = 1 / float(fs)
+    t = np.arange(0, N * ts, ts)
+    i = np.cos(2 * np.pi * t * fc) * 2**14
+    q = np.sin(2 * np.pi * t * fc) * 2**14
+    iq = i + 1j * q
+
+    return iq
+
+
+# %% connection
+sdr = adi.ad9361(uri="ip:192.168.3.1")
+
+# %% verify device configuration
+mode_2r2t = bool(sdr._get_iio_debug_attr("adi,2rx-2tx-mode-enable"))
+if not mode_2r2t:
+    raise ValueError("'adi,2rx-2tx-mode-enable' is not set in pluto. See README.md for instructions for changing this")
+# TODO: it might be possible to change this on the fly. I think we'll actually just fail in __init__ for sdr
+
+# %% switch control outputs
+# NOTE: this doesn't appear to work
+sdr._set_iio_debug_attr_str("adi,gpo-manual-mode-enable", "1")
+sdr._get_iio_debug_attr_str("adi,gpo-manual-mode-enable-mask")
+# but direct register access does
+# https://ez.analog.com/linux-software-drivers/f/q-a/120853/control-fmcomms3-s-gpo-with-python
+ctx = iio.Context("ip:192.168.3.1")
+ctrl = ctx.find_device("ad9361-phy")
+# https://www.analog.com/media/cn/technical-documentation/user-guides/ad9364_register_map_reference_manual_ug-672.pdf
+ctrl.reg_write(0x26, 0x90)  # bit 7: AuxDAC Manual, bit 4: GPO Manual
+ctrl.reg_write(0x27, 0x10)  # bits 7-4: GPO3-0
+
+
+# %% initialization
+sdr.rx_lo = int(2.0e9)
+sdr.tx_lo = int(2.0e9)
+sdr.sample_rate = 30e6
+sdr.rx_rf_bandwidth = int(4e6)
+sdr.tx_rf_bandwidth = int(4e6)
+sdr.rx_destroy_buffer()
+sdr.tx_destroy_buffer()
+sdr.rx_enabled_channels = [0, 1]
+sdr.tx_enabled_channels = [0]
+sdr.loopback = 0
+sdr.gain_control_mode_chan0 = "manual"
+sdr.gain_control_mode_chan1 = "manual"
+sdr.rx_hardwaregain_chan0 = 40
+sdr.rx_hardwaregain_chan1 = 40
+sdr.tx_hardwaregain_chan0 = -10
+
+config = get_config(sdr)
+config
+
+# %%
+sdr.tx_destroy_buffer()  # must destroy buffer before changing cyclicity
+sdr.tx_cyclic_buffer = True
+sdr.tx(generate_tone(1e6))
+
+# %%
+sdr.rx_destroy_buffer()
+data = sdr.rx()
+
+# %% Plot in time
+fig, axs = plt.subplots(2, 1, sharex=True, tight_layout=True)
+axs[0].plot(np.real(data).T)
+axs[1].plot(np.imag(data).T)
+axs[0].set_ylabel("Real")
+axs[1].set_ylabel("Imag")
+axs[-1].set_xlabel("Time")
+fig.show()
+
+# %% Plot in frequency
+f, Pxx_den = signal.periodogram(data, sdr.sample_rate, axis=-1, return_onesided=False)
+plt.figure()
+for cc, chan in enumerate(sdr.rx_enabled_channels):
+    plt.semilogy(f, Pxx_den[cc], label=f"Channel {chan}")
+plt.legend()
+plt.ylim([1e-7, 1e2])
+plt.xlabel("frequency [Hz]")
+plt.ylabel("PSD [V**2/Hz]")
+plt.grid(True)
+plt.show()
+
+
+# %% TX helper functions
+def set_output_power(power: float):
+    if power == -5:
+        # FIXME: this is a hack because I don't want to go through re-calibration
+        tx_gain = -8
+    else:
+        raise NotImplementedError()
+        # # TODO: correct over frequency
+        # tx_gain_idx = np.abs(pout.sel(tx_channel=0) - power).argmin(dim="tx_gain")
+        # tx_gain = pout.coords["tx_gain"][tx_gain_idx]
+    sdr.tx_hardwaregain_chan0 = float(tx_gain)
+
+
+def set_output(frequency: float, power: float, offset_frequency: float = 1e6):
+    sdr.tx_destroy_buffer()
+    set_output_power(power)
+    sdr.tx_lo = int(frequency - offset_frequency)
+    offset_frequency = frequency - sdr.tx_lo
+    sdr.tx_cyclic_buffer = True
+    sdr.tx(generate_tone(offset_frequency))
+
+
+# %%
+def vna_capture(frequency: npt.ArrayLike):
+    s = xr.DataArray(
+        np.empty(len(frequency), dtype=np.complex128),
+        dims=["frequency"],
+        coords=dict(
+            frequency=frequency,
+        ),
+    )
+    for freq in s.frequency.data:
+        set_output(frequency=freq, power=-5)
+        sdr.rx_destroy_buffer()
+        sdr.rx_lo = int(freq)
+        sdr.rx_enabled_channels = [0, 1]
+        sdr.gain_control_mode_chan0 = "manual"
+        sdr.gain_control_mode_chan1 = "manual"
+        sdr.rx_hardwaregain_chan0 = 40
+        sdr.rx_hardwaregain_chan1 = 40
+        rx = sdr.rx()
+        s.loc[dict(frequency=freq)] = np.mean(rx[1] / rx[0])
+
+    return s
+
+
+# %%
+s = vna_capture(frequency=np.linspace(70e6, 200e6, 101))
+
+# %% Plot Logmag
+fig, axs = plt.subplots(2, 1, sharex=True, tight_layout=True)
+
+axs[0].plot(s.frequency, db20(s), label="Measured")
+axs[1].plot(s.frequency, np.rad2deg(np.angle((s))), label="Measured")
+
+axs[0].grid(True)
+axs[1].grid(True)
+
+axs[0].set_ylim(-80, 0)
+axs[1].set_ylim(-200, 200)
+axs[1].set_xlim(np.min(s.frequency), np.max(s.frequency))
+axs[1].xaxis.set_major_formatter(EngFormatter(places=1))
+axs[1].set_xlabel("Frequency")
+
+axs[0].set_ylabel("|S11| [dB]")
+axs[1].set_ylabel("∠S11 [deg]")
+
+reference_sparams = None
+reference_sparams = dir_ / "RBP-135+_Plus25degC.s2p"
+if reference_sparams is not None:
+    ref = rf.Network(reference_sparams)
+    rbp135 = xr.DataArray(ref.s, dims=["frequency", "m", "n"], coords=dict(frequency=ref.f, m=[1, 2], n=[1, 2]))
+
+    axs[0].plot(rbp135.frequency, db20(rbp135.sel(m=1, n=1)), label="Datasheet")
+    axs[1].plot(rbp135.frequency, np.rad2deg(np.angle(rbp135.sel(m=2, n=1))), label="Datasheet")
+    axs[0].legend()
+    axs[1].legend()
+
+plt.show()
+
+
+# %%
+def s2net(s: xr.DataArray) -> rf.Network:
+    net = rf.Network(frequency=s.frequency)
+    net.s = s.data
+    return net
+
+
+# %% SOL calibration
+cal_frequency = np.linspace(70e6, 600e6, 2001)
+ideal_cal_frequency = rf.Frequency(np.min(cal_frequency), np.max(cal_frequency), len(cal_frequency))
+input("Connect SHORT and press ENTER...")
+short = vna_capture(frequency=cal_frequency)
+input("Connect OPEN and press ENTER...")
+open = vna_capture(frequency=cal_frequency)
+input("Connect LOAD and press ENTER...")
+load = vna_capture(frequency=cal_frequency)
+
+short_net = s2net(short)
+open_net = s2net(open)
+load_net = s2net(load)
+
+cal_ideal = rf.media.DefinedGammaZ0(frequency=ideal_cal_frequency)
+calibration = rf.calibration.OnePort(
+    [short_net, open_net, load_net],
+    [cal_ideal.short(), cal_ideal.open(), cal_ideal.load(0)],
+)
+
+
+# %%
+s = vna_capture(frequency=cal_frequency)
+
+# %%
+ham_bands = [
+    [135.7e3, 137.8e3],
+    [472e3, 479e3],
+    [1.8e6, 2e6],
+    [3.5e6, 4e6],
+    [5332e3, 5405e3],
+    [7e6, 7.3e6],
+    [10.1e6, 10.15e6],
+    [14e6, 14.35e6],
+    [18.068e6, 18.168e6],
+    [21e6, 21.45e6],
+    [24.89e6, 24.99e6],
+    [28e6, 29.7e6],
+    [50e6, 54e6],
+    [144e6, 148e6],
+    [219e6, 220e6],
+    [222e6, 225e6],
+    [420e6, 450e6],
+    [902e6, 928e6],
+    [1240e6, 1300e6],
+    [2300e6, 2310e6],
+    [2390e6, 2450e6],
+    [3400e6, 3450e6],
+    [5650e6, 5925e6],
+    [10e9, 10.5e9],
+    [24e9, 24.25e9],
+    [47e9, 47.2e9],
+    [76e9, 81e9],
+    [122.25e9, 123e9],
+    [134e9, 141e9],
+    [241e9, 250e9],
+    [275e9, np.inf],
+]
+
+# %%
+s_calibrated = calibration.apply_cal(s2net(s))
+
+plt.figure()
+s_calibrated.plot_s_smith()
+# ref.plot_s_smith(m=1, n=1)
+plt.show()
+
+plt.figure()
+for start, stop in ham_bands:
+    plt.axvspan(start, stop, alpha=0.1, color="k")
+s_calibrated.plot_s_db()
+# ref.plot_s_db(m=1, n=1)
+plt.gca().xaxis.set_major_formatter(EngFormatter())
+plt.grid(True)
+plt.xlim(s_calibrated.f[0], s_calibrated.f[-1])
+plt.show()
+
+plt.figure()
+for start, stop in ham_bands:
+    plt.axvspan(start, stop, alpha=0.1, color="k")
+# s_calibrated.plot_s_vswr()
+# drop invalid points
+vswr = copy.deepcopy(s_calibrated.s_vswr[:, 0, 0])
+vswr[vswr < 1] = np.nan
+plt.plot(s_calibrated.f, vswr)
+plt.axhline(1, color="k", linestyle="--")
+plt.ylabel("VSWR")
+plt.xlabel("Frequency [Hz]")
+# ref.plot_s_vswr(m=1, n=1)
+plt.gca().xaxis.set_major_formatter(EngFormatter())
+plt.grid(True)
+plt.ylim(0, 10)
+plt.xlim(s_calibrated.f[0], s_calibrated.f[-1])
+plt.show()
+
+# %%

pyproject.toml

@@ -3,7 +3,7 @@ requires = ["setuptools", "setuptools-scm"]
 build-backend = "setuptools.build_meta"
 
 [project]
-name = "charon-vna"
+name = "charon_vna"
 authors = [{ name = "Brendan Haines", email = "brendan.haines@gmail.com" }]
 description = "RF Network Analyzer based on the Pluto SDR"
 readme = "README.md"
@@ -50,3 +50,6 @@ exclude = '''
   | dist
 )/
 '''
+
+[tool.isort]
+profile = "black"