add working demo VNA script. Not sure why the first run after power cycling pluto this gets garbage data for the first plots

charon_vna/vna.py

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+# %% imports
+import time
+from typing import Optional
+
+import adi
+import matplotlib as mpl
+import numpy as np
+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
+
+
+# %% 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")
+
+# %% 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 = 10
+sdr.rx_hardwaregain_chan1 = 10
+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 = "/home/brendan/Documents/projects/bh_instruments/rbp135.npz"
+if reference_sparams is not None:
+    rbp135 = np.load(reference_sparams)
+    rbp135 = xr.DataArray(
+        rbp135["s"], dims=["frequency", "m", "n"], coords=dict(frequency=rbp135["frequency"], 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()