Python Script that Tells You the RMS Cycle-to-Cycle Jitter of Your Oscillator

$ python3 script.py phas_noi_export.csv f_center [f_lower or 0] [f_higher] # if specify only f_higher, then use 0 for arg2

import numpy as np

import pandas as pd

import sys

def read_phase_noise_file(filename):

    with open(filename, 'r') as f:

        first_line = f.readline()

    try:

        float(first_line.split(',')[0])

        df = pd.read_csv(filename, header=None)

    except ValueError:

        df = pd.read_csv(filename)

    freq = df.iloc[:, 0].values

    L_dbc_per_hz = df.iloc[:, 1].values

    return freq, L_dbc_per_hz

def calc_cycle_to_cycle_jitter(freq, L_dbc_per_hz, f0, f_min=None, f_max=None):

    # Apply frequency limits

    mask = np.ones_like(freq, dtype=bool)

    if f_min is not None:

        mask &= freq >= f_min

    if f_max is not None:

        mask &= freq <= f_max

    freq = freq[mask]

    L_dbc_per_hz = L_dbc_per_hz[mask]

    if len(freq) == 0:

        raise ValueError("No data points within specified frequency range.")

    # Convert to linear

    L_linear = 10 ** (L_dbc_per_hz / 10.0)

    # Weighting for cycle-to-cycle jitter

    w = 2 * np.sin(np.pi * freq / f0)

    integrand = (w ** 2) * L_linear

    # Integration and conversion (fixed warning)

    jitter_power = 2 * np.trapezoid(integrand, freq)

    sigma_ccj = np.sqrt(jitter_power) / (2 * np.pi * f0)

    return sigma_ccj

if __name__ == "__main__":

    if len(sys.argv) < 3:

        print("Usage: python3 ccjitter.py <phase_noise.csv> <f0_Hz> [f_min_Hz f_max_Hz]")

        sys.exit(1)

    csv_file = sys.argv[1]

    f0 = float(sys.argv[2])

    f_min = float(sys.argv[3]) if len(sys.argv) > 3 else None

    f_max = float(sys.argv[4]) if len(sys.argv) > 4 else None

    try:

        freq, L = read_phase_noise_file(csv_file)

        jitter = calc_cycle_to_cycle_jitter(freq, L, f0, f_min, f_max)

        print(f"Cycle-to-cycle RMS jitter: {jitter * 1e12:.2f} ps")

    except Exception as e:

        print("Error:", e)

        sys.exit(1)