.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "api/gallery/communications/propagation/plot_03_telstar_link_budget.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_api_gallery_communications_propagation_plot_03_telstar_link_budget.py>`
        to download the full example code or to run this example in your browser via JupyterLite.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_api_gallery_communications_propagation_plot_03_telstar_link_budget.py:


The Telstar satellite link budget
=================================

Telstar 1 (1962) relayed the first live transatlantic television. Engineers
planned such links with a *link budget*: transmitter power, antenna gains,
path loss and miscellaneous losses added in decibels
(:func:`~engineeringkit.communications.link_budget_db`), then compared with
the receiver noise floor. The figures below are representative of the
4 GHz Andover-Telstar downlink, not archival values.

.. GENERATED FROM PYTHON SOURCE LINES 14-27

.. code-block:: Python

    import matplotlib.pyplot as plt
    import numpy as np

    from engineeringkit.communications import (
        db,
        dbm,
        free_space_path_loss_db,
        friis_received_power,
        from_dbm,
        link_budget_db,
        thermal_noise_power,
    )








.. GENERATED FROM PYTHON SOURCE LINES 28-30

Budget at the closest and farthest points of the orbit
------------------------------------------------------

.. GENERATED FROM PYTHON SOURCE LINES 30-40

.. code-block:: Python


    pt_w, gt, gr, f = 2.25, 1.0, 10 ** (58 / 10), 4.17e9
    bandwidth, t_sys = 25e6, 60.0
    noise_dbm = float(dbm(thermal_noise_power(bandwidth, t_sys)))
    ranges = np.linspace(1000e3, 6000e3, 60)
    received = link_budget_db(float(dbm(pt_w)), float(db(gt)), float(db(gr)), free_space_path_loss_db(ranges, f), losses_db=3.0)
    assert np.allclose(from_dbm(received + 3.0), friis_received_power(pt_w, gt, gr, ranges, f))
    for r, p in [(ranges[0], received[0]), (ranges[-1], received[-1])]:
        print(f"range {r / 1e3:5.0f} km: received {p:6.1f} dBm, SNR {p - noise_dbm:5.1f} dB")





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    range  1000 km: received  -76.3 dBm, SNR  30.5 dB
    range  6000 km: received  -91.9 dBm, SNR  14.9 dB




.. GENERATED FROM PYTHON SOURCE LINES 41-43

The decibel ledger
------------------

.. GENERATED FROM PYTHON SOURCE LINES 43-62

.. code-block:: Python


    items = {
        "Pt": float(dbm(pt_w)),
        "Gt": float(db(gt)),
        "Gr": float(db(gr)),
        "path loss": -float(free_space_path_loss_db(ranges[-1], f)),
        "other": -3.0,
    }
    fig, axes = plt.subplots(1, 2, figsize=(10, 3.6))
    running = np.cumsum(list(items.values()))
    axes[0].bar(list(items), list(items.values()), bottom=np.r_[0, running[:-1]], color=["C0", "C2", "C2", "C3", "C3"])
    axes[0].axhline(noise_dbm, color="k", ls="--", label="noise floor")
    axes[0].set(ylabel="level [dBm]", title=f"Downlink at {ranges[-1] / 1e3:.0f} km")
    axes[0].legend()
    axes[1].plot(ranges / 1e3, received - noise_dbm)
    axes[1].set(xlabel="slant range [km]", ylabel="SNR [dB]", title="SNR over the pass")
    fig.tight_layout()

    plt.show()



.. image-sg:: /api/gallery/communications/propagation/images/sphx_glr_plot_03_telstar_link_budget_001.png
   :alt: Downlink at 6000 km, SNR over the pass
   :srcset: /api/gallery/communications/propagation/images/sphx_glr_plot_03_telstar_link_budget_001.png
   :class: sphx-glr-single-img






.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.192 seconds)


.. _sphx_glr_download_api_gallery_communications_propagation_plot_03_telstar_link_budget.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: lite-badge

      .. image:: images/jupyterlite_badge_logo.svg
        :target: ../../../../lite/lab/index.html?path=api/gallery/communications/propagation/plot_03_telstar_link_budget.ipynb
        :alt: Launch JupyterLite
        :width: 150 px

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: plot_03_telstar_link_budget.ipynb <plot_03_telstar_link_budget.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: plot_03_telstar_link_budget.py <plot_03_telstar_link_budget.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: plot_03_telstar_link_budget.zip <plot_03_telstar_link_budget.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_