Building a budget¶

This walk-through builds a small point-to-point microwave link from scratch.

1. Create the container¶

Give it the context the figures of merit need — a noise bandwidth and a data rate — up front:

import linkbudget

budget = linkbudget.LinkContainer(
    carrier_frequency=6e9,
    noise_bandwidth=20e6,
    data_rate=45e6,
)

2. Add the transmit side¶

A SignalSource injects power into the chain; a Gain applies the transmit antenna gain.

budget.add_component(linkbudget.SignalSource(
    "Transmitter", "1 W (0 dBW) at the PA output", signal_power=1.0))
budget.add_component(linkbudget.Gain(
    "Tx antenna", "36 dBi dish", gain=36.0, role="tx"))

3. Add the path¶

FreeSpacePathLoss is tagged as a propagation stage, so the signal power entering it becomes the budget's EIRP.

budget.add_component(linkbudget.FreeSpacePathLoss(
    "Free-space path loss", "12 km hop", distance=12e3, frequency=6e9))

4. Add the receive side¶

Mark the receive antenna with role="rx" so summary() can compute G/T. ThermalNoise establishes the noise floor (k·T·B in watts — so every power value in this budget is in watts); RFComponent is the LNA.

budget.add_component(linkbudget.Gain(
    "Rx antenna", "36 dBi dish", gain=36.0, role="rx"))
budget.add_component(linkbudget.ThermalNoise(
    "Noise floor", "290 K system temperature",
    temperature_k=290.0, bandwidth=20e6))
budget.add_component(linkbudget.RFComponent(
    "LNA", "low-noise amplifier", gain=30.0, noise_figure=1.5))

5. State the requirement¶

A LinkMargin stage compares the achieved link against a demodulator threshold. It passes signal and noise through unchanged — it only annotates the result.

budget.add_component(linkbudget.LinkMargin(
    "Link margin", "64-QAM, required Eb/N0 = 15 dB",
    required_ebno_db=15.0, noise_bandwidth=20e6, data_rate=45e6,
    implementation_loss_db=2.0))

6. Read the result¶

summary = budget.summary()
print(summary)

if summary.closes:
    print(f"link closes with {summary.margin_db:.1f} dB of margin")

summary is a BudgetSummary — every field is also available programmatically (summary.eirp_dbw, summary.g_over_t_db, summary.ebno_db, …) and as a dict via summary.as_dict().

7. Publish reports¶

budget.add_publisher(linkbudget.HTMLPublisher("link.html", title="6 GHz hop"))
budget.add_publisher(linkbudget.PDFPublisher("link.pdf", title="6 GHz hop"))
budget.add_publisher(linkbudget.WaterfallPublisher("link.png"))
budget.publish()

Inspecting individual stages¶

After compute() (or publish() / summary()), budget.data_list holds one dict per stage:

budget.compute()
for stage in budget.data_list:
    print(f"{stage['name']:20s}  SNR = {linkbudget.convert.linear_to_db(stage['snr']):6.1f} dB")