RF link-budget workspace

Assumptions to check

• The entered RF-link-budget values represent the stated operating condition.
• This standard approximation is evaluated in the declared lumped or first-pass model.
• A RF-link-budget calculation is not a component qualification or safety approval.

What this RF-link-budget calculation establishes

Calculate free-space path loss and received power from transmit power, antenna gains, distance, and frequency. The useful result is the stated electrical quantity and the decision it supports, not an unstated claim about a finished product. This engine keeps the governing relationship visible so an input, unit, condition, or model boundary can be reviewed before a value becomes a component or layout choice.

Free-space path loss follows the standard 20log10(d) + 20log10(f) - 147.55 relationship; received power sums transmit power and both antenna gains, then subtracts path loss and other entered losses. Treat the number as a first-pass result for the declared operating point. When a source, load, temperature, frequency, waveform, component tolerance, or measurement condition changes, repeat the calculation at the relevant corner rather than assuming the nominal answer persists.

Worked decision context

At 2.4 GHz and 100 m, FSPL is about 80.05 dB; 0 dBm transmit with two 2 dBi antennas and no other losses gives -76.05 dBm received. That example verifies the equation and illustrates the scale of the result, but it does not select a part by itself. Compare the result with available values, ratings, tolerance bands, and the receiving circuit or physical environment before implementation.

Use the primary output to identify the binding constraint. If it leaves little margin, document which input dominates and use selected-part data, a higher-fidelity model, simulation, or measurement. This is especially important when a small numerical difference changes a thermal, timing, noise, or reliability decision.

Limits and validation handoff

This ideal free-space model excludes fading, multipath, and atmospheric loss beyond the entered "other loss" term. Compare received power with sensitivity plus a required fade margin, not sensitivity alone. The calculation does not silently include omitted parasitics, installation conditions, manufacturing variation, or product policy. Those conditions can be decisive even when the arithmetic is exact for the selected model.

Record inputs, units, model assumptions, and the intended decision with the result. Verify the leading risk against the selected component data sheet and a representative measurement when the circuit has consequential energy, high voltage, safety, compliance, or reliability requirements.

Common mistakes

• Treating the RF-link-budget result as a guaranteed operating limit rather than a first-pass standard approximation estimate.
• Mixing a data-sheet value measured under one condition with this RF-link-budget calculation performed at another.
• Selecting a component before checking the boundary this calculation names: this ideal free-space model excludes fading, multipath, and atmospheric loss beyond the entered "other loss" term. Compare received power with sensitivity plus a required fade margin, not sensitivity alone.

Model limit and handoff

Keep the entered RF-link-budget conditions with the calculation, then validate the binding limit using the selected component, physical implementation, and representative operating corner.

FAQs