Link Budget Calculator and Antenna Patterns
Calculate received power, fade margin, and antenna coverage trade-offs for IoT wireless links
Link Budget and Antenna Pattern Workbench
Calculate whether a radio signal arrives above receiver sensitivity, then inspect how antenna gain changes coverage. The goal is not maximum power; it is enough fade margin for the deployment.
What
A link budget adds radio gains and subtracts losses to estimate received power at the far end.
Why
If received power is too close to sensitivity, rain, walls, fading, body loss, or interference can break the link.
Try First
Select Warehouse handheld. Watch the margin shrink because movement and body absorption need extra safety buffer.
Notice
A higher-gain antenna does not create energy. It focuses energy into a narrower beam and reduces coverage elsewhere.
Radio link model
LoRa field sensor: 915 MHz, 5.00 km, 14 dBm TX, 3 dBi antennas, -137 dBm sensitivity.
Signal path and link budget
Antenna pattern and range
Current explanation
Fade margin is the safety buffer above receiver sensitivity. The receiver can decode only if predicted received power stays above sensitivity. Margin absorbs weather, fading, body loss, obstruction, and installation uncertainty.1. Transmit
Start with transmitter power in dBm. More power helps, but regulation and battery limit it.2. Antennas
Add TX and RX antenna gain. Higher gain focuses energy into a narrower pattern.3. Path loss
Subtract free-space path loss from frequency and distance.4. Other losses
Subtract cables, walls, foliage, body loss, rain fade, and installation loss.5. Margin
Compare received power with sensitivity and judge whether the safety buffer is enough.Learning Support
Minimum Background
dBm is a power level. dB and dBi are ratios. In a link budget, gains add and losses subtract because the calculation is logarithmic.
Mental Model
Think of a radio path as a bank account. TX power and antenna gain are deposits; distance, walls, cables, and fading are withdrawals.
Design Meaning
A positive margin says the link may work. The size of the margin says how much uncertainty the design can tolerate.
Quick Reference
Received Power
RX dBm = TX dBm + TX gain + RX gain - path loss - other losses.
Free-Space Path Loss
FSPL dB = 32.44 + 20 log10(distance km) + 20 log10(frequency MHz).
Fade Margin
Margin dB = received power - receiver sensitivity. More margin means more tolerance for fading and obstruction.
Margin Targets
Use about 10 dB for clear fixed links, 15 dB indoors, 20 dB industrial, and 25 dB or more for mobile or critical links.
Antenna Gain
Gain redirects energy. A 12 dBi directional antenna narrows coverage but can improve signal inside the beam.
Range Rule
In free space, every 6 dB of extra budget roughly doubles range. Real environments often do worse.