Wireless Power Transfer Simulators
Place an RF emitter, drop walls of any material and thickness between it and a receiver, and see how much wireless power actually arrives. The heat map shows harvested DC power across the room, so you can see immediately where a battery-free sensor will work — and where a concrete wall ends the conversation. Switch to the near-field tab to compare inductive charging against magnetic resonance: the same transmitter power, a far larger charging zone and several receivers at once. A third mode simulates a 24 GHz phased array on the ground: add elements to narrow the beam and raise gain, then steer it onto drones transiting overhead to see how much power actually lands on a moving airframe.
Drag the teal RF emitter, the dark receiver, or any wall (grab its middle to move it, its ends to rotate or resize). Use the power slider to boost or cut the emitter EIRP. Grid squares are 1 × 1 m; the room is 12 × 8 m.
The coverage heat map and received power update live as you move elements or change frequency and power.
How the model works
The simulator computes received power along the direct ray between emitter and receiver. Free-space loss follows the Friis equation, so power falls with the square of distance and rises with frequency. Every wall the ray crosses adds attenuation proportional to its thickness, its material coefficient, and the angle of incidence — a ray crossing a wall at a shallow angle travels through more material and loses more.
Incident RF is then converted to usable DC through a rectifier efficiency curve. This is the step most back-of-envelope calculations skip: rectennas are inefficient at low input power, so a 10 dB drop at the antenna is more than a 10 dB drop at the sensor. The read-out shows both the incident level in dBm and the harvested DC power in microwatts.
The model deliberately ignores multipath, reflections and transmitter beam steering. Real rooms are reverberant and usually deliver somewhat more than the direct-ray estimate, so treat the result as a conservative floor.
Typical wall attenuation at 2.4 GHz
| Material | Thickness | Loss | Practical effect |
|---|---|---|---|
| Drywall / plasterboard | 12 cm | ≈ 2 dB | Negligible — power passes easily |
| Wood partition | 10 cm | ≈ 3 dB | Halves received power |
| Glass (single pane) | 1 cm | ≈ 0.6 dB | Coated / low-E glass is far worse |
| Brick | 12 cm | ≈ 9 dB | Roughly one eighth of the power survives |
| Reinforced concrete | 20 cm | ≈ 28 dB | Room-limiting — plan a transmitter per room |
| Metal sheet / lift shaft | any | > 40 dB | Effectively opaque to RF |
What the power levels mean
- Below 1 µW — not deployable. Move the emitter or remove the obstruction.
- 1–10 µW — a sensor can report every few hours after storing charge in a supercapacitor.
- 10–100 µW — a duty-cycled multi-sensor node reporting every minute or two.
- 100 µW – 1 mW — comfortable operation for temperature, humidity, occupancy and air-quality sensing.
- Above 1 mW — continuous Bluetooth Low Energy advertising with headroom.
Frequently asked questions
How much wireless power can you send through a wall?
A 12 cm drywall partition costs roughly 2 dB at 2.4 GHz, a 20 cm reinforced concrete wall roughly 28 dB, and a metal sheet is effectively opaque. Because path loss is logarithmic, one concrete wall can cut received power by more than 99%, which is why room-scale RF wireless power is designed one room at a time.
How far can RF wireless power reach indoors?
At the 36 dBm EIRP typical of ISM-band transmitters, a duty-cycled sensor with a small antenna can be sustained across roughly 5-8 m line of sight. Beyond that the harvested power drops below the microwatt budget the sensor needs to report usefully.
Which frequency is best for wireless power transfer?
Lower frequencies penetrate building materials better and suffer less free-space loss, so 868/915 MHz reaches further through walls. Higher bands such as 2.4 and 5.8 GHz allow much smaller antennas and tighter beam steering, at the cost of range and wall penetration.
How much power does a battery-free sensor need?
A duty-cycled temperature, humidity and occupancy node averages roughly 10-100 microwatts. A continuously advertising Bluetooth Low Energy node needs closer to 1 milliwatt. The simulator reports harvested DC power against those thresholds.
Is the simulator physically accurate?
It uses the Friis free-space path loss equation, published per-material attenuation coefficients scaled with frequency, oblique incidence through walls, and a realistic rectifier efficiency curve. It models the direct ray only, so it ignores multipath and reflections, which in real rooms usually help. Treat it as a first-order feasibility tool, not a substitute for a site survey.
Further reading
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