This simulator models a direct radio link plus two single-bounce wall reflections between a transmitter and a receiver. Move the receiver across a corridor, track each path's geometric length and delay, and see how phase and delay combine to produce reinforcement, deep fading, or separate pulse arrivals depending on receiver position.
• A real-time 3D scene of a transmitter mast and RF cabinet, a receiver on a lateral scan carriage, two reflecting wall planes with image-geometry ray paths, a direct line-of-sight path, and a receiver phasor/waveform instrument that distinguishes coherent addition from simple power summation. • Eleven experiment controls: carrier frequency (900–2,400 MHz), transmitter-receiver x separation (4–12 m), wall-to-wall width (4–10 m), receiver lateral position (−1.5 to 1.5 m), wall reflection magnitude (0–1) and phase (−180° to 180°), transmitter power (1–100 mW), enable/disable toggles for the direct path and each wall reflection, an automatic position-scan toggle, and signal type (continuous carrier or Gaussian envelope pilot). • Live metrics: current lateral position, carrier wavelength, direct/upper/lower path geometric lengths, coherent continuous-wave power (µW and dBm), the incoherent sum of separate path powers, RMS delay spread, active-path delay span, and instantaneous normalized signal/envelope. • A Curves & measurements tab with two live charts (rotating receiver phasors, and a position sweep with arrival delays), the full multipath summation equations, and snapshot measurement readouts. • An Experiments tab with four guided fixtures (direct path only, see spatial fading, separate pilot arrivals, remove reflected energy) and a Model verification bench, plus a timestamped event log and a copyable trial report. • A Learn & assess tab with four guided lessons, a knowledge-check quiz with reset, and a written model-scope statement with a technical-background reference link.
Each path contributes a complex amplitude carrying its own propagation phase and imposed wall reflection phase. Received power is proportional to the squared magnitude of the sum of these complex amplitudes — adding the separate path powers together, without accounting for phase, misses the interference entirely and can badly over- or under-predict what a receiver actually sees. At GHz carrier frequencies, moving the receiver by a fraction of a metre can substantially shift phase differences between paths, producing large, spatially localized fades.
Because the direct path is geometrically shortest, reflected paths always arrive later; a Gaussian pilot envelope exposes these separate arrival times directly, since its complex envelope is delayed by each path's individual travel time before being summed with the carrier phase factors. This is a geometric three-path narrowband scalar model — direct path plus one bounce from each of two parallel walls, with unity antenna gains and imposed wall coefficients.
It excludes multiple bounces, diffraction, polarization effects, absorption along the rays, dispersive walls and receiver noise. The automatic position sweep samples static channel positions for learning purposes and does not model Doppler shift from actual motion. One playback second represents 1 ns, and runs stop at 240 ns.
Complex field amplitudes, including each path's phase — not the separate path powers. Phase-sensitive amplitudes must be summed before taking the squared magnitude to get the correct coherent received power.
No. The paths can cancel coherently at the receiver even when each individual path carries significant power, because interference depends on relative phase, not just magnitude.
No, it samples a sequence of static channel positions for learning. It does not compute a moving-channel time evolution or true Doppler frequency shift from continuous receiver motion.
At GHz frequencies, the wavelength is only a few centimeters, so moving a fraction of a metre changes each path's phase substantially — this can shift multiple paths from reinforcing to canceling at the receiver.