Ray tracing analysis of Gaussian beamed millimetre wave propagation in circle tunnel

Millimetre-wave communication is regarded as a way to providing high speed digital transmission and resolve congestion of radio spectrum. Propagation characterization is one of the main building blocks for such usages. The Gaussian beam has attractive features to become a prospective wave form for millimetre radio communication application. A ray tracing method embedded with spectral features of Gaussian beam is employed to analyze millimetre wave propagation in a circle tunnel in this paper. In consideration of geometrical figure of the tunnel, the superposition behaviour of direct and reflective beams is analyzed with simplified approximation of Gaussian beam spectral feature to derive receiving wave´s amplitude, phase, and delay spread. A typical straight tunnel model is used to simulate the propagation behaviour, where strong multi-path effect with deeply fading of signal intensity and dramatically enhancing of delay spread emerges. Variations of receiving wave´s power intensity and delay spread along with the beam travelling down in the tunnel, and spectral features of them at a designated point are also investigated.