Specular and diffuse measurements of multipath from various terrain surfaces at 35 GHz

Abstract

Measurements of height–gain interference patterns at 35 GHz are carried out in order to obtain multipath interference data over various types of terrain viz. grass, road surface and concrete. The antenna with a beam width of 21° is used both at transmitting and receiving ends to ensure full illumination of Fresnel zones. The transmitting antenna height is kept at 1 m and receiving antenna height is vertically translated from 1 through 4 m, with a horizontal range separation of 74 m. The polarisation combination is vertical transmit and vertical receive. The system geometry provides low-grazing angle incidence. The recorded height–gain curves indicate the presence of specular and diffuse multipath components. Specular and diffuse multipath components are separated out using discrete fourier transform-based filtering technique and reflection coefficients are computed for various types of terrain covers. The results can be vitally useful for millimetre wave radar, guidance, remote sensing and communication systems operating near the surface in arid conditions.