The measurement of radio characteristics of building surfaces to aid urban clutter modelling

Future radio systems planning will rely heavily on the exact specification of building parameters. However, the precise building parameters which have a significant effect on radio propagation have not been identified. Therefore a programme to measure the type of reflections from building walls has been undertaken. Several wall structures have been measured and the results are being analysed to determine the specular reflection coefficient and scattering which may occur. It is possible that small variations in the wall structure may cause significant differences in the type of reflection. Factors being assessed are inner and outer brick types and thicknesses, cavity filling and width and the effects of steel portal frames or any periodic reinforcements or irregularities. The measurements are taken at 869 MHz using two 22-element Yagi antennas with a beamwidth of around 23 degrees. Two different experimental geometries have been used. In both, the transmitter is fixed so that it illuminates the wall with a given angle of incidence. In the first case the receiver is in a fixed location and is rotated. This allows the strength of reflection to be assessed and can be used to determine if the surface is causing the signal to be scattered. In the second type of trial the receiver is moved in an arc about the point on the wall upon which the transmitter is focused and is always aimed at this point. This allows severe scatter and specular reflections to be detected