Measured scattered signals at 4 GHz confirm strong specular reflections off buildings

The authors report measures of building reflections in the Fresnel region which clearly show the existence of large specular reflections which would severely interfere with radio links. Measurements of microwave terrestrial radio signals in the 4-GHz common carrier band were made using the Division 21320 van. Measurements were taken at several sites of specular and diffusely scattered signal levels. The measured specular reflection is 20 to 30 dB higher than the diffusely scattered energy and is caused by reflection from a building illuminated by a sidelobe 17 dB below the boresight beam of the transmitter, indicating that a reflection in the main beam would cause interference which may be 37 to 47 dB higher than that predicted by terrain scatter models