NUMERICAL EVALUATION OF PROPAGATION IMPAIRMENTS DUE TO MAN-MADE STRUCTURES ON DIGITAL MICROWAVE LINKS

Radio disturbances of digital microwave links are likely to increase a s man-made structures screen the radio propagation paths, and unwanted waves reflected or scattered by the structures interfere with radio s ignals. This paper describes a practical method for evaluating the inf luence of propagation impairments due to man-made structures on digita l microwave Links and provides some model calculations of those impair ments. Since multilevel and quadrature modulation techniques are emplo yed to achieve high spectral efficiency for recent digital transmissio ns, not only average level attenuation but also in-band distortion and intersymbol interference have to be taken into account. Propagation d istortion, diffraction loss and cross-polar interference due to reflec ted and scattered waves from man-made structures such as buildings and conductor structures are evaluated.