Measurement of multipath propagation over a line-of-sight radio link at 4Gc/s using frequency-sweep technique

Methods of measuring the amplitude and delay of echoes (multipath propagation) on line-of-sight microwave links are discussed, and the reasons for choosing the frequency-sweep method are given. The equipment used for measurements over a 55km (34 mile) path is described, and a Fourier method is evolved for deriving the multipath components from frequency-sweep records. Recordings were made continuously during the summer and autumn of 1963, and, although there was frequent evidence at night of an indirect propagation path of very short time delay, arising possibly from reflection at or near the ground, substantial multipath propagation of any appreciable delay was observed on only one occasion, again during the night, and this persisted for several hours. This appeared to coincide with an abnormal lapse of atmospheric refractive index at the appropriate height above ground.