Improved agile notch adaptive equaliser

A major source of `outage¿ in high-capacity digital radio-relay systems operating in the lower microwave bands is multipath propagation. Adaptive equalisation of the channel and other remedial measures such as the use of space diversity are often necessary for adequate system performance. A common type of adaptive frequency-domain equaliser employs a variable single-pole filter controlled by three fixed spectrum-sampling detectors. The effectiveness of this type is limited by extraneous causes of spectrum distortion such as tilts. The letter describes a new form of equaliser which searches for and equalises according to minima in the distorted spectrum and is insensitive to extraneous spectrum tilts.