Microminiature radio altimeter

Describes a low-level radio altimeter in which solid-state microwave techniques have been used. The aim was to achieve high reliability: the resulting equipment is also smaller and lighter than its predecessors, has lower power requirements and is more rugged. The original specification demanded a flexible and adaptable instrument, as future aircraft design was uncertain. The construction and design of transmitter, receiver and video circuit are discussed. The transmitter, radical in design, is of the varactor multiplier type because of power requirements, but as higher-frequency, higher -power transistors become available they will be fitted into the chain and more low-frequency elements will be discarded until an oscillator at 4300 MH is achieved. The improvements to the receiver are chiefly in the components. The video circuits are complex: the types of circuit available and the reasons governing the final choice are discussed. Possible future developments, chiefly in the component field, are mentioned in the conclusion.