A 5 db noise figure backward-wave amplifier at X-band

The Backward-Wave Amplifier is a very useful pre-amplifier for microwave receivers. Its selectivity, crystal protection and low noise figure offer advantages in various communication and radar systems. An X-band BWA has been developed which has produced minimum noise figures of 4.5" db. These tubes operate with the following characteristics over the 8.5 - 9.5 kMc frequency range: gain 20 db, noise figure less than 5.5 db with minimum of 4.5 db, bandwidth mc, 6.5 mc/volt tuning rate. The important parameters which determine these characteristics will be described. The tube is encapsulated in a novel waveguide package that uses semicircular waveguide. This package provides waveguide input and output terminations in a minimum cross-sectional area.