GB961445A - Improvements in or relating to microwave pulse amplifiers - Google Patents

Abstract

961,445. Parametric amplifiers. WESTERN ELECTRIC CO. Inc. Dec. 1, 1960 [Dec. 17, 1969], No. 41341/60. Heading H3B. To amplify a microwave pulse, the permeability or the permittivity of a transmitting medium in a waveguide is reduced over a period of time including the whole transit time of the pulse. The permeability or the permittivity is then increased in preparation for amplification of another pulse. Microwave pulses 31, 32, Fig. 3, are transmitted from source 20 over a guide 10 which is capacitively loaded by conductive rods or fingers 12 to slow the wave. Saw-tooth waves 33 of biasing current are applied to a strip line 13. The biasing current drives a ferrite insert 11 in the guide down a falling portion of the magnetic field/permeability characteristic Fig 2. Thus as the bias rises, the permeability falls. The wave velocity of the miro - wave pulse in the medium increases with the bias but as the spacial distribution of the pulse is unaffected, the frequency increases. There is also an increase in amplitude. In a modification, Fig. 4, the microwave pulse from a source 44 is transmitted through a band-pass filter 42 to the medium 41. The pulse is reflected backwards and forwards through the medium by filter 42 and high-pass filter 43 with consequent amplification and frequency shift until the frequency is high enough for filter 43 to accept it for the load 45. A sinusoidal wave may be used instead of the saw-tooth wave for bias. The slow-wave guide structure may be of the kind described in Specification 724,083 or in U.S.A. Specification 2,659,817.