GB1180218A - Improvements in or relating to Dispersive Devices - Google Patents

Abstract

1,180,218. Delay lines. MARCONI CO. Ltd. 23 March, 1967 [2 Aug., 1966], No. 34650/66. Heading H3U. [Also in Division H1] A dispersive device for pulse compression or for so-called " passive generation " comprises a number of couplings spaced along a pair of waveguides which are themselves non-dispersive or only slightly dispersive. The wave-energy may be compressional or electromagnetic. In the latter case the guide may be of the coaxial type and the apparatus may take the form of two coaxial guides 2A, 2B (central conductors not shown) coupled by apertures 3 and terminated by absorptive means 2D, 2E. The apertures constitute the sources which are fed by waveguide 2A and produce a compressed pulse in waveguide 2B. The arrangement shown is for compressing a signal consisting of a linearly increasing frequency sweep and the spacing of the holes increases in the direction of propagation of the input signal. A mathematical discussion of the spacing of the holes required to give a chosen dispersion is given and the case of a signal consisting of linearly increasing wavelength components is also discussed. The spacing may take in account slight dispersion in the coaxial guides and the size of the coupling holes may be graded to compensate for the attenuation in the guides or to provide a desired frequency/attenuation spectrum. Where compressional waves are used, the propagating medium may be gaseous, liquid or solid, e.g. air, sulphur hexafluoride, water, aluminium, used with or without temperature control. Torsional or transverse modes may be used in solid media. Where the waveguides are solid bodies, the coupling means consists of " necks " of solid material constituted e.g. by spots of welded material or of synthetic resin adhesive.