GB2408153A - Balun - Google Patents

Abstract

A broad band Balun (a device which converts balanced mode electromagnetic field structures such as twin lead, to an unbalanced field structure such as coaxial cable) can be produced by taking the approach of gradually perturbing the field structure from one form to the other over a given distance. The concept is shown in figure 1 in which the transition from one field structure to another is carried out by cutting a wedge shape out of the cable. Any shape however can be removed from the cable commensurate with forming a match condition, as long as the transition is gradual.

Description

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Description

The balun structure as presented in figure 1 is offered as a particular case of a general technique which can be used to create an inherently broadband balun structure. The technique employed is to gradually perturb the field structure form one form to another over a given distance. This technique offers several advantages over currently available balun structures: (1) The structure is frequency independent and is therefor inherently broadband.

(2) The structure is extremely simple and therefor cheap to manufacture.

(3) In most cases the structure can be made from cable assemblies that would already be present such as the example given, namely a length of coaxial cable terminated with twin lead.

The final form of the transition region is best determined with a scalar or vector network analyser because a certain amount of trimming will inevitably be required for the band of operation and bandwidth required. Slight changes of the distances involved between the coaxial inner and the gradually increasing ground plane will effect a narrow band high performance balun. Broadband performance will be achieved with a specially designed inner conductor in the transition region. Several octaves of bandwidth should be easily attainable.

Claims (1)

1. Claims (1) A broadband balun structure can be created by gradually

   perturbing the field structure from a balanced field structure to an unbalanced field structure.

   (2) As claimed in claim(l) reciprocity applies in this case and broadband balun structures can also be created from an unbalanced to a balanced field structure by

   the use of gradual field structure perturbation.

   (3) As claimed in claim(l) and claim(2) the balun structure is independent of the direction of flow of energy.

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   Amendments to the claims have been filed as follows (1) A Balun structure as depicted in figure 1 in profile and in all subsequent figures in cross section that functions on a broad band basis by gradually perturbing the electromagnetic fields from a balanced field structure to an unbalanced field structure over a given distance designated as the transition region.

   (2) As claimed in claim(l) the same scenario but based on perturbing the electromagnetic fields from an unbalanced field structure to a balanced field structure over a given distance designated as the transition region in figure 1.

   (3) Any structure similar to that depicted in figure I but with conductors other than circular that are constructed in a manner similar to claim(1) or claim(2) is also claimed.

   (4) Any structure similar to that depicted in figure 1 consistent with claim(1) or claim(2) or claim(3) or any combination of these claims with a relative permeability above unity and-or relative permitivity above unity is also claimed.

   (5) Anything similar to any of the above claims is also claimed.