Dielectrically-loaded antenna
First Claim
1. A dielectrically-loaded antenna for operation at frequencies in excess of 200 MHz, comprising an electrically insulative core of a solid material having a relative dielectric constant greater than 5, a feed connection, and an antenna element structure disposed on or adjacent the outer surface of the core, the material of the core occupying the major part of the volume defined by the core outer surface, wherein the antenna element structure comprises a plurality of laterally opposed groups of conductive elongate elements, said groups being spaced apart on said core outer surface and each group comprising first and second substantially coextensive elongate elements which are coupled together at respective first ends at a location in the region of the feed connection and at respective second ends at a location spaced from the feed connection, wherein the antenna element structure further comprises a linking conductor linking the second ends of the first and second elongate elements of each of the plurality of groups of elements with the second ends of the first and second elements of the other of said plurality of groups of elements, whereby the first and second elements respectively of each of said plurality of groups form parts of different looped conductive paths, said paths having different respective resonant frequencies within an operating frequency band of the antenna and each extending from the feed connection to the linking conductor, and then back to the feed connection, and wherein at least one of the said elongate antenna elements comprises a conductive strip on the outer surface of the core, the strip having opposing edges of different lengths.
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Accused Products
Abstract
In a dielectrically-loaded quadrifilar antenna for operation with circularly polarised signals, four coextensive composite helical elements are plated on the outer surface of a cylindrical dielectric core, each composite element comprising two mutually adjacent conductive tracks defining between them an elongate channel or slit. The track edges bounding each channel are longer than the opposite edges of the respective tracks in that they follow parallel meandered paths, with the result that each channel deviates from a mean helical path and is longer than the corresponding portion of the mean helical path. At a frequency within the operating band of the antenna, the channels have respective electrical lengths equivalent to a half wavelength. The bandwidth of the antenna is greater than the bandwidth of a correspondingly dimensioned antenna having single-track helical elements.
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Citations
56 Claims
- 1. A dielectrically-loaded antenna for operation at frequencies in excess of 200 MHz, comprising an electrically insulative core of a solid material having a relative dielectric constant greater than 5, a feed connection, and an antenna element structure disposed on or adjacent the outer surface of the core, the material of the core occupying the major part of the volume defined by the core outer surface, wherein the antenna element structure comprises a plurality of laterally opposed groups of conductive elongate elements, said groups being spaced apart on said core outer surface and each group comprising first and second substantially coextensive elongate elements which are coupled together at respective first ends at a location in the region of the feed connection and at respective second ends at a location spaced from the feed connection, wherein the antenna element structure further comprises a linking conductor linking the second ends of the first and second elongate elements of each of the plurality of groups of elements with the second ends of the first and second elements of the other of said plurality of groups of elements, whereby the first and second elements respectively of each of said plurality of groups form parts of different looped conductive paths, said paths having different respective resonant frequencies within an operating frequency band of the antenna and each extending from the feed connection to the linking conductor, and then back to the feed connection, and wherein at least one of the said elongate antenna elements comprises a conductive strip on the outer surface of the core, the strip having opposing edges of different lengths.
- 17. A dielectrically-loaded antenna for operation at frequencies in excess of 200 MHz, comprising an electrically insulative core of a solid dielectric material having a relative dielectric constant greater than 5, a feed connection, and an antenna element structure disposed on or adjacent the outer surface of the core, wherein the core has end surfaces and side surfaces and an axis of symmetry passing through the end surfaces, and wherein the antenna element structure comprises a plurality of groups of elongate antenna elements spaced apart on said side surfaces of the core, each group forming part of a plurality of looped conductive paths which extend from a first terminal to a second terminal of the feed connection and which have different electrical lengths at a frequency within an operating band of the antenna, and each group comprising first and second substantially coextensive elongate radiating elements which run side-by-side on or adjacent the side surfaces of the core and which form part of a different respective one of said looped paths of different electrical lengths, wherein at least one of the said elongate elements on or adjacent the side surfaces comprises a conductive strip having non-parallel opposing edges such that the opposing edges of strip are of different lengths.
- 20. A dielectrically loaded antenna for operation at frequencies in excess of 200 MHz, comprising an electrically insulative core of a solid material having a relative dielectric constant greater than 5, a feed connection, and an antenna element structure disposed on or adjacent the outer surface of the core, the material of the core occupying the major part of the volume defined by the core outer surface, wherein the antenna element structure comprises a plurality of groups of conductive elongate elements, each group comprising first and second substantially coextensive mutually adjacent elongate elements at least one of which comprises a conductive strip on the outer surface of the core, the strip having opposing edges of different lengths.
- 33. A quadrifilar helical antenna comprising first and second pairs of diametrically opposed antenna elements on a generally cylindrical dielectric substrate, at least one of the elements of each pair including a pair of mutually adjacent substantially parallel conductive tracks defining between them a channel, the track edges which define the channel being longer than the other edges of the respective tracks.
- 42. A helical antenna for circularly polarised electromagnetic radiation comprising first and second pairs of helical conductive track groups on or adjacent the outer generally cylindrical surface of a generally cylindrical insulative substrate, the track groups being substantially uniformly distributed around said outer surface and each comprising at least a pair of generally helical tracks which each have one edge longer than the other and each of which is nearer to the other track of said pair that it is to the tracks of the other groups.
- 47. A quadrifilar helical antenna for operation in a frequency band above 200 MHz, wherein the antenna comprises four coextensive composite helical antenna elements each of which is formed as the combination of at least two coextensive elongate conductors separated by a slit, the width of the slit being less than half of the spacing between the respective composite element and either of the neighbouring composite elements.
Specification