Antenna
First Claim
1. An antenna for operation at frequencies in excess of 200 MHz, comprising a substantially cylindrical electrically insulative core of a material having a relative dielectric constant greater than 5, with the material of the core occupying the major part of the volume defined by the core outer surface, a feeder structure extending axially through the core, a trap in the form of a conductive sleeve encircling part of the core and having a ground connection at one edge, and first and second pairs of antenna elements each connected at one end to the feeder structure and at the other end to a linking edge of the sleeve, the antenna elements of the second pair being longer than those of the first pair, wherein the antenna elements of both pairs follow respective longitudinally extending paths, and the said linking edge follows a non-planar path around the core, the antenna elements of the first pair being joined to the linking edge at points which are nearer to the connections of the elements to the feeder structure than are the points at which the antenna elements of the second pair are joined to the linking edge.
4 Assignments
0 Petitions
Accused Products
Abstract
An antenna for use at frequencies of 200 MHz and upwards has a cylindrical ceramic core with a relative dielectric constant of at least 5, and pairs of helical elements extending from a feed point at one end of the core to the rim of a conductive sleeve adjacent the other end of the core, the sleeve acting as a trap for isolating from ground currents circulating in the helical elements. To yield helical elements of different lengths, the sleeve rim follows a locus which deviates from a plane perpendicular to the core axis in that it describes a zig-zag path. The helical elements form simple helices with approximately balanced radiation resistances.
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Citations
13 Claims
- 1. An antenna for operation at frequencies in excess of 200 MHz, comprising a substantially cylindrical electrically insulative core of a material having a relative dielectric constant greater than 5, with the material of the core occupying the major part of the volume defined by the core outer surface, a feeder structure extending axially through the core, a trap in the form of a conductive sleeve encircling part of the core and having a ground connection at one edge, and first and second pairs of antenna elements each connected at one end to the feeder structure and at the other end to a linking edge of the sleeve, the antenna elements of the second pair being longer than those of the first pair, wherein the antenna elements of both pairs follow respective longitudinally extending paths, and the said linking edge follows a non-planar path around the core, the antenna elements of the first pair being joined to the linking edge at points which are nearer to the connections of the elements to the feeder structure than are the points at which the antenna elements of the second pair are joined to the linking edge.
Specification