Abstract: Disclosed herein are example embodiments of a dielectrically loaded multifilar antenna for circularly polarised radiation the antenna having a plurality of operating frequencies in excess of 200 MHz. In one embodiment, the antenna comprises: an electrically insulative core having proximal and distal surface portions and, between the proximal and distal surface portions, a laterally directed side surface portion; a pair of feed nodes; at least four elongate generally helical conductive radiating elements located on the core; and, arranged between and coupling together the feed nodes and the radiating elements, a phasing ring formed by a closed loop, wherein the phasing ring is resonant at least two of the operating frequencies, the elongate antenna elements being coupled to the phasing ring at respective spaced apart coupling locations and extending from the phasing ring in a direction away from the feed nodes.

Abstract: An antenna for circularly polarized radiation at an operating frequency in excess of 200 MHz has a substrate in the form of a disc-shaped dielectric tile with parallel planar surfaces. The upper surface bears a conductive pattern including a resonant ring and a number of open-circuit radiating elements each having an electrical length of a quarterwave at the resonant frequency of the ring. The radiating elements extend outwardly from the ring and are joined to the ring at uniformly spaced locations. Each radiating element extends in a direction which has both a radial component and a tangential component and follows a generally spiral path. A pair of central feed nodes are coupled to the inside of the ring by a pair of feed tracks lying on a diameter. Dual-frequency and dual-polarization variants are also disclosed.

Abstract: Disclosed herein are example embodiments of a dielectrically loaded multifilar antenna for circularly polarised radiation the antenna having a plurality of operating frequencies in excess of 200 MHz. In one embodiment, the antenna comprises: an electrically insulative core having proximal and distal surface portions and, between the proximal and distal surface portions, a laterally directed side surface portion; a pair of feed nodes; at least four elongate generally helical conductive radiating elements located on the core; and, arranged between and coupling together the feed nodes and the radiating elements, a phasing ring formed by a closed loop, wherein the phasing ring is resonant at at least two of the operating frequencies, the elongate antenna elements being coupled to the phasing ring at respective spaced apart coupling locations and extending from the phasing ring in a direction away from the feed nodes.

Abstract: A dielectrically loaded quadrifilar helical antenna has four quarter turn helical elements centered on a common axis. Each helical element is metallized on the outer cylindrical surface of a solid dielectric core and each has a feed end and a linked end, the linked ends being connected together by a linking conductor encircling the core. At an operating frequency of the antenna the helical elements and the linking conductor together form two conductive loops each having an electrical length in the region of (2n?1)/2 times the wavelength, where n is an integer. Such an antenna tends to present a source impedance of at least 500 ohms to receiver circuitry to which it is connected. The invention includes an antenna assembly including a dielectrically antenna and a receiver having a radio frequency front-end stage with a differential input coupled to the feed ends of the helical elements.

Abstract: A dual-band dielectrically loaded multifilar antenna has a first group of helical conductive antenna elements extending from feed connection nodes to an annular linking conductor 20U, and a second group of conductive helical antenna elements extending from the feed coupling nodes in the direction of the linking conductor to substantially open-circuit ends spaced from the linking conductor. The helical elements of the first group are half-turn elements having an electrical length of approximately one half wavelength at a first operating frequency of the antenna. The helical elements of the second group are approximately quarter-turn helical elements having an electrical length in the region of one quarter wavelength and a second operating frequency of the antenna. Each group of elements is associated with a respective mode of resonance for circularly polarized radiation.

Abstract: A dielectrically-loaded antenna has a cylindrical ceramic core, a three dimensional antenna element structure comprising co-extensive helical conductors plated on a cylindrical side surface of the core and a dielectrically-loaded antenna has a solid cylindrical core made of a ceramic material, helical antenna elements made of a ceramic material, co-extensive helical antenna elements plated on the core, connecting conductors on a distal end surface, a matching section in the form of a printed circuit board overlying the core distal end surface and a coaxial feeder housed in an axial bore passing through the core. For ease of manufacture, the laminate board of the matching section contains a ball grid array having a plurality of solder elements which serve to connect the matching network to both the surface connection elements on the distal core end surface and to the feeder.

Abstract: A dielectrically loaded quadrifilar helical antenna has four quarter turn helical elements centered on a common axis. Each helical element is metallised on the outer cylindrical surface of a solid dielectric core and each has a feed end and a linked end, the linked ends being connected together by a linking conductor encircling the core. At an operating frequency of the antenna the helical elements and the linking conductor together form two conductive loops each having an electrical length in the region of (2n?1)/2 times the wavelength, where n is an integer. Such an antenna tends to present a source impedance of at least 500 ohms to receiver circuitry to which it is connected. The invention includes an antenna assembly including a dielectrically antenna and a receiver having a radio frequency front-end stage with a differential input coupled to the feed ends of the helical elements.

Abstract: In a dielectrically-loaded multifilar helical antenna, a conductive phasing ring is arranged between and couples together feed nodes and the helical radiating elements. The phasing ring includes an annular conductive path having an electrical length equivalent to a full wavelength at the operating frequency so as to be resonant at that frequency. The helical elements are coupled to the outer periphery of the phasing ring at respective spaced apart coupling locations. The helical elements may include open-circuit or closed-circuit elongate conductive tracks, or a combination of both. In the case of the helical elements being closed-circuit tracks, these tracks are interconnected by a second resonant ring, which is resonant at the same frequency as or a different frequency from the first resonant ring. The invention is applicable to both end-fire and back-fire helical antennas.

Abstract: A dielectrically loaded antenna for operation at first and second frequencies above 200 MHz with circularly polarized radiation includes an electrically insulative dielectric core of solid material having a relative dielectric constant greater than 5, and a three-dimensional antenna element structure linked to a pair of feed coupling nodes. The antenna element structure is divided into a distal section and a proximal section respectively having a first set of elongate conductors on or adjacent a distal part of the core side surface portion and a second set of elongate conductors on or adjacent a proximal part of the core side surface portion, and wherein the first set of conductors is resonant at the first operating frequency and the second set of conductors is resonant at the second operating frequency.

Abstract: A method of manufacturing a dielectrically loaded antenna having an operating frequency in excess of 200 MHz, the antenna having an electrically insulative core, the method including steps of: forming a first patterned layer of conductive material having a plurality of inner conductive tracks on at least one surface of the core of the antenna; depositing a layer of insulative material over at least a portion of the first layer of conductive material; and forming a second patterned layer of conductive material having a plurality of outer conductive tracks, at least partially overlapping the inner conductive tracks.

Abstract: A dielectrically loaded backfire helical antenna has a cylindrical ceramic core and a feed structure which passes axially through the core to a distal end face of the core where it is connected to helical conductors located on the outside of the core. Opening out on the proximal end face of the core is a cavity which is coaxial with the feed structure. A conductive balun layer encircling a portion of the core extends over the proximal end face of the core and the wall of the cavity to connect the helical elements to the feeder structure when it emerges into the cavity. The presence of the cavity and accommodating some of the length of the balun in the cavity allows a reduction in the size and weight of a dielectrically loaded backfire antenna.

Abstract: A dielectrically loaded backfire helical antenna has a cylindrical ceramic core and a feed structure which passes axially through the core to a distal end face of the core where it is connected to helical conductors located on the outside of the core. Opening out on the proximal end face of the core is a cavity which is coaxial with the feed structure. A conductive balun layer encircling a portion of the core extends over the proximal end face of the core and the wall of the cavity to connect the helical elements to the feeder structure when it emerges into the cavity. The presence of the cavity and accommodating some of the length of the balun in the cavity allows a reduction in the size and weight of a dielectrically loaded backfire antenna.

Abstract: A dielectrically-loaded helical antenna has a cylindrical ceramic core bearing metallised helical antenna elements which are coupled to a coaxial feeder structure passing axially through the core. Secured to the end face of the core is an impedance matching section in the form of a laminate board. The matching section embodies a shunt capacitance and a series inductance.

Abstract: A dielectrically-loaded helical antenna has a cylindrical ceramic core bearing metallised helical antenna elements which are coupled to a coaxial feeder structure passing axially through the core. Secured to the end face of the core is an impedance matching section in the form of a laminate board. The matching section embodies a shunt capacitance and a series inductance.

Abstract: An antenna arrangement which includes two antennas which are resonant at a common operating frequency. The arrangement includes a circuit which combines output signals from each of the antennas to provide a combined signal output. Each antenna has an electrically insulative core of solid material having a relative dielectric constant greater than 5 and a three-dimensional antenna element structure. The structure includes at least a pair of elongate conductive antenna elements disposed on or adjacent a surface of the core.

Abstract: A dielectrically-loaded helical antenna has a cylindrical ceramic core bearing metallised helical antenna elements which are coupled to a coaxial feeder structure passing axially through the core. Secured to the end face of the core is an impedance matching section in the form of a laminate board. The matching section embodies a shunt capacitance and a series inductance.

Abstract: An antenna for circularly polarised radiation at an operating frequency in excess of 200 MHz has a substrate in the form of a disc-shaped dielectric tile with parallel planar surfaces. The upper surface bears a conductive pattern including a resonant ring and a number of open-circuit radiating elements each having an electrical length of a quarterwave at the resonant frequency of the ring. The radiating elements extend outwardly from the ring and are joined to the ring at uniformly spaced locations. Each radiating element extends in a direction which has both a radial component and a tangential component and follows a generally spiral path. A pair of central feed nodes are coupled to the inside of the ring by a pair of feed tracks lying on a diameter. Dual-frequency and dual-polarisation variants are also disclosed.

Abstract: A dielectrically loaded multifilar antenna has an electrically insulative solid core bearing an antenna element structure having four pairs of substantially helical radiating elements spaced apart around a central axis of the antenna. Each pair of oppositely located antenna elements forms part of a conductive loop having an effective electrical length in the region of N guide wavelengths at the operating frequency, where N is an integer and is at least 2. Typically, each helical element executes substantially a full turn around the axis on the outer surface of the core. The antenna offers an improved gain-bandwidth product compared with typical prior dielectrically loaded multifilar helical antennas, and a 3 dB beamwidth of at least 90° for circularly polarized radiation.

Abstract: A radio communication receiver which includes an antenna array having at least two antennas to provide antenna diversity. The receiver is for receiving signals containing orthogonally coded data sub-streams derived from a source data stream. The receiver also has receiver circuitry, coupled to the antenna array, having a detection stage to detect the data sub-streams and a combiner stage for combining the detected data sub-streams to recover the source data stream. Each antenna has an electrically insulative core of solid material having a dielectric constant greater than 5. Each antenna also has a three-dimensional antenna element structure disposed on or adjacent the outer surface of the core.

Abstract: A dielectrically loaded multifilar helical antenna having an operating frequency in excess of 200 MHz has an electrically insulative core with a relative dielectric constant greater than 5 occupying the major part of the interior volume defined by a three dimensional antenna element structure having, in one embodiment, eight coextensive helical tracks and, in another embodiment, six such tracks. The antennas are backfire or endfire antennas, all helical elements being phased so as to contribute to a circular polarization resonance at the operating frequency.