Antenna
First Claim
1. An antenna having an operating frequency in excess of 200 MHz comprising a cylindrical insulative body having a central axis and formed of a solid material which has a relative dielectric constant greater than 5, the outer surface of the body defining a volume the major part of which is occupied by the solid material, a conductive sleeve on the cylindrical surface of the insulative body, a conductive layer on a surface of the body which extends transversely of the axis, the conductive sleeve and layer together forming an open-ended cavity substantially filled with the solid material, and a feeder structure associated with the cavity, wherein the relative dielectric constant and the dimensions of the cavity are adapted such that the electrical length of its circumference at the open end is substantially equal to a whole number (1, 2, 3, . . . ) of guide wavelengths around the circumference corresponding to the operating frequency, wherein the antenna has a radiation pattern for circularly polarised radiation at the operating frequency, which pattern is cardioid-shaped with its maximum along the axis of the insulative body outwardly away from the open end of the cavity.
3 Assignments
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Accused Products
Abstract
A dielectric-loaded antenna for circularly polarized radiation has a generally cylindrical solid dielectric body with a relative dielectric constant greater than 5, upon which body is plated a conductive sleeve encircling the body and a conductive end layer which, together with the body, form an open-ended cavity substantially filled with the ceramic material of the body. The electrical length of the cavity rim is a whole number of guide wavelengths corresponding to the antenna operating frequency less than 5 GHz. A rotating standing wave is excited around the cavity rim by a feeder structure including two helical conductor tracks on the cylindrical surface of the body which are coupled between the cavity rim and a coaxial feeder passing axially through the body.
363 Citations
36 Claims
- 1. An antenna having an operating frequency in excess of 200 MHz comprising a cylindrical insulative body having a central axis and formed of a solid material which has a relative dielectric constant greater than 5, the outer surface of the body defining a volume the major part of which is occupied by the solid material, a conductive sleeve on the cylindrical surface of the insulative body, a conductive layer on a surface of the body which extends transversely of the axis, the conductive sleeve and layer together forming an open-ended cavity substantially filled with the solid material, and a feeder structure associated with the cavity, wherein the relative dielectric constant and the dimensions of the cavity are adapted such that the electrical length of its circumference at the open end is substantially equal to a whole number (1, 2, 3, . . . ) of guide wavelengths around the circumference corresponding to the operating frequency, wherein the antenna has a radiation pattern for circularly polarised radiation at the operating frequency, which pattern is cardioid-shaped with its maximum along the axis of the insulative body outwardly away from the open end of the cavity.
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24. A system adapted as a mobile telephone for receiving satellite signals with circular polarisation, adapted to receive, additionally, terrestrial telephone signals in a frequency band spaced from the frequency at which the satellite signals are received, comprising an antenna having an operating frequency in excess of 200 MHz, comprising a cylindrical insulative body having a central axis and formed of a solid material which has a relative dielectric constant greater than 5, the outer surface of the body defining a volume the major part of which is occupied by the solid material, a conductive sleeve on the cylindrical surface of the insulative body, a conductive layer on a surface of the body which extends transversely of the axis, the conductive sleeve and layer together forming an open-ended cavity substantially filled with the solid material and a feeder structure associated with the cavity, wherein the relative dielectric constant and the dimensions of the cavity are adapted such that the electrical length of its circumference at the open end is substantially equal to a whole number (1, 2, 3, . . . ) of guide wavelengths around the circumference corresponding to the operating frequency, wherein the antenna has a radiation pattern for circularly polarised radiation at the operating frequency, which pattern is cardioid-shaped with its maximum along the axis of the insulative body outwardly away from the open end of the cavity.
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25. A radio signal receiving and/or transmitting system comprising a radio frequency front end stage constructed to operate at a first signal receiving or transmitting frequency and, coupled to the front end stage, an antenna which comprises:
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a cylindrical insulative body having a central axis and formed of a solid material with a dielectric constant greater than 5, the outer surface of the body defining a volume the major part of which is occupied by the solid material, a conductive layer on a cylindrical surface of the body which extends transversely of the axis, a conductive sleeve on the cylindrical surface of the insulative body, the conductive sleeve and layer together forming an open-ended cavity substantially filled with the solid material, and a feeder structure associated with the cavity, wherein the relative dielectric constant and the dimensions of the cavity are adapted such that the electrical length of the rim of the cavity at its open ends is substantially equal to a whole number (1,2,3, . . . ) of guide wavelengths corresponding to the first signal frequency and wherein the antenna bas a radiation pattern for circularly polarised radiation at the operating frequency, which pattern is cardioid-shaped with its maximum along the axis of the insulative body outwardly away from the open end of the cavity. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32)
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- 33. A dielcrically-loaded cavity-backed antenna for circularly polarised waves at a required operating frequency in excess of 200 MHz, comprising a cavity with a conductive cylindrical side wall and a conductive bottom wall joined to the side wall, the side wall having a rim defining a cavity opening opposite the bottom wall, a dielectric core substantially filling the cavity and formed of a solid material having a relative dielectric constant greater than 5, and a rotational feed system, characterized in that the dielectric constant and the dimensions of the cavity are such that the circumference of the rim is substantially equal to a whole number (1, 2, 3 . . . ) of guide wavelengths at the required operating frequency, and wherein the feed system is adapted to excite a waveguide resonance in the cavity at the required operating frequency, which resonance is characterized by at least one voltage dipole oriented diametrically across the cavity opening and spinning about the central axis of the cavity thereby to produce a circular polarisation radiation pattern which is directed axially outwardly from the opening of the cavity and has a null in the opposite axial direction, wherein the antenna has a radiation pattern for circularly polarised radiation at the operating frequency, which pattern is cardioid-shaped with its maximum along an axis of the dielectric core outwardly away from the open end of the cavity.
- 35. A method of operating an antenna which has a cylindrical insulative body made of a material with a dielectric constant greater than 5, a conductive sleeve on the cylindrical surface of the body, a conductive layer arranged on a transversely extending surface of the body so as to form, with the sleeve, an open-ended cavity substantially filled with the dielectric material, and a feeder structure associated with the cavity, wherein the method comprises feeding signals absorbed from the surroundings to a radio signal receiver unit, and/or radiating to the surrounding signals from a radio signal transmitter unit, at least one frequency at which a ring mode of resonance occurs around the sleeve at its open end, wherein the antenna has a radiation pattern for circularly polarised radiation at the operating frequency, which pattern is cardioid-shaped with its maximum along an axis of the insulative body outwardly away from the open end of the cavity.
Specification