Abstract: An active receiving antenna for vehicles, including a slot-shaped antenna cut into the metallic vehicle body, and having small-depth cavity filled with a dielectric material which closes off the antenna toward the back or interior of the vehicle. A low-noise preamplifier, which is integrated into the dielectric material, is connected to the antenna via two feed lines of different length. The desired polarizations of the received signals are set via this preamplifier, which can be changed over and be switched off.

Abstract: A low cost window-mounted antenna system for mobile communication systems operating at frequencies in and above the 1.5 GHz band includes an annular ring aperture coupler fabricated on printed circuit boards on each side of the window, with a microstrip line etched on each of the printed circuit boards. A collinear array-type whip antenna with a 1/2-wavelength lower section is used with the coupler. A coplanar waveguide trace is printed on the outside coupling unit to form an impedance matching network for the active element. The RF signal is thus electro-magnetically coupled through the window.

Abstract: A feeder for a microwave antenna system which can be integrated together with electronic circuitry on a common circuit board. A slot antenna, preferably shaped as an annular slot, is provided on the circuit board, and can be etched on the backside of the circuit board, which is normally a ground plate. The antenna system can be used for reception of DBS signals.

Abstract: An antenna (10, 110, 210) comprising a ground layer (30, 130, 230), a feed layer (50, 150, 250), an antenna layer (40, 140, 240) and a transparent dielectric substrate (20, 120, 220) interposed between two of the layers (30 and 40, 140 and 150, 230 and 250). An electromagnetic field is produced between the ground layer (30, 130, 230) and the antenna layer (40, 140, 240) when the feed and ground layers (50 and 30, 150 and 130, 250 and 230) are exposed to a microwave frequency above 3,000 megahertz for transmission and when the antenna and ground layers (40 and 30, 140 and 130, 240 and 230) are exposed to a microwave frequency above 3,000 megahertz, for reception. The ground layer (30, 130, 230), feed layer (50, 150, 250) and antenna layer (40, 140, 240) are made of an optically transparent and electrically conductive material. About 30% of the visible light impinging on the antenna (10, 110, 210) passes through the antenna.

Abstract: A patch and a ground conductor are shortcircuited with two shortcircuit portions that are composed of conductive plates and that pass through a dielectric substrate. The shortcircuit portions are connected to the inner periphery of the patch and have large widths therealong. A first shortcircuit portion is disposed on a first line that connects a microstrip feeder line and the center point of the patch. A second shortcircuit portion is disposed on a second line that passes through the center point. The inner angle of the first line and the second line is in the range from 80 degrees to 110 degrees.

Abstract: A microstrip antenna has two dielectric layers bonded together with an array of conducting strips interposed therebetween, the strips being spaced to define a slot between each pair of adjacent strips. A conductive ground plane is disposed on a first outer side of the two bonded dielectric layers, and an array of radiating patches are disposed on a second outer side of the two bonded dielectric layers, each of which patches is positioned over a corresponding slot, the array of patches being spaced apart to form an aperture between each pair of adjacent patches. Responsive to electromagnetic energy, a high-order standing wave is induced in the antenna and a directed beam is transmitted from and/or received into the antenna.

Abstract: An array antenna in particular for space applications comprises radiating elements having a stratified type of structure. These elements are fixed on a support structure having openings beneath the radiating elements.

Abstract: A directional planar antenna is disclosed. The antenna has an array of coaxial ring-slot radiating elements formed through a conductive layer on a dielectric substrate. A number of probes, coupled to the ring-slot elements, selectively excite a separate resonant mode on each ring-slot element. The resonant mode supported by a ring-slot element depends upon the geometry of that ring-slot element. The resonant modes combine in the far field to form a radiation pattern directional in azimuth and elevation. By adjustment of the relative phase difference or relative amplitude between the excited modes, the radiation pattern can be steered.

Abstract: In an annular microstrip antenna element, an annular radiant conductor plate is mounted on a ground conductor plate via a dielectric layer. A coaxial transmission line is provided, whose external conductor is connected to the ground conductor plate, and whose central conductor is connected to the radiant conductor plate, via a feeding point, with a pair of microstrip lines. The pair of microstrip lines extend from the feeding point to two connecting points on the radiant conductor plate, forming an angle between them like a V shape. By varying the angle, it is possible to adjust the input impedance of the annular microstrip antenna element at the feeding point, so that impedance matching with the coaxial transmission line is achieved. In a radial line antenna system comprising a plurality of the antenna elements, the antenna elements are mounted on concentric circles with a constant space between the adjacent antenna elements, thereby reducing undesirable electromagnetic coupling.

Abstract: An elementary antenna embodies a constant thickness dielectric substrate having on one side a conductive metal layer forming a ground plane and on its other side a radiating patch electrically connected to a feed line. The patch is formed by a conductive loop of constant width l surrounding an inner parasitic patch which is not fed and is separated from the inner parasitic patch by a closed continuous slot of constant width e adapted to bring about coupling between the loop and the inner parasitic patch.

Abstract: The present invention relates to a compact, lightweight microstrip antenna that operates at two frequencies that are widely different. On a dielectric substrate are formed an element consisting of an annular conductive pattern, wherein a central edge side thereof is short-circuited to a ground electrode, and an element consisting of a circular conductive pattern within the annular conductive pattern. The circular conductive pattern is accommodated within the annular conductive pattern. The two antennas operate at different frequencies, with the element formed by the annular conductive pattern resonating in TM.sub.11 mode and the element formed of the circular pattern resonating in the TM.sub.01 mode. An antenna capable of being used in common by systems with widely different frequency bands, such as the GPS and VICS, is thus obtained.

Abstract: A plane antenna suitable for space applications in particular comprises a passive resonator coupled to a feedline by a looped slot.

Abstract: A broad band mobile telephone antenna comprises a first conductive circular plate and a second conductive circular plate. The first plate is located above and in parallel with the second plate. The diameter of the second plate is equal to or larger than that of the first plate. The second plate is used as a ground plate, is attached on a body of an automobile. A short-circuit rod, for matching an impedance between the first plate used as an antenna and a coaxial feeder cable for the antenna, is connected between the first and second plates. An upper end of a core rod is connected to the first plate at the substantial center thereof. A lower end of the core rod is extended toward an opening formed in the substantial center of the second plate. The opening is connected to a connector which is placed inside the automobile through an opening formed in the body. The connector connects the core rod and the coaxial cable which is connected to a transmitter/receiver of a mobile telephone system.

Abstract: A radiating device for a planar antenna, said device including a first ground plane and a second ground plane, a slot (25) provided in the first ground plane and being fed by electromagnetic coupling from a feed line (17), and an assembly of a plurality of thin conductive parts; the central portion of the radiating slot (25) being a conductive part (15) supported at its center by a supporting column (18). Application in particular to the space field.

Abstract: A dual frequency cavity backed slot antenna and method of tuning the antenna, wherein the antenna comprises a plurality of stacked layers including a layer having a substrate with an accessible surface, the surface including thereon a continuous slot, first electrically conductive metallization disposed within the slot and extending to the slot, second electrically conductive metallization disposed external to the slot and at least one pair of frequency adjusting tabs, one tab coupled to the first metallization and the other tab coupled to the second metallization. The tabs are electrically conductive metallization, the tab coupled to said first metallization extending outwardly toward the second metallization and the tab coupled to the second metallization extending inwardly toward the first metallization. A slot is provided between the tab coupled to the second metallization and the second metallization. Each tab of a pair is coaxial with the other tab of the pair and symmetrical about the axis.

Abstract: An antenna apparatus for receiving two distinct frequencies in the MHz or GHz range. A patch layer of electrically conducting material is positioned in the interior of a dielectric layer that has top and bottom surfaces. First and second ground planes are positioned on the top and bottom surfaces of the substrate, respectively. The patch is electrically connected by plated via holes to an annular strip of conducting material, positioned on the top substrate surface and surrounding the first ground plane. A patch antenna for receiving a first frequency is thus formed by the patch layer and the second ground plane. A cavity antenna for receiving a second frequency is formed from the patch layer, the first ground plane, and the annular strip. Two receiver feed connections, positioned at selected first and second positions on the patch resonator, receive distinct first and second frequencies.

Abstract: A slot antenna formed in combination with a vehicle window. An electrically conducting, optically transparent film panel is bonded to the window and terminates so that its outer peripheral edge is spaced from the innermost edge of the metal framing the window to define a polygonal antenna slot between the edges. An unbalanced transmission line is connected to the antenna by connecting the grounded conductor to the framing metal near the metal edge and coupling the ungrounded conductor to the conductive panel near the juxtaposed, interfacing edge of the conductive panel.

Abstract: New type of planar antenna of microwaves appropriate for operating in linear and circular polarization, free of welds and floating potentials, and therefore free of electrostatic discharges and problems related to passive intermodulation products, whose application is of particular interest in aircraft and space technologies. The antenna consists in the interconnection of a microstrip radiator with a spiral antenna of wires. For certain applications wherein the radiators are arranged in a same plane, the radiating effect of the patch may reduce the size of the spiral.

Abstract: A surface conforming sense antenna is integrated with the surface skin of an aircraft by removing a rectangular looped strip of a metallized exterior composite surface skin. The remaining interior metallized portion isolated from the exterior metallized section forms an antenna sense element. The inner metallized portion is connected to an ADF radio receiver to function as a sense antenna in conjunction with a loop antenna. The gap between the metallized inner portion of the exterior metallized section allows lightning energy to be discharged thereacross. The modification does not impose a weight penalty or a wind drag penalty and does not degrade lightning protection for the composite aircraft.

Abstract: Antenna apparatus for receiving two distinct frequencies in the MHz or GHz range. A resonator layer of electrically conducting material is positioned in the interior of a dielectric layer that has first and second opposed surfaces (front and back). First and second ground planes are positioned on the first and second opposed surfaces of the substrate. The resonator is electrically connected to an annular strip of conducting material, positioned on the first substrate surface and surrounding the first ground plane. Two receiver feed connections, positioned at selected first and second positions on the patch resonator, receive distinct first and second frequencies. This apparatus may be used to receive the two GPS operating frequencies, the two GLONASS operating frequencies or two wireless LAN operating frequencies.

Abstract: A system, according to an embodiment of the present invention, comprises a coupler, a remote antenna, and a handheld GPS receiver. The remote antenna has a microstrip RHCP receiving element and a low noise amplifier (LNA) powered by the coupler over an interconnect cable. The coupler has a slotline antenna and a driver circuit. The coupler re-radiates GPS satellite signals received by the remote antenna with a slotline antenna to the GPS receiver. In a typical installation, such as a car, a user holds the GPS receiver while in the front seat. The coupler mounts to the windshield and the cable runs to remote antenna mounted on the roof of the car. The coupler can then re-radiate GPS satellite signals effectively to the GPS receiver even when the two are separated by as much as six feet. The shielding of GPS signals by the metal of the car is thereby avoided as a problem that can prevent operation of the GPS receiver.

Abstract: An inexpensive, efficient, broadband, slot-type antenna with unidirectional sensitivity includes a slot-forming means defining a plurality of substantially concentric and generally coplanar annular slots and a non-resonant antenna connection means for transmitting electromagnetic energy to and from the plurality of annular slots. The antenna connection means forms a plurality of non-resonant, radially-extending cavities that are adapted to combine electromagnetic energy received at a plurality of concentric annular slots for transmission from the slots generally in phase and along the central slot axis that lies perpendicular to the two concentric annular coplanar slots. The antenna may also include a plurality of impedance-forming portions distributed around the periphery of at least one or two of the substantially concentric annular slots to enhance both left-handed and right-handed circular polarization, to provide dual linear polarization, and enhance the unidirectional sensitivity of the antenna.

Abstract: An inner-feed-type planar antenna of single-layered structure excited by an axially symmetric mode for propagating radio waves from the center toward the outer periphery within a propagation layer having an antenna surface. If the planar antenna is used for transmission, it is provided with a plurality of coupling slots formed and arrayed in one surface of an axially symmetric mode waveguide member in such a manner that the coupling factor of the external radiation is high at the outer periphery and becomes successively lower as the center is approached. A spiral or ring-shaped terminating slot is provided in the antenna surface at the outer portion of the axially symmetric mode waveguide member. A region not coupled with the outer portion is provided at the center of the antenna surface.

Abstract: A plane antenna for automobiles including a peripheral conducting surface, a first inner conducting surface provided in the peripheral conducting surface with a space in between, a second inner conducting surface provided in the first inner conducting surface with a space in between. A core conductor of a first coaxial line is connected to the first inner conducting surface and an outer skin of the first coaxial line is connected to the peripheral conducting surface, and a core conductor of a second coaxial line is connected to the second inner conducting surface and an outer skin of the second coaxial line is connected to the first inner conducting surface. The second coaxial line can be divided into two sections so that these sections are inductively connected to each other by coils.

Abstract: A diplexing radiating element comprising at least a first radiating element in which two radiating electrical currents flow which are spaced apart from each other, and at least one second element in which two radiating magnetic currents flow which are spaced apart from each other. The invention is particularly applicable to space telecommunications.

Abstract: An electromagnetic field is produced by an oscillating magnetic frill that is generated at a slot gap in a resonating toroidal cavity. The magnetic frill's generating structure is physically small in relationship to its operating wavelength. Due to its small size relationship, the structure would be classified as a small antenna. The internal placement of inductance or capacitance allows the ability to raise or lower the resonant frequency of the structure. The structure's function can be changed by moving the placement of the frill generating gap. The structure can be made to radiate, partially radiate or completely nonradiate. The invention can function for example as a small antenna, a nonradiating probe or coil, or a resonant transformer.

Abstract: A method of placing an electronic responder of an electromagnetic interrogation system or an antenna coil of an electromagnetic interrogator device in or near an electrically conductive article. An opening is made in the article, which is larger than the responder or antenna coil, and the responder or the antenna coil is mounted in registry with said opening. There is also provided a slit in the article, extending from the opening, said slit interrupting extraneous circular currents.

Abstract: An inexpensive, efficient, broadband, slot-type antenna with unidirectional sensitivity includes a slot-forming means defining a plurality of substantially concentric and generally coplanar annular slots and a non-resonant antenna connection means for transmitting electromagnetic energy to and from the plurality of annular slots. The antenna connection means forms a plurality of non-resonant, radially-extending cavities that are adapted to combine electromagnetic energy received at the plurality of concentric, annular slots substantially in phase and to divide electromagnetic energy between the plurality of concentric, annular slots for transmission from the slots generally in phase and along the central slot axis that lies perpendicular to the two concentric, annular, coplanar slots.

Abstract: A microstrip antenna has an annular radiation conductor with a central opening and a microwave circuit for connecting the annular radiation conductor to a feeder to thereby facilitate impedance matching.

Abstract: A novel scanning array antenna is provided with improved gain characteristic which enable a compact form to be employed. The resonant azimuthal modes of separate antenna elements are selected to satisfy certain mathematical relationships which, in effect, form a directional beam which can be steered by a relatively small number of phase shifters. An example of antenna structure is an array of circular microstrip patch in the form of concentric disks each in resonance at one of the azimuthal modes under the disk cavity.

Abstract: A coplanar patch antenna is formed, e.g as a printed circuit, on a dielectric support (1) by a metal patch (2) spaced from a coplanar ground plane (3) by a peripheral slot (4), and in the improvement is series fed by means of a slot line (5). The slot (4) can be made resonant by having a periphery of one wavelength or an odd multiple thereof, and a second slot line (7) can be fed into the slot (4) at a distance of one or an odd multiple of a quarter wavelength from the slot line (5) to provide an independent feed. The arrangement presents a feedpoint impedance of about 50 ohms at the ports (6,8) instead of about 400 ohms in prior arrangements.Balancing loads or 180 degree hybrid feeds to other quadrature ports (11,12) can be used to correct beam asymmetry due to the slot line feeders (5 and 7).

Abstract: A planar microwave antenna of the suspended line feed type has a substrate sandwiched between a pair of conductive plates, each of the plates having aligned openings defining radiation elements. The substrate is held in place by holding portions surrounding the openings and wide grooves between the openings house a plurality of parallel suspended lines.

Abstract: A compact, easy to manufacture quarter-wavelength microstrip element especially suited for use as a mobile radio antenna has performance which is equal to or better than conventional quarter wavelength whip-type mobile radio antennas. The antenna is not visible to a passerby observer when installed, since it is literally part of the vehicle. The microstrip radiating element is conformal to a passenger vehicle, and may, for example, be mounted under a plastic roof between the roof and the headliner.

Abstract: An FM antenna for a vehicle with a ground plane comprising a horizontal roof having supporting pillars at the front and rear corners comprises a side fed, looped, annular slot antenna in the roof of loop length substantially one wavelength in the commercial FM broadcasting band, the slot antenna being displaced from the center of the roof toward one of the front and rear of the roof.

Abstract: An electrically-small, cavity-backed slot antenna includes an electrically conductive sheet having an elongated slot contained within the perimeter of the sheet backed by a cavity formed in an electrically conductive housing connected to the sheet. A dielectric layer composed of material having a dielectric constant of ten or greater is coupled to the conductive sheet and overlies the slot so as to effect a reduction of the resonant frequency of the antenna which permits the antenna to be characterized as electrically small. Transmission conductors are electrically coupled to the conductive sheet across the slot and adapted to carry r.f. energy either to or from the sheet depending upon whether the antenna is being used in a transmit or receive mode. For fine tuning the resonant frequency of the antenna, a pair of capacitive elements are mounted across the slot and electrically coupled to the conductive sheet on opposite sides of the slot and at symmetrical loctaions therealong.

Abstract: The present invention relates to a multidirectional feed which can be used by itself or preferably incorporated within a surface wave structure to form a flush-mounted antenna on, for example, a mobile unit. The feed arrangement comprises a ground plane including an annular cavity with a smaller annular slot. The annular slot is connected by multiple, spaced-apart, leads to an associated transceiver. The annular cavity is also formed to prevent both a shorting of the radio waves therein and the radio waves from propagating away from the cavity in a direction opposite the slot. A surface wave structure is disposed preferably with the feed centrally mounted and can comprise any suitable structure including annular corrugations and/or a dielectric layer to provide a flush-mounted antenna arrangement which provides radiation in azimuth in all directions with moderate elevation gain.

Abstract: A radar antenna is shown in a first embodiment to have a ground plane and a feed line on opposite sides of a dielectric sheet and a ring-shaped antenna element on another dielectric sheet to form a microstrip assembly wherein such antenna element is capacitively coupled to the feed line. In a second embodiment the radar antenna has a parasitic antenna element on still another dielectric sheet, such parasitic antenna element being in register with the ring-shaped antenna element.

Abstract: An integrated planar antenna-mixer device for microwave reception utilizes a slot-ring antenna and a diode quad connected thereto. The device comprises a planar metallic sheet backed on one side by a dielectric layer. A circular ring pattern is cut from the metallic sheet forming a slot ring antenna with a central disc and a surrounding ground plane. Diodes of a diode quad are connected between the central disc and the ground plane with adjacent diodes being separated by 90.degree.. The incoming microwave signal is directed perpendicular to the device plane and polarized in a direction orthogonal to a local oscillator signal similarly directed. Operation is quasi-optical without waveguides.

Abstract: This invention relates to the structure of slotted cable antennas used in end-fire glide slope systems employed in the instrument landing of airplanes. The structure is an improvement over that described in my U.S. Pat. No. 3,699,582 titled Slotted Cable Glide Slope Antenna. An air-dielectric coaxial transmission line, carrying a travelling wave of radio frequency energy, has a number of probe-fed slots along the outer conductor which leak current onto the outside surface of the line, resulting in radiation. The magnitude of the radiation from each slot is controlled by the probe coupling to the inner conductor and by a slot shunt consisting of a coaxial shorted line section. The relative phase of the radiations from adjacent slots is controlled by the electrical spacing of the slots.

Abstract: The plate-type antenna is constituted by two tangent circular rings lying in a common plane and interconnected by a slit which is narrow and oriented in the direction of an axis which joins the centers of the rings. The slit extends from the internal edge or circumference of one ring to the internal edge or circumference of the other ring. The tangency zone has a given width which is small as possible in the direction which is perpendicular to the axis of the two rings. One edge of the slit is excited or energized in the immediate neighborhood of the center of symmetry of the antenna. Ground is connected to the middle point of at least one ring located on the axis on the other side of the center. The antennas may be assembled into networks. They may be constructed as double-faced printed circuits.

Abstract: A coaxial radiating waveguide antenna is disclosed, comprising two conductive concentric right circular cylinders forming a cavity. Equally spaced within the cavity is a set of probes phased in such a manner as to produce TE.sub.21 or a higher order difference mode of radiation. One side of the toroidal antenna is sealed by a flat conductive ring; the other side is generally open and terminates in two flared regions which serve to shape the beam in the desired fashion. A broad null surrounds the boresight axis with major lobes disposed approximately 45.degree. therefrom in the case of TE.sub.31 propagation. The resulting radiation can be circularly or linearly polarized.

Abstract: A multifrequency antenna for a missile is realized by an arrangement in which four microwave antennas are located under a narrow circumferential slot in the skin of the missile forming four separate antennas each with its own input connector. Each antenna consists of a probe fed annular quarter wavelength microwave cavity which radiate out of a top wall end slot. The cavity antennas are fed by a stripline distribution network directly under the antennas. Two L band antennas are positioned directly adjacent the inner surface of the missile skin and an S band antenna and a C band antenna are positioned beneath the L band antennas. A radome covers the circumferential slot.

Abstract: The antenna comprises an open-mouthed cylindrical cavity 1 defined by side 11 and bottom 12 walls. A conductive coating 5 on an insulative substrate 4 lies on the bottom wall 12. The coating 5 is spaced from the side wall 11 by an annular space 2. A coaxial line 7, 8 feeds microwave energy to the zone between the coating 5 and the wall 12. That zone acts as a radial transmission line which couples the coaxial line to the cavity.

Abstract: A broadband microstrip antenna including two overlapping PC boards. A plurality of concentric spaced apart radiating rings and an upper ground plane layer are etched in the conductive upper surface of the upper PC board. An RF feedline network is etched in the conductive lower surface of the upper PC board. A continuous ground plane layer overlies the lower surface of the lower PC board. Plated through holes in the upper PC board connect a pair of 90.degree. spaced feed points on each of the rings to the feedline network. The feedline network is made of a plurality of conductive strips and matching stubs which are dimensioned and interconnected to permit the transmission/reception of circular polarized RF electromagnetic radiation while also matching the impedance of the rings to the impedance of a plurality of coaxial connectors mounted to the lower PC board.

Abstract: A single input multifrequency antenna is disclosed which comprises a plurty of radiating elements connected in series. The device may comprise multiple conformal edge slot radiators.

Abstract: A multiple omnidirectional antenna, utilizing individual antennae for different frequencies, and/or different polarizations, disposed along a common axis, and employing a multiple coaxial feed from one side only, in which the omnidirectional antenna which is remote from the feed side, is in the form of an axial wave-guide section, with the portion defining the walls thereof being connected to the outer conductor of the innermost coaxial feed line, and at least, in effect, defining at least one slot therein which runs transversely to the desired polarization direction of such antenna, with the inner conductor of the innermost coaxial feed line forming the exciting element therefor and projecting into the interior of said wave-guide, and/or at least one other omnidirectional antenna in the form of a coaxial line section, the walls of which are connected to the outer conductor of another coaxial feed line, and are provided with at least one slot therein which runs transversely to the desired polarization directi

Abstract: This cavity-backed top-loaded annular slot directional antenna is particularly well suited for radio direction-finding applications. Its unique properties allow it to be flush mounted for camouflage use with three or more symmetrical outputs which may be sampled continually. Each output has a symmetrically related unidirectional beam pattern and is nearly constant in impedance. The radio frequency voltages at these outputs are symmetrically phase related, and when combined they produce a circular pattern. All of the antenna elements are in a single structure and the combined outputs are extremely uniform, thus producing reliable patterns such that amplitude comparison for radio direction-finding purposes will be of good accuracy. A single cardioid pattern can be obtained by simply terminating the other ports in a matched load. In this form the antenna would be well suited for use as one antenna in a large aperture array.

Abstract: An array antenna is disclosed wherein each one of the antenna elements includes at least two concentric slots formed in a conductive sheet. The conductive sheet is disposed on a dielectric support and a ground plane is found on the opposite surface of such support. The inner one of the slots enables the outer slot to radiate radio frequency energy having a wavelength greater than the circumference of such outer slot. When such antenna includes an additional concentric slot the antenna is adapted to operate over a pair of frequencies separated by greater than twenty percent while enabling the array antenna to have satisfactory grating lobe characteristics.

Abstract: A low profile transmitting antenna consisting of a circular slot in a coal cavity that is folded several times. The last inner fold of the coaxial cavity is loaded with the tuning coil. The tuning coil can in the alternative be connected in series with the transmitter leeds connected to the radiating slot. Concentric cylinders alternately attached to the top and bottom of the cavity are used to form the folded coaxial cavity that provides the equivalent of a tapered transmission line. Energy to be transmitted is fed across the circular slot of the antenna or in the alternative may be fed into the last inner fold in the center of the cavity. The antenna radiates energy out with the same radiation pattern as a vertical monopole antenna.

Abstract: Spherical antenna arrangements are disclosed utilizing annular slots in polar regions which are associated with resonant cavities having a TE.sub.01 mode or a TE.sub.11 mode of field distribution. This field distribution within the cavity produces a cosine field distribution around the annular slot which serves via proper cavity excitation to produce nearly hemispherical isotropic radiation characteristics. The resonant cavities may take on the form of a parallel-plate structure or a coaxial cylindrical structure. Circular polarization and hemispherical coverage with uniform gain is characteristic of the antenna when the cavities contain probes placed ninety degrees apart in azimuth at the same radius from center and coupled to the quadrature phase related ports of a signal coupler.