Abstract: An antenna (30) includes a gimbal structure (32) having a base (46) and first and second pivoting devices (52, 54) defining a first rotational axis (40). A reflector (36) is mounted to the pivoting devices for rotating about the first axis. Signals are routed from the base to a connector (68) mounted to the reflector with a cable (10) which is coiled around a second rotational axis (50) of the antenna.

Abstract: A communication apparatus having a first portion, a second portion and an extendible antenna is disclosed. The second portion is movable relative to the first portion. Such movement causes a corresponding movement of the antenna.

Abstract: An antenna arrangement is provided for use in a vehicle. It comprised an antenna element (601-606, 701a-704f, 901-907, 1203) and means (600, 801, 802, 803, 804, 900, 910, 1200, 1201, 1202) for moving the antenna element in relation to the vehicle. The means for moving the antenna element are arranged to move the antenna element in relation to the vehicle into a direction which is opposite to a direction of movement of the vehicle.

Abstract: An antenna control system enabling the remote variation of antenna beam tilt. A drive means (5, 30) continuously adjusts phase shifters (1, 2, 3; 36, 39, 40) of a feed distribution network to radiating elements to continuously vary antenna beam tilt. A controller (80) enables the beam tilt of a number of antenna at a site to be remotely varied.

Abstract: A stabilizer platform mounted to a vessel for positioning a satellite dish antenna in the azimuth and elevation directions. An azimuth motor and an elevation motor are mounted in a formed hollow interior of a housing. Azimuth motor control cables and elevation motor control cables are connected to the motors to carry signals and power for controlling the operation of the motors. On top of housing is mounted a platform which rotates in the azimuth direction with respect to the housing. The azimuth motor is coupled to the platform through a gear arrangement and rotates the platform. On top of the platform is mounted an elevation drive which holds the satellite dish antenna. Mounted in the platform is an elevation gear cluster which rotates with respect to the platform. The elevation gear cluster is coupled to the elevation drive. The elevation motor drives the elevation gear cluster so that the elevation motor can move the satellite dish antenna in the elevation direction.

Abstract: A user terminal (110) includes a rotating electronically steerable antenna system (210) which combines coarse mechanical beam steering with fine electronic beam steering to provide full hemispherical coverage and enable hand-offs in a satellite communication system. The antenna system (210) comprises at least one antenna unit (and preferably two antenna units) including a mechanically rotatable base (330), an antenna holder (320) coupled to the mechanically rotatable base, and two electronically steerable antenna subunit (310) mounted on the antenna holder. Antenna system (210) also includes an antenna unit controller (260) adapted to control rotation of the mechanically rotatable base (330).

Abstract: A coaxial rotary coupler assembly which includes a coaxial transmission region for transmitting RF energy between a stationary and rotating section of the rotary coupler. Compact stubs are associated with the input and output connections to associated input and output transmission lines. Stepped impedance chokes are formed between fixed and rotating portions of the outer and inner coaxial conductors of the rotary transmission line sections.

Abstract: A phased array antenna having stacked-disc radiators embedded in dielectric media. The phased array antenna has a rectangular arrangement of unit cells that are disposed on a ground plane. A lower dielectric puck with a high dielectric constant is disposed on the ground plane. An excitable disc is disposed within the perimeter of and on top of the lower dielectric puck. An upper low dielectric constant dielectric puck that has a dielectric constant lower than that of the lower dielectric puck is disposed on the excitable disc. A parasitic disc is disposed within the perimeter of and on top of the upper dielectric puck. Dielectric filler material having a dielectric constant that is lower than that of the lower dielectric puck surrounds the dielectric pucks. A radome 18 is disposed on top of the parasitic disc and the unit cell. Two orthogonal pairs of excitation probes are coupled to the lower excitable disc.

Abstract: An integrated point-to-point microwave radio frequency unit/antenna system includes a microwave transceiver/antenna unit, a housing support element affixed to the microwave transceiver/antenna unit, and a mounting structure support element engaged to the housing support element. The mounting structure support element includes a fixedly adjustable ball-and-socket element, with either the ball or the socket affixed to the housing support element and the other affixed to an attachment structure. The mounting structure support element permits the microwave transceiver/antenna unit to be adjusted in three degrees of freedom.

Abstract: A rotary microwave antenna system suitable for satellite or cellular microwave radio telecommunications features an integrated, low-profile, rotary microwave joint, slip ring and antenna assembly. The rotary antenna system includes a stator (i.e., stationary portion), for attachment to a mobile platform (e.g., an automobile or other vehicle), having a rotary joint coaxial microwave coupler for electrically coupling a microwave transmission line from a microwave telecommunications radio system to a microwave antenna element of an microwave antenna rotatable about an axis relative to the mobile platform. The rotary antenna system also includes a rotor (i.e., rotary portion) for attachment to the microwave antenna. The rotor includes a slip ring circuit (or brushes) for coupling power and low frequency electrical signals to the microwave antenna through contacting brushes (or slip ring) attached to the stator, rotates relative to the stator, and is concentric with the axis of rotation of the microwave antenna.

Abstract: An antenna structure has a rotatable dipole array constituting a driven antenna element, a cup mounted around the dipole, a first conductor connected to and extending from the antenna, and a first dielectric mounted around the first conductor. A second conductor is mounted around the first dielectric, and a second dielectric is mounted around the second conductor. A third conductor is mounted around the second dielectric, and the first and second conductors form a quarter-wavelength transformer. The first dielectric maintains a uniform spacing between the first and second conductors, and the third conductor defines a radio-frequency coupling cavity. The second dielectric electrically enlarges the cavity. Thus the physical dimensions of the structure can be reduced without sacrifice of its electrical properties.

Abstract: A tracking antenna for non-geostationary satellites is mounted on a three-axis positioner comprising an azimuth axis, an elevation axis mounted perpendicularly on the azimuth axis and a pseudo-azimuth axis mounted perpendicularly on the elevation axis and supporting the antenna. The positions of the axes are controlled by a pointing unit. The method of pointing the antenna carries out the following steps simultaneously when the position of the satellite is such that the elevation axis exceeds a predetermined elevation value: modifying the position of the azimuth axis at constant speed and modifying the position of the elevation axis and the pseudo-azimuth axis to track the satellite.

Abstract: A method and a device are disclosed relating to the stabilization of mechanical bodies. The method is based on supporting the body to be stabilized at its mass center, whereby no acceleration in any direction causes a torque induced by the inertial forces in the body. The body thus maintains its position in relation to the earth gravity field, even if accelerations and various kinetic states were effective at the point of support. Inching of the body from the desired position is compensated by a slow control system using actuators functioning on a contact-free principle. As a particularly advantageous embodiment, the invention can be applied for stabilizing bodies attached to moving objects.

Abstract: There is presented an antenna assembly comprising an elongated mast slida mounted in a support structure. A first electric motor is disposed at a proximal end of the mast for moving the mast along the axis of the mast, and a second electric motor is disposed at a distal end of the mast for moving the mast rotatively about its axis.

Abstract: A deployable satellite antenna system is intended primarily to be mounted to the roof of a vehicle, such as a recreational vehicle. The elevational position of the reflector is controlled by a reflector support having a lower portion pivotably attached to a base mounted to the vehicle. The elevational position of the reflector can be adjusted between a stowed position in which the reflector is stored face-up adjacent to the vehicle and a deployed position. The feed horn is supported at the distal end of a feed arm having a first segment attached to the reflector support extending outward between the base and reflector, and a second segment pivotably connected to the distal end of the first segment. The feed horn segments move between an extended position in which the feed horn is positioned to receive signals reflected from the reflector, and a folded position in which the feed horn is positioned adjacent to the reflector.

Abstract: An antenna for mobile communication includes a sleeve antenna having a feed point; at least one linear parasitic element insulated electrically form the sleeve antenna; and a supporting means for supporting the sleeve antenna and the linear parasitic element. The supporting means supports the sleeve antenna and the linear parasitic element so that the feed point of the sleeve antenna is located at a different elevation from an elevation of a central point of the linear parasitic element.

Abstract: A rotating antenna system subject to both tilt and translation forces includes first and second tilt sensors each having a pendulum assembly of a different length than the other sensor. The sensors provide identical output signals in response to a tilt, but different output signals in response to a translation of the antenna. Circuitry is provided for eliminating the effects of translation so as to obtain a tilt angle correction signal for correcting the radar height calculation.

Abstract: This plane array antenna for receiving satellite broadcasts is an optimal combination of the plane array antenna main body having a tilt angle, a converter connected with the antenna main body through the power supply portion, and the rotation mechanism for rotating the antenna main body within almost a horizontal plane for tracking the azimuthal angle direction. The plane array antenna main body has the power supply portion formed at the center of the rotation and the converter includes a dielectric substrate having a microstrip channel formed on the substrate and a casing accommodating the substrate. The converter is fixed downwardly of the antenna main body and supports the antenna main body. The power supply portion includes the power supply probe with an insulation covering, and has its front end portion inserted into a space formed with the antenna body, a central portion extending through the casing of the converter, and the lowest end portion combined with the microstrip channel.

Abstract: While carrying and rotating a tubular body to be inspected, an image pick up device is inserted into the tubular body to be inspected to pick up an image of the internal surface thereof to take out a corresponding video signal to transmit the video signal to an image processing device through an antenna device to carry out image processing to judge the internal surface of the tubular body to be inspected. In the antenna device, ring-shaped conductors are oppositely arranged in a ring-shaped hollow chamber provided within an electromagnetic shielding body wherein one ring-shaped conductor is rotated and the other is fixed.

Abstract: A passive, active or mixed platform type antenna orienting apparatus mounts on a vehicle such as a small-sized vessel or an automobile, which is subject to turns and complex vibrations, traces a target such as a communications satellite with a directive antenna. Between a rotational shaft connected to a platform supporting an antenna and a stationery shaft connected to base to be carried on a vehicle, there is interposed as electric rotary coupling for transmitting power and signals necessary for a transmission signal and an attitude control, so that the platform 43 supporting the antenna 1 may continuously rotate with respect to the vehicle 27. Midway of a post 41, moreover, there is disposed a horizontal damping mechanism 70 which includes a laminate 75 and facial pressure apply means 76 for applying a facial pressure to a laminate 75, to effect a damping action which is excellent in durability and even in the horizontal direction.

Abstract: A communication system for transmitting data between a transmitting platform and a receiving platform moving relative to each other. A phased array antenna forms the transmitting antenna rotated on the transmitting platform and a single dipole, oriented parallel to the transmitting antenna, forms the receive antenna located on the receiving platform. The phased array antenna is split into small sections, each section comprising dipole elements and a matching network, including a feedpoint. The receive antenna is mounted close to the transmitting antenna.

Abstract: An orientation adjusting device for a satellite transmitting signal antenna comprising a housing inside of which an electromechanical actuation system comprising a worm gear-worm pair driven by a motor through a reduction gear set is disposed. A rotatable antenna seat which constitutes, in part, the housing is mechanically connected to the worm gear so as to be driven by the motor. The worm, of which one end is pivotally fixed on the housing, is biased toward the worm gear by biasing means so as to maintain a more precise engagement between the worm and the worm gear and to reduce the backlash associated therewith. Microswitches are provided inside the housing to control the rotation range of the antenna.

Abstract: A multiple channel rotary joint design is described in which the channel components are laid out in a manner to reduce the number of layers of microwave circuitry necessary to provide rotary coupling with the antenna. The reduction of layers in each channel allows room for larger conductors in each channel, providing greater power handling capability. Compactness is also achieved through the use of a novel central extrusion that replaces the usual coaxial input lines, novel choke designs, and a novel stripline configuration that makes dual use of various components and minimizes losses within the joint. The central extrusion provides all the high power inputs, while allowing the passage through its center of a plurality of low power coaxial lines to low power channels residing on top of the high power channels. Cooling of the rotary joint is simplified by keeping the center of the joint stationary, and cooling air is fed through the transmission lines to make this function more efficient.

Abstract: A pointing system for reflector type antennas providing a high degree of accuracy with low loss over wide scan areas, including a fixed illuminator retained in fixed position at the focal point of the reflector of the antenna. Surrounding the illuminator is a Cardanic joint which acts as a spherical hinge capable of radial rotation around the illuminator. Attached to the Cardanic joint is a support arm which is connected to the reflector. The reflector is therefore freely movable in a spherical path defined around the illuminator with the illuminator coinciding with the center of the sphere. The illuminator is kept within the focal point of the reflector regardless of the position of the reflector as it spherically rotates around the illuminator. Tension springs in the Cardanic joint and guide wires controlled by motors are provided for finely positioning the support arm and reflector in any given position along the spherical rotative path through which the reflector is able to move.

Abstract: A stabilized antenna system. An inclination angle detector is mounted on an AZ frame and detects an inclination angle around an elevation, and the elevation of the antenna is controlled by a successive addition of the detected inclination angle to simplify control algorithm. Furthermore, the inclination angle detector includes a reciprocal combination filter for combining outputs of an inclinometer and a rate sensor. The reciprocal combination filter includes two reciprocal filters, and parameters of the reciprocal filters are adaptively controlled depending on frequency and amplitude of the inclination to ensure the reciprocity in a necessary frequency range.

Abstract: A pedestal assembly for rotatably carrying a load containing radio-sensitive equipment is disclosed, with the assembly having a turntable and base. The profiles of the turntable and base adjacent to one another are both stepped and define a tortuous path between them. The assembly further is designed to distribute any attached load directly to a driven bull gear, rather than to the turntable.

Abstract: A microstrip patch antenna structure is disclosed having increased bandwidth and reduced coupling while maintaining low profile capabilities. The structure includes a support member having an isolating recess in which an electromagnetically coupled patch pair of antenna elements is positioned, the upper element being substantially flush with the surface of the support member surrounding the recess. To enhance isolation of the elements, the recess walls and the support surface are preferably electrically conductive and connected to ground. Also preferably, the lower element is connected to a microstrip transmission line, coplanar with the lower element and suspended within an isolating channel through the support member. In one aspect of the invention, a transition means is interposed between the transmission line and a connector, which connects the support member to a transmitter/receiver, to permit relative rotation therebetween.

Abstract: An integrated antenna system for signal error tracking and correction capable of performing a mechanical conical scan. The mechanical conical scan imposes a modulation upon a received RF signal. This modulation is in turn imposed on an AGC circuit in the receiver of the antenna system, which modulates the AGC signal of the receiver in accord with the modulation imposed on the RF signal by the conical scan. This modulated AGC signal is compared in a detector circuit to a reference sinusoidal signal generated by a local oscillator in the system. This detector circuit outputs an error signal which is added to a reference sinusoidal signal which in combination drive an actuator. This actuator is responsible for imparting nutative motion to the antenna, for the purposes of producing the conical scan pattern.

Abstract: The disclosure concerns an assembly formed by a large-sized antenna with a supporting mast, the working of which brings the ground plane into play, and by a high-power transmitter. To reduce the distance between the transmitter and the radiating part of the antenna, and to reduce the cost of the architectural structure of the antenna and of the room sheltering the transmitter, this room is formed by the base of the mast which supports the antenna. The dimensions and bed of the base of the mast are designed as a function of the space needed and of the stability to be given to the antenna.

Abstract: A communication system for transmitting data between a transmitting platform and a receiving platform moving relative to each other. A circular strip-line transmission line forms the transmitting antenna located on the transmitting platform and a short segment of strip-line, similar in width to the circular strip-line, forms the receive antenna located on the receiving platform. The strip-line transmission line has at least two feedpoints for inputting data and at least two termination points that are terminated with a resistor to ground. The receive antenna is mounted close to the transmitting antenna.

Abstract: A method of, and apparatus for, controlling the directional aiming of an antenna device including: scanning the antenna along with a conical path and detecting a directional point at which a detected level of reception along the conical path is turned from increasing to decreasing; scanning the antenna along a directional path defined by a center point of the conical path and the directional point, and detecting a signal source point at which a detected level of reception along the directional path is turned from increasing to decreasing; and setting a directional aiming of the antenna at the detected signal source point.

Abstract: The device includes a fixed component (30) which is in two half-shells which clamp, sideways-on, around the fixed mast (3), and a rotatable component (28) which also is in two half-shells which, when assembled around the mast, are guided for rotation relative to the mast. Several rotation apparatuses (one per antenna) may be attached at different points on the height of the mast, so that each antenna (19) may be orientated independently of the other antennas towards the appropriate TV transmitting station. The stub shaft (29) on which the antenna (19) is carried may be rotatable relative to the housing (28), and so geared that a 180 deg rotation of the housing produces a 360 deg rotation of the shaft and antenna.

Abstract: A manually rotatable antenna is set forth including an antenna with a bearing sleeve rotatably mounted with upper and lower spaced bearing plates securable to a dwelling. First and second cables are directed through a guide plate and through associated and respective guide bushings and rollers to a position interiorly of the control housing, including a chain member operative through a control gear manually manipulatable by an associated handle to rotate an antenna gear coaxially mounted about the bearing sleeve of the antenna mast.

Abstract: Disclosed is a rotating joint used in radars to transmit electrical signals on several channels between a rotating antenna and a fixed support. The pass-band of the matched and coupled circuits of each channel is substantially improved by making these circuits on concentric, circular rings which have metallic ground strips deposited on both faces, said strips being connected by metallized holes, and metallic strips of coils connected by the facing sections of the rings.

Abstract: A seeker head for a target pointer/tracker and the like, the head comprising a rigid mounting plate, an optical seeker for receiving a target signal, the seeker having a longitudinal axis, a joint proximate the longitudinal axis for securing the seeker to the mounting plate with freedom for reciprocal movement about at least two pivot axes perpendicular to the longitudinal axes, an eccentric driving element mounted on the mounting plate for selectively engaging the seeker to move the seeker about the pivot axes, and a controller for controlling operation of the eccentric drive element.

Abstract: A broadcasting receiver for vehicles especially suited for receiving satellite broadcasting signals comprises a base plate rotatable horizontally, a main reflector tiltably attached to the base plate, a sub-reflector attached to the end portion of an arm of which the other end is attached to the base plate so as to be rotatable horizontally, and a signal detector fixed to the main reflector. The vertical angle between the main reflector and the arm are maintained at a predetermined angle, and the sub-reflector which is arranged to be rotatable around the end portion of the arm is caused to stand up when the main reflector is in a stand up position. All devices and parts arranged on the base plate including the arm and the sub-reflector are covered by the main reflector when the main reflector is turned down.

Abstract: A satellite antenna drive mechanism which includes a drive gear housing for reciprocally driving a satellite antenna dish. Generally, the satellite dish is supplied with a retaining bracket to which a U-shaped bow screw is mounted. The bow screw threadably engages the drive gear housing such that rotation of the drive gears causes a corresponding movement of the bow screw and the dish. The drive housing includes three meshed gears which cooperate to drive the bow screw. A first gear drive is connected to drive means for manually or mechanically driving the gears. An intermediate gear connects the first gear to a third internally threaded gear which receives the bow screw of the antenna dish. This third gear drive is positionally captured between the wall plates of the housing yet is free floating within the housing to provide smooth travel of the bow screw through the drive housing.

Abstract: This invention is a rotatable transmission line junction with an external rotary mechanical energy coupling it finds application in microwave polarization rotators, rotary joints, resolvers, amplitude modulators, and other devices. The rotatable conductor of the transmission line coupling is mechanically connected to devices outside of the transmission line system without electrically coupling to the outside in this manner, rotary energy and/or positional information may be input to and/or received from the coupled line. The device consists of the junction of a first transmission line and a second transmission line in which said second transmission line is coupled electrically to said first line and mechanically supported by and/or connected to a plastic rod. Said plastic rod also passes to the outside of the transmission line system to form a mechanical rotational coupling means for the coupled line. Either line may be considered to be input or output.

Abstract: An apparatus for maintaining an arbitrary orientation of the polarization of an antenna, such as an airborne microwave antenna, by using antenna pointing information and platform (aircraft) attitude information to position the input/feed signal.

Abstract: A conversion system for a controller for an antenna rotator which includes circuitry for generating an analog signal which varies as a function of the angular position of the antenna. The conversion system includes circuitry for converting the analog signal to a corresponding first digital signal representative of the angular position of the antenna relative to a first reference heading of the antenna. The conversion system also includes storage circuitry having a prestored table of digital values of angular positions of the antenna relative to a second reference heading of the antenna and which in response to the first digital signal produces a second digital signal corresponding to one of the prestored digital values, the second digital signal thereby being representative of the angular position of the antenna relative to the second reference heading. A digital display system and controller for an antenna rotator are also disclosed.

Abstract: A microwave primary source with a phase conical scan having a conical horn containing an obstacle which gives rise to a wave that propagates in the TE.sub.21 mode in quadrature with the TE.sub.11 fundamental mode in the opening of the horn; the obstacle is driven in rotation round the axis V of the horn.

Abstract: An antenna system for use in an automotive vehicle comprises a housing mounted on a body of the automotive vehicle and having at least a portion of an upper surface thereof made of a dielectric material which transmits radio waves, at least one planar antenna disposed rotatably within the housing to receive radio waves transmitted through the portion of the upper surface of the housing made of the dielectric material, and driving means for driving the planar antenna to effect scanning of a radio wave receiving direction to search for the radio wave receiving direction of higher sensitivity. The housing protects the antenna system and maintains the fine appearance of the automotive vehicle. Further, the housing has a shape like that of an air spoiler, which makes it possible to maintain the satisfactory aerodynamic characteristic of the automotive vehicle.

Abstract: The present invention relates to a conical scanning process in a radar antenna.The antenna comprises a principal parabolic reflector (1) and a primary rear-feed source (2) fed by a circular waveguide (3) and displaced with respect to the focus of the parabolic reflector (1). The conical scanning is produced by the rotary movement of the parabolic reflector (1) about the source (2), the said source (2) and the circular guide (3) remaining fixed.The present invention is applicable to tracking radars operating in the millimeter waveband.

Abstract: This invention relates to rotatable antenna feed polarizers for use in communication antenna systems, and seeks to provide, at economic cost, an antenna feed polarizer which is capable of being rotated accurately.The polarizer is rotated by a threaded member rotated by a motor. A drive member is moved longitudinally by the rotation of the threaded member. Two flexible connectors are each attached at one end to the drive member, pass around idler wheels, are wrapped partly around the polarizer, and are fixed to the latter. Movement of the drive member pulls one of the flexible connectors and thereby rotates the polarizer.Backlash is minimal because it occurs between only two moving parts, the drive member and the elongate member, and is achieved without using gears with minimum backlash, which may be expensive.

Abstract: A millimeter wave dual beam line scanning antenna integral with a tunable solid state oscillator is disclosed. The antenna provides two fan-shaped beams from opposite faces and when the antenna is rotated, a roughly conical shaped scan obtains. Furthermore, variation of the oscillator frequency causes a variation in radiation angle and provides two line scanning beams from opposite faces.

Abstract: A parabolic reflector having support structure, mounted upon a rotatable track, for supporting a parabolic dish framework to which is mounted one or more support panels to which, in turn, are pivotally mounted a plurality of reflectors for focusing rays on a linear collector. The support panels include a plurality of concave recesses operable to receive bowl-shaped reflectors provided with polygonal rims so that the sides of adjacent reflectors will be in registry with one another. The support panels are provided with bolts, outwardly extending from the base of each recess, the bolts being received in slotted apertures in each reflector bowl for pivoting and fastening the reflector in a pre-selected position for focusing solar rays upon the collector. The collector includes a heat exchange media operable to conduct heat at extremely high temperatures for production of steam. A novel tracking system is also provided.

Abstract: A modular matrixed cylindrical rotary joint for transferring channeled electromagnetic energy from the stationary part of a radar system to its rotatable portion and an inner modular stator which supports the outer portion on redundant bearing modules.

Abstract: The invention relates to a device for transmitting microwaves between two bodies which are rotatable relative to each other. Two annular waveguides are arranged on a common axis. Each waveguide has a coupling slot along its circumference. A transmitting aerial projects into each coupling slot and is moveable relative to the associated waveguide. The electromagnetic waves generated by the transmitting aerials are received by receiving aerials at the ends of the waveguides, respectively. The outputs of the receiving aerials are prepared for further processing.

Abstract: A rotary waveguide coupling including coupling members which are coaxially rotatable with respect to one another and comprise waveguide sections produced by dividing an annular waveguide in a longitudinal sectional plane. Inputs and outputs of the waveguides to be rotated with respect to one another disposed in the side walls of the waveguide sections.

Abstract: First and second annular r.f. radiating structures are mounted for concentric relative rotational motion with their r.f. radiation patterns directed toward one another. The annular r.f. radiating structures may be realized, for example, by cylindrically conformed microstrip antenna radiators which define tuned resonant cavities feeding one or more radiation apertures defined between an edge of a microstrip radiator "patch" and an underlying electrical reference or ground surface. The microstrip radiator "patch" may be either continuous in its circumferential dimensions or it may have occasional circumferential discontinuities formed by axially directed gaps therein. If the total circumferential dimension is greater than one wavelength at the intended operating frequency, then a corporate structured feedline provides plural spaced-apart feedpoints about the circumference so as to achieve a substantially uniform distribution of r.f. field amplitudes and phases about the circumference.