Showing papers on "Coaxial antenna published in 1971"

A variable-coverage satellite antenna system

Abstract: A multibeam antenna system and-combiner switch capable of producing a variable-coverage radiation pattern are described. The antenna consists of a waveguide lens illuminated by a 19-element feedhorn array. The combiner switch consists of a corporate arrangement of variable power dividers; the latter is made up of two phase shifters and two conventional hybrid power-dividers. An earth-coverage radiation pattern with less than 2-dB ripple and an antenna gain ≈ 20 dB is obtained by equally exciting all beams of the muItibeam antenna simultaneously. Excitation of a single feedhorn results in a narrow beam with an antenna gain ≈ 30 dB and a near-in sidelobe level less -20 dB. The side|obe level can be reduced appreciably by appropriately exciting the adjacent feedhorns. The frequency bandwidth corresponding to 0.5-dB decrease in antenna gain is 10 percent. A technique for computing the radiation properties of the antenna is described; the agreement with measured data is shown to be excellent.

Physically small combined loop and dipole all channel television antenna system

Abstract: A low cost, physically small, all channel television antenna system is provided for reception in high signal strength areas. The antenna is characterized by a loop having a pair of separated gaps, one of which is a feed gap and the other an impedance termination gap for operating as a directional reception antenna at the low and high VHF television frequency bands. Inboard the loop is placed a television band UHF dipole antenna. The input terminals of the dipole antenna and the feed terminal of the loop antenna are each coupled to a combiner with a single output from the combiner.

Serpentine antenna mounted on a rotatable capacitive coupler

Abstract: This disclosure teaches an antenna including a conductor disposed in a serpentine arrangement defined by a plurality of undulations, wherein the amplitude or size of the undulations determines the directivity of the antenna, and wherein the undulations function to cancel mutual inductance parameters of the antenna while increasing the capacitive reactance thereof, to yield broadband characteristics. The antenna can take a variety of shapes, as for example the undulations may all fall entirely in a common plane and generally define a circle, a square, or an ellipse, etc.; or, such undulations may be arranged to form a ring or other three-dimensional object. The said shape of the antenna and its disposition with the earth''s surface also contribute to the directivity of the antenna.

Multi-beam array antenna

Abstract: A multi-beam array antenna assembly is disclosed, such assembly being adapted to form a plurality of simultaneously existing beams of radio frequency energy, each one of such beams having the gain of the entire antenna aperture and a different scan angle. The preferred embodiment of the contemplated assembly is fabricated, using printed circuit techniques and matching sections on a dielectric substrate, to form an array of antenna elements and constrained electrical paths for radio frequency energy between each one of the antenna elements and a number of feed ports. The electrical length of each one of such paths is adjusted so as to focus radio frequency energy in each one of the desired beams at a different feed port. The preferred embodiment also illustrates a multi-beam array antenna assembly having antenna elements spaced to increase the scan angle of each desired beam.

Windshield antenna for automobile

Abstract: A glass antenna for automobiles which comprises a first antenna element set so as to be adapted for an FM broadcast band and a second antenna element. These antenna elements cooperate to receive an AM broadcast electric wave. The feeding points of the antenna elements are connected to each other through means for effecting reactance. The antenna elements are provided in relation to the window glass of the car.

Vehicle antenna for vehicular communication system using leaky coaxial cable

Abstract: A vehicle wireless communication system utilizing a leaky coaxial cable installed along the vehicle track and having an array of slots in its outer conductor. A coaxial type antenna is mounted aboard a vehicle traveling on the track. The outer conductor of the coaxial type antenna is provided with an array of slots in the axial direction which substantially coincides with the array of slots in the leaky coaxial cable with respect to slot structure and cycle of slot arrangement. A dielectric material is interposed between the inner and outer conductors of the antenna and is adjustable to equalize the wavelength contraction ratio of the antenna to that of the leaky coaxial cable.

Multiturn loop antenna

Abstract: The invention is a multiturn loop antenna of an efficient design suitable for use singly, in arrays, or for inductively exciting radiating currents on a structure - the surface and the elements radiating to achieve optimum system performance. The antenna may be fed balanced or unbalanced and its input impedance may be either capacitive or inductive. In a preferred embodiment for omnidirectional coverage the antenna is positioned in a dielectric or ferrite filled cavity; the antenna may be a single element for linear polarization or a pair of multiturn loops at right angles to each other and with 90* phasing to effect circular polarization.

Ferrite antenna coupled to radio frequency currents in vehicle body

Abstract: An antenna system in which a Faraday cage acts as the primary antenna which intercepts the electromagnetic waves and reradiates them to a secondary antenna located within the Faraday cage.

Omni-steerable cardioid antenna

Abstract: An airborne IFF transponder antenna system which produces either omnidirectional or steerable-cardioid azimuth plane patterns, by the use of a flush dual-mode coaxial-line type cavity radiator which operates in the TEM mode and in the crossed TE11 mode.

Helicopter uhf antenna system for satellite communications

Abstract: A UHF antenna comprising crossed dipoles in the shape of drooped bow ties, encased by a polyester fiberglass laminated cone, positioned above and rotating with the blades of the helicopter, and orthogonally fed by a coaxial transmission line running through the hollow rotating mast provides an antenna for overhead signal transmission and reception. A coaxial rotary joint is placed inside the mast at the lower end to make a rotating electrical connection with the feed line.

Radiation from a spherical antenna covered by a layer of lossy hot plasma. Theory and experiment

Abstract: A spherical antenna is covered by a finite layer of lossy hot plasma. The radiation of this antenna is quite different from that of the same antenna imbedded in an infinite plasma. The antenna radiation can be recovered or enhanced when the plasma frequency is increased beyond the antenna frequency. An electro-acoustic wave may be excited in the plasma layer and leads to some resonance. The electroacoustic resonances may lead to a very strong antenna radiation. A good agreement was obtained between theory and experiment.

Terminator for spiral antenna

Abstract: : The patent describes a spiral antenna wherein its radiating elements terminate in Archimedean spirals.

Van-atta array antenna device

Abstract: In a Van-Atta array antenna device of the type wherein a plurality of equally spaced antenna elements are disposed in parallel and respective pairs of antenna elements disposed symmetrically with respect to the center of the antenna array are interconnected by feeders of substantially the same length, impedance matching stubs having an adjustable length are connected to substantially the center of respective feeders in order to enable incoming electromagnetic waves to be reradiated either straight backward or in an opposite direction to that in which they are receiving, with respect to the antenna boresight, without changing the characteristic impedance of feeders.

Diffraction by a multilayered dielectric-coated sphere with an azimuthal slot

Abstract: The wall air-gap concept for low-loss lines and reactive-wall waveguides is employed in the exterior problem of a dielectric-coated sphere with an aximuthal slot. The results for the gain and radiation pattern for a specific case are based on a boundary-value solution, and are optimised numerically to establish the concept. It is shown that, for a spherical antenna of electrical radius k0a = 5, coated with a dielectric layer (of thickness and relative permittivity equal to 0.254λ and 16, respectively), which encloses a wall airgap (of 0.00303λ thickness), the increase in gain over the uncoated antenna is 5.17 dB, while the shift in the main lobe is 12.5°.

Shielded end-fire antenna

Abstract: The in ention is for an antenna comprising an end-fire radiator in a shielded structure. A specific case is an axial-mode helical antenna in a conical horn which produces a circularly polarized pencil beam with low sidelobe level over a 2-to-1 bandwidth with a gain in the order of four times that of a simple helix.

Antenna element including means for providing zero-error 180{20 {11 phase shift

Abstract: A system including an antenna, such as a phased array radiating element including a dipole, is provided including a digital phase shifter. The 180* bit of the digital phase shifter is implemented by reversing the polarity of the signal in the antenna.

Tunable omnidirectional antenna

Abstract: Two loaded, concentric, semicircular, radiating members provide a physically planar omnidirectional antenna having a relatively uniform nominal impedance and a tunable operation over approximately a 3:1 bandwidth with a protrusion above the ground plane of less than one-tenth wavelength at the high frequency end of the operating bandwidth.

Ground independent antenna

Abstract: A ground independent UHF antenna is described which has upper and lower coaxial radiators. The upper radiator provides a coaxial feed cavity presenting both inductance and capacitance so as to provide a broad bandwidth of operation. The lower radiator defines a choke cavity which affords ground independent operation.

Multifunction array antenna system

Abstract: A multifunction receiving array antenna system is provided which utilizes energy normally rejected (reflected or dissipated) by antennas employing amplitude tapering to derive auxiliary antenna outputs in addition to the main output. This is achieved at negligible degradation to the performance of the main antenna channel by configurationally redesigning the array feed structure so as to divert the normally rejected energy to additional antenna ports. The technique is compatible with applications, such as radar applications, in which the antenna must be used to transmit as well as to receive. The auxiliary outputs could, for example, have broad, relatively omnidirectional, patterns useful for side-lobe cancellation and side-lobe blanking applications.

Analysis and design of TEM-line antennas

Abstract: A novel antenna, the TEM-line antenna, is discussed and analyzed. The TEM-line antenna in its present principal form consists of small half-loops mounted perpendicular to a ground plane and interconnected with transmission lines. Adjusting the dimensions of the half-loops and/or the transmission line lengths provides considerable flexibility in design for a wide range of applications, primarily at VHF frequencies and above. The present geometrical form of the TEM-line antenna is the result of several years' investigation of various evolutionary forms of the TEM line. Most of this past work has heretofore been unavailable in the open literature and, therefore, is summarized in this paper. An exact analysis based on the principle of reaction is presented and applied to three-element coplanar configurations. The analysis includes the effects of cable and conductor losses and readily provides for the calculation of antenna efficiency. Numerous design data have been obtained subject to the constraint that the antenna performance be optimum with respect to both the gain in a specified direction and the VSWR. These design data have been tabulated and are presented in a form that should be useful to the antenna designer.

Antenna mast misalignment detector

Abstract: An antenna misalignment detector has two electrolytic transducers mounted on a mast carrying the antenna perpendicular to each other in the same horizontal plane. The antenna is mounted on a mast. The square root of the sum of the squares of the output from the transducers is generated and compared with a predetermined reference so that an alarm sounds when the antenna is misaligned along a vertical axis to the ground.

Broadband VLF loop antenna system

Abstract: A loop antenna system including a negative reactance circuit and having a bandwidth of several octaves in the low frequency bands.

Antenna system for vhf and uhf radio direction finders

Abstract: An antenna system for a VHF and UHF radio direction finder comprises a loop antenna formed by turns which are arranged on an elongated magnetodielectric core. The antenna system has also an omnidirectional antenna member and a switch means which shapes the resultant directivity pattern by adding up signals from the loop and omnidirectional antennas and changing the position of this pattern discretely by 180 DEG in the horizontal plane to obtain its mirror image. The omnidirectional antenna is made in the form of a closed turn arranged on the core of the loop antenna so that it is substantially perpendicular to the turns of the loop antenna. A portion of the closed turn is disposed in the direction of the longitudinal axis of the core is elevated above the core surface through a known distance whereby the magnitude of the signal from the omnidirectional antenna is such that the two resultant directivity patterns of the antenna system intersect only at two points in a horizontal plane.

Multimode discone antenna

Abstract: A turnstile antenna includes four arms disposed concentric of a vertical axis and orthogonally related to each other so that diagonally related arms form a dipole. The four arms are physically and electrically coupled to a circular member disposed coaxially of the vertical axis. The four arms extend downward at an angle less than 90* with respect to the vertical axis. The pair of dipoles have a first energy coupling arrangement for orthogonal energy coupled to adjacent orthogonal arms to provide right and left hand circularly polarized omnidirectional patterns. A cylinder disposed coaxially of the vertical axis and spaced from the circular member extends through the turnstile antenna to support a disc therefrom in a perpendicular relation to the vertical axis and above the turnstile antenna. A second energy coupling arrangement for inphase energy is coupled to the disc and diagonally disposed arms of the turnstile antenna. The thusly formed combination provides a discone antenna having a vertically polarized omnidirectional pattern. Two variations of both the first and second energy coupling arrangements are disclosed.

A log-spiral antenna with selectable polarization

Abstract: It is possible to obtain polarization diversity from one multiple arm logarithmic-spiral antenna. The log-spiral antenna with more than 2 arms can be excited by a single hybrid matrix connected to the antenna terminals at the origin of the antenna geometry, and operated such that currents flow on the arms with phase progression away from the origin and reflected currents flow back along the arms with phase progression toward the origin. These two components of current radiate fields of opposite sense of essentially circular polarization.

Double ridged wave guide feed for signal antenna

Abstract: A microwave antenna system comprising a balanced two-arm spiral antenna or pyramidal antenna is directly fed at its center pole by a double ridged wave guide.

Broad band, polarization diversity monopulse antenna

Abstract: A broadband, polarization diversity, monopulse antenna comprising a body celed current array and radial arm-coupled log periodic loop antenna in combination with associated mode forming, beam forming and feed networks.

Multiband quad and loop antenna

Abstract: The specification discloses a structure of a single and a dual band antenna utilizing two loading units, each comprising a single inductor and a single capacitor connected in series therewith and mounted 180* apart at the high voltage points of the quad or loop antenna, and with the feed point midway between.

A new analysis of the sandwich-wire antenna

Abstract: It is hypothesized that the exact shape of the center conductor of a sandwich-wire antenna, provided it is of fairly simple form, is not important in determining the radiating properties of the antenna. An analysis is therefore made by standard principles of a sandwich-wire antenna having a particularly simple shape for the center conductor. This approach leads to an explicit formula for the structure attenuation constant in terms of its geometrical parameters which may be used for design purposes. Experimental measurements which support the theory and justify the shape-independence hypothesis are presented.

Extended aperture log-periodic and quasi-log-periodic antennas and arrays

Abstract: An extended aperture log-periodic antenna in which each element is capacitively loaded to tune out a portion of the element''s inductive reactance, so that at any frequency within the antenna''s frequency range series resonance occurs at an element whose physical length exceeds one-fourth free space wavelength of the applied signals. An extended aperture quasi-log-periodic antenna is also disclosed, in which only selected elements are capacitively loaded resulting in increased beam sharpness which is not in a true log-periodic relationship even though the antenna impedance remains constant over the antenna''s entire operating range, as in a true log-periodic antenna. Linear and circular arrays, employing capacitively loaded elements, are also disclosed.