Showing papers on "Coaxial antenna published in 1972"

A numerical solution for the near and far fields of an annular ring of magnetic current

Abstract: A simple method for calculating the near and far zone fields from an annular ring of circumferentially directed magnetic current which may be used to represent coaxial apertures is presented. Near-field contours are given for two ring sizes. The utility of the method has been illustrated by its application in several practical antenna problems where the magnetic ring current serves as the primary source. Among these are the analysis of dipole antennas mounted on a conducting sphere or cylinder, the impedance of a coaxially fed Yagi-Uda antenna, a coaxially driven wire loop, and the radiation from a coaxial aperture at the base of a cone.

A portable coaxial collinear antenna

Abstract: A novel collinear antenna constructed of coaxial cable with inner- and outer-conductors interchanged at half-wavelength intervals is described. A 26-element antenna of this type has been constructed and evaluated. Design criteria presented allow extension to the use of coaxial cable of different types in a variety of radio/radar arrays.

An experimental study of a balun-fed open-sleeve dipole in front of a metallic reflector

Abstract: The characteristics of a balun-fed open-sleeve dipole mounted in front of a metallic reflector for operation in the 225 to 409 MHz band are investigated. A parametric study is made of the VSWR response as a function of dipole and sleeve diameter, sleeve length, and sleeve-to-dipole spacing. It is shown that an open-sleeve dipole can be operated over a bandwidth of 1.8:1 as compared with an operating bandwidth of approximately 1.25:1 for a conventional cylindrical dipole with the same diameter. Pattern and gain data are presented for an open-sleeve dipole mounted in front of a flat metallic reflector. Preliminary results on mutual coupling effects are also discussed.

The Toeplitz matrix: Its occurrence in antenna problems and a rapid inversion algorithm

Abstract: A special form of the Toeplitz matrix which frequently occurs in the numerical solution of antenna analysis and synthesis problems is discussed. Specific examples are presented illustrating its occurrence in the solution of the integral equation for a thin cylindrical antenna and in the theory of arrays. A matrix inversion algorithm is presented which, by exploiting the unique symmetry properties of the Toeplitz matrix, specifies the inverse matrix elements in terms of recurrence relationships. In this way computational time is proportional to the square of the matrix order rather than the cube as is the case with a general algorithm.

The extended boundary condition solution of the dipole antenna of revolution

Abstract: By applying Waterman's extended boundary condition a general formulation is developed for the dipole antenna of revolution. Both transmission and scattering from the antenna are considered with no formal restrictions on the antenna dimensions. As examples, the prolate-spheroidal and solid-cylindrical geometries are considered.

Radiation from an Axial Slot Antenna Coated with a Homogeneous Material

Abstract: Radiation from a slotted-cylinder antenna coated with a homogeneous material is investigated. It is found that for some values of the coating thickness certain modes may resonate, which greatly enhance the radiated power and affect the shape of the radiation patterns.

Rectangular backfire antenna with dielectric surface-wave structure

Abstract: A rectangular backfire antenna with a dielectric surface-wave structure is studied experimentally and theoretically. It consists basically of two plane rectangular reflectors and a dielectric structure as a rectangular-waveguide prolongation. The antenna construction is compared with those of ordinary dielectric and horn antennas, which are more than twice the length of the backfire antenna. Simple expressions for the far-field radiation pattern are derived in terms of the near-field amplitude distribution.

Antenna array for aircraft navigation system

Abstract: An electronically phased control antenna array having a number of radiators which are to be controlled so as to form two beams respectively pointed toward two separate earth satellites in an aeronautical satellite navigation system and wherein the two antenna arrays are controlled through a Butler matrix comprising a distribution network having phase rotation elements and wherein a plurality of outputs which differ in phase are selectively obtained so as to control the direction of the antenna beam, thus maintaining the antenna arrays respectively pointed at the satellites. The selection of the switching control for the matrices which control the antenna arrays may be accomplished by the use of a computer which has a memory for programming the switching in response to a prior flight path over the same region. Alternatively, the outputs from the antenna arrays and matrix may be sampled and the switches of the matrices controlled so as to obtain the largest signal thus assuring that the arrays are pointing toward the satellites.

Compact multifrequency band antenna structure

Abstract: A compact multifrequency band antenna structure is disclosed. Such antenna structure is comprised of a first and second antenna section, each one thereof arranged to form an integral antenna structure. The first antenna section is a slotted waveguide planar array antenna (designed for operation in one frequency band) which serves as the ground plane for the second antenna section (the latter section being designed for operation in a second frequency band). The second antenna section is constructed such that the polarization of the radiation associated therewith is orthogonal to the polarization of the radiation associated with the slotted waveguide planar array antenna, thereby increasing the electrical isolation of the two antenna sections. In disclosed embodiments the second antenna section is formed from stripline and microstrip and the radiating front face portion of the slotted waveguide planar array antenna forms a ground plane for such stripline and microstrip.

Near field spiral antenna

Abstract: A near field antenna is formed of a coil printed on an insulating board mounted in parallel fixed spaced relationship to its own ground plane. The coil is capacitively shunt tuned and capacitively coupled serially to a coaxial line. A planar ferrite sheet may be incorporated to enhance the sensitivity of the antenna. The printed coil is provided with means for adjustably fixing its length.

Shortened turnstile antenna

Abstract: An electrically short turnstile type antenna array which effectively provides vertical or overhead right or left hand circularly polarized coverage in for example satellite communications from a very restricted space volume as characterized particularly in submarine or aircraft antennas. A pair of electrically short dipoles are arranged normal to each other with the axes thereof intersecting at their mid-points. Coaxially arranged about each leg of these dipoles is an open-ended cylindrical sleeve. The feed to the array is by way of a coaxial cable running to the inside of the coaxial cavity formed by one of the sleeves in an end-feed orientation. A mutual coupling link couples signal energy from the inside of the fed coaxial cavity to the inside of one of the coaxial cavities associated with the other dipole. The entire array is mounted on a support mast less than one-eighth lambda from the horizontal base portion of a tin can-shaped ground plane whose vertical sides are sufficiently high to substantially house the array.

Cylindrical antenna in a rectangular waveguide driven from a coaxial line

Abstract: The problem of a cylindrical antenna in a rectangular waveguide driven from a coaxial line, where the antenna spans the entire guide height, is analysed, and the admittance evaluated. An experimental investigation shows the theory to be very accurate.

Broadband plane antenna with log-periodic reflectors

Abstract: A broadband unidirectional linear or circularly polarized plane antenna with or without reflecting cavity is constructed with a plurality of log-periodically related reflecting rings or bands stacked behind the antenna elements symmetrically of the antenna axis. The conductive rings reflect backwardly directed radiation and comprise the exposed peripheral portions of a series of stacked plates, the dimensions and spacings of which increase progressively in increments of a predetermined ratio from a minimum adjacent the antenna elements to a maximum remote from the elements. In order to prevent the formation of an electromagnetic field in the spaces between axially aligned portions of the plates, field arresting material is located in these spaces.

Turnstile slot antenna

Abstract: A novel turnstile slot antenna is disclosed, the antenna being for and integral with a spacecraft having a substantially cylindrical body portion. The antenna comprises a circumferential slot about the periphery of the spacecraft body portion with an annular wave guide cavity defining a radial transmission line disposed within the spacecraft body portion behind and in communication with the circumferential slot. Feed stubs and associated transmission apparatus are provided to excite the annular cavity in quadrature phase such that an omnidirectional, circularly polarized, rotating radiation pattern is generated. The antenna of the instant invention has utility both as a transmitting and receiving device, and ensures continuous telemetry and command coverage with the spacecraft.

Frequency extension of circularly polarized antenna

Abstract: The frequency response of a cavity-backed planar microwave antenna having an element including a pair of spiral antenna tracks fixed to a substrate of insulating material is substantially extended by connecting a pair of cavity-backed outwardly extending dipole elements to the outer ends of each of said spiral tracks. The lower range of useful frequency response is thereby changed from a minimum operating frequency wherein the diameter of the spiral tracks constitutes approximately one-half wave length to a value wherein one-half wave length is approximately equal to the width of the antenna elements including the dipoles. This composite structure may be curved to some degree to enable it to conform to the inside surface of a curved radome.

Magnetic antenna with time variations of core permeability

Abstract: An antenna system using a magnetic core provided with coils wound thereon such as to cause time variations of the permeability of the core itself is disclosed. With the time variations of the core permeability the inductances of the antenna coil and output coil wound on the core is changed for parametric amplification of the reception signal to obtain amplified antenna output. Also, by using a plurality of such antenna systems an array antenna having desired and controllable directional characteristics are obtained.

High-frequency waveguide feed in combination with a short-backfire antenna

Abstract: A high-frequency waveguide feed in combination with a short-backfire antenna having a cavity and multiple reflectors to permit high power handling capabilities and high frequency applications. An open end of a waveguide is used as the primary radiator in the antenna cavity. The waveguide intrudes into the cavity from behind the larger reflector plate. The polarization response of the antenna is determined by the type of waveguide chosen.

Coaxial tracking signal coupler for antenna feed horn

Abstract: Tracking signals are extracted from the antenna feed horn by means of a two-stage coaxial coupler. The first stage consists of irises located on the horn end of a coaxial spear that extract signals in the first order circular transverse electric mode. The second stage consists of a probe located at the waveguide end of the coaxial spear that extracts TEM energy derived from signals in the first order transverse magnetic mode. Only one coupling stage is required for tracking circularly polarized signals, while both are required for tracking linearly polarized signals. In either case, fundamental mode transverse electric energy is passed without significant coupling or obstruction.

Electrooptical processing of phased-array antenna data.

Abstract: An on-line two-dimensional optical processor has been used to process simulated linear and planar phased-array radar data off-line but at real-time data rates. The input transducer is an electron-beam-addressed KD2 PO4 light valve.

Electromagnetic wave receiver

Abstract: Video pulse radio frequency receivers are rendered sensitive to continuous waves by means of an amplitude modulation technique involving coupling between circularly polarized antennas. The circularly polarized antennas incorporate semiconductor diodes as an integral part of the antenna structure. Two circularly polarized antennas with diodes incorporated therein are mounted in tandem with counter rotating faces directed toward a source of linearly polarized electromagnetic wave. One circularly polarized component of the electromagnetic wave excites the first antenna, while the counter rotating component passes through the first antenna and excites the second antenna. The integral diode of the antennas acts respectively as a detector and modulator, with radio frequency coupling being provided by the tandem arrangement which locates the antenna faces of like polarization sense adjacent each other. By arranging a multiple of the pairs of tandem mounted antennas in a distributed pattern, direction finding capabilities are provided.

Broadband characteristics of an open-sleeve dipole

Abstract: An antenna radiating element capable of providing a broadband VSWR response and unidirectional radiation patterns over nearly an octave bandwidth is described. The basic radiating element consists of a balun-fed dipole with one or more parasitic elements (sleeves) added. Addition of these parasitic elements results in an antenna bandwidth many times greater than that of a conventional cylindrical dipole, VSWR, pattern, and gain measurements were made in the UHF band for a variety of dipole/sleeve configurations.

Leaky wave guide planar array antenna

Abstract: A planar array antenna for producing four squinted beams required for an airborne Doppler navigation system is disclosed. The antenna includes a pair of slotted feed rectangular wave guides arranged to permit input energy to be applied at any one of four ports. Interconnecting and coupled to the feed wave guides by means of slots in the feed wave guides is a radiating member which includes a leaky grid structure through which radiates beam-forming electromagnetic energy. The antenna is a symmetrical structure and the four beam positions, or for the case of a lobe switched antenna system, the four beam sets, are symmetrically located with respect to the vertical axis of symmetry of the array.

Super-balanced feed-through dipole antenna

Abstract: The invention provides a novel LOS dipole antenna arrangement which permits substantial improvement in pattern characteristics by correspondingly reducing spurious coupling to adjacent structure, which may occur particularly where the antenna is situated closely adjacent to unrelated structure in a spacerestricted environment. Pattern improvement is based on the principle of the antenna''s symmetry being rigorously maintained, wherein a pair of adjacently arranged cylindrical radiators are fed by a double-ended balun structure created from the supporting and cable feed-through antenna mast. This balun feed assembly comprises a pair of oppositely arranged slots within the antenna cylindrical radiators, with each conductor of the coaxial feed cable running to the balun being coupled to either side of one of the slots proximate the center thereof. The excitation energy is transferred to the cylindrical radiators by way of symmetrically placed radial posts extending from either side of the energycoupled slot to the inside of the cylinders.

Broad band spiral antenna

Abstract: Antenna elements for substantially circularly-polarized electromagnetic energy are shown. The disclosed elements, formed on a tapered form having an elliptical cross section, are particularly well suited for use as elements in an antenna array because such a cross-sectional shape permits individual elements to be more closely positioned with respect to each other, thereby raising the frequency of the electromagnetic energy at which grating lobes occur.

The loop antenna with director arrays of loops and rods

Abstract: Experiments indicate that the gain of a Yagi-Uda antenna arrangement depends only upon the phase velocity of the surface wave traveling along the director array and not to any significant extent upon the particular forms of the director elements.

Unidirectional dipole antenna

Abstract: A new small unidirectional wire antenna, useful for an indoor television receiving antenna, has been developed for use in the v.h.f. band. This antenna consists of two closely spaced dipoles. This letter describes the principle involved and introduces the equations for input impedance and gain. Experimental results show fairly close agreement with the theory.

Radiation by a dielectric-loaded cylindrical antenna with a wall airgap

Abstract: Previous solutions for the radiation by a cylindrical antenna loaded with a single dielectric layer are extended to the multilayered case. For the sake of convenience, and without any loss of generality, only the 2-layered method of loading is considered by a boundary-value approach. Graphical results are presented to show the effect of the dielectric on the radiation pattern and conductance when the first layer is a thin air gap. It is shown that significant improvement in the pattern may be achieved with critical dimensions of the air gap.With a single or double layer, the dimensions may be selected to produce a broadside pattern similar to that of the unloaded dipole of less than half a wavelength. It is expected that this behaviour will be employed to improve the radiation characteristics when the antenna length is finite, provided that optimisation techniques are employed in designing the critical dimensions.

Tv/fm/am antenna coupler

Abstract: An antenna system using a standard dipole antenna capable of receiving television, AM and FM signals employing signal isolation means wherein the antenna may be automatically used to receive AM, FM and television signals without adjustment or control. A coaxial cable is employed from the antenna coupler to the AM/FM radio receiver, and a coaxial cable stub is disposed adjacent the radio antenna lead-in and is of a length equal to substantially 1/4 of a wavelength in the FM band, the shields of the antenna lead-in and the coaxial stub being electrically connected, and the inner conductors being connected to the dipole antenna such that the stub coaxial cable functions as a "short circuit" providing correct coupling to the dipole antenna when receiving FM signals, but does not interfere with AM signal reception.

Radiation patterns of an antenna near a conducting strip

Abstract: Horizontal patterns of a linear antenna near a conducting strip are found by solving a two-dimensional problem using an integral equation method Because of practical interest, the computed patterns are shown for only small to moderate sizes of the strips and small to moderate separation distances of the antenna

Doppler antenna calibration apparatus

Abstract: Apparatus which permits near-field calibration of a doppler antenna in the laboratory avoiding the high costs and uncertainties of flight calibration is shown. The antenna and an associated transmitter are mounted over and very close to a scattering surface and means provided to effect relative motion between the antenna and the surface. In one embodiment the scattering surface is on an endless belt which is driven under the antenna and, in another, the antenna is placed on an arm and rotated over an annular trough containing granular material.