Showing papers on "Monopole antenna published in 1973"

The insulated dipole antenna in a relatively dense medium

Abstract: The properties of an insulated dipole antenna are derived when the wavenumber of the surrounding infinite, homogeneous, and isotropic medium is large compared with that of the insulation. It is shown that even when the surrounding medium is a perfect dielectric, the distributions of current and charge along the antenna and its driving-point admittance are substantially like those of a section of transmission line with a distributed radiation loss appearing as a part of the series impedance per unit length.

Stripline slotted balun dipole antenna

Abstract: A stripline slotted balun dipole antenna, suitable for use as a single antenna or as an array antenna element, is fabricated from two metal-clad dielectric sheets, from which metal has been removed in predetermined patterns, and then the sheets are sandwiched together to form both the slotted balun dipole antenna and its stripline feed. The metal remaining on the exterior of the laminated structure constitutes a slotted balun dipole and the metal remaining between the dielectric sheets constitutes the center conductor of the stripline feed. The structure obviates the need for metallic connections in the antenna area.

The Elevation Angle of Mobile Radio Signal Arrival

Abstract: Field measurements of mobile radio signals have shown that signal arrival is concentrated in elevation angles lower than 16°. This suggests use of an omnidirectional antenna with vertical directivity, instead of the usual whip antenna, to increase average signal strength as a further improvement in the advantages of diversity reception.

A cavity-backed dipole antenna with wide-bandwidth characteristics

Abstract: This communication describes a cavity-backed dipole antenna that has a broad-band VSWR response, unidirectional radiation patterns, and almost constant gain ( 10.5 \pm 1 dB) over an operating bandwidth of 1.8: 1. Measured pertinent electrical characteristics are presented.

Miniaturized transmission line top loaded monopole antenna

Abstract: A miniaturized antenna having high radiation efficiency consists essentially of an open circuit transmission line top-loading a short monopole over a metal ground plane. The currents in the two sides of the transmission line, being oppositely directed, tend to cancel each other''s effect in the distant field. Thus, only the short vertical monopole contributes to the distant field radiation. The omnidirectional monopole is a constant current radiating element operating at near RF ground potential (high current, low impedance).

The performance of transistor fed monopoles in active antennas

Abstract: The performance of radiating elements in the form of monopoles and driven by transistors is examined theoretically and experimentally. A single element comprising a printed monopole over a ground plane and fed at its terminals by a microwave transistor is shown to have superior frequency characteristics compared to the passive element. Using a two-element array configuration, it is verified that the mutual impedance values are suppressed. The improved individual characteristics of the active elements together with their mutual behavior combine to produce a significantly improved frequency performance of the array. The results presented suggest that the transistorized array principle offers a means both of maintaining directivity of a transmitter, and discriminating against interfering sources by a receiver, over a greater frequency band.

Multipurpose antenna system for a submarine

Abstract: There is disclosed herein a multipurpose antenna system for a submarine having a hollow mast capable of movement into and out of a submarine hull. A first antenna system is mounted at the top of the mast with this first antenna system being capable of transmitting and receiving in a time shared relation a radar signal and a satellite communication signal. A second antenna system is disposed in the mast below the first antenna system. This second antenna system is capable of receiving an electronic countermeasure signal. The second antenna system includes a plurality of different antennas disposed in spaced relation with respect to each other about the circumference of a transverse cross-section of the mast. The plurality of different antennas are flush mounted with respect to the outer surface of the mast. Each of the plurality of different antennas of the second antenna system employs two printed circuit spiral antennas stacked in the same plane one above the other with one of the spiral antennas being responsive to right-hand circular polarization and the other spiral antenna being responsive to left-hand circular polarization. A switching arrangement is coupled to each of the spiral antennas to appropriately cause the plurality of spiral antennas to scan 360* in both left-hand and right-hand circular polarization.

Phased array scanning antenna

Abstract: A landing system antenna in which a plurality of antenna elements arranged in a circular pattern are sequentially energized to project a scanning planar beam with fine scanning control maintained by controlling the phase in a plurality of small steps.

Coaxial horn antenna

Abstract: A wide band, multi-mode antenna having a plurality of coaxial, independently fed, radiating horns. Each horn has multiple feeds which can be energized in various phase relationships to control polarization. The antenna can be used as a direct radiator, or to illuminate a reflector, has transmit or receive capabilities, and is adaptable to monopulse operation. The antenna is a compact rigid unit of very simple construction.

Dual polarization spiral antenna

Abstract: An element antenna for use with a plurality of similar element antennas in an array. The element antenna receives and reradiates circular polarized electromagnetic energy such that the reradiated energy is of the same polarity as the received energy, independently of the geometric polarization element antenna. The element antenna includes a plurality of elongated, electrically conductive arms, each having an intermediate portion located in an annular active antenna region where circular polarized electromagnetic energy is received and reradiated. The arms of the element antenna are configured so that they define a geometric polarization element antenna of a given circular polarity so that currents induced in the respective intermediate arm portions from received energy, flow towards specific arm ends in dependence upon the polarity of the received energy. The currents are acted upon so that they re-enter the active region having their relative phases controlled in such a manner that the reradiated energy is of the same circular polarity as the received energy.

Thin sandwich telemetry antenna

Abstract: A thin sandwich slot antenna is provided which produces a cardiod shaped antenna pattern. The antenna structure requires no antenna cavity or other remote structure behind the antenna. A thin-film antenna is supported by a thin dielectric strip and contoured to the shape of support structure. A metallic support structure becomes the ground plane for the antenna otherwise a metallic ground plane is placed behind the radiating element.

Ship-borne gravity stabilized antenna

Abstract: A gimballed-platform-mounted antenna arrangement for semi-stabilizing the orientation of the antenna of said arrangement on a ship, said arrangement being semi-stabilized in use by means of its having a long natural period of oscillation and a high moment of inertia as hereinbefore defined.

Absolute calibration of antennas at extremely low frequencies

Abstract: To calibrate electric-field sensors at extremely low frequency (ELF) the measured terminal voltage V at a receiving antenna is compared with the Analytically predicted V for a precisely known incident field. That incident field is generated by an electrically very short thin linear radiator. Formulas are given for the field in the immediate vicinity of such a radiator above a perfectly conducting ground. Also given is an expression for the integral of this field along a vertical path starting at ground level. The expressions involve the magnitude of the current at the base of the radiator and methods are described for establishing that quantity precisely by measuring the base-to-ground voltage and the very small capacitance (about 20 pF) of the radiator. The methods for small capacitance measurement are also applied to linear and spherical receiving antennas, and experiments are described in which it was possible to predict the terminal voltage at a receiving antenna to within \pm3 percent when the voltage applied to the transmitting radiator, located at a relatively short distance ( \approx 16 to 21 m) was known. Details of measurement circuitry are given including descriptions of an extremely high input impedance ( \approx 5000 M\Omega ) amplifier and a circuit for the compensation of cable capacitance. For a uniform incident field the effective height of both, a vertical linear receiving antenna and of a spherical antenna, is equal to the distance between ground level and the center of the conducting part of the antenna. Typical values for the natural, ambient ELF field in the frequency range 3 to 30 Hz are shown to be in the vicinity of 0.1 mV/m/Hz1/2.

Sensitivity improvement of spaced-loop antenna by capacitive gap loading

Abstract: An improved antenna system having a plurality of loop antennas surrounded coaxial shields which have dual electrostatic shield gaps therein. A shunt capacitance is placed across each of the shield gaps. The shunt capacitances are matched and variable among discrete values. Variation of the capacitances provides increased antenna sensitivity without a change in physical dimensions of the antenna.

Measurement of the radiation patterns of full-scale HF and VHF antennas

Abstract: A system has been developed to measure the directivity patterns of full-scale antennas when located in their operational environments. The primary component of this system is an aircraft-towed multifrequency transmitter that is designed to approximate an elementary dipole antenna. An HF and a VHF version of this transmitter provide frequency coverage from 2 to 100 MHz. Techniques have been developed to measure the entire radiation pattern, from the horizon to the zenith, for several antennas simultaneously. Data derived from this system are processed to provide the radiation patterns as contour plots of the measured signal strength on azimuthal equal-area projections. The measurement hardware, data acquisition, and data processing techniques are described, and examples are given of measured and processed data derived from the system.

Magnetic wave communication system

Abstract: A receiver for a magnetic wave communication system comprising antenna means, a signal treating circuit, an amplifier and a reproducing means. The antenna means includes a casing and an antenna member consisting of a core conductor, a magnetic thin film, and a coil. The signal treating circuit comprises an impedance means and a diode detector. The antenna means receives the transmitted audio frequency magnetic field signal and converts the magnetic field signal to a current corresponding with the audio frequency magnetic field signal.

Dual-band array antenna

Abstract: A unitary antenna comprising two different arrays. The first is a group of waveguide antenna elements in alternately displaced rows forming a triangular grid structure and the second is another group of waveguide antenna elements forming a triangular grid structure within the first grid structure. The two groups of elements are dielectrically loaded, are polarized to radiate orthogonally to each other, and are designed to radiate at different frquency bands.

Antenna gain calibration on a ground reflection range

Abstract: The absolute gain of wide-beam antennas may be accurately measured using the method described. Both the theoretical and practiced aspects of gain calibration on a ground reflection antenna range are presented. The measurement procedures developed were used to calibrate a log-periodic antenna at selected frequencies from 250 to 400 MHz. Measured data at 300 MHz is tabulated and error contributions are analyzed, yielding a measurement accuracy of \pm0.27 dB with a 95 percent confidence interval.

Reception Characteristics of Monopole Antennas for Electron Plasma Waves

Abstract: The radiation patterns of a longitudinal electron plasma wave excited in a warm unbounded plasma by a grid and parallel plane grids and the reception patterns for wire antennas and the grid having a grounded plate were measured experimentally. The results agreed well with theoretically predicted radiation patterns based on a fluid model description for electrons. The dependence of the received amplitude of a gridded parallel plate on the D. C. potential of the antenna was studied. The possibility of estimating the wavelength from measured amplitudes of the wire antenna and the gridded parallel plate is also discussed.

Low-frequency loop antenna arrays: Ground reaction and mutual interaction

Abstract: An investigation is presented dealing with the ground reaction and the mutual interaction of horizontally and vertically oriented loops in antenna arrays of arbitrary configuration located above the ground and contains the calculation of appropriate reaction coefficients. Because of the similarity of the derivations for systems of vertical and horizontal loops, only the calculation technique for systems of vertical loops is performed in detail.

Shipboard yardarm half-wave antenna

Abstract: Two frequency-adjustable antennas of the type having a helix and cylinder coaxially arranged end-to-end are themselves arranged inversely end-to-end in a 1/2-wave dipole antenna arrangement that is entirely ground plane independent. The end-to-end radiators are arranged about a common drive means which, while providing the main structural support of the antenna arrangement, provides simultaneous synchronous tuning of each leg of the antenna arrangement.

Built-in FM dipole antenna

Abstract: A component type of FM stereo broadcast receiver is provided with a built-in dipole antenna by making use of the cables that connect the left and right speakers to the receiver. Since these speakers are usually placed at least one half wavelength apart at the received carrier frequencies, the system lends itself to efficient dipole antenna operation. By using an r-f impedance raising circuit at the amplifier output, and a frequency selective coupling system between the speaker jacks and the antenna terminals, a high performance ''''built-in'''' antenna is achieved.

Log periodic pole mounted marker beacon antenna

Abstract: An ILS marker beacon antenna of the type wherein a pair of parallel conductors form a balanced transmission line and support a plurality of lateral radiators of graded lengths. An unbalanced RF transmission line extends through one of the conductors to the apex feed point of the antenna with one conductor of the unbalanced line connected to one of the pair of conductors and the other conductor of the unbalanced line connected to the other of the pair of conductors for flow of RF current from the feed point along the balanced transmission line to the radiating elements. An electrically small dipole monitor antenna mounted on the parallel conductors terminates the balanced transmission line by short circuit in a region near the back of the log periodic antenna to prevent back radiation and monitor antenna operation.

Impedance and large signal excitation of satellite-borne antennas in the ionosphere

Abstract: The input impedance of a spacecraft-borne electric antenna operating below approximately 30 kHz in the ionosphere is investigated with emphasis on sheath effects. The impedance concept is generalized to be applicable to nonlinear antenna-magnetoplasma systems. Explicit formulas are obtained for the generalized impedance of a near cylindrical antenna taking into account the effects of large signal excitation, induced electromotive forces due to antenna motion across the Earth's magnetic field, the influence of the ion collection surface of the space vehicle, and of dc bias between antenna and vehicle. Comparison is made of the pertinent part of the theory and LOFTI-IIA satellite data.

Thin monopole antenna: finite-size belt-generator representation of coaxial-line excitation

Abstract: The real system of a vertical monopole, obtained as a simple protrusion of the inner conductor of a coaxial line through the ground plane, is approximated by a monopole base driven by a finite-size belt generator. A simple formula is derived for determining the size of the belt generator so that it is equivalent to the coaxial-line excitation. The integral equation for current obtained with the finite-size belt generator is similar to the well known equation for the delta-function generator. However, the new equation has an integrable solution, convergent at all points. In particular, the monopole admittance obtained from the modified integral equation closely approaches, in the limit, the apparent admittance of the monopole, as measured by reflection measurements on the coaxial line and referred to the ground plane.

Broad-band antenna having folded dipoles with hairpin transformers

Abstract: A broad-band antenna characterized by having a folded dipole that includes first and second open center portions with a broadband transformer element spanning one of said open center portions while transmission line feed points are located at the opposed sides of the other open center portion, with this arrangement permitting the transformer element to electrically lengthen the antenna into half-wave folded dipole antenna for the reception of low-band signals while also simultaneously electrically opening the antenna into a full-wave dipole antenna for high-band reception. By the use of a single antenna to receive two bands from a broad-band spectrum, size and weight are reduced while simultaneously achieving a greater gain in decibels than would otherwise occur absent the use of the arrangement above-described.

Roof mounted vehicle antenna

Abstract: An antenna particularly suited for Citizens Band frequency use, and is particularly designed for mounting upon the roof of vehicles. The antenna is of a U-shaped configuration having a base portion and parallel leg portions. The leg portions are adjustable in length, and the antenna is supported in spaced relation to the vehicle roof to reduce standing wave reflected frequencies. A gamma assembly is attached to the base region of the antenna constituting a tuning capacitor, and the spacing of the leg portions causes a reflection and multiplication of radio frequencies, during transmission, causing a vertical directional orientation of the transmitted signals resulting in superior transmitting characteristics.

Optimization of the loop-coupled log-periodic antenna

Abstract: Varying the spacing between the transposed transmission line feeder and the radiating elements of the loop-coupled antenna is investigated experimentally using far-field swept-frequency techniques. An optimum spacing is found in the sense that anomalous frequency performance is minimized. A theory using dispersion relationships is developed and used to explain some of the experimental phenomena observed.

Slot antenna with flare

Abstract: A slot antenna with a flare having flare member having integrally formed therewith a first half section of antenna member and a second half section of antenna member having formed therein slots, in which the second half section of antenna member is mechanically assembled with the first half section of antenna member to provide a slot antenna member.