Showing papers on "Antenna (radio) published in 1976"

Adaptive arrays

Abstract: A method for adaptively optimizing the signal-to-noise ratio of an array antenna is presented. Optimum element weights are derived for a prescribed environment and a given signal direction. The derivation is extended to the optimization of a "generalized" signal-to-noise ratio which permits specification of preferred weights for the normal quiescent environment. The relation of the adaptive array to sidelobe cancellation is shown, and a real-time adaptive implementation is discussed. For illustration, the performance of an adaptive linear array is presented for various jammer configurations.

Absolute calibration of millimeter-wavelength spectral lines

Abstract: A detailed analysis of the chopper-wheel method of calibrating the intensity of a millimeter-wavelength spectral line is presented. Special techniques were used to construct a receiver which eliminates most of the usual calibration difficulties. The zenith atmospheric extinction between 3.5 mm and 2.6 mm wavelength was measured, and the intensities of six spectral lines in this range were absolutely calibrated with an estimated uncertainty (1 sigma) of 7 percent. The effects of the antenna power pattern on the corrected antenna temperature T*/sub A/ are calculated for several simple models of the source brightness distribution. (auth)

Cellular radiotelephone system structured for flexible use of different cell sizes

Abstract: The use of plural cell sizes in cellular high capacity mobile telecommunications systems is facilitated by providing dual service availability in an essentially geographically continuous large-cell grid and an overlaid and essentially geographically discontinuous small-cell grid When using certain frequency channel set assignment plans, large-cell antenna sites employ their ordinary channel set assignments whether or not a small-cell antenna site is also present When a large-cell site is operated in the vicinity of a co-channel small-cell site, the respective channels of the large-cell site are operated in a large-cell mode or a small-cell mode as required to cooperate with the overlaid small-cell site When using frequency channel set assignment plans requiring departures from ordinary large-cell channel assignments, the departures are similarly effected on the large-cell site channels that are operated in the small-cell mode Also shown is an arrangement for channel-sharing around the faces of a directional antenna site to reduce the impact of adjacent channel interference

Method of molding fiberglass reflecting antenna

Abstract: Fiberglass antenna for reflecting electromagnetic radiation. The antenna includes metal reflecting surface embedded within the fiberglass. The antenna is fabricated in a heated, vacuum injected mold.

Directive antenna with reflectors and directors

Abstract: An antenna system of the type wherein the radiating pattern may be controlled to direct the radiation of a signal in a selected direction. The system includes a plurality of radiating elements which are affixed to a coplanar in planes which are equiangular from each other. In response to a selected direction of radiation, control circuitry applies the signal to the coplanar antenna elements which are in a plane perpendicular to the selected radiating direction. Further, the control circuitry varies the electrical length of the remaining elements such that some act to direct, and other reflect the radiated signal.

Microwave antenna system

Abstract: An antenna for use in propagating or receiving microwave radiation having both left-hand and right-hand circular polarization. The left-hand and right-hand circularly polarized radiation may be transmitted or received simultaneously without interference with one another, that is, they are isolated from one another by 27 dB or more. The preferred antenna comprises an array of closely clustered waveguide elements each of which converts respective linearly polarized signals to left-hand and right-hand circularly polarized signals and vice versa. Isolation means also are provided in each of the waveguide elements for preventing radiation either propagated or received by a waveguide element from being coupled into the radiation being propagated or received by other waveguide elements in the array. Preferably, square waveguide is utilized for the array elements and the isolation is provided by a plurality of conductive elements mounted on each of the open ends of the waveguide elements. The cluster array of waveguide elements may include dummy elements, may be fed with electromagnetic signals having various phase and power differences to produce desired radiation transmission or reception patterns and may be used to illuminate a parabolic reflector having a secondary radiation pattern. A single waveguide element or an array of them may be used in communications satellites and the like or may be used in radar or other applications.

Coplanar stripline antenna

Abstract: A coplanar stripline antenna including a layer of dielectric material supporting a lower ground plane of conductive material on one side of the layer of dielectric material, a patch of conductive material on the other side of the layer of dielectric material, and an upper ground plane of conductive material on the other side of the layer of dielectric material and with the upper ground plane substantially surrounding and spaced from the patch of conductive material. Electrical signals are fed to the antenna between the patch of conductive material and the upper ground plane. A number of patches of conductive material may each be surrounded by the upper ground plane to form an antenna array and with the patches interconnected by coplanar stripline fed at a point equidistant from each patch.

Conical horn antenna having a mode generator

Abstract: A conical horn antenna is disclosed having dual dielectric bands mounted therein for improving the rotational symmetry or elipticity of the radiated beam as well as the efficiency. The first and second dielectric bands are coaxially mounted to each other and to the conical horn. The lengths of the bands are determined by the frequencies being propagated. A circularly polarized dominant wave such as TE 11 mode is applied to the antenna and excites a series of higher order waves such as the TM 11 mode. The circularly polarized dominant and the higher order modes are propagated toward the aperture where they are in phase and therefore add vectorially. The dual dielectric band acts as a slow wave structure and higher order waves which in turn provide an improved phasing between the dominant modes.

Analysis of antennas and scatterers with nonlinear loads

Abstract: Two methods for analyzing antennas or scatterers having nonlinear resistive loads are discussed. The first is a direct time-domain integral equation approach, whereas the second involves the use of frequency domain data to compute the time-dependent currents and voltages across the nonlinear load. Both transient and time-harmonic excitations are considered in the sample problems illustrated here which involve a center-loaded linear antenna. Although it is difficult to do so with the direct time-domain approach, the second method of analysis may be readily applied to an arbitrary antenna whose frequency response is either measurable or calculable.

Ultimate sensitivity limit of a resonant gravitational wave antenna using a linear motion detector

Abstract: The sensitivity of a resonant-mass gravitational radiation antenna coupled to a motion detector with given noise properties is calculated in detail. It is shown that the quantum-mechanical limit of linear amplifier performance implies an important restriction on the sensitivity for any system using a linear motion detector. For a signal frequency ${\ensuremath{\omega}}_{a}$, this fundamental limit requires that the gravitational radiation pulse be capable of driving the antenna from rest to an energy level exceeding $2\ensuremath{\hbar}{\ensuremath{\omega}}_{a}$.

Antenna radiation patterns in the whistler wave regime measured in a large laboratory plasma

Abstract: Antenna radiation patterns of balanced electric dipoles and shielded magnetic loop antennas are obtained by measuring the relative wave amplitude with a small receiver antenna scanned around the exciter in a large uniform collisionless magnetized laboratory plasma in the whistler wave regime. The boundary effects are assumed to be negligible even for many farfield patterns. Characteristic differences are observed between electrically short and long antennas, the former exhibiting resonance cones and the latter showing dipole-like antenna patterns along the magnetic field. Resonance cones due to small electric dipoles and magnetic loops are observed in both the near zone and the far zone. A self-focusing process is revealed which produces a pencil-shaped field-aligned radiation pattern.

Dielectric coated wire antennas

Abstract: An electrically thin dielectric insulating shell on an antenna composed of electrically thin circular cylindrical wires is examined. A moment method solution is obtained, and the insulating shell is modeled by equivalent volume polarization currents. These polarization currents are related in a simple manner to the surface charge density on the wire antenna. In this way the insulating shell causes no new unknowns to be introduced, and the size of the impedance matrix is the same as for the uninsulated wires. The insulation is accounted for entirely through a modification of the symmetric impedance matrix. This modification influences the current distribution, impedance, efficiency, field patterns, and scattering properties. The theory is compared with measurement for dielectric coated antennas in air.

Coupling converter for vehicle antennas

Abstract: A coupling converter for use of a broadcast-receiving antenna both with its broadcast receiver and with a citizens band transceiver, including impedance matching means and a priority switch to protect the transceiver from overload by transmission without sufficient antenna loading.

Serially connected microstrip antenna array

Abstract: Radio frequency antenna arrays of radiating slot apertures serially connected along a predetermined path transverse to the radiating slot apertures. In the exemplary embodiments, the radiating slot apertures are formed by parallel edges of conductive radiator surfaces where the edges are spaced apart by substantially one-half wavelength at the anticipated antenna operating frequency. Such radiator surfaces are, in some embodiments, dimensioned in a direction parallel to the apertures in relation to the relative proportion of radio frequency energy which is to be radiated to/from the slot apertures associated therewith to thus determine the total array aperture amplitude taper while the spacing between the radiator surfaces determines the phase taper across the total array aperture. Other exemplary embodiments utilize internal reflections in an array to determine the array amplitude taper and still other exemplary embodiments combine a plurality of such arrays to form two-dimensional special purpose arrays.

Dielectric Rod Antennas for Millimeter-Wave Integrated Circuits (Short Papers)

Abstract: The design of dielectric rod antennas for millimeter-wave integrated-circuit applications is described. The experimental investigation was initially performed for sealed models at Ku band and then developed at V band. A moderately high-gain alumina dielectric rod antenna that is entirely compatible with insular integrated circuits has been designed and tested. The antenna has been fabricated and integrated, as one of the system components, into short-range V-band transmitter and receiver moduIes. The measured gain was found to be 15.2 dB. Radiation characteristics are discussed.

Satellite tracking dish antenna

Abstract: In a small satellite earth station a directional antenna is rocked about a single axis, corresponding to an oscillatory change in declination, but constant hour angle. The rocking is approximately sinusoidal and has a period of one sidereal day. In a preferred arrangement the antenna is mounted on a rocking axis pivot which is fixed at right angles to, and rotatable for adjustment about, a polar axis member. The polar axis member is set up parallel to the earth's axis and the pivot is rotated about the polar axis member to set the hour angle. The rocking of the antenna is achieved by a crank and tie-rod arrangement driven by a clock motor mounted on the polar axis member. The arrangement is particularly simple and will, when set up, track a synchronous satellite without needing frequent adjustment.

Thin conformal antenna array for microwave power conversion

Abstract: A structure of a circularly polarized, thin conformal, antenna array which may be mounted integrally with the skin of an aircraft employs microstrip elliptical elements and interconnecting feed lines spaced from a circuit ground plane by a thin dielectric layer. The feed lines are impedance matched to the elliptical antenna elements by selecting a proper feedpoint inside the periphery of the elliptical antenna elements. Diodes connected between the feed lines and the ground plane rectify the microwave power, and microstrip filters (low pass) connected in series with the feed lines provide DC current to a microstrip bus. Low impedance matching strips are included between the elliptical elements and the rectifying and filtering elements.

Electronic monitoring system and responder device

Abstract: An electronic monitoring system for monitoring the passage of objects, such as persons, past a monitoring station. An antenna is provided flat on the floor of the station to generate electromagnetic fields in the vicinity of the station and to generate electrical alarm signals whenever the electromagnetic fields are disturbed by the passage of an object carrying a special responder device. The responder device comprises an elongated bar of ferromagnetic material about which is wound the coil of a resonant electrical circuit. A mounting strap is provided to mount a responder device the leg of each object to be monitored such that the elongated bar is held perpendicular to the floor whereby maximum electrical interaction is provided between the antenna and the resonant electrical circuit.

An approximate formula for calculating the directivity of an antenna

Abstract: An approximate general formula to calculate the directivity of an antenna based upon the E -plane and H -plane patterns is proposed. For narrow beam patterns, the directivity is expressed in terms of the half-power beam widths of the main patterns. The better approximation of the formula presented here over the geometrical mean formula is pointed out.

Multibeam adaptive array

Abstract: An antenna system utilizing the multibeam advantages of the Butler matrix achieve beam steering with the additional capability of placing nulls in the direction of undesired radiation. The system comprises essentially a Butler matrix with an adaptive circuit interposed between each of the antenna elements and a corresponding one of the hybrid matrices of the Butler matrix. Switch means are also provided for separating the transmit and receive functions.

Notch fed magnetic microstrip dipole antenna with shorting pins

Abstract: A notch fed magnetic microstrip dipole antenna consisting of a thin electally conducting, rectangular-shaped radiating element formed on one surface of a dielectric substrate, the ground plane being on the opposite surface with the radiating element shorted to the ground plane. The length of the element determines the resonant frequency. The feed point is located in a notch along the centerline of the antenna length and the input impedance can be varied by moving the feed point along the centerline of the antenna without affecting the radiation pattern. The notch extends from an edge of the element to the feed point. The element is shorted through the dielectric to the ground plane by means of plated thru holes or rivets at one end of the element.

Wide beam microstrip radiator

Abstract: A radio frequency antenna structure is disclosed wherein a raised pedestal portion of the ground plane surface is provided and above which pedestal portion a microstrip radiator is disposed. The microstrip radiator is thus disposed on a pedestal at a predetermined distance above the base ground plane to produce mirror image or apparent radiating aperture(s) therebelow. The combined radiation pattern from the real radiating aperture(s) and the mirrored image(s) thereof produces an increase in radiation power at low pointing angles located near the ground plane, thus producing a wider radiation beam without sacrificing radiation efficiency. This form of raised pedestal microstrip radiator is especially useful in phased arrays where it is desired to steer the beam of the array to angles near the ground plane itself.

The many faces of the insulated antenna

Abstract: The development of the insulated antenna is outlined from its beginnings as an ocean cable. The generalization of the theory from that applicable only to coaxial lines with an outer conductor of infinite extent to an insulated antenna embedded in a relatively dense medium that may be a dielectric or a conductor is described. The properties of the eccentrically insulated antenna and their usefulness in traveling-wave directional arrays for lateral-wave transmisson are reviewed. The diagnostic applications of the insulated antenna are considered with special reference to the measurement of the electric field in an ambient medium independent of its permittivity and to a study of the properties of a plasma-filled tube.

Antenna for combined surveillance and foliage penetration radar

Abstract: An L-band radar and antenna array operating with an existing X-band surveance radar to provide a foliage penetration capability. The foliage penetration antenna consists of an array of L-band, stripline dipole/director elements placed in front of an array of broadwall waveguide slots which define an X-band aperture. The X-band aperture in addition to its own function, serves as a reflector for the dipole/director elements. Aperture sharing is thus provided for a dual frequency antenna without increasing the size of the existing X-band aperture.

Randomly agglomerated subarrays for phased array radars

Abstract: A phased array radar for providing a beam cluster whose average direction is determined by phase shifters associated with each antenna radiating element, and whose illumination function is determined by the phase and amplitude provided to subarrays of randomly agglomerated radiating elements which provide an aperiodic illumination error function that substantially reduces the grating lobes of the antenna pattern.

Radio frequency beam forming network

Abstract: A radio frequency beam forming network is disclosed wherein a plurality of antenna feed elements arranged in the focal plane of a radio frequency lens is coupled to corresponding input ports of a radio frequency energy distributing means. Output ports of such radio frequency energy distributing means are coupled to a receiver/transmitter through different paths. Disposed in the different paths are active elements, including variable phase shifters and attenuators. The active elements, in response to control signals, provide proper attenuation and phase shift to the signals passing therethrough thereby to form a desired antenna beam. Such antenna beam is comprised of one or more "spot" beams. With such arrangements failure of a single one of the active elements will only slightly degrade system performance without resulting in a complete loss of any one of the "spot" beams.

The tapered antenna and its application to the junction problem for thin wires

Abstract: When electrically thin conductors of different cross sectional size meet, the continuity of current is assured by Kirchhoff's current law. Additional conditions must be imposed on the derivatives of the currents or the charges per unit length. The nature of the required conditions is determined from an analysis of the tapered antenna.

HF Antenna matching device

Abstract: An antenna matching device comprises a directional coupler and, respectively connected, in a prior art manner, to two conjugate ports of the directional coupler, one of which is a high-power port, and the other of which a low-power port, a matching circuit in series with the antenna to be matched, and a matched load A switching device makes it possible, during the matching phase, to reverse the connections of the aforementioned ports and thus to substitute the directional coupler low-power path for the high-power path in the link between the transmitter and the antenna

Security apparatus for vehicle communications accessory

Abstract: A citizen band radio is secured within a vehicle by a high strength cable which is coupled to the radio by a locking device mounted on the antenna connector of the radio.