Showing papers on "Antenna (radio) published in 1982"

Antenna Theory: Analysis and Design

Abstract: The most-up-to-date resource available on antenna theory and design Expanded coverage of design procedures and equations makes meeting ABET design requirements easy and prepares readers for authentic situations in industry New coverage of microstrip antennas exposes readers to information vital to a wide variety of practical applicationsComputer programs at end of each chapter and the accompanying disk assist in problem solving, design projects and data plotting-- Includes updated material on moment methods, radar cross section, mutual impedances, aperture and horn antennas, and antenna measurements-- Outstanding 3-dimensional illustrations help readers visualize the entire antenna radiation pattern

Method and apparatus employing received independent magnetic field components of a transmitted alternating magnetic field for determining location

Abstract: The location method uses relatively low frequency electromagnetic fields, e.g., 1-1000 Hz, for determining the relative position and/or orientation of a transmitting magnetic dipole antenna by using a vector field receiver. The transmitting antenna for subterranean location, is preferably a single axis, elongated solenoid with a ferromagnetic core. The receiving sensor may be a precise three-axis magnetic field detector of either a magnetometer or search coil type. Measurements are made for one or more positions of either the transmitter or receiver, or with one or more transmitters or receivers. The relative location of the transmitter and the receiver is calculated with respect to some known survey station by a method of successive approximations. The operating frequency is chosen to minimize field distortion from common steel structures, such as pipe, casing or railroad tracks, and to minimize field scattering such as from conducting inhomogeneities in the earth. Either the transmitter or receiver can be operated within metal structures such as casing. The method can be used for location of underground boreholes or pipelines; location of trapped miners; as a means of blind surveying such as in underground mines; or as a means of navigation such as in relatively shallow horizontal or vertical drilling and tunneling or in raise bore mining.

Dual mode radio frequency-infrared frequency system

Abstract: A combined RF/IR system in which a common surface is used in the dual modes of radiating and absorbing RF energy and of reflecting and focusing IR energy. The common surface is structured, configured, and used as the slotted array antenna for the RF energy and as the primary mirror of a Cassegrain optical subsystem for the IR energy.

Planar receiver antenna coil for programmable electromedical pulse generator

Abstract: An implantable programmable pulse generator provides electrical stimulation signals to the heart of a patient. The operating parameters of the pulse generator, such as stimulation rate, refractory period duration, and operating mode are programmable by a physician after the pulse generator has been implanted surgically in the patient. An external programmer device includes a transmitter of coded radio frequency (RF) signals. The pulse generator includes a receiver antenna for receiving the coded RF signals. The receiver antenna includes a first wire-wound, air core, planar coil antenna carried on a flexible insulating substrate adjacent an inner wall of a first major side surface of the pulse generator housing and a second wire-wound, air core, planar coil antenna carried on the flexible insulating substrate adjacent an inner wall of a second major side surface of the pulse generator housing. The planar coils are series additive connected to the programmable pulse generator circuit so that the RF signals will be received regardless of the orientation of the pulse generator when it is implanted in the patient. The planar receiver coil antenna provides reliable reception of the RF signal even when the transmitter coil of the programmer is slightly misaligned or tilted with respect to the receiver coil antenna. In addition, the antenna provides a shallow Q factor so that individual high tolerance tuning of the receiver circuits of the pulse generator is not required.

A method for measuring amplitude and phase of each radiating element of a phased array antenna

Abstract: In the phased array system, excitation amplitudes and phases based on the design are specified for each antenna element in order to synthesize desired beam scannings and radiation patterns. However, due to fluctuations of antenna and feed network characteristics, the amplitude and phase of each antenna element deviate from the desired values. To correct these deviations, the amplitude and phase of each antenna element must be accurately measured under specific operating conditions. In this paper, we employ variable phase shifters connected to the antenna elements and measure only the amplitude variation of the composite electric field of the entire array when the phase of each element is modified. The rotating element electric field vector method in which the measured amplitude variation is numerically processed for obtaining the amplitude and phase of the particular element is theoretically discussed and experimentally tested for its usefulness. The present method can be easily attained by simply adding software to the computer-controlled phased array system.

Wireless telephone extension unit with self-contained dipole antenna

Abstract: A remote unit for use in a wireless extension telephone system having a self-contained dipole antenna. Utilizing the unique construction of the telephone instrument housing one element of the dipole is included in a planar element that functions normally to direct sound to a self-contained microphone and the other element of the antenna is a static shield used to protect components on printed circuit board included within the extension unit.

Accuracy potentials for large space antenna reflectors with passive structure

Abstract: Analytical results indicate that a careful selection of materials and truss design, combined with accurate manufacturing techniques, can result in very accurate surfaces for large space antennas. The purpose of this paper is to examine these relationships for various types of structural configurations. Comparisons are made of the accuracy achievable by truss- and dome-type structures for a wide range of diameter and focal length of the antenna and wavelength of the radiated signal.

An improved design method of Rotman lens antennas

Abstract: A Rotman lens is used to feed a linear array antenna for wideband use. A relationship between design parameters for realizing a Rotman lens has been derived by introducing a new design variable. The design method which minimizes the phase error on the aperture of the linear array antenna has been shown. For large array length, the above phase error due to this method becomes considerably smaller than that due to a conventional method. This improved method makes it possible to design small and low-loss Rotman lens antennas.

Efficient computation of antenna coupling and fields within the near-field region

Abstract: The theory, techniques, details of the important equations, and description of two computer programs are presented for calculating efficiently the mutual coupling at a single frequency between any two antennas arbitrarily oriented and separated in free space. Both programs emphasize efficiency and generality, and require, basically, the complex electric far field of each antenna, and the Eulerian angles designating the relative orientation of each antenna. Multiple reflections between the antennas are neglected but no other restrictive assumptions are involved. If an electric field component is desired instead of coupling, the receiving antenna is replaced by a virtual antenna with uniform far field. The first computer program computes coupling (or fields) versus transverse displacement of the antennas in a plane normal to their axis of separation. An efficient fast Fourier transform (FFT) program was made possible by "collapsing" the far-field input data and showing that inmost cases the spectrum integration need cover only the solid angle mutually subtended by the smallest spheres circumscribing the antennas. Limiting the integration to this solid angle artifically band limits the coupling function, thereby allowing much larger integration increments and reducing run times and storage requirements to a feasible amount for electrically large antennas. The second program is based on a spherical wave representation of the coupling function and rapidly computes coupling (or fields) versus separation distance between the antennas. The spherical wave representation emerged naturally from an intriguing characteristic proven for the mutual coupling function; it, like each rectangular component of electric and magnetic field in free space, satisfies the homogeneous wave equation.

Influence of fabrication tolerances on the surface accuracy of largeantenna structures

Abstract: One of the sources of error in radio frequency antennas is the lack of dimensional precision of the surface. This paper presents an approach for estimating the amount of error caused by random dimensional imperfections of the many structural elements which make up a truss-type antenna. A principle of equivalence between the analyses of statistical errors and of the natural vibration frequencies of the structure is developed. Examples are presented to show the application of this equivalence principle to the determination of average surface errors of several types and proportions of antenna structures.

Wrist AM radio receiver

Abstract: A wrist AM radio receiver is housed in a bracelet-like structure adapted to be removably wrapped about a user's wrist and includes at least a bar antenna, a circuit board with an oscillating element thereon forming a reference oscillation source, and a speaker, and the bar antenna and the circuit board are spaced apart within the bracelet-like structure in the direction in which the latter is wrapped with the speaker also disposed in the bracelet-like structure between the bar antenna and the circuit board so as to minimize the influence on the bar antenna of pulses from the reference oscillation source.

Spatial correlations in adaptive arrays

Abstract: A receiving array antenna can steer its main beam toward any direction by adjusting the complex weight in each element. However it cannot always steer one beam and one null toward two prespecified directions simultaneously with a single set of weights. The ability for an array to steer one beam and one or more nulls simultaneously is determined by five factors: 1) element positions, 2) orientations of elements, 3) antenna patterns of elements, 4) polarizations of signals, and 5) directions of the beams and/or nulls. A coefficient is defined, called spatial correlation, which includes these factors and completely characterizes array beam pointing and nulling. Its application to adaptive arrays is demonstrated. The adaptive array performance is dominated by this coefficient and can be improved by properly choosing the first three factors. Several examples on the selection of element placement in adaptive arrays are presented.

A first-order treatment of aberrations in Cassegrainian and Gregorian antennas

Abstract: The decrease in aperture efficiency caused by small aberrations in a reflector antenna is determined The important case of a Cassegrainian (or Gregorian) antenna with a feed placed in the vicinity of the focal point is treated in detail For this case the various aberration components due to astigmatism, coma, etc, are derived explicitly, their effect on aperture efficiency is shown, and the conditions that optimize performance are given The results are useful for the design of multibeam antennas in ground stations and satellites

Satellite broadcast signal receiving system

Abstract: A satellite broadcast signal receiving system for receiving a plurality of signals of individual transmission bands, which are mutually different in frequency and/or polarization angle, transmitted through an artificial satellite, wherein the signals picked up by an antenna or antennas are first applied to a plurality of outdoor units each corresponding to one transmission band and comprising a convertor for converting the incoming signal into an IF signal, and the converted IF signals are then applied through a change-over switch to a common indoor unit including a demodulator to be demodulated for application to a conventional television set or the like.

Glass antenna system for an automobile

Abstract: A glass antenna system for an automobile comprises a main antenna disposed at an upper part of a glass plate for a rear window of the automobile and a defogging electric heating element disposed below and separate from the main antenna and comprising a plurality of heating strips and a pair of bus bars for supplying electricity to the heating strips. The glass antenna system is characterized in that a lead wire is connected to a predetermined portion of the lower most heating strip among said heating strips and a feeding point for connection to an antenna feeder line is provided on the lead wire, whereby the defogging electric heating element constitutes a subsidiary antenna having a directivity different from the directivity of the main antenna.

Effect of directional elements on the directional response of circular antenna arrays

Abstract: The paper analyses the effect of directional elements on circular antenna arrays fed by phase-mode excitations. These phase modes represent a convenient pattern-synthesis technique for circular arrays as they correspond to Fourier terms of the far-field pattern. A serious limitation on circular arrays, when employing omnidirectional elements, relates to rapid variations in the amplitude of the modes due to changes in array diameter or frequency. The analysis shows how the phase-mode synthesis technique may be extended to take account of directional elements. It also reveals that the use of directional elements can overcome the above limitations and can enable circular arrays to synthesise wide-bandwidth directional patterns. The choice of element patterns of the form 1 + cos o seems particularly suitable. The analysis also shows that the directional elements can prevent the deterioration of pattern shape with elevation angle (angles away from the plane of the circle).

Far-infrared imaging antenna arrays

Abstract: A far-infrared imaging antenna array has been demonstrated for the first time. The array is a line of evaporated silver bow-tie antennas on a fused-quartz substrate with bismuth-microbolometer detectors. The measured optical transfer function shows that the system is diffraction limited. This imaging array should find direct application in fusion plasma diagnostics. If the microbolometers can be replaced by more sensitive diode detectors, the array should also find application in radiometry and radar.

Capacitively coupled machine tool safety system

Abstract: A safety system for a machine tool is characterized by a capacitively coupled electric field generator (transmitter) and a capacitive receptor antenna. An electrical signal is induced in the capacitive receptor antenna by the action of the electric field. The magnitude of the induced signal is monotonically related to the distance between the electric field generator and the capacitive receptor antenna. When the magnitude of the electrical signal exceeds a predetermined threshold, a machine tool safety indicator is developed.

Antenna shape synthesis using characteristic modes

Abstract: An initial effort is described to develop an antenna synthesis procedure by which the shape of a surface of rotation and its current density are deduced from a given far-field radiation pattern which satisfies the conditions of a characteristic mode. Typical results obtained to date are presented to substantiate the method and to illustrate some antenna shapes. A variety of research topics suggested by present efforts are discussed and suggested for future investigation.

Broad-band antenna structure having frequency-independent, low-loss ground plane

Abstract: To optimize antenna bandwidth and efficiency in broad-band antenna elements of the planar, multiarm spiral and log periodic types, a conically shaped ground plane characterized by progressively sized circumferential chokes, is arranged on a common axis with the axial center of the spiral or log periodic elements so that the electrical spacing between the excited regions of the log periodic of spiral elements and the ground plane maintains a constant one-quarter wavelength relationship. The progressively sized circumferential chokes on the ground plane cut off the flow of excessive radial currents along the ground plane surface to achieve an improved mix of excitation and reexcitation modes. In one embodiment, the circumferential chokes on the conical ground plane are partially shunted by shunting strips that electrically or capacitively bridge the choke walls to reestablish limited radial currents along the ground plane for sustaining certain desirable antenna modes. In another disclosed embodiment, the equivalent one-quarter wavelength relationship between the driven spiral or log elements and the reflecting ground plane is maintained in an antenna structure in which the driven elements are disposed on the surface of a dielectrically shaped cone and the ground plane and progressively sized circumferential chokes are arranged in a generally planar array. In still another disclosed embodiment, the circumferential, progressively sized chokes are disposed on the interior reflective surface of a center-fed antenna horn, wherein the array of chokes has the effect of broad-banding the otherwise inherently narrow band characteristics of the horn.

Method and apparatus for intrusion detection

Abstract: CW intrusion detection method and apparatus are shown comprising first and second CW Doppler radar systems which include first and second antennas, respectively. The first antenna is located adjacent ground level for illumination of a protected area adjacent the ground. The second antenna is located directly above the first antenna a spaced distance therefrom, and illuminates the same protected area adjacent the ground. In response to movement of an intruder along the ground in the protected area, first and second Doppler difference frequency signals are obtained from the first and second radar systems. Using the first and second Doppler difference frequency signals, a signal proportional to distance of the moving intruder from the first antenna is generated. Memory elements for storage of combinations of amplitude, range and/or velocity criteria signals are provided and, when the signal proportional to distance and at least one of the first and second Doppler difference frequency signals match the criteria signals, an alarm signal is produced.

Three-element antenna formed of orthogonal loops mounted on a monopole

Abstract: A three-element directional/omnidirectional antenna adapted for use in both transmitting and receiving modes. Crossed loop antennas are mounted on top of a monopole whip antenna and are electrically coupled thereto. Each of the loop antennas consists of an outer larger primary loop and an inner secondary loop joined at its base to the primary loop. Both the primary and secondary loops are interrupted at their top ends opposite the point where they join the monopole antenna. A tuning capacitor is coupled between the two halves of each of the primary loops, while a coaxial antenna feeds the two secondary loops. The coaxial cables feeding the secondary loops pass through a dual ferrite choke disposed within the monopole antenna.

Device for applying a high frequency electromagnetic field to living tissue to promote healing thereof

Abstract: A portable therapy device for attachment to a patient to promote tissue healing by exposure to an r.f. field, comprises an oscillator (5) which energizes an antenna having a transmitting element (1) the natural directive pattern of which is modified by a reflector (8) and a parasitic element (10) such that a major part of the r.f. field emitted by the antenna passes to the patient. In another embodiment the antenna is configured to produce a spatially substantially uniform field strength over the area of the patient being treated. The device subjects the tissue to r.f. power levels which produce no significant tissue heating.

Multi-frequency antenna employing tuned sleeve chokes

Abstract: The invention comprises an antenna capable of effective operation at a number of different frequencies, not necessarily harmonically related, that may be separated in frequency by as little as twenty-five percent. The elements of the antenna are decoupled by loaded coaxial chokes that form part of the active portion of the antenna at the resonant frequency of the chokes. The chokes are loaded with a solid dielectric insert dimensioned so that the inner surface of the shell of the choke and the outer surface of the conductor extending through the choke form a quarter wave shorted transmission line to produce an infinite impedance at the open end of the choke. The chokes may be arranged in series, parallel or series-parallel configurations.

Microstrip-Franklin Antenna

Abstract: Phasing stubs are employed to achieve a cophase current distribution in microstrip rectangular patch arrays. This technique, originally proposed for resonant long wire antennas by Franklin, avoids spurious radiation from half-wavelength connecting transmission lines as used in conventional patch antenna arrays. A slot-radiator model is derived to describe the basic radiation mechanism of the resultant new type of antenna and experimental results for the slot radiation resistance are given. The design of a 13-element resonant array for 12 GHz is presented together with measured radiation patterns.

Microstrip notch antenna

Abstract: A broadband radiating element design is disclosed which provides a smooth, continuous transition from a microstrip feed configuration to a flared notch antenna for transmitting or receiving radio frequency signals.

Tuned small loop antenna and method for designing thereof

Abstract: The invention is directed to a tunable loop antenna design which provides impedance matching between the loop antenna and a feed line despite variations of the resonant frequency fo over a wide range of frequencies. The antenna has a maximum length of one tenth of the wavelength, and comprises a loop conductor and a variable capacitor connected in series with the conductor for providing a resonant circuit. The loop area of the conductor, the circumferential length and equivalent radius thereof are adjusted so that the ratio of the resonant frequency fo of the antenna and the resonant frequency fm, at which the input admittance is a minimum, is within the range: 0.5-fo /fm -3.0.

Antenna arrangement for personal radio transceivers

Abstract: An antenna arrangement for personal radio transceivers in which a main antenna extends from the housing of the transceiver which is excited by a high frequency connector thereof, includes an auxiliary antenna which is coupled to a cold terminal of the connector to form a counterweight for the main antenna. Both the main and auxiliary antennas are resonant and shorter than the quarterwavelength, whereby the housing is placed at a potential minimum and the effects of the close presence of a human body on radiational properties for the arrangement will be reduced.

Antenna having electrically positionable phase center

Abstract: Antenna (50) whose phase center may be electrically moved relative to a main receiving/radiating element. The main receiving element (56) is located in a cavity (54) in a ground plane (52). Spaced around the main receiving element are a number of paracletic elements (58, 60, 62, 64), each of which has at least two switchable reactance states. In one state, there is little coupling between the paracletic element and the main receiving element. In another state, coupling is increased so that the phase center of the antenna shifts towards the paracletic element. A sequencer (100) supplies bias voltages to switching diodes (84, 86) to control the reactance states of the paracletic elements and thus the position of the phase center of the antenna. The antenna may be used as a tracking feed (14) for a directional lens or reflector system (12).