Showing papers on "Dipole antenna published in 1971"

Amplitude modulation using phased-array antennas

Abstract: An antenna system for producing an amplitude modulated signal at a receiver by properly varying the spatial amplitude distribution of the antenna beam. The antenna beam variation is accomplished by varying the relative phase of a phase-array antenna at the desired modulation rate. A variable DC bias signal is applied to each element of the antenna which is used to steer the beam in angle. An AC signal is also applied to each element which will qppear as AM modulation at a distant receiver.

Antenna spacing requirement for a mobile Radio base-station diversity

Abstract: The minimum required antenna spacing between two base-station antennas in order to take advantage of spatial diversity technique was investigated. The measurements were made for two cases: (i) the incoming radio signal was perpendicular to the axis of two base-station antennas (the broadside case), and (ii) the signal was in-line with the axis of two base-station antennas (the in-line case). The correlation of signals received from two separated antennas at the base station was found to be much higher for the in-line case than for the broadside case with any given antenna spacing. For correlation up to 0.7, from which most of the advantage of two-branch diversity can still be obtained, we found the minimum required antenna spacing is around 70λ–80λ for the in-line case and 15λ–20λ for the broadside case. In order to achieve a correlation always less than 0.7 between two base-station signals regardless of the arrival direction of the incoming signal, a triangular configuration with a three-antenna array used with a three-branch diversity receiver is proposed, requiring less antenna spacing in the array than for a two-antenna setup.

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.

Receiving antenna for miniature radio receiver

Abstract: Receiving antenna for miniature radio receiver formed by conducting U-shaped member having substantially parallel elongated arms which form sides of the housing of the receiver and a connecting portion which forms one end of the housing. When the receiver is in the normal position for use, the arms are positioned vertically with the connecting portion at the top, and the U-shaped member acts as an inductive loop antenna to detect the H-field of the electro-magnetic wave. A reactance network, which is capacitive in the frequency range of interest, is connected to the open ends of the arms. The reactance network can be adjustable to tune the antenna for various frequencies, the antenna having been found suitable for use in the frequency range from 148 to 173 megacycles.

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.

Base-band radiation and reception system

Abstract: A base-band transmitter and receiver antenna system for operation in subnanosecond pulse radio systems of the type detecting the presence or range of near-by reflecting objects utilizes directive, dispersionless, broad band traveling wave transmission line radiator and receiver antenna elements arranged cooperatively to limit the effect of base-band energy directly coupled from the transmitter to the receiver.

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.

Dipole antenna arrangement for radio with separate speaker-microphone assembly

Abstract: A speaker microphone assembly, used with a portable radio unit containing receiving and transmitting equipment for receiving and transmitting radio signals, includes a housing with a helical antenna element mounted to the top wall to form one element of a dipole antenna. A coaxial cable having inner and outer conductors is connected from the portable unit equipment to the speaker microphone housing. The center conductor is connected to the helical antenna and the outer conductor is terminated in the housing at a first point which is ground potential. A second outer conductor surrounds and is insulated from the first outer conductor, and is connected to the first outer conductor at the first point. The second outer conductor extends for a predetermined length along the first outer conductor to form the other element of the dipole antenna.

Tables Of Antenna Characteristics

Abstract: 1. The Complex Wave Number k and the Normalizing Factor ?.- Fig. 1.1 The functions f(p) and g(p) and related quantities.- Fig. 1.2 The functions f(p)/p and g(p)/p.- Table 1.1 The functions f(p), g(p), f(p)/p, and g(p)/p.- 2. Characteristics of Cylindrical Dipoles and Monopoles.- a. The Apparent Admittance.- Fig. 2.1 Cylindrical antennas driven from open-wire and coaxial lines.- Fig. 2.2 Cylindrical monopoles with open, closed flat, and closed hemispherical ends.- b. The Monopole Driven from a Coaxial Line.- Fig. 2.3 Admittance of the tubular monopole.- Table 2.1 Admittance of the tubular monopole.- Table 2.2 Distribution of current along tubular monopoles.- Table 2.3 Admittance of a hemispherically capped monopole.- c. Electrically Thin Antennas.- Fig. 2.4 Apparent susceptance of tubular monopole driven from coaxial line.- Table 2.4 Admittance of thin tubular monopoles.- Table 2.5 Distribution of current along thin tubular monopoles.- Table 2.6 Transmitting and receiving characteristics of thin cylindrical dipoles.- d. Electrically Long Dipoles in Dissipative Media and in Air.- Table 2.7 Normalized admittances ( Y /?) in millimhos of thin dipole antennas in dissipative media.- Table 2.8 Admittances in millimhos of long dipole antennas in air.- Table 2.9 Admittance and effective length of long dipole antennas in air.- Table 2.10 Far field of long dipole antennas in air.- e. Measured Admittances of Monopoles Comparison of Theory with Experiment.- References for Section 2.- Fig. 2.5a Measured and theoretical circular graphs of the admittance of a monopole with a/? = 0.00926.- Fig. 2.5b Measured and theoretical circular graphs of the admittance of a monopole with a/? = 0.0159.- Fig. 2.5c Measured and theoretical circular graphs of the admittance of a monopole with a/? = 0.05.- Fig. 2.6 Measured and theoretical conductance and susceptance of a monopole with h/? = 0.5.- Fig. 2.7 Measured and theoretical susceptance of a monopole with a/? = 0.007022.- Table 2.11 Measured admittance of tubular, flat-topped, and hemispherically capped monopoles driven from coaxial line.- Table 2.12 Measured admittance of hemispherically capped monopoles.- Table 2.13 Admittance of tubular monopoles.- 3. Imperfectly Conducting Dipoles.- References for Section 3.- Fig. 3.1 Distribution of current along imperfectly conducting half-wave dipoles the parameter is ?i = 2?ri/?0.- Fig. 3.2 Distribution of current along imperfectly conducting full-wave dipoles the parameter is ?i = 2?ri/?0.- Fig. 3.3 Admittance Y = G + jB of an imperfectly conducting dipole.- Fig. 3.4 Impedance Z = R + jX of an imperfectly conducting dipole.- Fig. 3.5 Radiating efficiency of imperfectly conducting half-wave and full-wave dipoles as a function of ?i = 2?ri/?0.- Table 3.1 Admittance of resistive antennas.- Table 3.2 Impedance of resistive antennas.- 4. The Circular Loop Antenna.- References for Section 4.- Fig. 4.1 Circular loop antenna.- Fig. 4.2 Distribution of current around circular loops in air.- Fig. 4.3 Distribution of current along circular loops in dissipative media.- Fig. 4.4 Normalized admittance of circular loops in dissipative media.- Table 4.1 Normalized admittance Y/? of loop antennas in dissipative media ? = 10.- Table 4.2 Normalized admittance Y/? of loop antennas in dissipative media ? = 11.- Table 4.3 Normalized admittance Y/? of loop antennas in dissipative media ? = 12.- Table 4.4 Normalized admittance Y/? of loop antennas in dissipative media ? = 15.- Table 4.5 Normalized admittance Y/? of loop antennas in dissipative media ? =17.- Table 4.6 Normalized admittance Y/? of loop antennas in dissipative media ? = 20.- 5. Broadside and Endfire Arrays.- References for Section 5.- Fig. 5.1 Curtain array: seven identical elements.- Fig. 5.2 Horizontal field patterns of 20-element broadside arrays.- Fig. 5.3 Horizontal field patterns of 20-element unilateral endfire arrays h/? = 0.25.- Fig. 5.4 Horizontal field patterns of 20-element unilateral endfire arrays h/? = 0.5.- Table 5.1 Driving-point admittances and impedances of broadside arrays.- Table 5.2 Driving-point admittances and impedances of unilateral endfire arrays.- Table 5.3 Self- and mutual admittances.- Table 5.4 Self- and mutual impedances.- Table 5.5 Radiation patterns of broadside arrays.- Table 5.6 Radiation patterns of unilateral endfire arrays.- 6. The Two-Element Array.- Table 6.1 Driving-point admittances and impedances of two-element broadside arrays.- Table 6.2 Driving-point admittances and impedances of two-element bilateral endfire arrays.- Table 6.3 Two-element arrays: Self- and mutual admittances.- Table 6.4 Two-element arrays: Self- and mutual impedances.

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.

Determination of both polarisation and power gain of antennas by a generalised 3-antenna measurement method

Abstract: A method enabling determination of polarisation and power gain of three unknown antennas, requiring no prior quantitative knowledge of polarisation, is developed. An application of the method using a new near-zone extrapolation technique (introduced by Wacker and Bowman), which permits accurate antenna measurements at reduced distances in spite of proximity effects, is described.

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.

Multi-function antenna coupler

Abstract: The antenna coupling circuit facilitates simultaneous reception and transmission of information carrying radio signals through a common antenna A single filter having a plurality of helical resonator sections forms the harmonic filter of the transmitter, the preselector of the receiver, and a duplexer for connecting both the transmitter and receiver to a single antenna A first plurality of the helical resonator sections are connected between the antenna and the input stage of a receiver which passes the band of frequencies to be received while reflecting the frequencies to be transmitted A second plurality of helical resonator sections are connected between the output of a transmitter and the antenna which passes the frequencies to be transmitted while reflecting the frequencies to be received The coupling between individual helical resonators is arranged to discriminate against frequencies higher than the passband All of the cells of the filter circuit are mechanically connected together to form an integral compact structure

A study of the antenna array configuration of an M-branch diversity combining mobile radio receiver

Abstract: The theoretical analysis in this paper is based on the assumption that the angles of signal arrival on the mobile receiver are uniformly distributed. From the analysis and experimental studies, we find that if the antenna spacing between two adjacent antennas in a space diversity array is greater than 0.5λ the array configuration does not affect the cumulative distribution curves nor the shapes of the level-crossing-rate (LCR) curves, and only slightly affects the signal level at which the maximum LCR occurs. Hence a three-element array with a triangular shape or a four-element array with a rectangular shape can be considered a good arrangement, provided each side (antenna spacing) is greater than 0.5λ. Two slightly better arrangements than those we just mentioned for improving the signal fading are also proposed for three-branch and four-branch diversity signals, respectively.

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.

Bandwidth extension for dipole antennas by conjugate reactance loading

Abstract: Periodically loaded transmission line theory is employed to indicate a loading scheme for broad banding a linear dipole antenna. A conjugate reactance load element (negative inductance) is suggested and a design concept developed. Numerical techniques are used to solve Hallen's integral equation, and it is shown that a broad-band (8:1 frequency range) dipole with broadside radiation and VSWR < 2 can be realized.

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°.

Analysis of multiple-arm conical log-spiral antennas

Abstract: An N -arm log-spiral antenna may be excited in N - 1 orthogonal modes of N -tuple input A rigorous solution to the spiral antenna of more than two arms is obtained by numerical solution of the integral equations Results for a four-arm spiral, including current distribution, half-power beamwidth, beam orientation, and gain and phase centers, are presented The propagation constant of the current waves along each spiral arm is found to be approximately the speed of light An approximate k-\beta diagram is given which may be used to estimate the size of the antenna for each mode of operation

Note on transistor-fed active-array antennas

Abstract: The feed requirements for an active radiating array in which each element is independently excited by a transistor are shown to be less dependent on the elemental mutual coupling effects than in the corresponding passive case. Using a simple transistor equivalent network, it is predicted that as the limit of ideal transistors is approached the input impedance of the active array should exhibit less variation with frequency.

Automatic level measuring and control system

Abstract: A single length of insulated, stranded steel cable extends vertically through a bin or other material container and functions as a radiating antenna for an electrical signal transmitter. The reactance of the antenna, which varies as a function of the level of material in the container adjacent the antenna, is inductively linked to an oscillator circuit in the transmitter. The transmitter''s signal is altered in frequency with changes in the antenna''s reactance is combined with that of a constant frequency reference signal. The frequency of the resulting difference signal is employed to form a remote indication of the material level and to provide control information for automatically maintaining or varying material levels.

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.

Phased array of six log-periodic dipoles

Abstract: A direction finding antenna for accurate direction finding over broad conuous frequency spectrums, independently of polarization, comprising a phased array of six log-periodic dipole antennas with loaded elements.

Magnetic antenna having a block or circuit components therein

Abstract: An antenna for a receiver comprising a magnetic core in the form of a thin layer having a thickness less than 50 microns superposed on a casing of a receiver or on a block of components of the receiver, and a winding wound on said magnetic core and connected electrically to the components in the casing or in the block, the winding serving as the antenna for the receiver. A receiver which comprises said antenna.

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.

Active loop-dipole aerials

Abstract: A theoretical study of the input impedance of active loop-dipole aerials which possess height-reduction properties at resonance is made. This is compared with measurements on an aerial containing a BFY 90 transistor at 200 MHz for which the transistor parameters are available. Reasonable agreement is obtained. The existence of separate power gains and radiation patterns for transmitting and receiving is also established, and a comparison of the theoretical and experimental radiation patterns in the two cases is made. Numerical values of radiation resistance for these aerials are also calculated.