scispace - formally typeset
Search or ask a question

Showing papers on "Antenna (radio) published in 1973"


Journal ArticleDOI
01 Dec 1973
TL;DR: In this paper, the aperture phase and amplitude distributions are sampled by a scanning field probe, and then the measured distributions are transformed to the far field by a plane wave that is created by a feed and large reflector in the immediate vicinity of the test antenna.
Abstract: In many cases, it is impractical or impossible to make antenna pattern measurements on a conventional far-field range; the distance to the radiating far field may be too long, it may be impractical to move the antenna from its operating environment to an antenna range, or the desired amount of pattern data may require too much time on a far-field range. For these and other reasons, it is often desirable or necessary to determine far-field antenna patterns from measurements made in the radiating near-field region; three basic techniques for accomplishing this have proven to be successful. In the first technique, the aperture phase and amplitude distributions are sampled by a scanning field probe, and then the measured distributions are transformed to the far field. In the second technique, a plane wave that is approximately uniform in amplitude is created by a feed and large reflector in the immediate vicinity of the test antenna. And in the third technique, the test antenna is focused within the radiating near-field region, patterns are measured at the reduced range, and then the antenna is refocused to infinity. Each of these techniques is discussed, and the various advantages and limitations of each technique are presented.

232 citations


Journal ArticleDOI
TL;DR: In this paper, the authors developed a method for determining the far field pattern of an antenna from probe compensated near-field measurements over the surface of a right circular cylinder enclosing the antenna.
Abstract: A new method is developed for determining the farfield pattern of an antenna from probe compensated near-field measurements over the surface of a right circular cylinder enclosing the antenna. The method is derived by first expanding both the field radiated by the antenna and the field radiated by the measurement probe, when it is used as a transmitter, into cylindrical wave expansions. The Lorentz reciprocity theorem is then used to solve for the field radiated by the antenna from the probe output voltage. It is shown rigorously that the antenna pattern can be determined independently of the characteristics of the measurement probe provided that certain calibration data are known. A method for determining these data from the measured far field radiated by the probe is described. It is shown that the necessary numerical integration can be performed with the fast Fourier transform algorithm. Experimental results are presented to validate the theory and to demonstrate its practicality from a measurement and computational viewpoint.

226 citations


Journal ArticleDOI
TL;DR: The possibility of analyzing scattering and antenna problems from a singularity expansion point of view is discussed in this article, where a thin-wire scatterer is considered by first determining the locations of the exterior natural resonant frequencies and then constructing the time response of the current on the body, much in the same manner as in classical circuit theory.
Abstract: In this paper, the possibility of analyzing scattering and antenna problems from a singularity expansion point of view is discussed. As an example of the method, a thin-wire scatterer is considered by first determining the locations of the exterior natural resonant frequencies and then constructing the time response of the current on the body, much in the same manner as in classical circuit theory. The numerical techniques used will be presented, and some advantages of the singularity expansion method over the other conventional ways of treating this problem will be mentioned.

205 citations


01 Apr 1973
TL;DR: In this paper, a viscous shock-layer analysis was developed and used to calculate nonequilibrium-flow species distributions in the plasma layer of the RAM vehicle, and the theoretical electron-density results obtained are in good agreement with those measured in flight.
Abstract: A viscous shock-layer analysis was developed and used to calculate nonequilibrium-flow species distributions in the plasma layer of the RAM vehicle. The theoretical electron-density results obtained are in good agreement with those measured in flight. A circular-aperture flush-mounted antenna was used to obtain a comparison between theoretical and experimental antenna admittance in the presence of ionized boundary layers of low collision frequency. The electron-temperature and electron-density distributions in the boundary layer were independently measured. The antenna admittance was measured using a four-probe microwave reflectometer and these measured values were found to be in good agreement with those predicted. Measurements were also performed with another type of circular-aperture antenna and good agreement was obtained between the calculations and the experimental results. A theoretical analysis has been completed which permits calculation of the nonequilibrium, viscous shock-layer flow field for a sphere-cone body. Results are presented for two different bodies at several different altitudes illustrating the influences of bluntness and chemical nonequilibrium on several gas dynamic parameters of interest. Plane-wave transmission coefficients were calculated for an approximate space-shuttle body using a typical trajectory.

175 citations


Journal ArticleDOI
22 Apr 1973
Abstract: For many years, The Geometrical Theory of Difraction (GTD) has been applied to antenna and scattering problems for which the structure is large in terms of wavelength. GTD solutions have mainly been concerned with pattern computations with little information concerning antenna impedance and/or aperture distributions. This is especially true for wire-type antennas. On the other hand, The Method of Moment (MM) has been applied to such problems for which the structure is small in terms of wavelength. This paper presents a technique which can be used to combine these two solutions such that a whole host of new problems can be handled.

165 citations


Patent
07 May 1973
TL;DR: In this article, a compact, rapidly scannable, high frequency directional antenna system provides wide-angle space scanning in one or more dirctions by employing a moving feed for commutating energy flow through a wave guide array illuminating or receiving high frequency energy from a cylindrical or spherical energy collimator.
Abstract: A compact, rapidly scannable, high frequency directional antenna system provides wide-angle space scanning in one or more dirctions by employing a moving feed for commutating energy flow through a wave guide array illuminating or receiving high frequency energy from a cylindrical or spherical energy collimator.

161 citations


Journal ArticleDOI
TL;DR: In this article, the theoretical wave nature of the electromagnetic fields about various types of dipole sources placed on the surface of a low-loss dielectric half-space and two-layer earth was examined.
Abstract: Radio interferometry is a technique for measuring in‐situ electrical properties and for detecting subsurface changes in electrical properties of geologic regions with very low electrical conductivity. Ice‐covered terrestrial regions and the lunar surface are typical environments where this method can be applied. The field strengths about a transmitting antenna placed on the surface of such an environment exhibit interference maxima and minima which are characteristic of the subsurface electrical properties. This paper (Part I) examines the theoretical wave nature of the electromagnetic fields about various types of dipole sources placed on the surface of a low‐loss dielectric half‐space and two‐layer earth. Approximate expressions for the fields have been found using both normal mode analysis and the saddle‐point method of integration. The solutions yield a number of important results for the radio interferometry depth‐sounding method. The half‐space solutions show that the interface modifies the directio...

127 citations


Patent
16 Jul 1973
TL;DR: In this article, a Cassegrainian antenna system has a planar array as the feed and an intermediate reflector is positioned in the near field of the array for substantially collimated illumination with all array elements operating in phase.
Abstract: A Cassegrainian antenna system has a planar array as the feed. An intermediate reflector is positioned in the near field of the array for substantially collimated illumination with all array elements operating in phase. Accordingly, an on-axis main beam is radiated from the main reflector upon illumination by energy from the intermediate reflector. By impressing a linear phase gradient across the array, the main beam is controllably tilted off-axis.

119 citations


Journal ArticleDOI
TL;DR: In this paper, liquid helium cooled InSb hot electron bolometers are used in a balanced mixer configuration as detectors for an imageless microwave receiver at the National Radio Astronomy Observatory (NRAO) 11 m antenna at Kitt Peak, Arizona, for the study of rotational line spectra of interstellar gas molecules.
Abstract: Liquid helium cooled InSb hot electron bolometers are used in a balanced mixer configuration as detectors for an imageless microwave receiver. The system is designed for mounting at the prime focus of the National Radio Astronomy Observatory (NRAO) 11 m antenna at Kitt Peak, Arizona, and is suitable for the study of rotational line spectra of interstellar gas molecules. Currently the operating frequency is in the 90–140 GHz band where the double sideband system noise temperature is 250 K.

101 citations


Patent
17 Apr 1973
TL;DR: In this article, a microstrip antenna structure formed from a unitary conducting surface separated from a ground plane by a dielectric film where the r.f. radiators are fed from an outside edge to selectively produce linearly and/or circularly polarized radiation at a selected resonant frequency(s).
Abstract: A microstrip antenna structure formed from a unitary conducting surface separated from a ground plane by a dielectric film where the r.f. radiator and feedlines form a generally planar arrangement of unitary integrally formed electrical conductors. The r.f. radiators are fed from an outside edge to selectively produce linearly and/or circularly polarized radiation at a selected resonant frequency(s). Necessary fixed phase shifting circuits are integrally formed by printed circuit techniques in the generally planar arrangement of electrical conductors for the circularly polarized radiators. A plurality of such antenna elements are also formed into a phased antenna array to achieve substantially ideal array gain thus producing an extremely high gain antenna with inexpensive printed circuit board construction techniques. Furthermore, appropriately controlled phase shifting networks may be integrally formed within the generally planar array of electrical conductors in combination with switchable diode elements to achieve any desired relative phase shifts between the array elements and thus to steer the array beam in a desired direction.

88 citations


Journal ArticleDOI
TL;DR: In this paper, experiments were described for determining the distributions of current, the driving point impedance, and the electromagnetic fields characteristic of dipole antennas immersed in the sea near the surface.
Abstract: Experiments are described for determining the distributions of current, the driving-point impedance, and the electromagnetic fields characteristic of dipole antennas immersed in the sea near the surface. Measured and theoretical results are compared at two frequencies with good agreement.

Patent
31 Jul 1973
TL;DR: In this article, a linearly polarized mat-strip phased antenna array was proposed, where the antenna array is phased by incorporating in series relationship one or more matstrip loaded line type phase shifters in the distribution network.
Abstract: There is disclosed herein a linearly polarized mat-strip phased antenna array wherein the antenna array is phased by incorporating in series relationship one or more mat-strip loaded line type phase shifters in the mat-strip power division distribution network for the mat-strip dipole elements and/or a combined mat-strip dipole element and phase inverter. Two embodiments are illustrated.

Patent
04 Sep 1973
TL;DR: In this paper, an automatic antenna coupler is described which includes a matching network having adjustable reactive elements, and control for these elements is provided by a system for detecting the real part of the complex impedance presented by the antenna or matching network.
Abstract: An automatic antenna coupler is described which includes a matching network having adjustable reactive elements. Control for these elements is provided by a system for detecting the real part of the complex impedance presented by the antenna or matching network. A logic and control system for adjusting the reactive elements is operated in accordance with the real part detector output so as to provide the desired impedance match.

Journal ArticleDOI
Abstract: Strong cosmic radio sources provide a constant broadband and accurately positioned test transmitter for measurements of large antennas. Some sources have their flux density determined absolutely and can be used to calibrate the antenna gain. This paper presents up-to-date data on the radio sources which are useful for antenna measurements. The measurement of pointing and focusing corrections is discussed. The main part of the paper is concerned with the derivation of major antenna parameters such as aperture and beam efficiency, beam solid angle, sidelobe levels, error pattern characteristics from measurements on radio sources. The effects of a finite angular source size are discussed, and it is shown how measurements on sources of different size increase the information on the derived antenna parameters. The methods to measure very weak sidelobes are treated and the external factors, solar and galactic radiations influence of the earth and atmosphere, which might limit the accuracy of the measurement are described. The paper takes a practical approach to the subject and contains graphs with numerical data.

Patent
26 Jun 1973
TL;DR: In this article, a mismatch protection circuit is proposed to protect power output transistors of a communications transmitter from damaging excessive reflected power, as might occur when the antenna is disconnected or broken, which circuit continuously monitors and compares parameters indicative of forward and reflected power or VSWR and when there is excessive mismatch, instantaneously cuts back the dc power delivered to the transistors to a safe low level, but a level sufficient for continued cutback operation of the protection circuit, when and for so long as the excessive mismatch continues.
Abstract: A mismatch protection circuit to protect power output transistors of a communications transmitter from damaging excessive reflected power, as might occur when the antenna is disconnected or broken, which circuit continuously monitors and compares parameters indicative of forward and reflected power or VSWR and when there is excessive mismatch, instantaneously cuts back the dc power delivered to the output transistors to a safe low level, but a level sufficient for continued cutback operation of the protection circuit, when and for so long as the excessive mismatch continues.

Patent
13 Aug 1973
TL;DR: In this paper, an electronically rotatable antenna consisting of several radially arranged Yagi antennae having a common drive element is proposed, where the reflector and the director elements of each YAG antenna are sequentially rendered operative by biasing suitable diodes short-circuiting them to a ground-plate.
Abstract: This invention relates to an electronically rotatable antenna which includes several radially arranged Yagi antennae having a common drive element. Reflector and director elements of each Yagi antenna are sequentially rendered operative by biasing suitable diodes short-circuiting them to a ground-plate. The radiation pattern is step-by-step rotated. Directivity is increased by short-circuiting other elements belonging to other arrays than the main one, those elements defining generatrices of a parabola having the driver element as a focus and the reflector element as an apex.

Patent
26 Dec 1973
TL;DR: In this paper, a function generator is connected to an airborne phased array radar antenna for steering a beam between high and low positions, and the generator blanks short range target signals.
Abstract: A function generator is connected to an airborne phased array radar antenna for steering a beam between high and low positions. During receiving on the high beam, the generator blanks long range target signals. During the low beam, the generator blanks short range target signals. A receiver is connected to the output of the antenna and a display is connected to the receiver output. By sequentially switching between low and high beams, with the described blanking, short and long range targets are displayed simultaneously, relatively free of ground clutter.

Journal ArticleDOI
TL;DR: The difference in the performance of the two systems was shown to be primarily due to time delay inherent in the remote antenna switching technique.
Abstract: A theoretical and experimental comparison of performance has been made between two types of predetection switching space diversity mobile radio systems. This comparison was made at a frequency of 840 MHz using simulated Rayleigh fading for a vehicle speed of about 80 mi/h. The switch diversity system was a conventional receiver antenna switching technique with two simulated physically separated receiving antennas and a single transmitting antenna. The feedback diversity system used a single receiving antenna with two simulated physically separated transmitting antennas. The transmitting antennas were switched remotely from the receiver. The difference in the performance of the two systems was shown to be primarily due to time delay inherent in the remote antenna switching technique.

Journal ArticleDOI
TL;DR: In this paper, the authors derived the properties of an insulated dipole antenna when the wavenumber of the surrounding infinite, homogeneous, and isotropic medium is large compared with that of the insulation.
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.

Patent
23 Nov 1973
TL;DR: In this article, a monopulse radar tracking system employing four tracking channels, one for each of range, velocity, azimuth and elevation, is described, and the two angle channels are referenced directly to antenna coordinates.
Abstract: A monopulse radar tracking system is disclosed employing four tracking channels, one for each of range, velocity, azimuth and elevation. The two angle channels are referenced directly to antenna coordinates. Each channel is mechanized by a stored program in a digital computer, and the mechanization employs Kalman filtering with gain factors continually optimized for measured signal-to-noise ratios. Angular rate commands for the antennas are obtained by passing pointing error estimates from the angle channels through a compensator for antenna motion and adding line-of-sight rate estimates from the angle filter channels. Cross-coupling between channels is provided, and each channel is aided by outputs from an inertial navigation platform. Preaveraging of discriminants received between computational cycles is provided.

Patent
03 May 1973
TL;DR: In this paper, a stripline slotted balun dipole antenna 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 bifilament antenna and its strip feed.
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.

Patent
26 Jun 1973
TL;DR: In this paper, a passive radio direction finder consists of an array of antennas to sample the phase of incoming wavefronts, a plurality of mixers separately connected to individual antennas, a phase lock loop or bandpass limiter connected between any individual antenna and an input of each mixer to provide a mixer reference signal, a multi-channel analog to digital converter attached to the output of each mixer, and a digital computer programmed to make fast Fourier transform calculations.
Abstract: A passive radio direction finder monitors wavefronts across an aperture, produces a radio-frequency hologram, and numerically reconstructs the hologram. The direction finder consists of an array of antennas to sample the phase of incoming wavefronts, a plurality of mixers separately connected to individual antennas, a phase lock loop or bandpass limiter connected between any individual antenna and an input of each mixer to provide a mixer reference signal, a multi-channel analog to digital converter attached to the output of each mixer, and a digital computer programmed to make fast Fourier transform calculations. In lieu of the plurality of antennas and mixers, a moving probe antenna and single mixer may be used if a sample and hold circuit is added to the phase lock circuit to provide a reference signal.

Patent
14 Nov 1973
TL;DR: In this article, a high Q resonant loop antenna for providing a deactivation field, and a coplanar sensing loop antenna isolated from the sensing circuitry during operation of the deactivation antenna.
Abstract: For use in an electronic security system wherein a resonant tag circuit is sensed to denote an alarm condition, an antenna system which senses the presence of a resonant tag circuit and, upon such sensing, can automatically activate a deactivation field for destruction of the resonant properties of the tag circuit at its sensing frequency and provide an output indication that tag deactivation has been achieved. The antenna system includes a high Q resonant loop antenna for providing a deactivation field, and a coplanar sensing loop antenna isolated from the sensing circuitry during operation of the deactivation antenna.

Journal ArticleDOI
TL;DR: Field measurements of mobile radio signals have shown that signal arrival is concentrated in elevation angles lower than 16°, suggesting 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.
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.

Journal ArticleDOI
TL;DR: In this article, the design procedure of the log-periodic dipole (LPD) antennas is discussed and the results of the calculations carried out by the use of the more recent and accurate methods of the analysis for the arrays of unequal dipoles, are compared with those already available in the literature.
Abstract: The design procedure of the log-periodic dipole (LPD) antennas is discussed. The results of the calculations carried out by the use of the more recent and accurate methods of the analysis for the arrays of unequal dipoles, are compared with those already available in the literature. The calculations refer to the gain of LPD antenna as a function of Z_{0} , the characteristic impedance of the exciting transmission line, of h/a , the ratio between the half-length and the radius of dipoles, of \tau and \sigma , two parameters which describe the geometry of the LPD antenna. The values of gain are lower than those given by earlier calculations. The degradation of the gain is more consistent, when the values either of Z_{0} or h/a are increased with respect to Z_{0} = 100 \Omega and h/a = 125 , which are parameters often used in the literature. The many diagrams included in this paper for different values of \tau, \sigma, Z_{0} , and h/a can be useful in a more accurate design of an LPD antenna. Confirmation of the computer data has been obtained by the tests performed on various scale models and on a full scale antenna.

Journal ArticleDOI
D.C. Cox1
01 Apr 1973
TL;DR: In this article, a delay-Doppler scattering function for multipath propagation at 910 MHz from a vertical antenna 120 m above a street to a mobile vehicle on another street is presented.
Abstract: A delay-Doppler scattering function is presented for multipath propagation at 910 MHz from a vertical antenna 120 m above a street to a mobile vehicle on another street The direct path between the transmitting antenna and the mobile vehicle was blocked by many tall (over 100 m) buildings Major features of the scattering function correspond to gross features of the area

Proceedings ArticleDOI
01 Sep 1973
TL;DR: In this article, the authors proposed a conformai, thin antenna that would neither, disturb the aerodynamic flow, nor would it protrude inwardly to disrupt the mechanical structure.
Abstract: High velocity aircraft, missiles, and rockets require conformai, thin antennas. Ideally, an antenna "paper thin" would best suit the aerodynamic and mechanical engineer. This antenna would neither, disturb the aerodynamic flow, nor would it protrude inwardly to disrupt the mechanical structure.

Patent
16 Apr 1973
TL;DR: In this paper, an attack warning system for alerting ground troops or ships to the possiity of attack by enemy aircraft is presented, which consists of a detection shell at a range of 3 miles covering 360° in azimuth and 60° in elevation.
Abstract: An attack warning system for alerting ground troops or ships to the possiity of attack by enemy aircraft. The system establishes a detection shell at a range of 3 miles covering 360° in azimuth and 60° in elevation. The bearing measurement is obtained by a combination of antenna pattern shape and P-N Code modulation. A pair of oppositely facing receiving antennas and a pair of oppositely facing transmitting antennas located orthogonally with respect to the receiving antennas provide the 360° coverage. The azimuth pattern of each antenna covers 180°. The system provides target bearing information by applying different codes to each of the two opposed transmit antennas and multiply decoding the received signals.

Patent
B Bogner1, D Bowman1
23 Apr 1973
TL;DR: In this article, a circular phased array (CPA) system is described which utilizes a lens feed to simplify the problem of commutating the RF distribution system through 360* of steering of the antenna beam.
Abstract: A circular phased array system is described which utilizes a lens feed to simplify the problem of commutating the RF distribution system through 360* of steering of the antenna beam. The lens feed consists of a circular parallel-plate radial transmission line with a central set of probes and a ring of peripheral probes. The peripheral probes are coupled via switches to an array of radiating elements arranged in a circle. The central set of probes can be energized and phased to produce electromagnetic energy with an amplitude distribution within the parallel-plate line in any given direction. By selective settings of phase and amplitude of the energy coupled to the central set of probes to achieve the proper energy distribution to the peripheral probes and by operating the switches to determine which radiating elements are coupled to the peripheral probes, a desired directive antenna pattern with low side lobes is provided.

Patent
Fruktow G1, Kurland R1
14 Dec 1973
TL;DR: In this article, a lightweight deployable helical antenna having a thin, flat electrically conductive radiator strip helically coiled about an axially extensible and contractable supporting structure and pivotally secured at intervals to the structure in a manner such that the antenna is longitudinally contractable to a collapsed configuration and extendible to a deployed configuration.
Abstract: A lightweight deployable helical antenna having a thin, flat electrically conductive radiator strip helically coiled about an axially extensible and contractable supporting structure and pivotally secured at intervals to the structure in a manner such that the antenna is longitudinally contractable to a collapsed configuration and extendible to a deployed configuration. In the preferred embodiment, the antenna supporting structure is a truss frame structure constructed of tubular, resiliently flexible elastic strain energy deployable beams which deform when the frame structure is contracted to store elastic strain energy for extending the antenna to its deployed configuration.