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Showing papers on "Dipole antenna published in 1991"


Journal ArticleDOI
TL;DR: In this paper, the concept of true-time-delay steering for phased array antennas and its advantage over phase shifters in broadband applications are described with particular emphasis on the potential advantages offered by fiber-optic delay lines.
Abstract: The concept of true-time-delay steering for phased array antennas and its advantage over phase shifters in broadband applications are described with particular emphasis on the potential advantages offered by fiber-optic delay lines. The system architecture of the phased array antenna and the design and performance of the fiber-optic time-shifter networks in the antenna are described. The radiation patterns of the phased array antenna at L and X bands are presented. Using semiconductor laser switching to implement the delay times, the absence of beam squint in the antenna pattern and its frequency was switched from L to X band is demonstrated. >

421 citations


Journal ArticleDOI
TL;DR: A novel antenna structure formed by combining the Yagi-Uda array concept and the microstrip radiator technique is discussed, and experimental results demonstrate the performance of this antenna.
Abstract: A novel antenna structure formed by combining the Yagi-Uda array concept and the microstrip radiator technique is discussed. This antenna, called the microstrip Yagi array, has been developed for the mobile satellite (MSAT) system as a low-profile, low-cost, and mechanically steered medium-gain land-vehicle antenna. With the antenna's active patches (driven elements) and parasitic patches (reflector and director elements) located on the same horizontal plane, the main beam of the array can be tilted, by the effect of mutual coupling, in the elevation direction providing optimal coverage for users in the continental United States. Because the parasitic patches are not connected to any of the lossy RF power distributing circuit the antenna is an efficient radiating system. With the complete monopulse beamforming and power distributing circuits etched on a single thin stripline board underneath the microstrip Yagi array, the overall L-band antenna system has achieved a very low profile for vehicle rooftop mounting, as well as a low manufacturing cost. Experimental results demonstrate the performance of this antenna. >

248 citations


Journal ArticleDOI
TL;DR: A new class of wire antennas called meander antennas is introduced as possible elements for size reduction, and an increase in the number of meander sections introduces less size reduction in return for an improved bandwidth.
Abstract: A new class of wire antennas called meander antennas is introduced as possible elements for size reduction. Efficiency is affected only by the ohmic losses in the wire, and cross polarization is negligible. An increase in the number of meander sections introduces less size reduction in return for an improved bandwidth. These antennas can be used to reduce the size of existing wire antennas such as Yagi-Uda antennas and log-periodic dipole arrays. A size reduction in the resonant length typically from 25-40% is obtained. More size reduction is obtained by decreasing the radius of the wire or increasing the separation of the folded arms. >

146 citations


Patent
19 Apr 1991
TL;DR: In this article, the antenna elements are connected in a one-to-one correspondence in both number and form to a lattice of identical, multiport, isotropic, wave-coupling networks physically located under the antenna element array as a backplane of antenna element layer.
Abstract: An array of antenna elements are configured in a lattice-like layer, each element being similarly oriented such that the elements form a two-dimensional antenna aperture that may form a planar or curved surface of a desired shape. The antenna elements are connected in a one-to-one correspondence in both number and form to a lattice of identical, multiport, isotropic, wave-coupling networks physically located under the antenna element array as a backplane of the antenna element layer. Each wave-coupling network or "unit cell" couples signals to and/or from its corresponding antenna element and further functions as a phase delay module in a two-dimensional signal distribution network. This invention can be embodied in a two-dimensional signal distribution network and in a wrap-around, conformal, millimeter-wave, phased array antenna, such as on the nose of a missile. A backplane of densely-packed resonant cavities feeds an outboard-facing layer of resonant slots configured in a rectangular or hexagonal lattice for maximum density. Instead of using a corporate feed network to feed each element, the array can be fed from circumferencial points on the edge of the array farthest from the nose of the missile, with each element being electromagnetically coupled to each of its four or six adjacent elements by either dielectrically-loaded irises with concentric probes or simple irises. By differently tuning the individual cavities, the beam may be directed off-axis azimuthally in any forward direction.

140 citations


Patent
05 Aug 1991
TL;DR: An antenna for transmitting electromagnetic energy for deactivating a resonant tag circuit of an electronic article surveillance tag without regard to the orientation of the tag while minimizing far field radiation was proposed in this paper.
Abstract: An antenna for transmitting electromagnetic energy for deactivating a resonant tag circuit of an electronic article surveillance tag without regard to the orientation of the tag while minimizing far field radiation. The antenna includes a substantially planar dielectric substrate having a first side and a second side. The antenna also includes four substantially coplanar conductive loops on the first side of the dielectric substrate. The conductive loops are arranged in a two-by-two sequence and connected in series such that current flowing through any one of the conductive loops is out of phase with respect to current flowing in each adjacent conductive loop. The antenna also includes a ground trace on the second side of the substrate.

138 citations


Patent
19 Jul 1991
TL;DR: In this paper, a multichannel, multipoint distribution services (MMDS) dipole antenna for receiving multiple channels in the S-band frequency range of 2000 and 3000 MHz is formed from a printed circuit board which is directly connected to a coaxial cable.
Abstract: A multichannel, multipoint distribution services (MMDS) dipole antenna for receiving multiple channels in the S-band frequency range of 2000 and 3000 MHz is formed from a printed circuit board which is directly connected to a coaxial cable. On the printed circuit board are etched two stacked dipoles. Each of the dipoles has a first one-half element etched on the first side of the printed circuit board and the second one-half element etched on the second side of the printed circuit board. The first and second dipoles are oriented to be in phase with each other and are separated from each other at a wavelength spacing between 0.25 lambda and 0.40 lambda. The antenna of the present invention further uses a phase combining circuit and an impedance matching circuit etched on the printed circuit board for combining in phase the polarized signals, for canceling the non-polarized signals at 0° and 180°, from the two stacked dipoles and for matching the impedance from the two dipoles to the impedance of the coaxial cable.

133 citations


Patent
16 May 1991
TL;DR: A linear conformal array antenna consisting of double-ridged waveguide elements which are all tapered in the E-plane or the H-plane is proposed in this paper.
Abstract: A linear conformal array antenna consisting of double-ridged waveguide elements which are all tapered in the E-plane or the H-plane. The array of waveguide elements is fed by a Gent lens whose amplitude and phase characteristics can be adjusted to cause the waveguide element array to produce a desired radiation pattern. The linear array antenna, which has been tapered in the E-plane, can be operated to scan an electromagnetic endfire beam in one predetermined direction with a maximum scan loss of 3 dB. The array of waveguide elements can be substantially conformal with the fuselage of an airborne craft carrying the linear array antenna, thereby reducing aerodynamic drag and radar cross section. The linear array antenna has a bandwidth that is greater than an octave wide.

129 citations


Patent
28 Feb 1991
TL;DR: In this paper, a directional microstrip antenna is designed to provide end-fire beam directivity without requiring power dividers or phase shifters, but the phase shift between signals applied to feed points for circularly polarized signals must be greater than the conventionally required 90° and depends upon the antenna configuration.
Abstract: A directional microstrip antenna includes a driven patch surrounded by an isolated reflector and one or more coplanar directors, all separated from a groundplane on the order of 0.1 wavelength or less to provide endfire beam directivity without requiring power dividers or phase shifters. The antenna may be driven at a feed point a distance from the center of the driven patch in accordance with conventional microstrip antenna design practices for H-plane coupled or horizontally polarized signals. The feed point for E-plane coupled or vertically polarized signals is at a greater distance from the center than the first distance. This feed point is also used for one of the feed signals for circularly polarized signals. The phase shift between signals applied to feed points for circularly polarized signals must be greater than the conventionally required 90° and depends upon the antenna configuration.

127 citations


Journal ArticleDOI
TL;DR: In this paper, an improved interstitial microwave antenna design was investigated in static phantom experiments at 915 MHz and different insertion depths, and the presented dipole microwave antenna showed heating patterns which are concentrated on the dipole irrespective of the insertion depth.
Abstract: An improved interstitial microwave antenna design was investigated in static phantom experiments at 915 MHz and different insertion depths. Compared with conventional interstitial antennas, the presented dipole microwave antenna shows heating patterns which are concentrated on the dipole irrespective of the insertion depth. By analogy to interstitial radiotherapy, the microwave antenna allows a high concentration of energy in the target volume with as little damage as possible to the healthy surrounding tissue. The undesired heating of healthy tissue along the feeding line observed with conventional interstitial antennas is avoided. A lambda /4 sleeve on the feeding line (which does not radiate microwave energy itself to the surrounding tissue) transforms an open end, i.e. a high impedance at the generator end of the dipole antenna. The current flowing back along the outside of the outer conductor of the feeding line in the direction of the generator is zero at this point. Both dipole sections have the same terminating impedance. Since the lambda /4 sleeve is mounted outside the antenna, its mechanical length is not restricted by the mechanical length of the antenna. It can be charged with dielectric materials of low dielectricity constants. >

113 citations


Journal ArticleDOI
TL;DR: In this paper, an aperture-coupled microstrip stacked patch antenna with the goal of obtaining wide bandwidth, low cross-polarization, and weak parasitic radiation from the feeding aperture for applications in printed phased array antennas was studied.
Abstract: An aperture-coupled microstrip stacked patch antenna is studied with the goal of obtaining wide bandwidth, low cross-polarization, and weak parasitic radiation from the feeding aperture for applications in printed phased array antennas. Recently, it has shown that the poor bandwidth of this type of antenna can be increased by coupling the resonant patch to the slot near its resonance. In this case, although the bandwidth is increased drastically, this technique induces a quite high back radiation level, due to the proximity of the resonance of the slot that radiates on both sides of the ground plane. To alleviate this problem, stacked patches were used to achieve the bandwidth. In this case, the resonance of the slot is chosen to be as far as possible from the operating band of the antenna so that its radiation level will be small. The comparison of the calculated and measured impedance loci of C band antenna shows good agreement. >

89 citations


Patent
09 May 1991
TL;DR: In this article, a branching filter is proposed to suppress mutual interference between signals transmitted to and from the communication device, which converts an antenna impedance with respect to a signal in a lower frequency, and reduces loss resulting from a capacitive antenna impedance.
Abstract: A branching filter, which is operatively connected between an antenna and a communication device which utilizes different frequency bands, suppresses a mutual interference between signals transmitted to and from the communication device. An antenna circuit, which is operatively connected between the antenna, or a branching filter, and the communication device, converts an impedance with respect to a signal in a frequency band having a lower frequency, and reduces loss resulting from a capacitive antenna impedance.

Journal ArticleDOI
TL;DR: A survey of possible applications of high-temperature superconductors (HTSs) to antennas and antenna feed networks is presented in this paper, where the frequency range considered is 1 MHz for 100 GHz.
Abstract: A survey of possible applications of high-temperature superconductors (HTSs) to antennas and antenna feed networks is presented The frequency range considered is 1 MHz for 100 GHz Three antenna application areas seem appropriate for HTS material: electrically small antennas and their matching networks; feed and matching networks for compact arrays with enhanced directive gain (superdirective arrays); and feed networks for millimeter-wave arrays Preliminary experimental results are presented on YBaCuO and TlBaCaCuO 500 MHz half-loop antennas that show an increase in radiation efficiency (compared with a copper antenna at the same temperature) by a factor of 5 for the HTS antennas >


Journal ArticleDOI
TL;DR: In this article, the far-field pattern and input impedance of a dipole-fed horn antenna in a ground plane are calculated using full-wave analysis, based on the numerical evaluation of the pertinent Green's function for the horn structure and the application of the method of moments.
Abstract: The far-field pattern and input impedance of a dipole-fed horn antenna in a ground plane are calculated using full-wave analysis. The solution is based on the numerical evaluation of the pertinent Green's function for the horn structure and the application of the method of moments. The convergence characteristics of the full-wave analysis method are investigated, along the the resonant properties of the strip-dipole and the corresponding behavior of the far-field patterns. >

Patent
02 May 1991
TL;DR: A sea surface antenna comprises a cylindrical tube of metallic material 13 on a dielectric former, coupled at its midpoint to a coaxial feed, bridged by two groups of capacitances each group being distributed along a respective half of the slot as mentioned in this paper.
Abstract: A sea surface antenna comprises a cylindrical tube of metallic material 13 on a dielectric former. The tube has a longitudinal slot shorted at each end and coupled at its midpoint to a coaxial feed. The slot is bridged by two groups of capacitances each group being distributed along a respective half of the slot. The length of the antenna is less than 0.25 λ and the diameter of the antenna is less than 0.02 λ, where λ is the free space wavelength at the operating frequency. The antenna is dimensioned so as to operate in an evanescent mode at a resonant frequency less than the cut-off frequency.

Patent
Nabeel A. Riza1
24 Apr 1991
TL;DR: In this article, a phase array antenna system with free space delay units and associated spatial light modulators is described, where the same optical architecture is used to process electromagnetic signals detected by the antenna array to produce an output signal for display or processing which corresponds to the radiation detected at the selected beam angle.
Abstract: A phased array antenna system has optical architecture comprising free space delay units and associated spatial light modulators compatible for operation with temporally incoherent or coherent laser light to produce signals having selected time delays to actuate antenna elements of an antenna array to transmit electromagnetic radiation at a selected beam angle from the phase array. The same optical architecture is used to process electromagnetic signals detected by the antenna array to produce an output signal for display or processing which corresponds to the radiation detected at the selected beam angle.

Journal ArticleDOI
D.K. Cheng1
TL;DR: In this paper, the authors present a personal account of the search for a design procedure for Yagi-Uda antenna arrays yielding a maximum gain, or directivity if element losses are neglected.
Abstract: The author presents a personal account of the search for a design procedure for Yagi-Uda antenna arrays yielding a maximum gain, or directivity if element losses are neglected. Results on current distributions in the array are briefly reviewed. The analytical approach used to achieve gain optimization by means spacing and length perturbations is sketched. By using both spacing and length perturbations, it was possible to find the optimized array analytically in a systematic way, some examples having gain increases of nearly 80%. The effects of finite dipole radius and mutual coupling were included in the theoretical treatment. >

Patent
07 Feb 1991
TL;DR: In this paper, the variable reactance component of the antenna is adjusted until the ratio between the transmitted and reflected power on the feedline indicates that the standing wave ratio on the ground wire is at a minimum, whereupon the antenna will be tuned.
Abstract: In an automatic tuning system for an antenna having a single variable reactance element, the power transmitted to the antenna and the power reflected from the antenna on the feedline are sensed. The variable reactance component of the antenna is adjusted until the ratio between the transmitted and reflected power on the feedline indicates that the standing wave ratio on the feedline is at a minimum, whereupon the antenna will be tuned. The adjustment of the variable reactance component is by a stepping motor controlled by a microprocessor, which is programmed to make calculations to determine when the standing wave ratio reaches a minimum.

Patent
14 Jun 1991
TL;DR: In this paper, the authors describe a high voltage, very short pulse, microwave radiating source using low-cost components, and capable of operating at high pulse repetition frequencies (prf).
Abstract: This invention describes a high voltage, very short pulse, microwave radiating source using low-cost components, and capable of operating at high pulse repetition frequencies (prf). The source is activated by an ordinary video trigger commensurate with driving TTL logic. A trigger will cause a chain of N (where N may be 12 or greater) avalanche transistors connected in a Marx generator configuration to threshold resulting in a 1,200 volt or greater baseband pulse having a rise time of less than 100 ps and a duration of about 3 ns driving the input port of a dipole antenna. The dipole is excited by a balun. This invention achieves very short pulse duration broadband microwave radiation at pulse repetition frequencies as high as 30 kHz or greater.

15 Apr 1991
TL;DR: In this paper, the authors describe a successful cross-field antenna which is only 1.6% of a wavelength high, and is in daily service at 60 kW for AM broadcasting.
Abstract: Describes a successful MF antenna which is only 1.6% of a wavelength high, and is in daily service at 60 kW for AM broadcasting. Poynting (1884) showed that wherever electrical energy is moving it flows as a field disturbance in the volume surrounding the conductors. The construction details of the crossed-field antenna are included together with the results of impedance, bandwidth, and field strength measurements. >

Patent
28 Jan 1991
TL;DR: In this paper, the antenna system includes a complementary "bowtie" dipole-slot antenna, the antenna having symmetrical halves about a plane of symmetry, and the two halves of the antenna are slanted at the planes of symmetry such that the total included angle between the halves is between 70 degrees and 120 degrees.
Abstract: The antenna system includes a complementary "bowtie" dipole-slot antenna, the antenna having symmetrical halves about a plane of symmetry. The two halves of the antenna are slanted at the plane of symmetry such that the total included angle between the halves is between 70 degrees and 120 degrees. A ground plane is positioned between the halves of the antenna extending through the plane of symmetry. A circuit is included for independently exciting the halves of the antenna. In a second embodiment the ground plane incorporates a pair of notch antennas. Thus, both vertical and horizontal polarization can be achieved independent of each other.

Journal ArticleDOI
TL;DR: In this paper, a numerical approach to line or wire antennas printed on dielectric materials is presented, where the current on the line is expanded by piecewise sinusoidal functions.

Patent
Erkki Juhani Kuisma1
07 Jan 1991
TL;DR: In this article, a signal combining circuit is proposed to switch between two or more antennae without substantial alterations in the mobile telephone itself, without substantial modifications in the actual mobile telephone.
Abstract: The invention relates to a circuitry by means of which it is possible to switch to a mobile telephone that antenna out of two or more antennae which has the best signal, without substantial alterations in the mobile telephone itself. According to the invention, the antennae (A, B), the antenna selection switch (2) and the peripheral circuits (5, 6) connected to it constitute an integrated part which is separate from the actual mobile telephone (1) but can be coupled to it by means of an antenna cable (3), and the antenna cable (3) is coupled to the radio part of the mobile telephone (1) by mediation of a signal combining circuit (4) which transfers to the antenna cable (3) the supply voltage (V) and the antenna selection switch (2) control pulse, and transfers and selects the RF signal.

Patent
15 Aug 1991
TL;DR: In this article, a pane antenna installed in a heated window pane of a motor vehicle to receive frequencies above the high frequency range is described, which includes at least one wire-shaped first antenna conductor extending across parallel heating conductors of a heating field.
Abstract: Disclosed is a pane antenna installed in a heated window pane of a motor vehicle to receive frequencies above the high frequency range. The antenna includes at least one wire-shaped first antenna conductor extending across parallel heating conductors of a heating field. The crossing points of the first antenna conductor with heating conductors are preferably in galvanic contact to create a capacitive antenna region along the first antenna conductor. The capacitive antenna region is coupled via a second antenna conductor extending also perpendicularly to the heating conductors, to an antenna terminal arranged on the window pane in proximity to a rim. The window pane is surrounded by a conductive frame and a grounding point is created on the frame opposite the antenna terminal.

Patent
Takashi Oda1
07 Aug 1991
TL;DR: In this article, an antenna structure comprises a loop antenna electrically connected to a high-frequency circuit of a portable radio device, and a supplemental antenna including a coil spring which is used for fixing a dry battery powering the portable radio devices.
Abstract: An antenna structure comprises a loop antenna electrically connected to a high-frequency circuit of a portable radio device. The antenna structure also comprises a supplemental antenna including a coil spring which is used for fixing a dry battery powering the portable radio device, and a negative cylindrical conductor of the dry battery which conductor is electrically connected with the coil spring. The coil spring is placed to be inductively coupled to the loop antenna. The longitudinal axis of the dry battery is substantially perpendicular to a plane including the loop antenna. Thus, deterioration in signal reception sensitivity due to the directivity of the loop antenna can be compensated by the supplemental antenna.

Journal ArticleDOI
TL;DR: In vivo temperature studies were also used to evaluate antenna performance in large and small canine brain tissues and specific absorption rate (SAR) was measured in a brain/skull phantom and isoSAR contours were plotted.
Abstract: An experimental canine brain model was developed to assess the effects of hyperthermia for a range of time and temperature endpoints, delivered within a specified distance of an interstitial microwave antenna in normal brain. The target temperature location was defined radially at 5.0 or 7.5 mm from the microwave source at the longitudinal location of maximum heating along the antenna in the left cerebral cortex. Temperatures were measured with fiberoptic probes in a coronal plane at this location in an orthogonal catheter at 1.0 mm intervals. Six antennas were evaluated, including dipole, modified dipole, and four shorted helical antennas with coil lengths from 0.5 to 3.9 cm. Antenna performance evaluated in tissue equivalent phantom by adjusting frequency at a fixed insertion depth of 7.8 cm or adjusting insertion depth at 915 MHz showed dipoles to be much more sensitive to insertion depth and frequency change than helical antennas. Specific absorption rate (SAR) was measured in a brain/skull phantom and isoSAR contours were plotted. In vivo temperature studies were also used to evaluate antenna performance in large and small canine brain tissues. A helical antenna with a 2.0 cm coil length driven at 915 MHz was chosen for the beagle experiments because of tip heating characteristics, well-localized heating along the coil length, and heating pattern appropriate to the smaller beagle cranial vault. Verification of lesion dimensions in 3-D D was obtained by orthogonal MRI scans and histology to document the desired heat effect, which was to obtain an imagable lesion with well-defined blood-brain-barrier breakdown and necrotic zones. The desired lesion size was between 1.5 to 2.5 cm diameter radially, in the coronal plane with the greatest diameter.

Journal ArticleDOI
TL;DR: In this paper, the phase velocity mismatch due to material dispersion in traveling-wave LiNbO/sub 3/ optical waveguide modulators can be greatly reduced by breaking the modulation transmission line into short segments and connecting each segment to its own surface dipole antenna.
Abstract: A new technique of phase velocity matching in electrooptic modulators was demonstrated. The results show that the phase velocity mismatch due to material dispersion in traveling-wave LiNbO/sub 3/ optical waveguide modulators can be greatly reduced by breaking the modulation transmission line into short segments and connecting each segment to its own surface dipole antenna. The array of antennas is then illuminated by the modulation signal from below at the proper angle to produce a delay from antenna to antenna that matches the optical waveguide's delay. A phase modulator 25 mm in length with five antennas and five transmission line segments was operated from 4.6 to 13 GHz with a maximum phase modulation sensitivity of over 100 degrees /W/sup 1/2/. >

Journal ArticleDOI
TL;DR: In this article, a 2 x 2 dual-polarized microstrip array antenna with high isolation between the two input ports and low crosspolarization level has been developed.
Abstract: A 2 x 2 dual-polarized microstrip array antenna with high isolation between the two input ports and low cross-polarization level has been developed. The technical background for this achievement and antenna performance results are presented.

Patent
28 Oct 1991
TL;DR: In this article, a controllable reactive element is coupled to the antenna and has a variable reactance for tuning the antenna in a resonant circuit to the frequency of a desired signal in a predetermined frequency range.
Abstract: A tunable antenna system operates over a predetermined frequency range with an antenna having a length and width each significantly less than a quarter wavelength within the predetermined frequency range. A controllable reactive element is coupled to the antenna and has a variable reactance for tuning the antenna in a resonant circuit to the frequency of a desired signal in the predetermined frequency range. An antenna-tuning circuit is responsive to the frequency to which the antenna is tuned for providing an antenna-tuning signal to the controllable reactive element to control the reactance of the controllable reactive element so that the antenna remains tuned to the desired signal. The antenna tuning signal includes a dither component of dither frequency for varying the tuning of the antenna around the desired signal. The antenna tuning circuit includes a level detector for providing a level signal representative of a signal transduced by the antenna. The level signal includes a second harmonic component of frequency twice the dither frequency. A second harmonic detector responds to the second harmonic component to provide a dither amplitude control signal that reduces the amplitude of the dither signal with increasing amplitude of the second harmonic component.

Patent
10 Dec 1991
TL;DR: In this paper, a high-isolation antenna system with collocated antennas and cancellation of intercoupled signals is proposed, where the antennas are mounted atop a mast with a receive antenna comprising a multi-element array of vertical dipoles supported on the same mast below the transmit antenna.
Abstract: The need to widely separate antennas (e.g., transmit and receive antennas) for VHF radio and other applications is avoided by high-isolation antenna systems with collocated antennas and cancellation of intercoupled signals. A transmit antenna in the form of a vertical dipole can be mounted atop a mast with a receive antenna comprising a multi-element array of vertical dipoles supported on the same mast below the transmit antenna. Opposing pairs of the dipole receiving elements are located in 180° positions on opposite sides of the mast so as to be symmetrically located in the omnidirectional antenna pattern of the transmit antenna. Resulting intercoupling to the receive dipoles is equal and in-phase and is cancelled out by the antiphase combining of signals from the dipoles of each pair of the receive dipoles. Reciprocally, cancellation of coupled signals is achieved with reversal of the receive and transmit functions of the respective collocated antennas. Dipole and monopole high-isolation antenna systems can also be configured on yardarms and ground planes.