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Showing papers on "Antenna (radio) published in 1987"


Journal ArticleDOI
TL;DR: The mutual resistance condition offers a powerful design tool, and examples of new mobile diversity antennas are discussed along with some existing designs.
Abstract: The conditions for antenna diversity action are investigated. In terms of the fields, a condition is shown to be that the incident field and the far field of the diversity antenna should obey (or nearly obey) an orthogonality relationship. The role of mutual coupling is central, and it is different from that in a conventional array antenna. In terms of antenna parameters, a sufficient condition for diversity action for a certain class of high gain antennas at the mobile, which approximates most practical mobile antennas, is shown to be zero (or low) mutual resistance between elements. This is not the case at the base station, where the condition is necessary only. The mutual resistance condition offers a powerful design tool, and examples of new mobile diversity antennas are discussed along with some existing designs.

1,423 citations


Journal ArticleDOI
TL;DR: In this article, the authors present the results of indoor radio propagation measurements of two signal distribution approaches that improve the picture dramatically and show that, with either approach, the signal attenuation can be reduced by as much as a few tens of decibels and the rms delay spread becomes limited to 20 to 50 us, even in large buildings.
Abstract: The idea of implementing an indoor radio communications system serving an entire building from a single central antenna appears to be an attractive proposition. However, based on various indoor propagation measurements of the signal attenuation and the multipath delay spread, such a centralized approach appears to be limited to small buildings and to narrow-band FDMA-type systems with limited reliability and flexibility. In this paper, we present the results of indoor radio propagation measurements of two signal distribution approaches that improve the picture dramatically. In the first, the building is divided into many small cells, each served from an antenna located in its own center, and with adjacent cells operating in different frequency bands. In the second approach, the building is divided into one or more large cells, each served from a distributed antenna system or a "leaky feeder" that winds its way through the hallways. This approach eliminates the frequency cell handoff problem that is bound to exist in the first approach, while still preserving the dramatic reductions in multipath delay spread and signal attenuation compared to a centralized system. For example, the measurements show that, with either approach, the signal attenuation can be reduced by as much as a few tens of decibels and the rms delay spread becomes limited to 20 to 50 us, even in large buildings. This can make possible the implementation of sophisticated broad-band TDMA-type systems that are flexible, robust, and virtually building-independent.

568 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of anisotropy on the resonant frequency and surface wave excitation of the antenna was considered, and the radar cross section (RCS) was calculated.
Abstract: The problem of a rectangular microstrip antenna printed on a uniaxially anisotropic substrate is treated. The effect of anisotropy on the resonant frequency and surface wave excitation of the antenna is considered, and the radar cross section (RCS) of the antenna is calculated. The RCS calculation includes the effect of the load impedance (antenna mode scattering). Results for the resonant frequency of a patch on a uniaxial substrate are compared with measurements, and the RCS of a patch on an isotropic substrate is compared with measurements. The derivation of the uniaxial Green's function in spectral form, the associated moment method analysis for the input impedance and scattering of the microstrip patch, and the expressions for the far-zone fields of a source on a uniaxial substrate are presented.

367 citations


Journal ArticleDOI
TL;DR: In this article, the authors used reciprocity and a transmission line model to determine the radiation properties of printed circuit antennas (PCA's) in a multilayered material configuration.
Abstract: Reciprocity and a transmission line model are used to determine the radiation properties of printed circuit antennas (PCA's) in a multilayered material configuration. It is demonstrated that extremely high directive gain may result at any scan angle, with practical materials, if the thickness of the substrate and multiple superstrate layers is chosen properly. This model is also used to analyze the radiation characteristics of printed circuit antennas in inhomogeneous substrates.

326 citations


Journal ArticleDOI
TL;DR: In this article, the characteristics of a two-layer electromagnetically coupled rectangular patch antenna were investigated for s between 0.31λ0 and 0.37λ0, and the variations of pattern shape, 3 dB beamwidth and impedance bandwidth with spacing s between the two layers were studied.
Abstract: Experimental results on the characteristics of a two-layer electromagnetically coupled rectangular patch antenna are presented. The variations of pattern shape, 3 dB beamwidth and impedance bandwidth with spacing s between the two layers are studied for s between 0 and 0.37λ0. A relatively high-gain region is found for s between 0.31λ0 and 0.37λ0.

325 citations


Journal ArticleDOI
TL;DR: In this article, a microstrip feedline on a substrate proximity-coupled to a rectangular microstrip patch on a covering superstrate is constructed, and a small open-circuit tuning stub is connected in shunt with the feed line.
Abstract: The letter presents experimental results for a proximity-coupled microstrip patch antenna capable of 13% bandwidth. The impedance match (VSWR ≤ 2), copolarised radiation patterns and crosspolarised radiation were measured over this bandwidth to confirm operation. The construction is quite simple, consisting of a microstrip feedline on a substrate proximity-coupled to a rectangular microstrip patch on a covering superstrate; a small open-circuit tuning stub is connected in shunt with the feed line.

301 citations


Patent
05 May 1987
TL;DR: A catheter for insertion into a body cavity, comprising a tubular shaft formed with a passageway extending longitudinally there through closed at one end and open at the opposite end, is described in this article.
Abstract: A catheter for insertion into a body cavity, comprises a tubular shaft formed with a passageway extending longitudinally therethrough closed at one end and open at the opposite end and a probe removably received within the passageway through its open end The probe includes a temperature sensor for sensing the heat produced by a heating applicator applied to an adjacent area of the body The heating applicator includes a microwave antenna producing an electromagnetic field for heating the body tissue adjacent to the body cavity, and the sensor including an electromagnetic field detector for detecting the peak of the electromagnetic field produced by the applicator antenna

253 citations


Journal ArticleDOI
TL;DR: The pattern averaging gain (PAG) method to estimate the average gain of mobile antennas in a multipath propagation environment is proposed and the antenna configuration with the PIFA element mounted on the lateral side of the radio case is found to be most suitable for portable radio units.
Abstract: The pattern averaging gain (PAG) method to estimate the average gain of mobile antennas in a multipath propagation environment is proposed. By using this method and a wire-grid model, the radiation characteristics of the planar inverted F antenna (PIFA) mounted on a portable radio case is analyzed. In particular, the variation of the antenna gain with the radio case dimensions and inclination angle of the radio case during operation is clarified. Also, the effect on antenna patterns of the operator holding the portable radio is experimentally investigated. Based on this analysis, the antenna configuration with the PIFA element mounted on the lateral side of the radio case is found to be most suitable for portable radio units. In addition, an appropriate selection of the radio case dimensions is found to result in further improvements in the antenna bandwidth.

239 citations


Journal ArticleDOI
TL;DR: In this paper, a two-probe feed was used to overcome the radiation pattern distortion, high crosspolarization and low efficiency due both to higher-order modes and surface-wave generation.
Abstract: In thick microstrip patches, probe inductance prevents matching of the patch impedance to the input connector. The probe inductance can be tuned out with a capacitive gap. To maintain simplified construction the gap is here etched on the patch surface. Bandwidths equal to or greater than that theoretically predicted are realised. Use of a single probe-compensated feed results in radiation pattern distortion, high crosspolarisation and low efficiency due both to higher-order modes and surface-wave generation. Two-probe feeding is used here to overcome these problems and to give a wide-band antenna with good radiation pattern control and high efficiency.

216 citations


Journal ArticleDOI
TL;DR: In this paper, a printed circuit antenna element is coupled to a pair of microstriplines on another substrate via two orthogonal, rectangular apertures in a common ground plane.
Abstract: A new method for radiating dual or circular polarisation with a printed circuit antenna element is described. A square microstrip patch on one substrate is coupled to a pair of microstriplines on another substrate via two orthogonal, rectangular apertures in a common ground plane. Quadrature excitation of the system results in circularly polarised radiation.

209 citations


Book
05 Jun 1987
TL;DR: The evolution and uses of Passive Direction Finding DF Receiver Theory and Antenna Elements for Microwave Passive Direction finding DF Receiver Configurations are studied.
Abstract: Evolution and Uses of Passive Direction Finding DF Receiver Theory Antenna Elements for Microwave Passive Direction Finding DF Receiver Configurations DF Antenna Arrays Interferometer DF Techniques Methods for Signal Detection Probability of Detection Accuracy of DF Systems Signal Processing and Display Methods Future Trends Index.

Patent
25 Feb 1987
TL;DR: In this paper, the authors present a "tethered remote" surveillance system that uses a command and control transmitter/receiver to activate selectively a number of audio and video sensors.
Abstract: The present invention is a "tethered remote" surveillance system that uses a command and control transmitter/receiver to activate selectively a number of audio and video sensors. The system generally comprises a plurality of remote sensors which are selectively controllable through a plurality of remote integral modules to which the sensors are connected. Each integral module is a physically compact unit which includes an antenna for transmitting the outputs of the plural sensors to a command and control station and an antenna for receiving encrypted command signals from the command station. The command station includes an encrypter for generating the command signals, an antenna for transmitting the signals to the integral modules and an antenna for receiving the signals transmitted by the integral modules, as well as devices for displaying and recording the signals received.

Journal ArticleDOI
TL;DR: In this paper, the radiation pattern of a bow-tie antenna of finite length and infinitesimal thickness, placed on a lossless dielectric substrate, is analyzed based on a representation of the current density on the metal surface of the antenna as a sum of an imposed quasistatic term and a set of current modes with unknown amplitudes.
Abstract: A new formulation is discussed for the rigorous calculation of the radiation pattern of a bow-tie antenna of finite length and infinitesimal thickness, placed on a lossless dielectric substrate. The analysis is based on a representation of the current density on the metal surface of the antenna as a sum of an imposed (quasistatic) term and a set of current modes with unknown amplitudes. Free-space fields that are expressed in terms of continuous spectra of symmetrized plane waves are matched to the current modes using the method of moments. The resulting set of equations are solved for the unknown current amplitudes. The calculations show that for increasing bow length the antenna impedance spirals rapidly to a value predicted by transmission line theory. The theory also shows that the E -plane pattern of a two wavelength, 60\deg bow-tie antenna is dominated by low-loss current modes propagating at the dielectric wavenumber. As the bow tie narrows, the loss of the modes increases, and the dominant wavenumber tends to the quasistatic value. Pattern measurements made at 94 GHz are shown to agree well with theoretical predictions. Measurements for a long-wire antenna, a linear array of bow-tie elements, and a log-periodic antenna are also presented.

Patent
06 Apr 1987
TL;DR: In this article, an apparatus and method for measuring formation parameters by transmitting and receiving electromagnetic signals by antennas disposed in recesses in a tubular housing member and including apparatus for reducing the coupling of electrical noise into the system resulting from conducting elements located adjacent the recesses and housing.
Abstract: An apparatus and method for measuring formation parameters by transmitting and receiving electromagnetic signals by antennas disposed in recesses in a tubular housing member and including apparatus for reducing the coupling of electrical noise into the system resulting from conducting elements located adjacent the recesses and housing. More particularly, a method and apparatus employing electrostatic, but not magnetic, shielding of the low impedance antenna systems and inductive signal coupling to enhance the signal at the receiver is disclosed. This system is capable of measuring formation parameters in the presence of conducting bodies, e.g., the drill string, permitting incorporation of the apparatus in a measuring while drilling (MWD) logging system. In a particular embodiment, high frequency electromagnetic energy is used to measure formation resistivity. Small low impedance coils are arranged in the wall or around the outer circumferential surface of a steel drill collar and spaced from the surface a minimum distance to allow efficient propagation and reception. The low impedance receiver antennas are substantially electrostatically, but not magnetically, shielded and include inductive current coupling devices to further improve the signal. In a preferred embodiment, the coils are circularly configured about the collar and longitudinally spaced thereon to serve as transmitting and receiving elements which together with associated circuit components employ high frequency electromagnetic wave propagation techniques to measure formation parameters. The received signals are phase shifted and amplitude attenuated as they pass through the formation, and formation parameters are determined by detecting variations in travel time and attenuation between longitudinally spaced receivers.

Patent
19 May 1987
TL;DR: In this paper, a method and a system are disclosed for measuring the baseline vector b between a pair of survey marks on the ground by radio interferometry using radio signals broadcast from the earth orbiting satellites of the NAVSTAR Global Positioning System (GPS).
Abstract: A method and a system are disclosed for measuring the baseline vector b between a pair of survey marks on the ground by radio interferometry using radio signals broadcast from the earth orbiting satellites of the NAVSTAR Global Positioning System (GPS), the radio signals broadcast by the satellites being double-sideband modulated with their carriers suppressed. An antenna is positioned at each survey mark. The signals received by one antenna during a predetermined time span are separated into upper and lower sideband components. These separate components are filtered, converted to digital form, and then multiplied together. Their product is analyzed digitally by means of correlation with quadrature outputs of a local oscillator to determine the power, and the phase relative to that local oscillator, of the carrier wave that is implicit in the double-sideband signal being received from each satellite. Differences in Doppler shift are utilized to distinguish the carriers of different satellites. The signals received at the same time by the other antenna are processed in the same manner. Thus, the powers and carrier phases of the signals from a plurality of satellites are measured simultaneously and numerical data representing the measurement results are obtained at each survey mark. The measurements are performed in real time at each mark without reference to signals that are received at any other place and without knowledge of any of the coded signals that modulate the GPS carriers. The data from the measurements performed simultaneously but independently at the two survey marks.

Journal ArticleDOI
TL;DR: In this paper, a dual-frequency microstrip antenna consisting of two stacked annular rings of outer radii 5 cm and inner radii 2.5 cm was constructed on a Duroid substrate with relative permittivity 2.32 and thickness 0.159 cm.
Abstract: Experimental results of a dual-frequency microstrip antenna consisting of two stacked annular rings of outer radii 5 cm and inner radii 2.5 cm are presented. Fabricated on a Duroid substrate with relative permittivity 2.32 and thickness 0.159 cm, the separations of the two resonant frequencies range from 6.30-9.36 percent for the first three modes. The frequency separations can be altered by means of an adjustable air gap between the lower ring and the upper substrate.

Patent
10 Dec 1987
TL;DR: In this paper, a three resonator capacitively coupled microstrip antenna structure is described, which includes an inverted stacked array of elements with a lowermost driven element directly connected to a transmission line connector.
Abstract: A three resonator capacitively coupled microstrip antenna structure includes an inverted stacked array of elements with a lowermost driven element directly connected to a transmission line connector, and passive elements stacked above the driven element and separated from the driven element and from one another by dielectric layers. The dimensions, spacings and quality factors of the elements are chosen so that at least one, and possibly two elements are resonant at any given frequency within a desired frequency operating range. The resulting antenna structure offers very broad bandwidth at relatively low VSWR in a compact, rugged package. The manner in which parameters of the stacked antenna structure are specified to achieve desired VSWR bandwidth and radiation efficiency is also described.

Patent
29 Jul 1987
TL;DR: In this article, the authors proposed a dual-chamber antenna with a substrate, an upper planer conducting antenna element disposed on one side of the surface of the substrate and having a first curved edge, and a second curved edge having two curved edges being closely related to one another and spaced apart in close proximity at one point.
Abstract: The subject invention relates to an antenna having broadband characteristics. The antenna is a dual notch device capable of receiving or transmitting electromagnetic waves comprising a substrate, an upper planer conducting antenna element disposed on one side of the surface of said substrate and having a first curved edge, a second conducting antenna element disposed on the other side of said substrate and having a second curved edge, said first and second curved edges being closely related to one another and spaced apart in close proximity at one point to define a feed-point therebetween with adjacent curved edges gradually tapering outwardly therefrom to define flared notches interfacing one another and interconnected by said gap.

Patent
George J. Monser1
31 Jul 1987
TL;DR: In this paper, a vertical monopole antenna is coupled to a first feed on a ground plane conductor and a dipole antenna consisting of a plurality of horizontal dipole antennas is employed to produce a predetermined (such as omni-directional) radiation pattern about the first feed.
Abstract: An antenna system comprising a vertical monopole antenna coupled to a first feed on a ground plane conductor and a dipole antenna comprising a plurality of horizontal dipole antenna elements coupled to a corresponding plurality of feeds on the ground plane conductor, the plurality of dipole antenna elements being disposed about the first feed. The vertical monopole antenna comprises a plurality of monopole antenna elements, the plurality of monopole antenna elements and the plurality of dipole antenna elements being alternately radially disposed about the first feed. With such arrangement, the plurality of vertical monopole elements produce a vertically polarized beam having a predetermined (such as omni-directional) radiation pattern about the first feed, and the plurality of horizontal dipole antenna elements produce a horizontally polarized beam having a predetermined (such as omni-directional) beam pattern about the first feed; that is, the antennas are provided with substantially coincident phase centers. The monopole antenna elements do not substantially adversely affect (i.e. shadow) the omni-directional beam pattern produced by dipole antenna elements, and the dipole antenna elements do not substantially adversely affect the omni-directional beam pattern produced by the monopole antenna elements. Thus, the vertically polarized antenna elements may be disposed in close proximity to the horizontally polarized antenna elements, with no substantial degradation of the omni-directional beam patterns of either antenna, thereby allowing the total size of the antenna system to be reduced.

Patent
21 Aug 1987
TL;DR: In this paper, the authors proposed a matching circuit which has a cylindrical dielectric projecting into a hollow circular waveguide 3 from a loaded waveguide 4 along the center axis of the waveguide.
Abstract: PURPOSE:To prevent the opening efficiency of a parabolic antenna from decreasing by filling a dielectric in a mode generator. CONSTITUTION:A dielectric matching element 5 is a matching circuit which has a cylindrical dielectric projecting into a hollow circular waveguide 3 from a dielectric loaded waveguide 4 along the center axis of the waveguide. The TE11 mode in the hollow circular waveguide 3 is coupled with the TE11 mode in the dielectric loaded circular waveguide 4 without disordering an electric field distribution while an electromagnetic field is converged on the center of the waveguide by the circular dielectric. This multiple mode horn antenna is reducible in shape to one over the square root of the dielectric constant of the filled dielectric and the width of a 10dB down antenna beam can be expanded to >=90 deg., so it operates as the primary radiator of a parabolic antenna which has a >=120 deg. opening angle normally to obtain excellent radiation directivity without decreasing the opening rate of the parabolic antenna.

Journal ArticleDOI
TL;DR: In this paper, the appropriate correction factor to use in the resonant frequency formula of an equilateral triangular patch antenna obtained from the cavity model with perfect magnetic walls is discussed, and the appropriate error correction factor for an EAF with a perfect magnetic wall is discussed.
Abstract: The appropriate correction factor to use in the resonant frequency formula of an equilateral triangular patch antenna obtained from the cavity model with perfect magnetic walls is discussed.

Patent
16 Nov 1987
TL;DR: A compact, easy to manufacture quarter-wavelength microstrip element especially suited for use as a mobile radio antenna has performance which is equal to or better than conventional quarter wavelength whip-type mobile radio antennas as mentioned in this paper.
Abstract: A compact, easy to manufacture quarter-wavelength microstrip element especially suited for use as a mobile radio antenna has performance which is equal to or better than conventional quarter wavelength whip-type mobile radio antennas. The antenna is not visible to a passerby observer when installed, since it is literally part of the vehicle. The microstrip radiating element is conformal to a passenger vehicle, and may, for example, be mounted under a plastic roof between the roof and the headliner.

Patent
16 Nov 1987
TL;DR: In this paper, the authors describe a printed circuit loop antenna pattern that is vacuum-depositioned onto the thermoplastic base and/or cover, where the antenna pattern is disposed on both the cover and the base, and a portion of the antenna (e.g., 1002K) is also disposed on the hinge to join the main portions of antenna on the base and cover.
Abstract: The preferred housing includes an integrally molded thermoplastic base (102) and cover (104) assembly. The cover is joined to the base by a living hinge (106) and a peripheral wall (108) extends around the perimeter of the base. In one embodiment, the antenna is a wire loop (204), the wire being wound in an external circumferential groove (202A) in the peripheral wall or, alternatively, integrally molded into the peripheral wall. Other embodiments use printed circuit loop antenna patterns that are preferably vacuum deposited directly onto the thermoplastic base and/or cover. When the antenna pattern is disposed on both the cover and the base, a portion of the antenna (e.g., 1002K) is also disposed on the hinge to join the main portions of the antenna on the base and cover. In one embodiment of the printed circuit loop antenna, the plane of the loop lies parallel to the base and may include one or more turns or loops (e.g., 402C, E, G and J). In another embodiment, the loop includes a 90 degree bend (e.g., 504) and both planes of the loop lie perpendicular to the base. In still another embodiment, the loop includes three 90 degree bends, a crossover at one of the bends (e.g., at 704), and all four planes of the loop lie perpendicular to the base.

Patent
03 Jun 1987
TL;DR: In this article, a self-supported ring focus reflector was proposed to improve the performance of a rotationally symmetric reflector antenna with self-sustained feed, which consists of a waveguide tube, a dielectric joint and a sub-reflector.
Abstract: The invention consists of improvements of reflector antennas with self-supported feeds. The feed consists of a waveguide tube, a dielectric joint and a sub-reflector. The tube is attached to the center of the rotationally symmetric reflector and extends to the focal region of it. The sub-reflector is located in front of the tube, and the surface of this sub-reflector is provided with rotationally symmetric grooves also called corrugations. The improvements of the present invention are (1) a ring focus reflector to improve the gain of the antenna, (2) an elevated central region of the reflector to reduce the return loss, (3) metal screws or cylinders to strongly fasten the sub-reflector to the tube, (4) corrugations or other similar means around the rim or the reflector in order to reduce far-out sidelobes, (5) dual-band operation by means of a coaxial waveguide outside the circular waveguide in the tube, and (6) dielectric filling or covering of the corrugations or of the region between the corrugations and the waveguide tube end, both in order to avoid the gathering of water, dust or other undesired material in this area which could destroy the performance of the antenna.

Journal ArticleDOI
TL;DR: The photophysics of energy migration and trapping in photosystem I is examined by investigating the spectral and temporal properties of the fluorescence from the core antenna chlorophylls as a function of the antenna size, and a linear dependence of the excitation lifetime on antenna size is predicted.
Abstract: We have examined the photophysics of energy migration and trapping in photosystem I by investigating the spectral and temporal properties of the fluorescence from the core antenna chlorophylls as a function of the antenna size. Time-correlated single photon counting was used to determine the fluorescence lifetimes in the isolated P700 chlorophyll a-protein complex and in a mutant of Chlamydomonas reinhardtii that lacks the photosystem II reaction center complex. The fluorescence decay in both types of sample is dominated by a fast (15-45 psec) component that is attributed to the lifetime of excitations in the photosystem I core antenna. These excitations decay primarily by an efficient photochemical quenching on P700. The measured lifetimes show a linear relationship to the core antenna size. A linear dependence of the excitation lifetime on antenna size was predicted previously in a lattice model for excitation migration and trapping in arrays of photosynthetic pigments [Pearlstein, R.M. (1982) Photochem. Photobiol. 35, 835-844]. Based on this model, our data predict a time constant for photochemical charge separation in the photosystem I reaction center of 2.8 +/- 0.7 or 3.4 +/- 0.7 psec, assuming monomeric or dimeric P700, respectively. The predicted average single-step transfer time for excitation transfer between core antenna pigments is 0.21 +/- 0.04 psec. Under these conditions, excitation migration in photosystem I is near the diffusion limit, with each excitation making an average of 2.4 visits to the reaction center before photoconversion.

Journal ArticleDOI
TL;DR: A new microwave antenna design with improved heating at the tip for interstitial hyperthermia and thermocoagulation and an improved steady-state temperature distribution over the active region of the radiator is presented.
Abstract: This paper presents a new microwave antenna design with improved heating at the tip for interstitial hyperthermia and thermocoagulation. Temperature distribution patterns surrounding a conventional insulated antenna and the new sleeved coaxial slot radiator are measured in a saline phantom under transient and steady-state conditions. The new design provides an improved steady-state temperature distribution over the active region of the radiator. In contrast to the cold zone at the tip of a conventional insulated antenna the new sleeved coaxial slot antenna provides maximal (sixfold greater) power deposition at its tip.

Patent
14 Jul 1987
TL;DR: In this paper, a reader transmits interrogating rf signals to a transponder including an antenna having a particular impedance, and the signals received by the antenna are converted to a direct voltage which is introduced to a first terminal of a switch such as an emitter of a semi-conductor device having conductive and non-conductive states of operation.
Abstract: A reader transmits interrogating rf signals to a transponder including an antenna having a particular impedance. The signals received by the antenna (30) are converted to a direct voltage which is introduced to a first terminal of a switch such as an emitter of a semi-conductor device (42) having conductive and non-conductive states of operation. A second terminal of the switch, such as the base of the semi-conductor device, receives a voltage variable between first and second magnitudes in accordance with a pattern of binary 1's and 0's in a data source such as a read-only memory (ROM). This pattern of binary 1's and 0's is individual to an object identified by the reader The variable voltage on the base of the semi-conductor device causes the emitter-collector current of the semi-conductor device to vary between first and second amplitudes. When this current has the first amplitude, the impedance of the semi-conductor device and the ROM substantially matches the antenna impedance. When this current has the second amplitude, the impedance of the semi-conductor device and the ROM is substantially greater than the antenna impedance. Capacitance (54) may be connected to the collector of the semi-conductor device and the ROM to store energy in accordance with the current flow through the semi-conductor device. This stored energy provides for an energizing of the semi-conductor device and the ROM. A diode (56) may be connected between the emitter and collector of the semi-conductor device to increase the second amplitude of the current through the semi-conductor device.

Patent
16 Nov 1987
TL;DR: A compact, easy to manufacture quarter-wavelength microstrip element especially suited for use as a mobile radio antenna has performance which is equal to or better than conventional quarter wavelength whip-type mobile radio antennas as discussed by the authors.
Abstract: A compact, easy to manufacture quarter-wavelength microstrip element especially suited for use as a mobile radio antenna has performance which is equal to or better than conventional quarter wavelength whip-type mobile radio antennas. The antenna is not visible to a passerby observer when installed, since it is literally part of the vehicle. The microstrip radiating element is conformal to a passenger vehicle, and may, for example, be mounted under a plastic roof between the roof and the headliner.

Journal ArticleDOI
TL;DR: In this paper, a microwave printed planar log-periodic dipole array (LPDA) antenna analysis and design procedure is presented together with the description of a planar feeding technique.
Abstract: A microwave printed planar log-periodic dipole array (LPDA) antenna analysis and design procedure is presented together with the description of a planar feeding technique. The effects of the dielectric substrate on the antenna design are also discussed and taken into account. A numerical technique using the finite element method is employed to obtain the characteristic impedance and effective dielectric constant of the transmission lines involved, i.e., an unbalanced stripline and a balanced line having only two parallel strips. A 4-8 GHz printed LPDA antenna was manufactured and tested, showing very good radiation pattern and voltage standing-wave ratio (VSWR) values over the entire frequency range.

Journal ArticleDOI
15 Jun 1987
TL;DR: In this article, a printed wire antenna of arbitrary configuration is analyzed and the electric field tangential to the wire is derived using the current expanded by piecewise sinusoidal functions.
Abstract: A printed wire antenna of arbitrary configuration is analyzed. The electric field tangential to the wire is derived using the current expanded by piecewise sinusoidal functions. These functions are also used to form the impedance matrix elements. Use of the stationary phase method leads to a simple expression for the radiation field. Numerical analyses based on the present formulation yield radiation characteristics of a zigzag dipole antenna, a loop antenna, and a round spiral antenna. >