Showing papers on "Slot antenna published in 1986"

A reciprocity method of analysis for printed slot and slot-coupled microstrip antennas

Abstract: A method is presented for the analysis of slot-type discontinuities in microstripline. The approach is based on the reciprocity theorem and uses the exact Green's functions for the grounded dielectric slab in a moment method solution for the unknown antenna currents. The method is applied to two specific geometries: a radiating slot in the ground plane of a microstripline, and an aperture coupled microstrip patch antenna. Results for antenna impedance are compared with measurements, and far-zone patterns are calculated. The method is shown to be quite versatile, and should find application to related problems.

Analysis of the tapered slot antenna

Abstract: A method for calculating the radiation pattern of end-fire tapered slot antennas with or without dielectric substrate is presented. The method involves a two-step procedure: 1) determine the field distribution of a traveling wave along the tapered slot, and 2) compute the radiation from this slot field by using the half-plane Green's function to account for termination effects. Acceptable estimates of the slot field usually can be obtained from a stepped approximation to the tapered geometry. The method has been verified by comparisons to measured patterns for various dielectric substrates and antenna dimensions. However, the effect of lateral truncation has not yet been successfully modeled. Experimental patterns showing this effect are presented.

The design of slot arrays including internal mutual coupling

Abstract: Improved slot array performance (lower side lobe levels, a better input match) calls for elimination of approximations in earlier design procedures. One important change is to include internal higher order mode coupling. That has been done and is found to cause a simple but significant modification in existing design formulas.

Microstrip leaky wave strip antennas

Abstract: During the late 1870's. a paper presented by H. Ermert at the European Microwave Conference stimulated instant controversy. The paper was devoted to the properties of higher modes on microstrip line, and one of its conclusions was that a "radiation" region exists close to the cutoff of those modes. Because the description of this region, made in that talk and in published papers [1,2], was incomplete and therefore unclear to many, confusion persisted and certaln practical consequences remained hidden. Also in this general perlod. a paper by W. Menzel [3] presented a new traveling-wave antenna on microstrip line fed in its first higher mode and operated near t~ the cutoff of that mode. Menzel proposed his structure as a competitor to a microstrip patch antenna, and he therefore made his antenna short in terms of wavelength. He also assumed that the propagation wavenumber of the flrst higher mode was real in the very region where Ermert said no such solutions exist; since his guided wave, with a real wavenumber, was f a s t in that frequency range, Menzel presumed that i t should radiate. His approximate analysis and his physical reasoning were therefore also incomplete, but his proposed antenna was valid and his measurements demonstrated reasonably successful performance. The present paper flrst explains that the "radiation" region of Ermert is directly related to leaky modes, and that such a representation for this region is both convergent and practical. It then shows that Menzel's antenna Ls in reality a leaky wave antenna that was made too short: an accurate analysis of it not only explatns quantitatively the performance features of the antenna, but also indicates how they can be improved. Numerical values are presented to show what performance characteristics can be expected when leaky wave antennas of this class are properly designed.

Electromagnetic logging apparatus using vertical magnetic dipole slot antennas

Abstract: An electromagnetic logging apparatus is disclosed which utilizes vertical magnetic dipole antennas for propagation logging, preferably at a frequency greater than 100 MHz. Slot antennas having conductive probes which are perpendicular to the borehole axis, and also perpendicular to a borehole radius, are employed to obtain the desired vertical magnetic dipole antenna characteristics. The depth of investigation is improved as compared to devices of this type which employ horizontal magnetic dipole antennas. Also, the antennas are tuned in a manner which provides advantageous operation.

Analysis of the transverse electromagnetic mode linearly tapered slot antenna

Abstract: A theoretical analysis of the radiation characteristics of the transverse electromagnetic mode linearly tapered slot antenna is presented. The theory presented is valid for antennas with air dielectric and forms the basis for analysis of the more popular dielectric-supported antennas. The method of analysis involves two steps. In the first step, the aperture distribution in the flared slot is determined. In the second step, the equivalent magnetic current in the slot is treated as radiating in the presence of a conducting half-plane, and the far-field components are obtained. Design curves for the variation of the 3-dB and 10-dB beamwidths as a function of the antenna length, with the flare angle as a parameter, are presented.

Stacking resonators to increase the bandwidth of low-profile antennas

Abstract: A method of increasing the bandwidth of low-profile cavity-hacked slot and microstrip patch antennas without appreciably adding to the antenna dimensions is presented. This idea incorporates the stacking of structures which have close resonant frequencies. Energy is coupled between cavities via carefully placed slots in the common wall. An approximate two-and-a-half fold increase in input impedance bandwidth has been observed for a certain cavity-backed slot antenna.

Planar antenna with patch radiators

Abstract: A planar antenna includes a first slotted waveguide serving as a power-feed unit, and a second slotted waveguide of planar type coupled with the power-feed waveguide, for radiating circularly polarized microwaves into space. The second waveguide has a metal plate in which a two-dimensional slot array consisting of a plurality of rows of slots is formed. An insulative layer is provided on the second waveguide to cover the slot array. A plurality of rows of metal patch radiators are provided on the insulative layer. These patch radiators are electromagnetically coupled with the slots, respectively, in such a manner that each radiator is directly excited by the corresponding slot through the insulative layer, thereby radiating circularly polarized microwaves.

Application of the minimum scattering antenna theory to mismatched antennas

Abstract: The mutual impedance between canonical minimum scattering (CMS) antennas can be calculated directly from their far-field radiation patterns. While having the potential to greatly simplify array analysis and design, the theory has limited practical applicability because, by definition, CMS antennas are matched to their terminations. It is shown here that the theoretical basis of the mutual coupling calculation does not require the antennas to be matched and that the theory is simply extended to mismatched antennas. The only requirement is that the antennas are invisible, i.e., do not scatter, when open-circuited. This does not impose a greater restriction on the practical applicability of the method, since characteristic mode theory indicates that dipoles and loops, and perhaps other antennas, can be made very nearly invisible by a suitable reactive termination if the frequency is near or below first resonance. A new antenna, consisting of the original antenna plus a particular length of transmission line, will then be almost invisible on open circuit. The theory is applied to calculating the active impedance in an array of small monopole-like elements in a parallel plate waveguide and the results compared with experiment.

Two-frequency slotted planar antenna

Abstract: A two-frequency planar antenna incorporates a resonant antenna and a slot antenna which are arranged in a superposed manner on the same dielectric substrate so as to be operable independently without interfering with each other. The two-frequency planar antenna includes a front conductor plate arranged on one surface of a dielectric substrate to serve as a radiation conductor plate of a resonant antenna and a slotted conductor of a slot antenna, a back conductor plate arranged on the other surface of the dielectric substrate to serve as a grounding conductor of the resonant antenna and a reflector of the slot antenna, and a slot antenna feed line embedded in the dielectric substrate. The slot antenna feed line is arranged along an axis where an electric field in an excitation mode of the resonant antenna is reduced to zero and at least one slot is formed in the front conductor plate along the feed line.

Analysis of a slot microstrip antenna

Abstract: The slot microstrip antenna is used as a folded slot dipole symmetrically fed across a gap by means of a strip line. A theoretical model equivalent to several lossy transmission lines had been described previously to explain the bandwidth and the radiation admittance. The theory is improved when coupling between the two equivalent radiating lines of every slot is taken into account, and explains a fourth resonance near the third one, which had been measured on several models. Theoretical results and experiments are in good agreement. They are radiation admittance in a wide frequency band, current distribution along each slot and radiation patterns.

Vehicle roof mounted slot antenna with lossy conductive material for low VSWR

Abstract: Slot antenna apparatus for a motor vehicle roof made of an electrically conducting material with a central non-conducting portion comprises a horizontal sheet of electrically conducting material attached to the roof, the horizontal sheet including a looped slot adjacent the central non-conducting portion which divides the sheet into inner and outer portions, the slot having a total loop length of substantially one wavelength in the commercial FM broadcasting band. The horizontal sheet material has a comparatively high sheet resistance of 1 to 2 ohms per square to produce a maximum VSWR of 5 and preferably below 3. The material may be comprise a coating of nickel in an acrylic binder on the underside of an SMC roof panel. The horizontal sheet may be grounded at DC and commercial AM frequencies by a direct conductive connection between the outer portion thereof and the conducting portion of the roof and at commercial FM frequencies by the capacitive coupling of an overlap of substantially the complete periphery of the outer portion and the conducting portion of the roof. A common AM/FM feed point may be provided at the front center of the slot, or separate AM and FM feed points may be provided at the side center and front center, respectively, of the slot.

Portable receiving antenna system

Abstract: A portable receiving antenna system for providing communication with a transmitting station carried by a geostationary satellite. The system includes a portable case, a flat plate antenna arranged to cover an opening of the portable case, and an adjustable support arranged within the portable case to support the flat plate antenna at an incident angle capable of receiving electromagnetic waves from the transmitting station. The flat plate antenna is in the form of a micro strip line slot array antenna including a dielectric layer, a metallic earth film formed with a plurality of spaced slots and secured to the surface of the dielectric layer in such a manner that the slots are arranged to receive the electromagnetic waves from the transmitting station, and a feeder line circuit secured to the rear surface of the dielectric layer. Preferably, an azimuth compass and a converter are mounted within the portable case, the converter being connected to an output terminal of the feeder line circuit.

A new integrated slot element feed array for multibeam systems

Abstract: A feed array consisting of constant width slot antennas (CWSA), fed from a block containing fin-line transitions, has been developed. The array has a two-dimensional configuration, with five elements each on five parallel substrates. Beamwidths are compatible with use in f/D = 1.0 multibeam systems, with optimum taper. Array element spacings are close to a factor of two smaller than for other typical arrays, and spillover efficiency is about 65 percent.

Nonuniformly spaced slot array antenna with low sidelobe pattern

Abstract: A numerical design method for a waveguide slot array antenna is proposed, by which the array, which has a low sidelobe pattern, is numerically designed. The slots are resonant, and the sources with cophasal excitations and desired amplitudes are designed by adjusting the space between the adjacent slots. It is shown theoretically that the desired low sidelobe pattern can be obtained by this method. Next, another design procedure is proposed to obtain the impedance matching at the feed point. This is a forward design from the feed point, and the slots are designed in an opposite sequence to the conventional one, it is also shown theoretically that the desired pattern is obtained.

Microstrip tee-fed slot antenna

Abstract: A microstrip tee-fed slot antenna is made up of only a single printed circuit board having the tee feed and slot on the front side and a microstrip transmission line feed on the back side. A plurality of holes in the board surrounding the slot are electrically connected front to back to provide the antenna cavity. Since only a single board is used having all of the components of the antenna on either side, no disassembly is required to add to or modify the elements of the antenna.

Calibration of microwave antenna gain standards

Abstract: Techniques for precision calibration of microwave antenna gain standards are described with discussions of applicability and associated uncertainties. Included are the three-antenna, extrapolation, swept-frequency, and near-field techniques.

Electromagnetic energy seal of a microwave oven

Abstract: A microwave leakage shielding apparatus of microwave oven which can cut off the leakage of high-frequency electromagnetic wave as well as that of second harmonic. The slot antenna is installed in such a manner that a serial resonant circuit is provided within the attenuating cavity of the choke installed in the door of microwave oven. Also, the apparatus can reduce the thickness of door by performing the one-quarter impedance inversion in the nearer position then λ/4 through the serial resonant circuit, thereby enlarging the capacity of heating room.

Conformal Microstrip Communication Antenna

Abstract: Antennas are a key component of all military communication systems that use free space as a propagation medium Many advanced military missions require conformal antenna designs Microstrip antennas are well suited as conformal antennas since they are very thin and can be curved to fit contours This paper will discuss a variety of conformal microstrip antennas Four types of antennas will be discussed: ? Single element antennas with broad coverage ? Wraparound Omni, missile and satellite antennas ? Fixed beam conformal microstrip antennas ? Electrically scanned microstrip arrays

Electromagnetic Subsurace Radar Using the Transient Field Radiated by a Wire Antenna

Abstract: A radar based on the propagation of a short pulse of current along a wire parallel to the ground surface is described. The wire acts both as a traveling-wave transmitting antenna and as a receiving antenna. For applications to civil engineering, the depth of exploration may be less than 1 m, the purpose being, for example, to detect discontinuities situated near the ground surface, to measure the thickness of a thin layer (10-50 cm), or to characterize a change in its reflection coefficient. Therefore, the width of the pulse of current is about 1 ns. The theoretical approach shows that the wire must be situated at about 10 cm above ground and that there is an optimum position for the current probe that detects the induced current due to a reflecting layer. Several experiments will also be described showing the feasibility of the method.

Radiation pattern analysis of the tapered slot antenna, appendix 1

Abstract: A theoretical model for the tapered slot antenna is presented. The model is valid for any smooth taper of the slot. The problem is solved by modeling the slot electric field and using the half plane Green's function to compute the far fields. The aperture field is obtained by affecting a stepped approximation to the continuous taper and utilizing the uniform wide slot line data. The uniform wide slot line is solved by the spectral Galerkin's technique and closed form experssions are developed for the slot wave length and the slot characteristic impedance. Numerous comparisons with measurement are made to demonstrate the versatility of the model in treating an arbitrary slot taper.

Integrated travelling-wave antenna for nonradiative dielectric waveguide

Abstract: A travelling-wave antenna for integrated use in nonradiative dielectric waveguide is described. The antenna is constructed by cutting a longitudinal slot in the waveguide side wall. Results are presented showing the comparison between measured and calculated data.

Model Experiments with Slot Antenna Arrays for Imaging

Abstract: We have developed a prototype imaging system at 31 GHz, which employs a two-dimensional (5x5) array of tapered slot antennas, and integrated detector or mixer elements, in the focal plane of a prime-focus paraboloid reflector, with an f/D=1. The system can be scaled to shorter millimeter waves and submillimeter waves. The array spacing corresponds to a beam spacing of approximately one Rayleigh distance and a two-point resolution experiment showed that two point-sources at the Rayleigh distance are well resolved.