Showing papers on "Slot antenna published in 1982"

Calculation of Site Attenuation from Antenna Factors

Abstract: A site-attenuation model expressed in terms of the antenna factors of the transmit and receive antennas is presented. Both horizontal and vertical polarizations are included, as are the effects of mutual coupling between closely spaced horizontal antennas. Expressing site attenuation in terms of antenna factors allows the use of broad-band antennas with their attendant advantages over tunable dipoles. Measured and calculated results for a variety of sites, antennas, and geometries are compared in the frequency range of 30 MHz to 1 GHz.

Efficient computation of antenna coupling and fields within the near-field region

Abstract: The theory, techniques, details of the important equations, and description of two computer programs are presented for calculating efficiently the mutual coupling at a single frequency between any two antennas arbitrarily oriented and separated in free space. Both programs emphasize efficiency and generality, and require, basically, the complex electric far field of each antenna, and the Eulerian angles designating the relative orientation of each antenna. Multiple reflections between the antennas are neglected but no other restrictive assumptions are involved. If an electric field component is desired instead of coupling, the receiving antenna is replaced by a virtual antenna with uniform far field. The first computer program computes coupling (or fields) versus transverse displacement of the antennas in a plane normal to their axis of separation. An efficient fast Fourier transform (FFT) program was made possible by "collapsing" the far-field input data and showing that inmost cases the spectrum integration need cover only the solid angle mutually subtended by the smallest spheres circumscribing the antennas. Limiting the integration to this solid angle artifically band limits the coupling function, thereby allowing much larger integration increments and reducing run times and storage requirements to a feasible amount for electrically large antennas. The second program is based on a spherical wave representation of the coupling function and rapidly computes coupling (or fields) versus separation distance between the antennas. The spherical wave representation emerged naturally from an intriguing characteristic proven for the mutual coupling function; it, like each rectangular component of electric and magnetic field in free space, satisfies the homogeneous wave equation.

Impedance of a radiating slot in the ground plane of a microstripline

Abstract: An expression for the complex admittance of a radiating slot in the ground plane of a microstripline is obtained from the complex radiated power and discontinuity in the modal voltage. The complex radiated power is obtained from the angular spectrum of plane waves. The electric field distribution in the microstripline, required for the determination of the discontinuity in the modal voltage, is determined from the analysis presented by Yamashita and Atsuki. The theoretical results are compared with experimental data.

Microstrip-Franklin Antenna

Abstract: Phasing stubs are employed to achieve a cophase current distribution in microstrip rectangular patch arrays. This technique, originally proposed for resonant long wire antennas by Franklin, avoids spurious radiation from half-wavelength connecting transmission lines as used in conventional patch antenna arrays. A slot-radiator model is derived to describe the basic radiation mechanism of the resultant new type of antenna and experimental results for the slot radiation resistance are given. The design of a 13-element resonant array for 12 GHz is presented together with measured radiation patterns.

Design of waveguide-fed series slot arrays

Abstract: A design procedure is presented whereby the length and tilt of every slot in a series array can be determined, in the presence of external mutual coupling, in order to provide a specifield pattern and input impedance. The slots are cut in a broadwall of rectangular waveguides, centered but inclined, and resonantly spaced to form linear or planar arrays. The design procedure parallels earlier treatment ot tne longitudinal shunt slot case, and combines Stevenson's method with a modified form of Booker's relation to treat non-resonant series slots. Two coupled design equations result, one linking slot voltage and mode current, the other linking active slot impedance to the active impedance in an equivalent dipole array. Simultaneous solution of these design equations is illustrated for the cases of a two by four array, a three by five array, and a five by five array. Experimental results for the two by four array are presented, and validate the theory satisfactorily.

A high-frequency analysis of radome-induced radar pointing error

Abstract: An analysis is presented of the effect of a tangent ogive radome on the pointing accuracy of a monopulse radar employing an aperture antenna. The radar is assumed to be operating in the receive mode, and the incident fields at the antenna are found by a ray tracing procedure. Rays entering the antenna aperture by direct transmission through the radome and by single reflection from the radome interior are considered. The radome wall is treated as being locally planar. The antenna can be scanned in two angular directions, and two orthogonal polarization states which produce an arbitrarily polarized incident field are considered. Numerical results are presented for both in-plane and cross-plane errors as a function of scan angle and polarization.

Blade antenna with shaped dielectric

Abstract: A Tee slot blade antenna for aircraft and other high speed vehicles has a pair of dielectric sections, one section extending longitudinally along the blade and the other extending transversely from an intermediate location along the longitudinal section. The resonant frequency of the antenna is determined by the length of each section and the position of the transverse section along the longitudinal one, while the characteristic impedance is a function of the width of each section. The Tee slot antenna is capable of operating over a wide bandwidth on a smaller blade than prior single slot antennas. A Tee slot antenna designed for one frequency range can be combined with either a single slot antenna or another Tee slot antenna designed for another frequency range on the same antenna blade, without impairing the bandwidth of either antenna.

A formulation of the finite-length narrow slot or strip equation

Abstract: A formulation of the integro-differential equation for the electric field (or equivalent surface magnetic current) in a finite-length narrow slot in a perfectly conducting planar screen of infinite extent is presented. An analogous developement leads to the dual equation for a finite-length narrow conducting strip. The derivation proceeds from the general aperture equation and incorporates the known field in a narrow slot of infinite extent. The formulation is not based upon the concept of an equivalent radius but, as a by-product, width/4 emerges as the value of the equivalent radius of a strip or a slot.

Slotted antenna array excited by a coplanar waveguide

Abstract: The letter gives a new concept of exciting slotted antenna arrays. There both the slots and the feeder are etched on the same side of the printed circuit board. A channel is cut perpendicular to the slots and a coplanar waveguide for exciting the slots is inserted into the channel. The concept has been experimentally verified on a model.

Vivaldi Antennas for Single Beam Integrated Receivers

Abstract: Slot line antennas intended for rnm-wave single beam applications as well as for imaging systems are experimentally investigated. In particular the Vivaldi antenna is investigated, and it is found that a 3 dB beam width of typically 30° is obtained and a 10 dB beam width of about 60° can be achieved. The 10 dB beam efficiency as defined in the text can be made about 60% as compared to 70% for a corrugated scalar horn.

Single-Frequency Electronic-Modulated Analog Line Scanning Using a Dielectric Antenna

Abstract: A line scanning antenna is described whereby means of periodic perturbations and conductivity changes in p-i-n diode modulators, analog angular shifts of 5° can be obtained. The system is electronically modulated with relatively small power requirements.

Tapered-width leaky-waveguide antenna

Abstract: A leaky waveguide slotted traveling wave antenna having several elongated nonresonant slots (2) oriented with their long axes substantially orthogonal to the direction of propagation within waveguide (1) filled with a dielectric material having a dielectric constant greater than 1. The length (m) of each slot (2) gradually increases as one traverses the waveguide (1) along the direction of propagation, whereas the width (W) of the wall of the waveguide (1) in which the slots (2) are cut gradually decreases as one traverses the waveguide (1) along the direction of propagation. Any angle of radiation between 0° and 135°, including endfire and broadside radiation, can be achieved. The width (w) of each slot (2) and the inter-slot spacing (d) can vary; the increase in slot length (m) can be non-uniform.

Mutual coupling between rectangular slot antennas on a conducting concave spherical surface

Abstract: The surface fields excited by a horizontal magnetic source located on a conducting concave spherical surface have been formulated. The field expressions are obtained as a combination of ray-optical fields and simplified integrals under the condition that the radius of the spherical surface is much greater than the wavelength. Numerical calculations have been performed, and the calculated results for the surface fields have been corroborated with experiments. The results of these basic studies have been used in calculating the mutual coupling between rectangular slot antennas on the conducting concave spherical surface assuming the aperture field as the dominant mode in the wave guides connected with the slots. The numerical results have been compared with those for slots on a convex conducting surface. Experimental investigation of the mutual coupling has also been carried out.

Stripline slot array

Abstract: This specification discloses how to control the resonant slot length fed by a boxed strip line and a slot array antenna which uses a standing wave to form a broadside and an off broadside main beam. A plurality of linearly arranged elongated slots are fed by one continuous stripline feed conductor. The conductor has conductor portions each associated with one slot and each having a longitudinal axis which is angled with respect to the longitudinal axis of the associated slot. The conductor portions form a zig-zag pattern, adjacent slots having conductor portions angled at a different direction with respect to the direction of alignment of the slots.

Slot antenna with face mounted baffle

Abstract: An improved planar slot array antenna comprising a conducting fence or baffle interposed between the two halves of the antenna in a plane perpendicular to the flat plate or E-field.

Moment method analysis of a T-shaped slot radiator in bifurcated waveguide

Abstract: Slot radiators in polarisation-selective dual-mode waveguide arrays present an unusual analytical problem in that the apertures may be three dimensional, when a typical slot on the outer face of the waveguide feed is shunted by a perpendicular clearance slot. The paper describes a moment method of analysis of such an aperture and compares the computed results with measurements.

Plural microstrip slot antenna

Abstract: A microwave antenna has three rectangular conductive elements on the surface of an insulative board. The elements are arranged side-by-side and are separated from one another by longitudinal slots formed of non-conductive regions. Each element has a lateral slot that divides the element into two identical pads. The central element is fed at its slot with microwave energy, either by electrical contact with the periphery of the slot or capacitively from behind the slot. Microwave energy is supplied to the side elements from the central element by means of the longitudinal slots. In operation, microwave energy is propagated or received by the lateral slots to reinforce energy propagated or received by the conductive elements.

Frequency scan antenna utilizing supported dielectric waveguide

Abstract: A dielectric waveguide of rectangular cross-section has periodically spaced, transverse slots in its upper surface. When traveling waves of varying millimeter wavelength frequencies are applied to the waveguide, the slots perturb the waves resulting in radiation having a main lobe that scans as the frequency changes. The antenna is made rigid by the use of a dielectric support.

Parallel plate waveguide antenna

Abstract: A parallel plate waveguide microwave antenna is presented in which transmission or reception of microwave energy is effected by radiating waveguide slots or apertures in a metallized glass plate or plate of other rigid dielectric material. The metallized glass plate cooperates with another metallized glass plate or other rigid dielectric material or a metal plate to define a parallel plate waveguide with air or an inert gas or vacuum as the dielectric between the plates. When used as a transmitter antenna, a central electrode propagates waves in the dielectric medium in expanding circles; and the slots or apertures in the metal layer act as scattering sites to couple the waves to free space. When used as a receiver antenna, the reverse will occur.

Planar Millimeter Wave Antennas With Application To Monolithic Receivers

Abstract: A number of applications of millimeter waves can benefit from development of low-cost, planar antenna elements, which can be combined into either phased arrays or arrays with imaging properties. Such applications range from communication, navigation and battle-field passive and active systems to remote sensing and space science instrumentation. This paper discusses the general requirements on such planar antenna elements, with specific data for three examples: (i) the Vivaldi (tapered slot) antenna, (ii) printed dipole arrays, and (iii) planar slot arrays. It is shown that such elements can be used for both prime-focus paraboloids and Cassegrain systems, with excellent aperture efficiency and beam efficiency, with the potential number of elements in the hundreds. In order to be optimally useful, planar antennas should be suitable for integration with receiver elements, i.e. mixer diodes and IF-amplifiers. It seems feasible to construct monolithic versions of these arrays in the future.

Experimental study of embedded insulated antennas

Abstract: Experimental studies are reported of several coaxial structures useful us embedded antennas and transmission lines These include the insulated coaxial line with extended inner conductor, the insulated dipole with choke section, and the insulated sleeve dipole The purpose of the experiments is to confirm theoretical calculations that involve numerous approximations

Focused aperture microwave antennas operating in the near field zone

Abstract: Focusing a microwave antenna is often convenient in order to produce a Fraunhofer-type pattern at short distance from the aperture. The characteristics of the radiation patterns produced by some specimens were experimentally tested and compared with theoretical predictions. Basic criteria are given to design focused antennas, once their radiation pattern characteristics are specified.

Low and medium gain microwave antennas

Abstract: The isolated and relatively small microwave antenna is the topic in this chapter. Array elements and large antennas are covered in other chapters. The basis for the selection has been novelty, either in design or in theory of operation. Most of the material in this chapter has not appeared in previous antenna design books, which date back 10 to 15 years, although of course some overlap is unavoidable. An understanding of the physical principles, in network theory or wave propagation, is the underlying philosophy, since this seems to be the basis for new, innovative design. The mathematics has been kept to a minimum, but the references will carry the reader on to greater details.