Showing papers on "Slot antenna published in 1981"

Microstrip antennas with frequency agility and polarization diversity

Abstract: A technique is investigated for controlling the operating frequency and polarization of microstrip antennas. The control is achieved by placing shorting posts at appropriate locations within the antenna's boundaries. By changing the number and locations of the posts, the operating frequency can be tuned over a 1.5-to-1 range, and the polarization can be changed from horizontal to vertical, right-hand circular, or left-hand circular. All of these changes are obtained without significantly altering the input impedance or radiation patterns of the antenna and without increasing the complexity of the external microwave feed network. The frequency and polarization can be electronically controlled by using microwave switching diodes for the shorting posts. Antennas that have two feeds and operate simultaneously in two orthogonal polarizations have been constructed with the capability to switch between linear and circular polarization. Also, a thin frequency-scanned array has been built with the frequency-agile microstrip elements.

Current distribution and input impedance of printed dipoles

Abstract: Printed dipole antennas find increasing use in microwave as well as far infrared frequencies. The current distribution, input impedance, and radiation pattern are computed for wire antennas printed on a dielectric substrate. The current distribution is obtained by solving Pocklington's equation by moment methods. The Green's function pertinent to the problem involves improper Sommerfeld-type integrals. These integrals are computed by a real-axis integration technique which involves analytical and numerical steps. The effect of surface modes is carefully taken into account.

Stripline fed hybrid slot antenna

Abstract: A planar antenna is described which employs a pair of closely spaced parallel ground planes and a radiating element which is a composite aperture (hybrid slot) formed into the upper ground plane. One portion of the radiating element is a long narrow slot which may have the shape of a rectangle of high aspect ratio. The other portion is an annular slot which may be circular in shape. Electromagnetic energy is conveyed to and from the slots in the upper ground plane by means of a feed conductor parallel to and sandwiched between the two ground planes. The maximum of the resulting field pattern is in the plane of the antenna and the pattern may be either directional or omnidirectional in that plane. When used as a receiving antenna, this antenna responds to both the electric and magnetic fields.

Design of transverse slot arrays fed by a boxed stripline

Abstract: A design procedure is described whereby the lengths and offsets of an array of transverse slots can be determined, in the presence of mutual coupling, when the slots are excited by a boxed stripline and when pattern and input impedance are specified. The design is based on two sets of simultaneous equations. One set relates the TEM scattering off each slot to the field distribution in the slot, in the manner of Stevenson. The other set relates the stripline-fed slot array to an equivalent, properly loaded slot array, center-fed by two-wire lines, whose mutual impedance terms are easily calculated. The procedure is illustrated by the design of an eight element linear array. Experimental data in support of the theory will be presented.

Waveguide slot antenna

Abstract: This invention relates to an arrangement of waveguide coupling mechanisms in a two-layer structure that will produce accurate excitation of the array radiating slot elements over a wide bandwidth, handle high input power and be useful either as a very small array or sub-array of a larger array

Characteristics of a slotted parallel-plate waveguide filled with a truncated dielectric

Abstract: A slotted parallel-plate waveguide filled inside with a material which is truncated is analyzed. An integral equation is formulated for the slot electric field, and it is solved by the moment method. Data are presented for the slot electric field, a special aperture admittance, scattering parameters, and a far-field pattern. The special aperture admittance is a useful quantity in microstrip antenna design and is presented for various truncation lengths of the interior dielectric.

Characteristics of circular loop antennas above a lossless ground plane

Abstract: The circuit and radiation characteristics of a circular loop antenna above a lossless ground plane are studied. It is shown that the gain of this antenna is higher than that of a half-wave dipole above the ground plane. A gain as high as 10 dB is obtainable with this simple geometry.

Embedded insulated antennas for communication and heating

Abstract: The properties of insulated antennas that make them useful for subsurface communication or heating are discussed. Several antennas and associated feed lines suitable for use in bore holes or for in...

Highlights of antenna history

Abstract: A look at the major events in the development of antennas.

Receiver for car

Abstract: PURPOSE:To effectively perform diversity reception, by providing the 1st and 2nd antennas at upper or lower parts of a heating conductor wire group attached on a front window glass of a car respectively and coupling one of them to the heating conductor wire group in terms of high frequencies. CONSTITUTION:The 1st and 2nd antennas 10 and 11 having different pattern are provided at the upper or lower part of a heating conductor wire group 2 of a front window glass 1, and the 2nd antenna elements 11 are coupled with the group 2 on the center line of the window glass. An antenna with better reception state is switched and selected with an antenna switching circuit 17. Since the 1st and 2nd antennas are different for the pattern, height from the ground surface and the relation to the group 2, even if an output of one antenna is decreased depending on the direction of the driving car, the reception directivity with less dip can be obtained by switching the antenna to the other.

Conformal Antenna Array Design Handbook

Abstract: : Contents: Conformal Geometry; Aperture Synthesis; Modal Calculation of Slots on Cylinder; Modal Calculation of Slots on Cone; GTD Calculation of Slots; and Conical Array Experiments.

Rod-excited waveguide slot antenna

Abstract: A power-radiating slotted waveguide comprises one or more rods mounted inside the waveguide adjacent a non-inclined slot. The rod causes power to be radiated and because the slot is non-inclined, undesirable cross-polarized radiation is minimized. The energy radiated from the slot can be varied by varying the area between the rod and the waveguide walls.

Conformal and Small Antenna Designs

Abstract: : Select antennas are described that can be used effectively on conformal surfaces. Most of these antennas are compact, are electrically and physically small, and can be easily integrated into conical and cylindrical bodies. Edge-slot, microstrip, and dielectric rod radiator design techniques are employed in the development of these antennas. Critical design parameters, modes of radiation, empirical data, and theoretical considerations are discussed. The intrinsic properties and characteristics of selected dielectric materials are considered.

Missile multi-frequency antenna

Abstract: A multifrequency antenna for a missile is realized by an arrangement in which four microwave antennas are located under a narrow circumferential slot in the skin of the missile forming four separate antennas each with its own input connector. Each antenna consists of a probe fed annular quarter wavelength microwave cavity which radiate out of a top wall end slot. The cavity antennas are fed by a stripline distribution network directly under the antennas. Two L band antennas are positioned directly adjacent the inner surface of the missile skin and an S band antenna and a C band antenna are positioned beneath the L band antennas. A radome covers the circumferential slot.

Slot ring resonator and dispersion measurement on slot lines

Abstract: Slot ring resonators are used for measuring slot line wavelength The advantage is that no end effects need be considered The experimental results agree well with the theoretical results in the 26–33 GHz region

Broadband trapped multiple-wire antennas

Abstract: A vertical monopole consisting of 13 wires and 39 trap circuits, as a 10:1 scale model of an antenna for the 2- to 30-MHz band was built and tested. In the range from 18 to 600 MHz, the measured VSWR referred to 160 \Omega exceeds 4:1 in only a few relatively narrow frequency ranges. The results agree well with a simple design theory, which is based on Schelkunoff's transmission-line equivalence. My belief is that refinement of this approach may lead to antennas that are efficient and reasonably well matched over three or four octaves.

Reflector and Lens Antennas for Millimetre-Wave Radiometers

Abstract: A reflector antenna trade-off study for a multi-beam airborne radiometer is described. Two different types of plano-convex lens antennas are compared. Beam broadening characteristics of the antennas are examined and a novel conical scan arrangement introduced. The compatibility of different scanning and tracking techniques is examined.

Missile antenna and missile provided with such an antenna

Abstract: The invention relates to slot antennas. The utilisation of an axially symmetric wave guide consisting of two parallel metal plates (6, 7) one of these plates (7) being drilled with slots, and fed with the aid of an exciting probe (8), permits utilisation of the volume inside the antenna. Application to missiles.

The First Candelabra for Circularly Polarized Broadcast Antennas

Abstract: A study of a circularly polarized (CP) television multiple antenna installation shows that improved measurement and theoretical techniques are required to model the scattered horizontal pattern circularity and video response in a candelabra. Previously developed guidelines for horizontally polarized antennas in a candelabra are inadequate to describe the expected performance of CP antennas in the same configuration. Results of calculations and measurements of model CP antennas for a Columbus, Ohio candelabra are included.

Wideband Constant Beamwidth Horn Antenna

Abstract: Work is reported on the development of a new wide band H-plane sectoral horn antenna which is not subject to the usual l/f variation of beamwidth with frequency. The upper frequency limit of wide band horn operation is dictated by the onset of TE30 mode in the horn feeder and throat. A compensating moding device in the feeder is optimised so that operation over greater than 3:1 bandwidths can be obtained.

Antenna system for locating the position of a microwave signal source.

Abstract: not available for EP0023606Abstract of corresponding document: US4334225An antenna system for locating a microwave signal source utilizing two directional finding antennas (1,2) which have major radiation lobes (3,4) which are identical and are angularly offset relative to each other in the bearing plane but overlap so that the angular position of the signal source can be identified within the overlapping range of the lobes of the two antenna by using signal level comparison or ratio formation of two signal voltages received from the two antennas (1,2). False or ambiguous bearings occurring from side lobes which overlap are avoided by the use of a pair of auxiliary radiators (13, 14) which are associated with each of the primary directional finding antennas (1,2) and wherein the primary radiation direction of the auxiliary radiators are offset in the bearing plane by a specific angle relative to the direction of the primary direction finding antennas. The result is that the radiation level of each of the direction finding antennas (1,2) is accentuated on one side relative to the primary radiation direction. The antenna system with the present invention are also useful in intelligence radio transmitting and receiving systems.

New technique to improve antenna measurements in the presence of site reflections

Abstract: Accuracy in antenna pattern measurements is affected by the quality of the testing site. Stray reflections can be particularly troublesome if they distort the uniformity of the field required in the region of the test antenna. A novel technique to improve the performance against these effects is presented and discussed.

Field solution and electrical characteristics of slotted waveguides

Abstract: The tangential field on the surface of a narrow axial slot on the wall of a hollow circular, or a coaxial waveguide, due to an incident TE11 mode is obtained. The slot is assumed to be semi-infinite in length and located symmetrically in the E-plane. A solution for the fields in the solid and the slotted protions of the waveguide, as as well as in the slot itself, is ontained by assuming proper wave functions with unknown coefficients in both waveguide sections. The unknown coefficients are determined from the two matrix equations obtained by applying the continuity condition to the transverse fields at the boundary between the solid and the slotted portions of the waveguide. The coefficient values are then used to determine reflection and transmission coefficients and the slot field which satisfies the edge conditions. The results are also extended to the case of two indentical and diagonally-symmetric slots. In a similar manner, the problem of a slotted coaxial waveguide is also solved, and the corresponding results are presented.