Showing papers on "Conformal antenna published in 1972"

Microstrip antennas

Abstract: Microstrip antennas consist of a planar resonant radiating element parallel to, but separated, from a ground plane by a thin dielectric substrate ( t \ll \lambda ). These antennas are very thin and consequently rugged and easy to mount. They may be fed from the back through the ground plane or from the edge by depositing microstrip lines on the dielectric substrate. Several varieties of microstrip antennas are discussed in this paper. Design procedures are given for both linearly and circularly polarized antennas. Measured patterns are presented for antennas from UHF through C band.

A Novel Slots-and-Monopole Antenna with a Steerable Cardioid Pattern

Abstract: The outputs of a vertical monopole and two mutually perpendicular slots in a horizontal plane can be properly combined to yield a steerable cardioid-shaped pattern for vertically polarized waves. The required weighting factors for placing the pattern null in any desired direction are presented in graphical form. The shape and the half-power beamwidth of the steerable pattern are examined. This combination antenna unit offers important advantages in direction finding and other applications, especially at microwave frequencies.

Engineering approach to the design of tapered dielectric-rod and horn antennas

Abstract: The taper profile of optimized dielectric-rod and horn antennas is synthesized as a series of non-interacting planar radiating apertures. The method is semi-empirical, straightforward to apply, enables the dielectric-rod antenna to be satisfactorily optimized and provides a means of evaluating and optimizing a dielectric-horn antenna with variable wall thickness. The optimum profiles are taken as those which smoothly transform the surface-wave power from the launcher to the radiating aperture. The optimization of the dielectric-rod antenna considerably improves the radiation pattern while computations supported by measurements confirm earlier reports that a dielectric-horn can have a higher gain than a metal horn of similar dimension but side-lobe level is seen to be an important issue. Wide flare-angle horns give ideal E-plane patterns at the expense of a high side-lobe level in the H-plane; for small flare angles the dielectric horn gives similar patterns to the tapered rod antenna and thus preserves rotational symmetry. Calculations throughout are restricted to cylindrical geometry but other geometries and variations on the dielectric-horn principles are described. Useful engineering design data have been compiled for both the dielectric-horn and rod antennas and curves are given which determine near-optimum parameters for gains up to about 20 dB which is seen to be a practical operating limit for these surface wave devices. A unified impression of dielectric antennas emerges with the important conclusion that, when optimized, dielectric-rod and horn antennas are in fact competitive with small metal horns for some applications; furthermore the dielectric-horn antenna, used singly or in arrays, is an ideal device for producing a low side-lobe level in the E-plane.

Sidelobe control of antenna patterns

Abstract: Using the iterative sampling method, sidelobe peaks can be made to conform to a specified shape within a given tolerance The iterative sampling method allows the specifications for a given problem to be just satisfied, thereby avoiding an overdesigned pattern which may have a complicated current distribution or wide main beam The type of calculations involved are typically only summations of series of elementary functions and, consequently, the method is easy to apply to both large and small antennas Several computer examples are presented, all of which have low ratios of maximum to minimum current amplitudes and low super directive ratios

Design and performance of four buried UHF antennas

Abstract: As a result of a 10-month study by the Institute for Telecommunication Sciences, four UHF antennas were designed and fabricated, and their absolute power gains for elevation angles from 1\deg to 45\deg and azimuthal patterns at 5\deg elevation angle were measured with each antenna buried beneath 1 m of refractory concrete. Relative response of the four antennas, placed in solid granite, to a signal transmitted from an aircraft at ranges up to 300 km were recorded. The performance of the best buried antenna was comparable to that of a \lambda/4 monopole fed against a 1\lambda diameter ground plane resting on the ground surface near the buried antenna.

Multiple beam antenna

Abstract: PROBLEM TO BE SOLVED: To provide a small multiple beam antenna capable of suppressing spurious radiations and avoiding the increase of the loss due to multi-stage of a switch by simplifying the switching mechanism of termination/power feeding. SOLUTION: The multiple beam antenna is provided with two patch antenna elements 301, 302 for connecting power feeding means 501, 502 via switches 701, 702 and a terminating means 6 to via switches 703, 704 to different points of one element; patch antennas 310 arranged in a line so as not to be overlapped with an N element (N being natural number) between the two patch antennas; and a coupling means or an electromagnetic coupling means by a line 4 between all the adjacent patch antenna elements. The switches 701 704 (702, 703) are connected, and the switches 702, 703 (701, 704) are opened, thereby forming a beam on one side, and the connection and opening of all the switch are replaced, thereby forming a beam on the other side. COPYRIGHT: (C)2005,JPO&NCIPI

Signal-to-noise performance of cryogenic electrically small receiving antennas

Abstract: The performance of electrically small antennas in the presence of noise is studied. Signal-to-noise ratios (S/N) are formulated and compared to the ideal case. It is found that cooling can result in a considerable increase of the product (bandwidth) \times (S/N) . Some practical examples are presented.

Conical-reflector antennas

Abstract: The mechanical advantages of a singly curved conical reflector are demonstrated by the experimental test of a furlable 1.83 m conical-Gregorian antenna at 16.33 GHz. The measured gain of 47.5 dB corresponds to a net efficiency of over 57 percent. A ray-optics analysis of conical-reflector antennas is presented, and data useful in the design of conical antennas is given. The conical-Gregorian antenna, in which a subreflector is used in conjunction with a conventional horn feed, is considered in detail. A physical-optics analysis of the conical-Gregorian antenna is used to investigate diffraction and other effects, and to analytically confirm the high performance of the antenna. It is concluded that conical antennas are a valuable addition to available antenna-design concepts.

Measurement of Circularly Polarized Broadcast Antennas

Abstract: This paper reviews, by way of illustration, some of the terminology used in describing antennas radiating rotating polarization, and demonstrates how the parameters necessary to specify such antennas are measured.

Investigation of L-band shipboard antennas for maritime satellite applications

Abstract: A basic conceptual investigation of low cost L-band antenna subsystems for shipboard use was conducted by identifying the various pertinent design trade-offs and related performance characteristics peculiar to the civilian maritime application, and by comparing alternate approaches for their simplicity and general suitability. The study was not directed at a single specific proposal, but was intended to be parametric in nature. Antenna system concepts were to be investigated for a range of gain of 3 to 18 dB, with a value of about 10 dB considered as a baseline reference. As the primary source of potential complexity in shipboard antennas, which have beamwidths less than hemispherical as the beam pointing or selecting mechanism, major emphasis was directed at this aspect. Three categories of antenna system concepts were identified: (1) mechanically pointed, single-beam antennas; (2) fixed antennas with switched-beams; and (3) electronically-steered phased arrays. It is recommended that an L-band short backfire antenna subsystem, including a two-axis motor driven gimbal mount, and necessary single channel monopulse tracking receiver portions be developed for demonstration of performance and subsystem simplicity.

Omnidirectional tracking weapon control system

Abstract: A rear looking radar antenna system with a look angle of ± 120° installed on a missile launching aircraft which has a conventional front looking antenna with a look-angle of ± 60°. This permits a full 360° to be covered. The search and track circuitry of the existing weapon control system is shared between the back and front antennas. As a target passes beyond the look-angle of one of the antennas, the other antenna picks it up. The weapon control circuitry is switched from the one to the other antenna at this time.

Power-Handling Capability of ECM Antennas.

Abstract: : The electrical breakdown characteristics of the LPJ-1 and the SLOT L-1 antennas furnished by Lincoln Laboratory were measured. Modifications to increase the power-handling capability of the SLOT L-1 antenna were suggested. The effect of laser irradiation on antenna breakdown was investigated using ruby and CO2 lasers. The antenna studied was a dielectric plugged X-band waveguide. Blackout times and altitudes were estimated for the TBV vehicle C-band beacon and S-band telemetry antennas. (Author)

Microstrip technology and its application to phased array compensation

Abstract: A systematic analysis of mutual coupling compensation using microstrip techniques is presented. A method for behind-the-array coupling of a phased antenna array is investigated as to its feasibility. The matching scheme is tried on a rectangular array of one half lambda 2 dipoles, but it is not limited to this array element or geometry. In the example cited the values of discrete components necessary were so small an L-C network is needed for realization. Such L-C tanks might limit an otherwise broadband array match, however, this is not significant for this dipole array. Other areas investigated were balun feeding and power limits of spiral antenna elements.