Showing papers on "Reflective array antenna published in 1969"

Analysis of yagi-uda-type antennas

Abstract: A method of analyzing Yagi-Uda-type antennas is presented. Since the Yagi-Uda array is a fairly well-known antenna, it is used as an example to demonstrate the application and accuracy of the method. However, the method of solution is not limited to a planar array, such as the Yagi, but can be applied to arrays of nonplanar linear elements. The approach taken in analyzing Yagi-Uda antennas is based on rigorous equations for the electric field radiated by the elements in the array. All interactions are taken into account. Calculated results are presented for the Yagi-Uda array that show excellent agreement with experimental results reported in the literature. In addition, the dependence of the far-field patterns on the phase velocity is shown. It is also demonstrated that the phase velocity is generally nonuniform along the array.

Mutual coupling between log-periodic antennas

Abstract: Numerical techniques are used for the analysis of mutual coupling in arrays of log-periodic dipole antennas. The analysis is formulated in terms of impedance and admittance matrices for the dipole and transmission line networks. Approximations are made to allow the solution for moderately sized arrays to be practical with the existing generation of computers. Antenna patterns for the array are expressed in terms of the current incident on each log-periodic antenna. Results are presented for systems of one, two, and three log-periodic antennas.

a Class of Boundary Value Problems-Part II: Waveguide Phased Arrays, Modulated Surfaces, and Diffraction Gratings

Abstract: URRENT applications in radio astronomy and radar have generated great interest in electronically scanned or phased array antennas. One such antenna is the phased array of open-end rectangular waveguides, a segment of which is shown in Fig. 1. An essential consideration in design of such antennas is that of matching the antenna over a wide range of scan angles to maximize power transfer from antenna to the space region. Thus, in the analysis of these arrays, the essential properties to be determined are the aperture fields, from which the radiation pattern may be calculated, and the reflection coefficient in each waveguide as a function of scan angle.

A data-gathering antenna array for transhorizon propagation research

Abstract: A versatile vertical antenna array and receiving system have been developed for measuring relative phase and amplitude along the wavefront of an S -band transhorizon signal The array, which operates at 3200 GHz, consists of 12 parabolic antennas 122 meters (4 feet) in diameter which are spaced 139 meters apart on a tower for a total effective vertical aperture of 1524 meters ( 162 \lambda ) The raw data outputs from the array are amplitude and differential phase successively sampled from the 12 elements Data can be taken at variable rates of up to 100 passes per second over the 12 elements The data are processed in a computer to form conventional uniformly illuminated array beams 03 degree wide with a grating lobe spacing of 39 degrees or to produce many combinations of correlation functions A reference signal is used to cancel the effects of relative motion of the array support structure from the phase data The array and receiving system and actual performance characteristics are described

Experimental investigation on spherical arrays

Abstract: The radiation pattern of an equally spaced spherical array is obtained experimentally and is compared with theoretical patterns obtained previously. Due to the great difficulty of exciting each element of the array, an incident plane wave was used to excite the array. A method to eliminate the incident plane wave on the measurements of the fields scattered by the array is discussed.

VHF antenna systems for spin-stabilized satellites

Abstract: Lincoln Laboratory has developed two circularly polarized VHF antenna systems for use on spin-stabilized satellites, Both are described, and test results are discussed. One is a low-gain (3-dB) antenna with omnidirectional coverage in the equatorial plane. The second is a high-gain (10-dB) antenna with a despun beam electronically scanned to always be Earth directed. Development of the component dipole and slot array elements is explained, and performance data are given for the final flight configuration.

Long wire v-antenna system

Abstract: Long wire antenna arrays comprising combinations of V antennas have wide-band directive characteristics when the antennas are inclined above ground and spaced from each other to make side lobe nulls and peaks of the pattern of each V antenna substantially coincide with peaks and nulls, respectively, of the array factor. Pairs of V antennas can be connected end-to-end with their apexes at the extreme ends to form tandem-V antennas, which can be arrayed with other tandem-V antennas. The arrayed antennas (V and tandem-V) are generally aligned laterally but offset from each other longitudinally and/or vertically. Space-saving arrays of V and tandem-V antennas have corresponding apexes coincident in the lateral and longitudinal directions and have the intermediate connections of one antenna longitudinally spaced from the corresponding interconnections of the other antenna. In other arrangements, V antennas having successively increasing apex angles are arrayed in circular sectors with all the Vantenna legs extending along radial paths from a common center.

A simple antenna with good circular polarization

Abstract: Simple antenna with good circular polarization over wide space sector, showing geometry, normalized orthogonal field distributions and beamwidth range, considering slot combinations

Scattering of a plane electromagnetic wave by a linear array of cylindrical elements

Abstract: An approximate method for numerically calculating the scattered field of a linear array of center-loaded cylindrical elements illuminated by a plane wave incident in the H plane of the array is described. To illustrate the use of the approximation technique, the H -plane scattered field of an eight-element model array is calculated for various conditions of impedance loading and illumination. From extensive calculations, it is found that the H plane scattered field of the array can be represented approximately by the product of the electric field scattered in the reflected direction and an interference factor. The interference factor is the equivalent of the complex array factor of the model array when excited with uniform amplitude and an element-to-element phase progression proportional to the sine of the angle of incidence of the illumination.

Circular arrays of radial and tangential dipoles for turnstile antennas

Abstract: A method of obtaining a turnstile antenna from a circular array of radial or tangential dipoles is presented. Approximate current distributions, terminal admittances, and radiation fields are given for arrays of 3, 4, and 5 half-wavelength elements for various array diameters.

Mast-mounted loop antenna

Abstract: An antenna assembly including separate antennas for receiving UHF and VHF signals disposed along spaced points on an antenna mast. The UHF antenna forms a closed configuration aligned in a plane at the top of the mast while the VHF antenna is characterized by two triangular members fastened to the mast in side-by-side relation aligned in a plane at an angle to the mast. Specially formed cylindrical insulative blocks, connected to the mast, furnish anchoring mounting support for the antennas.

A method of controlling current distributions on long antennas

Abstract: It is shown that a long cylindrical antenna with multiple excitations can be made to have desirable current distributions along its structure when the driving voltages and the positions of the generators are properly chosen. Applications of this technique to practical problems are discussed.

Polarization discrimination for satellite communications

Abstract: It appears feasible for satellite relay systems to provide polarization discrimination of 20 to 30 dB (or more with adaptive antennas) in the antenna main beam Thus if the systems are designed to operate with smaller wanted to unwanted signal ratios than those provided by polarization discrimination, it should be possible to double the effective spectrum available by using it independently on two orthogonal polarizations

On the receiving properties of a small horizontal bare circular loop antenna buried in the ground

Abstract: It is shown that when a small bare circular loop antenna is buried in the ground it will respond to a vertically ( E field) polarized ground-wave or sky-wave source with a directional azimuthal pattern. The response to a horizontally polarized skywave source is greatly enhanced by burying the antenna and is also shown to be far from omnidirectional in azimuth. These results depend upon the presence of a relatively small departure from a constant current distribution on the loop when it is regarded as a driven element. The current distribution formulas of Chen and King permit easy analytical estimates of these effects.

Design of a VHF Suppressed Antenna

Abstract: The paper presents the design details and the experimental results of an E-fed cavity type suppressed antenna for operation in the VHF region. Empirical formula has been derived for critical dimensions. The radiation pattern of two antennas back to back is omnidirectional.

Spacecraft phased array configurations

Abstract: Ideas of spacecratt phased array configurations are described in this communication. The aperture of the phased array is 28.5 by 28.5 feet.

Computation of radiation patterns of rhombic antennas with log periodic dipole array termination

Abstract: In this letter, the effect of terminating resistance loss in the case of rhombic antennas has been studied. Generalized analysis has also been made to compute the radiation pattern of rhombic antennas with the log periodic dipole array termination. Theoretical radiation patterns are plotted and it is observed that this new method improves the directivity and lowers the sidelobe level.