Parallel Wire Grid Research Articles

Demonstration of Magnetic Domain-Wall Storage and Logic

The operations of read-in, shifting, conditional erase, and fan-out in a system of domain-wall storage and logic proposed by Smith have been experimentally demonstrated. The several operations were performed by controlling the current flowing through a configuration of wires placed closely under a 5 to 40 mil wide, 50 to 300 A thick Permalloy strip, and the sequence of events was observed on the top side of the film using the Bitter technique. The basic wiring geometry was a narrow-spaced grid of series-connected parallel wires that made an angle of 50° to 75° with the strip of film, the smaller angles being necessary for the thinner films. Conditional erase was most successful in films below 100 A thick, as in this thickness range walls of the same sense form double walls which require relatively large fields for erasure.

Transmission and reflection by a parallel wire grid

Transmission and reflection by a parallel wire grid

Magnetic coupling by parallel-wire grids and soldered cross-lateral grids in disc-seal triodes

The parallel-wire grids frequently used in disc-seal triodes exhibit a perceptible magnetic coupling of the grid which neutralizes the anodecathode capacitance within the range of application of the tubes (self-neutralization). Detailed investigations show that the magnetic coupling is considerably less with a new type of grid?the soldered cross-lateral grid, where the self-neutralization frequency lies above the range of application of disc-seal triodes. Comparison measurements performed on parallel-wire grids and soldered cross-lateral grids with the aid of a measuring circuit that is described in detail showed a good approximation to curves computed for a triode as a passive four-pole with the aid of an equivalent circuit diagram. An indication is given of the significance of this problem to valves.

Reflection at arbitrary incidence from a parallel wire grid

Reflection at arbitrary incidence from a parallel wire grid

Reflection at arbitrary incidence from a parallel wire grid

A solution is outlined for the problem of a plane wave, incident obliquely, with arbitrary polarization, on a planar grid. It is assumed that the wires composing the grid are of homogeneous material and that their diameter is small compared with the separation. The general result when specialized to parallel polarization agrees with published results.

REFLECTION FROM A WIRE GRID PARALLEL TO A CONDUCTING PLANE

A solution is outlined for the problem of a plane wave incident obliquely on a parallel-wire grid which is backed by a plane conducting surface. The electric vector of the incident wave is taken to be parallel to the grid wires. The equivalent transmission line problem is pointed out. It is shown that, in certain cases, a resistive wire grid will absorb all the energy in the incident wave.

Transmission of Electromagnetic Waves through Pairs of Parallel Wire Grids

The control and direction of electromagnetic waves is accomplished, in general, by the use of boundary materials and structures which produce desired effects on such waves when irradiated by them. An important class of boundary structure for this purpose is a surface having alternate areas of conducting and nonconducting material. Grids formed of a large number of parallel cylindrical conductors of circular cross section, uniformly spaced and lying in a common surface, are among the most generally useful of this class of boundary structure. Single layer parallel wire grids have received considerable study in the past. However, little information is available concerning the characteristics of multiple layers of such grids An analytical solution is obtained for the power transmission coefficient of a double grid system. Power transmission coefficients for various combinations of system parameters are computed from the analytical solution and tested experimentally. The solution is found to yield excellent correlation with experiment until the interwire spacing approaches the wavelength.

Filter action of parallel wire grids

Filter action of parallel wire grids

Passive Four-Pole Admittances of Microwave Triodes

Measurements have been made of the passive, four-pole admittances of parallel-plane triodes over a wide range of cathode-to-grid and grid-to-plate spacings at a frequency of 4060 megacycles. Results are given for a parallel wire grid and a cross-lateral grid. The microwave transadmittances are found to be much higher than the values measured at low frequencies.

Surface impedance of an infinite parallel-wire grid at oblique angles of incidence

A study is made of the scattering of a plane wave incident obliquely upon an infinite plane grid of parallel equidistant circular wires. A simple means is described of picturing the mechanism by which side waves are produced as the angle of incidence is varied. Exact formulae and curves for the shunt reactance of the grid are given for the most useful case in which the spacing is less than a wavelength. Thus the reactance of the grid referred to the component of the wave impedance of the incident plane wave which is normal to the grid, viz. 376.5 sec θ ohms, isXg = 376.5d/λ[logε (d/2πa)+F(d/λ,θ)] ≃ 376.5d/λ[logε (d/2πa) for a ≪ b ≪ λ,where d = spacing of wires, a = radius of each wire, θ = angle of incidence. The correction term is plotted in Fig. 6. The reflection coefficient is r = − 1/(1 + 2Xg/Zsec θ), Z0 = 376.5 ohms

Electrostatic Electron Lenses

AN article by K. Spangenberg and L. M. Field (Elec. Comm., 21, No. 3; 1943) describes and discusses the measured characteristics of a number of electrostatic lenses, giving the characteristic curves of nine different lenses belonging to three basic types. The forms tested were cylinder lenses of various spacings and diameter-ratios, aperture lenses (parallel plates with circular apertures on the beam axis) of various spacings, and, for comparisons, a lens formed by a cylinder and an aperture in a plate. By interpolating between the sets of curves given, approximate predictions of the properties of lenses of slightly different spacings or diameter-ratio may be made. The test method employed makes use of a conventional electron-gun with parallel wire grids which, for measurement purposes, are placed before and after the lens to be tested. All the lens characteristics are deducible from measurements made on shadows cast by these measuring grids upon a fluorescent screen placed in the electron beam at a suitable distance from the gun.