US2870442A - Ferromagnetic antenna systems - Google Patents

Description

Jan. 20, 1959 w. J. POLYDOROFF 0,

FERROMAGNETIC ANTENNA SYSTEMS Filed March 26, 1956 7H ..s I 6 III" a 'm'" United States Patent FERROMAGNETIC ANTENNA SYSTEMS Wladimir J. Polydorolf, Kensington, Md. Application March 26, 1956, Serial No. 573,713

6 Claims. or. 343-787) This invention relates to ferromagnetic antenna systems, which generally comprised a pick-up coil associated with h. f. ferromagnetic material to increase the efliclency of such devices.

In the usual systems such as described in my U. S. Patents 2,266,262 and 2,624,004 the pick-up coil is placed vertically, or with its axis towards the direction of propagation and a magnetic core in the field of the coil enhances the generation of electromagnetic effects in the antenna thus making it more efficient, and, as the second quoted patent shows, still more by elongating the core and the coil.

In my U. S. Patent 2,804,617, of which present invention is a continuation in part, it has been shown that in addition to the above described effects the magnetic material actually attracts, deflects and conducts electromagnetic component of radiated field in a desired direction and to a location where a coil may be installed. In the previously known systems the pick-up coil per se was used as a loop antenna with or without reinforcing action of the magnet so that its rotation along the vertical axis produced well known figure eight pattern with its maxima and minima.

In the present invention the search coil is used with its plane horizontally or With its axis perpendicular to the direction of propagation, at which position the search coil is completely devoid of its own pick-up of radiated energy. The energy is conducted to the coil by stationary or rotating ferromagnetic elements depending on what pattern, omnidirectional or figure-eight, is desired to achieve. It follows that in the new system the antenna effect, due to direct pick-up of electrostatic component is entirely eliminated, as well as the static disturbanoes picked up by the coil as a vertical rod.

The principal object of the invention is to provide an antenna system employing ferromagnetic means and a search coil placed with its axis vertically for vertically polarized waves in a permanent fixed position thus dis pensing with commutating means for the coil and eliminating electrostatic pick-ups of the signal and static.

Another object is to avoid the troubles associated with atmospheric conditions, as the search coil and its cable may be completely sealed.

A further object is to provide a collector of electromagnetic radiations which produces an omnidirectional pattern without the disadvantages of a vertical antenna which, as it is known, contributes greatly to the generation of static disturbances.

Those and other objects will be better understood if reference is made to the accompanying drawing in which:

Fig. 1 shows a schematic representation of the invention.

Fig. 2 shows a modification of Fig. 1.

Fig. 3 shows a schematic presentation of another form.

Fig. 4 and Fig. 5 show detailed construction. of the invention.

Fig. 6 shows another variant of the construction.

a cylindrical piece 2 of high frequency ferromagnetic.

material, preferably of ferrite. Search coil 1 is connected through a cable 13 with a transformer 3 whose secondary may be tuned to the incoming frequency by a capacitor 4. Thus far the described circuit if properly shielded is incapable of receiving any signal from an outside source. Two elongated rods 5 of a ferromagnetic material of high permeability are now added as shown with their ends close to or in contact with the top and bottom ends of the cylinder 2. These rods now pick up the radiated energy and transmit electromagnetic lines throughout their length, into the cylinder and through the bottom rod. The search coil now picks up the energy and transmits it in the form of current to the receiving system.

When rods are simultaneously rotated in the horizontal plane it is established that the maximum pick-up occurs when their direction is perpendicular to theemitter and very sharp minimum in excess of 20 db is observed when the rods are in line with the emitter. Thus a directional antenna system is produced without rotation of the coil producing a conventional figure eight pattern by simple mechanical rotation of plurality of magnetic elements.

In Fig. 2 the pair of rotating elements may be placed not in line but at an angle, as before, one at the top and the other at the bottom of cylinder 2 in which case if both rods are simultaneously rotated a similar pattern is obtained, the maxima and minima corresponding to the direction of bisector of the angle between two rods.

When two or more rods are placed on top and the bottom of cylinder 2 in the diametrically opposed manner, the antenna shown on Fig. 3 exhibits a somewhat reduced pick-up completely devoid of direction properties, similar to the pattern obtainable by a vertical rod antenna, except that the pick-up is due solely to the electromagnetic component of the wave. The vertical antenna has been used in directional finding systems to determine the sense of the signal and has been found to be the source of electrostatic disturbances. By proper phasing of the signal obtainable from the antenna of Fig. 3 and combining same with the "figure eight pattern of above described directional antennas one can obtain a signal for sense determination.

Referring now. to Fig. 4 and Fig. 5 one can see the actual construction of one embodiment of directional antenna. A ferrite spool 2 is surrounded by the coil 1 which is moulded in a plastic container 6 with flanges 7 and supports 8 throughwhich flanges and supports the connections are made to the cable 13. The ferromagnetic spool 2 and tworods 5 are assembled together on shaft 9 which rotates in the bearing lllof mounting plate 11. rounded ends and a taper to a greater width at the outer ends for greater pick-up of energy.

The construction of Fig. 6 is somewhat difierent from that of previous figure in that the search coil 1 and its ferromagnetic spool 2 are permanently fixed on the tubular bearing 10 and the shaft 9 terminates on top with two brackets 12 to which bracketsthe ferromagnetic rods 5 are attached. The inner ends of rods 5 are shaped to conformwith the cylindrical surface of the spool 2 and adjusted to form a small circular gap between the spool and the rods. In addition, the lower 'revolving end may be Z-shaped so as to have both rods As Fig. 5 shows the rods 5 may have V iead-in wires from the coil may be brought out within the bearing 10 and terminated by a cable 13.

As can be seen from the description the search coil is placed horizontally for vertically polarized wave, so that direct pick-up of electromagnetic component is-elirninated and its axial length is very small so that antenna efiect is negligible even without screening. The coil, being in a fixed position, can be easily treated against moisture and the commutating means are entirely eliminated.

Having thus described my invention, what I claim is:

1. A directional antenna system for the reception of electromagnetic radiations having a ferromagnetic core of high permeability in the form of a hollow body of rotation, the axis of said core being in the direction of polarization of said radiations, a search coil around said core, a pair of elongated ferromagnetic bars, each being in the plane perpendicular to said axis, said pair being connected together for rotation by a common shaft protruding through the hollow of said core, the respective inner ends of said elongated oars being connected through the smallest possible airgap to the opposite end portions of said core.

2. A directional antenna system according to claim 1, characterized in that said ferromagnetic bars have rectangular cross-sections.

3. A directional antenna system according to claim 2, characterized inthat-said cross-sectionsare increasing towards the outer ends of said bars.

4. A directional antenna system according to claim 1, characterized in that said search coil has self-supporting means independent of said rotation.

5. A directional antenna system according to claim 4, characterized in that said supporting means contain connecting leads to said coil.

6. A directional antenna system according to claim 1, characterized in that said ferromagnetic core and said bars are made of high permeability ferrite.

References Cited inthe file of this patent UNITED STATES PATENTS 2,624,004 Polydoroff Dec. 30, 1952 2,718,003 Hemphill Sept. 13, 1955 2,740,113 Hemphill Mar. 27, 1956 2,755,468 Mountjoy July 17, 1956 FOREIGN PATENTS 735,429 Germany May 14, 1943

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