US2598914A - Aperiodic electronic blocking valve - Google Patents

Description

June 3, 1952 Filed Jan. 24, 1948 INVENTORS HARRY HUBER LOTHAR BRUCK BY +C0.

AGENT-S Patented June 3, 1952 APERIODIC ELECTRONIC BLOCKING VALVE Harry Huber and Lothar kriick, Paris, France,

assignors to Compagnie Generale de Telegraphic Sans Fil, a corporation of France Application January 24, 1948, Serial No. 4,138 In France January 29, 1947 3 Claims. (01. 315-39 1. The present invention relates to an aperiodic blocking tube and is concerned with tubes of the type used in radar apparatus when the transmitter and the receiver are connected to the same aerial. mit-receive-switch or T. R. S. tubes.)

For a fixed wavelength, such tubes operate with a circuit having a high quality factor but for a fairly broad range of wavelengths it is necessary to use aperiodic blocking tubes. In this case it is customary to use blocking tubes without any electrodes (so-called Nullodes), which are placed inside a coaxial transmission line. But, as is well known, the size of these tubes becomes so small when they are used for centimetre-wave work that it is difficult to obtain a discharge which is reliably accurate either in respect of its position or as regards the control of its intensity. The thickness of the glass wall becomes proportionately too great as compared with the space occupied by the discharge, so that when the tube strikes the characteristics of the line are not sufficiently modified.

The blocking tube which is the subject of the present invention affords a better solution of the difiiculties referred to. One practical embodiment of the said invention is shown (by way of example only) in the accompanying drawing, which shows the tube in section. The blocking tube B adapted to operate on centimetre wavelengths, is interposed between the transmitter and the receiver in the path of a concentric or coaxial transmission line indicated by references L and L. The walls or envelope D of the tube are united with the outer surfaces of the said line, the outer surfaces being designated by E and E" on the drawing, the inner conductors by I and I'. The parts J, J' are airtight insulating joint-pieces, adapted to seal off the blocking tube and at the respective levels of these joint-pieces a sudden change occurs in the diameter of the internal conductor of the concentric line. The amount of this change of diameter is such that, although there is a change of medium, there is no discontinuity in the value of the characteristic impedance of the line. Similarly, and according to the invention, in a definite zone, at the centre of the tube, the diameters of the outer and inner conductors of the line both taper simultaneously at R and R, without there being any variation of the said impedance. At the place where this variation of diameters occurs, the electric field is of greater intensity than elsewhere; that is why this particular place is favourable for the discharge.

(These tubes ar known as trans-' 'Furthermora'in order to obtain a certain and definite discharge at this point, it is advantageous to provide for a suitable degree of preionization in the vicinity thereof. This can be obtained by means of an auxiliary discharge in the actual atmosphere used for the principal discharge of the tube. Such auxiliary discharge takes place between a ring A, which is supplied by the lead H, and the outer conductor E, E (E and E are connected electrically by the constricted part which, at the point of constriction, is provided with radially distributed perforations designated T on the drawing which allow the ionization electrons to pass). Brackets K, K mounted upon insulating members C, C' aiford means for mechanically supporting the discharge system.

It is possible to provide other means of preionization. One of such means consists in irradiating the discharge space, by means of a luminous lamp of toroidal shape, such lamp having its own mercury vapour discharge and occupying the place of the ring A mentioned hereinbefore. This system has the advantage that when it is used the life of the tube is longer.

I Furthermore, the inner wall of the outer conductor of the line, adjacent the constriction which promotes the discharge, may be coated with a light sensitive layer, so as to use the photo-electrons by the action of the external mercury vapour lamp. Alternatively, this same portion of wall may be coated with a radio-active layer, and in that case no other auxiliary exciting source is required.

Of course, the manufacture of the tube is so arranged that its parts can readily be assembled for example, by interfitting the various'simple elements.

In contradistinction to the T. R. S. tube, provided with a resonant cavity of high quality factor, there is no voltage transformation in the tube according to this invention (just as in the socalled Nullode tubes). In many cases, however, this is a small disadvantage when compared with the advantage of being able to use wide frequency ranges with the possibility of having a variable wavelength. There is no signal reflection, owing to the constancy of the characteristic impedance. If desired, the coupling between the tube and the outer line may be such that it does not alter the value of the characteristic impedance.

We claim:

1. In a coaxial transmission line comprising an interio and an exterior conductor for ultra.

7 and insi'desaid portionof the line, a'zone where said interior and exterior conductors taper s imultaneously to constitute two truncated cones united at their tops by a cyl ndricalpo tipg 2. A device according to claim 41 in which means are provided on theziiiterior oi said en: velope for producing a pfei'oiiisati oniinl in; terior of said envelope in the vicinity of thesaid zone defined by the simultaneous? taper of the exterior and interior conductors of said linfsaid means surrounding the reduced portion of the exterior conductor of the said line.

4.. 9m? wa d n to claim 1 c ei on the interior of said tube, a ring surrounding the exterior conductor of said line, in the tapered portion, and means disposed on the exterior of said envelope for impressing from outside of said envelope onto said ring a voltage sufiicient to produce a preionisation in the zone defined by. thesimultaneous reduction of the two line conductors.

HARRY HUBER.

LOIHAR BRiicK.

BatnR NoEs CITED Theiollowing references are of record in the file -of this patent;

UNITED STATES PATENTS Number Name Date 2,403,302 Richmond July 2, 1946 2,422,190 Fiske June 1'7, 1947

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