US2054895A - Short wave radiation - Google Patents

Description

Sept. 22, 1936.

w. DALLENBACH 2,054,895

SHORT WAVE RADIATION Filed June 26, 1953 /n ventor: W- d g'lll -finbal c/h Patented se t. 22,1936 v v 2,054,895

UNITED STATES PATENT OFFICE 2.054.895 snon'r WAVE RADIATION Walter Dillenbach, Berlin-Charlottenburg, Germany, assignor to N. V. Machinerieen-en Appar'aten Fabrieken "Meat", Utrecht, Netherlands Application June 26, 1933, Serial No. 847,733 Infiermany July 6, 1932 Claims. (Cl. 250-11) It is difficult when communicating with ultrain the accompanying drawing, in which Figures short waves to cause sender and receiver to oper- 1, 2 and 3 are diagrams of embodiments of ate selectively so that neither an undesired rethe invention. I ception of foreign stations by one's own re- Fig. 1 shows an arrangement having an elec- 5 ceiver nor the unauthorized reception of one's tric dipole represented by the linear oscillator ST 5 own transmissions by third persons or'their inwhich coincides with the axis X-X of a .paraterl'erence is possible. In order to obtain high bolic mirror having coinciding axes of rotation selectivity it has been proposed to send the sender and symmetry, the focus of the mirror being at F on a very narrow and constant wave band and and the apex at A. The direction of propagation to provide the receiver with the best possible of the rays emitted by the mirror also coincides l0 screening means. with the direction X-X and thus with the axis of In order to render messages inaccessible to unthe linear oscillator ST. authorized persons during the transmission of in- Such an arrangement produces radiation which telligence, it has been proposed to build senders differs in essential points from the known arfor a very narrow wave range and thus make rangements for producing directional waves, and 15 reception more difiicult. Furthermore, arrangefurther explanation will be given with reference ments have been proposed which, as far as posto the example shown in Fig. 1. Corresponding sible, permit the bunching together of the rays to the direction diagram of the emitter indiin one direction to prevent, or render difiicult, cated, the radiated energy will preferably be reception in other directions, but such arrangeemitted in the equatorial plane MNF while only 20 ments fail to give satisfaction in view of the invery slight portions of the rays will fall into the creasing use of receiving devices. angular space PFQ where the radiation leaves the By producing a wave of peculiar structure the mirror without being reflected and concentrated. invention provides a means for rendering recep- This means that stray radiation falling, in the 5 tion by unauthorized persons extraordinarily usual arrangements, in the angular space PFQ difficult, is practically eliminated in the arrangement ac- An electromagnetic oscillator, such as an eleccording to Fig. 1, which produces greater concentric or magnetic dipole, has an axis of symmetry tration of the rays in the interest of secrecy and in which it practically does not radiate at all. in order to avoid interference with adjacent sta- The rays emitted by it extend chiefly vertically tions. Simultaneously, the new arrangement 30 to the axis in the equatorial plane and decrease makes it possible to reflect practically the entire in the direction towards the pole in the square radiated energy emitted by the sender ST on the of the cosine of the geographical latitude. To mirror in the direction XX, which involves a permit utilization ofthe directional radiation, an considerable saving in expenditure of energy or emitter of this type has always been arranged so a higher field intensity at the point of reception. 35 that its axis was adjusted vertically to the direc- However, the new arrangement affords another tionof propagation into which the rays were to advantage. The energy emitted by the radiator be thrown. In wireless telegraphy, the axis of leaves the mirror without passing over the radisymmetry of an aerial is, therefore, as a rule, ator again, as is always the case with arrangeoriented vertically to the earths surface. Ultraments in which the emitter is disposed vertically 4') short electric waves in the sphere of centimeter to, the mirror axis. In an arrangement of the and decimeter waves permit concentration of hitherto customary type a coupling will thereradiation for instance by means of reflectors. fore be produced between the mirror and emitter, Applying the fundamental principle mentioned which makes it necessary to choose the focal disabove, when such reflectors were used, the artance of the mirror at a certain ratio to the wave rangement of the axis of symmetry of the emitter length, whereas in the arrangement shownin relative to the direction of' propagation of the Fig. 1 such a coupling between reflectors and rays has been retained, so that even in case of a emitters is not required, so that the focal disreflector, the axis of symmetry is adjusted vertance ofthe mirror may be chosen independently 5o tically to the direction of propagation. from the wave length. 5 It has been found, however, that an essential The new arrangement further possesses a speadvance may be made by arranging the axis of cial feature by supplying a ray of a certain strucsymmetry of the emitter in a different way if a ture, The intensity of radiation is greatest on a reflector is used. cylindrical face having the axis X-X and the By way of example, the invention is illustrated circle above the diameter MN'as cross section, 55

' ray to be received possesses and radially decreases from this surface both outwardly and inwardly. The magnetic lines of force are circles about the axis X-X, but the electric lines of force extend as cross sectional lines of torus faces which also have the axis of symmetry X-X for their axis of'rotation. In Fig. 3, this is shown in perspecti the general arrangement being the same as in Fig. 1. The points of greatest intensity of radiation are located on the circular cylinder'constructed above the diameter MN with the axis X-X. A section made vertically to the axis of this circular cylinder represents a magnetic line of force H. The intensity of the magnetic field strength along such a line of force H varies for a certain length of time periodically in the direction of the axis X-X in so far as the field strength, dropping from maximum to zero, attains after half a wave length the maximum value in opposite direction. The electric field strength for points near the circular cylinder of maximum'intensity of radiation is chiefly radially directed, i. e., in distances length with maximum intensity or outwardly. At distances amounting to a few wave lengths from the cross sectional surface MN the 'maxima of magnetic field strength will coincide with the maxima of electric field strength. Magnetic and electric field strengths are, therefore, arranged relative to one another as indicated by the vectors E and H. Vertically to the latter the vector U of the energy flow points in the direction X-X, so that the electric lines of force extend in the meridional planes through the axis x-x and form closed curves K, as indicated for the meridional plane by the point M.

The novel arrangement of the emitter relative to themirror thus permits the formation of a tube-like ray which possess the advantage of extremely sharp concentration and which permits reception by another station only if transmitting and receiving stations are accurately adjusted to one another.

It is evident that the effect described can be attained also in a manner differing from the arrangement according to Fig. 1. For example, Fig. 2 shows an arrangement in which the electric dipole is replaced by amagnetic dipole in the form of a circular conductor disposed in the focus coaxially with the mirror and traversed by a high frequency current. This arrangement shows the lines of force disposed in a manner coinciding with that of Fig. 3, provided the magnetic lines of force are substituted for the electric lines.

The arrangement described in connection with a transmitter can be used also for a mirror system intended for reception, provided that the the tube-like form mentioned above, since only in this case will an emitter adjusted with its axis of symmetry to the direction of propagation respond. The formation of the beam according to the invention compared with an ordinary plane may therefore be likened to a safety key while the plane wave represents an ordinary key. The highly complicated structure of the beam compared with a plane wave requires a corresponding adaptation of the reception to the transmitted wave and thus protectsthe receiving station to a very high degree against responding due to any electromagnetic interferences of other kinds, so that reception is rendered free from interferences.

Rays of the kind described are particularly suited also for electric train protection.

work requiring great accuracy,

findings for fixing routes for aircraft and hydro- 8 of symmetry of the reflector,

aosascs Furthermore, the use of structured electromagnetic rays with axis of rotation or a plane of sym metry is advisable also for all position finding such as direction aeroplanes or the like.

Theemitters disposed in the mirror may be tubes or serials connected with tubes by high frequency circuits. Instead of a parabolic mirror having coinciding axes of metry a cylindrical mirror disclosing a parabola in cross section may be employed. If in this arrangement the axis of the dipole is disposed again in the direction of propagation of the ray coming from the mirror, the wave leaving the mirror is no 15 longer rotation-symmetrical but. has a plane of symmetry, 1. e., the plane determined by the parabola and the direction of the surface lines of the cylinder.

In the customary arrangement, for instance, 20

the axis of the electric dipole is disposed vertically in the focus of a parabolic mirror adjusted with horizontal axis. The beam leaving the mirror is then, over the entire cross section, approximately linearly polarized in such a way that at 25 all points of the cross section of the beam the electric field strength is directed approximately vertically and the magnetic field strength approximately horizontally, so that the beam corresponds accurately to a space.

0n the other hand, if, according to the invention, the axis of the dipole lies in the axis of the parabolic mirror, that is, is disposed in the direction of propagation of the ray, a tube-like ray 35 will be produced which completely deviates from the plane wave. It is as impossible to change the structure of this ray to that of a plane wave by steady transformation as it is to convert a torus surface to a spherical one by steady deformation.

If instead of a parabolic mirror having coinciding axes of symmetry and rotation a parabolic mirror is chosen whose cross section, vertically to the axis of symmetry, will produce an ellipse, the cross section of the tubular ray will also be elliptically deformed and, if the major axis of the elliptical cross section is extended to infinity, pass into the fall of the ray with the axis of symmetry.

I claim:

1. A system for the transmission of messages by short electric waves, consisting of a sender and a receiver, the sender .comprising a rotarysymmetrical reflector and an electric dipole, the receiver comprising a rotary-symmetrical refiector and an electric dipole, each dipole arranged in the focus of the associated reflector and extend ing in the direction of the axis of the reflector, whereby the sender produces a tubular parallel radiation field, the receiver receiving this tubular radiation field.

2. A system for the transmission of messages by short electric waves, consisting of a sender and a receiver, the sender comprising a rotarysymmetrical reflector anda magnetic dipole, the receiver comprising a rotary-symmetrical reflector and a magnetic dipole, each magnetic dipole arranged in the focus of the associated reflector and its axis of symmetry coinciding with the axis whereby the sender produces a tubularradiation field, the receiver receiving this tubular radiation field. V

3. A system for transmitting messages with short electric waves, consisting of a sender and a receiventhe sender containing a rotary-sym- 1 rotation and syml0 plane wave limited as to 30 metrical reflector and a dipole, the receiver conup by the receiver practically over its entire cross taming a rotary-symmetrical reflector and a disection. pole, each dipole being disposed in the focal point 5. A system for transmitting messages through of the associated reflector, and its axis of synrshort electric waves, consisting of a sender and a metry coinciding with the axis of symmetry of receiver, the sender comprising a reflector and an s the reflector, whereby the sender generates a oscillator, the receiver comprising a reflector cortubular parallel radiating field, the receiver reresponding to the reflector of the sender and an ceives this tubular radiatinrfield. oscillator, which is disposed in the reflector of 4. A system for transmitting messages through the receiver in the same position as the oscillator short electric waves, consisting of a sender and a of the Sender n he eflecto 0f the S d each 10 receiver, the sender comprising a reflector and an oscillator dispos d in e focal P i f h oscillator, the receiver comprising a reflector corflector, its axis coinciding with the direction of responding to the reflector of the sender and an the m tt d a t n. wh y th nd r pr oscillator, each oscillator disposed in the focal duces anon-homogeneous, parallel radiation field point of the reflector, its axis coinciding with the and substantially the entire cross section of the 145 direction 01 the emitted radiation, whereby the m e a i n m is taken p y th receiver sender produces a non-homogeneous parallel practically over its entire cross section. radiation field and substantially the entire cross section of the emitted radiation beam is taken WALTER DALLENBAOH.

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