US2299619A - Ultra short wave signaling - Google Patents

Description

Oct. 20, 1942. K, FRITZ ULTRA-SHORT WAVE SIGNALING Filed May 2', 1940 WAVE LEA/G77! MUDULA-TED WAVE lA/PUT CON VERT ED WA VE OUTPUT CONVERTED WA VE OUTPUT WAVZ" LENGTH MODULATFD WAVE INPUT INVENTOR K F 72 A TORNEY Patented Oct. 20, 1942 ULTRA SHORT WAVE SIGNALING Karl Fritz, Berlin, Germany;

Propel-tr Application May 2, 1940, Serial No.

vested in the Alien Custodian In Germany January 13, 1939 4 Claims. (01. 178-44) The present invention relates to amethod of converting phase modulation, or frequency modulation into amplitude modulation, or vice versa, in the case of ultra-short waves, which method is to be employed more especially for the demodulation.

In the case of ultra-short waves it is extremely diflicult, as is known, to carry out a uniform modulation with a higher degree of modulation, since the oscillation lines of the generators reveal rupture regions and because, furthermore, amplitude variations always entail variations in the phase and in the frequency and vice versa. If the modulation degree is very small, the demodulation is obviously very difllcult and freedom from distortion can hardly be attained. These difficulties are eliminated in accordance with the present invention in that the modulation degree can be increased to any desired extent in the course of the conversion process of the one modulation type into the other modulation type, wherefore the actual demodulator need have but a low sensitivity.

In accordance with the present invention the modulated wave is applied to the working circuit across two paths having different travel time such that the phase variations of the wave are converted into amplitude variations and vice versa while increasing at the same time the degree of modulation.

The present invention can be employed to particular advantage in transmission system which operate with travel time generators for instance with magnetron tubes, or retarding fleld tubes. In these generators a frequency modulation having a small frequency variation can b conveniently and safely carried out.

In practicing the invention use may be made of a great many diflerent measures. ble wire lines, or coaxial lines may be'used, or the hollow tube lines which have come into use recently. It is obvious that an entirely wireless operation with the use of concentrated ultrashort wave likewise is within the scope of the present invention.

A simple example of execution of the invention is shown in Fig. l in which a line L branches into two lines LI and L2 having different electric lengths and which then form again a common line. If a high-frequency wave arrives from one side of the line whereby the frequency of said wave is modulated with small variation, this wave will be split up into two components which after passing through the paths LI and L2 meet again Thus, douindividual waves can constant, thickness of amplitude modulation it can be easily seen that already the slightest frequency variations of the original wave result in a high amplitude variation of the wave resulting from the interference of the two part waves, if the travel difference is suitable, i. e., if it is chosen in such manner whereby at the upper limit of the frequency an addition of the amplitudes of the two part waves occurs, while at the lower limit a subtraction occurs. The degree of modulation of the resultant wave can be increased up to 100%. In order to set the resultant degree of modulation, it is of advantage to render the electrical length of one of the two paths variable.

If the very shortest waves are an arrangement according to Fig. 2 more especially is of advantage in which a so-called hollow tube line is considered. In'such a line L the wave All shown in broken lines propagates. the end of the line a mirror R of dielectric material is arranged which reflects a part of the wave All into the extension of the line L, namely into the line L! but admits another part. The latter part which is designated by A3 passes through a detour loop LI and meets again the mirror from the rear thus entering the line L2 in part as wave A4. reflected at the rear to be employed,

part the line L2, etc. ,The directly reflected part of the wave A0 is formed by the two components Al and A2 which derive from the reflection of the original ray at the front side and rear side of the mirror surface. The amplitudes of the waves AI and A2 must have the same phase which condition can be easily realized through suitable choice of the thickness, the dielectric added to these waves a second wave which has passed once, or several times the detour line Ll. Now, if the length of the detour loop is suitably dimensioned such as was explained already on hand of Fig. 1, a weak frequency modulation of the wave A0 can be converted into a 100% amplitude modulation, if the interfering waves have the same amplitude. The amplitude ratio of the be easily set through suitable choice of the various constants (dielectric the reflection plate, etc.) Aside from the conversion of the frequency modulation into an amplitude modulation also the production of a phase modulation through is possible. However, it

where they are brought into interference. Now. 55 is to be presupposed hereby that'the travel time The part of Al which is difference of the two part waves assumes the order of a modulation period such as can be realized only in case of very high modulation frequencies. Then two waves having an amplitude-modulated constant phase difierence form together a resultant oscillation whose phase depends on the amplitude diflerence of the quantities of the sum, 1. e., the amplitude modulation has changed into a phase modulation.

In all cases care is to be taken that as much as possible only progressing waves'appear, i. e., thatthe lines are well matched to which end suitable means are known as such.

' What is claimed is:

1. In means for converting wave length modulations on ultra-high frequency wave energy into corresponding amplitude modulations on ultra-high frequency wave energy, a hollow tube line having an intake and an output, means for supplying wave length modulated ultra-high frequency wave energy to said intake, and means within said hollow tub'e line for increasing the length of the path over which some of said wave energy flows between said intake and said output, whereby the waves in following said two paths are relatively displaced in phase and the wave length modulations thereon are converted to corresponding amplitude modulations in the wave energy at said output.

2. In a device for converting modulations of one type on ultra-high frequency wave energy into corresponding modulations of another type on said ultra-high frequency wave energy, a hollow conductor having an intake opening and an output opening, means for supplying modulated ultra-high-frequency wave energy to said intake, means for deriving modulated ultra-high frequency wave energy from said output opening, and wave phase displacing means in said conductor between said openings, said phase displacing means including a wave reflector which provides path of different length, for said wave energy, between said openings to produce conversion of the modulation type.

3. In apparatus for converting modulations of a given character on wave energy into corresponding modulations of a different character on wave energy, a wave guide having an opening through which said first mentioned wave energy, a given characteristic of which is modulated, is fed to said guide and having an opening from which said second mentioned wave energy, a different characteristic of which is modulated, is derived, and wave phase displacing means within said guide so constructed and arranged as to cause portions of the wave energy to follow paths 1 of different length as they pass from said first mentioned opening to said second mentioned opening, and to convert the modulations of one character to modulations of a different character.

, 4, In a device for converting wave length modulations on ultra-high frequency wave energy into corresponding amplitude modulations on said ultra-high frequency wave energy, a branched wave path, having an input and an output, th branches of said wave path comprising tubularwave guides of different lengths, means for supplying wave length modulated ultra-high frequency wave energy to the input of said branched pathand for deriving correspondingly amplitud modulated ultra-high frequency wave energy from the output of said branched paths, said branched paths of difierent'lengths being so constructed and arranged as to produce relative phase displacement in the wave energy portions flowing thereover from said input to said output to convert the wave length modulations thereon to corresponding amplitude modulations.

KARL FRITZ.

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