US2410748A - Pulse transmitter - Google Patents

Description

Nov. 5, 1946. w. VAN B. ROBERTS PULSE TRANSMITTER Filed Aug. 1, 1942 N NKN m m: k M ai wzzfizis 0 A: .i A: .i i u imm umm R n 0 M T 35m 53 u c c c c m cm 95% mm 0 98 Qskusm L E E. r E E Ev. mo fibo Mm QEQEQEQEQGEQQ sE @EEEEQEQQ M952 Q v 7 [Q vs 8E5: 3R3 QEYSBQQ 328E Patented Nov. 5, 1946 I PULSE TRANSMITTER. Walter van B. Roberts, Princeton, N. J., asslgnor to Radio Corporation of America,

of Delaware a corporation Application August 1, 1942, Serial No. 453,170 11 Claims. (Cl. 250-'17) the generator of said waves.

A more specific object is to provide a modulating system which includes a source of constant,

frequency waves, a non-reflecting load, a line connected between the source and the load, and

' reactance tube network means connected across the line and arranged to control the timin of arrival of waves at the load, with means for compensating for attenuation of the waves by circuits of the reactance tube network means.

An exposition of the principles underlying the 8 present invention will now be given: It is known to employ reactance tube circuits which include a multi-electrode vacuum tube having a condenser connected between, the anode and the control grid and a resistor connected between the control grid and the cathode of the tube. A variwaves traveling along the line will sufier attenuation as well as variations of velocity of propagation. To avoid this undesired attenuation,- it is proposed in accordance with the invention to introduce a. time delay between the arrival of waves at the phase shifting portion of the reactance network and the arrival of the waves at the anode-cathode terminals of the tube. The action of the complete network of the invention is best described with reference to the accompanying drawing, of which:

Fig, 1 shows, by way of example only, one embodiment of the present invention; and

Fig. 2 shows, graphically, the timing variation of pulses traveling along the system shown in Fig.1. p In Fig. 1, there is shown a pulse transmitter system which includes a blocking oscillator l adapted togenerate relatively widely spaced pulses of constant amplitude and frequency,

which are fed into a concentric transmission line 2 for subsequent utilization by a transmitter 4 able reactance can thus be obtained across the anode and cathode which constitute, in effect, terminals for the circuit. It is known that such a combination behaves with respect to a sinusoidal voltage applied to the aforesaid terminals like a combination of capacity'and resistance whose magnitudes may be varied by varying the biasing potential of the control grid of the tube. I have found, however, that this behaviour is not limited to sinusoidal waves and that such a reactance tube system behaves like a combination of capacity and resistance with respectto waves of any shape whatsoever impressed upon the network terminals. A similar result is reached for other reactance tube systems employing phase shifting elements of other natures than the caand antenna 5. In series with the line 2 and forming part thereof there are provided loops or adjustable length folded portions 3, 3, and another line 2'. The folded portions 3 are shown in the form of lecher wire lines with adjustable sliders, by way of example. The transmitter 4 is adapted to convert energy pulses received from line 2 into corresponding pulses of ultra high frepacity-resistance combination which is discussed above by way of illustration. 1

Inasmuch as the reactance tube network described behaves like a combination of capacity and resistance, it is now proposed in accordance with the invention to connect a sumcient number of such reactance tube networks across a transmission line to effectively control the ve-.

locity of propagation of waves along said line by varying the effective distributed shunt capacity across the line. However, since each of these networks introduces a resistance component as well as a capacity component across the line,

quency waves and to radiate these waves from antenna 5. A number of identical reactance vacuum tube circuits l2 are connected across the terminals 9 and II of the folded portions 3 and the outer conductor of the transmission line. Each of these networks comprises a. phase shifting circuit which includes capacity 6 and resistor l in series, and by-pass condenser 8. One armature of condenser 6 is connected to terminal 9 while the other armature of this condenser is connected to the control grid ofthe reactance tube intimately associated therewith. The resistor 7 and by-pass condenser 8 are connected in series between the ground lead of the cathode and the control grid. This phase shifting network produces a voltage across resistor 1 as a result of voltage at-terminal 9 of foldedflin por tion 3. The anode [0 of the reactance tube is connected, to the other terminal ll of the folded part 3 so that anode current produced by the aforesaid grid voltage occurs earlier with respect to the arrival of a traveling pulse the longer the folded part 3 of the line. The result of this is that the anode current pulse may be analyzed into not only a wattless or energy-less compothan that of the blocking oscillator. est line C of Fig. 2 are shown the pulses of ultra invention will be achieved so long as the effective velocity of propagation along the line'is capable of being varied by the application of modulating potential to the grid of the reactance tube. It will be appreciated that the phase or-frequency modulated pulses emanating from transmission line 2 may be employed for other purposes than to excite ultra high frequency radiation, if desired.

- pulse will be increased in passing through thesystem Preferably, the length'of the folded portion 3 should be adjusted to permit the pulse to.

pass-without change of energy. Whereshort" pulses are dealt with, each reactance tube net-- work l2 producesa certain displacement of the traveling pulse with respect to its normal position, and any number of networks may be'connected across the line at will. However, the invention is not limited to such pulses and in case waves having shapes more nearly sinusoidal are employed, it is preferable to connect a considerable number of reactance networks (for example ten or twelve, uniformly spaced) per wavelength measured along the line, In this way, the a line behaves to the operating frequency as though its capacity were uniformly distributed. Three identical networks are shown in Fig. l of the drawing, but it will be realized that the. actual number employed will depend uponthe length of the line and the amountpf modulation desired. f

The grid potential for each of. the reactance tubes is obtained from lead extending to a e ngle source of modulating voltage which might, forjexample, be audio frequency. In this case,

the pulses arriving at thetransmitter 4 will be phase modulated in accordance with audio voltage. Howevenit is well known that the audio I voltage may be suitably-predistorted so that the pulses arriving attransmitter 4 are frequency modulated with respect to the original voltage prior todistortion.

Fig. 2 represents-along illustrated so that while the average frequency of arrival is the same as the frequency of the blocking oscillator, yet their momentary phase or frequency of arrival is alternately greater and less In the lowshort waves'radiated from antenna 5, which pulses are substantially identical in position and length but occur with variable frequency determined by the frequency of the pulses shown in the line 13 immediately above.

It will be appreciated that by the use of, the present invention, it is not necessary to modulate the operation of the blocking oscillator in any respect to obtain a modulation ofthe pulses, as

ajresult of which; the construction of such an oscillator is greatlysimplified. Furthermore, in view of this advantage of the invention, the blocking oscillator. may be operated under crystal control for improved stability.

It will also be realized. that the phase shifting v the upper line A the series of constant amplitude constant frequency pended claims is intended to' designate any shape pulse other than a continuous sinusoidal wave.

What is claimed is: 1. In a transmission system, a source of nonsinusoidal wave pulses, a transmission line connected to said source for feeding said pulses to a load, means for relatively displacing the positions of said pulses on said line comprising a phase shifting circuit shunted across said line, a vacuum tube excited from said phase shifting circuit, and

a connection from the output of said tube to said line at a'point displaced along said linefrom the point of connection of said phase shifting circuit, whereby the energy component of anode current fed into said lines reduces the energylosses of said waves traveling along said line while the energylessccmponent acts effectivelyto shift the posi-1 tion of said wave along said line. I

2. A pulse transmitter comprising a source of non-sinusoidal wave pulses, a transmitter of ultra short waves, and a transmission line extending between'said'source and transmitter, a pluralityof physically spaced adjustable line sections inserted in series at different locations along said line, a reactance tube network across the terminals of each adjustable line section corresponding to the junction points to said line, and a connection from the control electrodes of said reactance tube networks to a common source of audio frequency modulating potential.

3. A pulse transmitter comprising a source of substantially rectangular wave pulses, a transmitter, aline connection between said source and said transmitter, a plurality of lecher w e lines inserted in series with said line at different locations along said line, a slider for each lecher wire line for adjusting the eflective length thereof, a reactance tube network connected across the junction points of each lecher wire with said line,

, by-pass capacity, a connection from the anode of each tube to the other junction point of its associated lecher wire line which is nearest the transmitter, and a connection from the grid of each tube to a common source of modulating voltage,

' whereby the energy component of anode current circuit connected across'the' transmission line 2 at point 9, for example, can take other specific forms than that illustrated. The object of the fed into said line by said first source reduces the energy lossesof the waves traveling along the line.

4. A pulse transmitter comprising a source of pulses, a utilization circuit, a line connected between said source and utilization circuit, and. a

reactance tube network connected to spaced points on said line and having a source of modulating voltage connected thereto for varying the relative timing of the pulses along said line, said network including a phase shifting circuit and a vacuum tube. f.

5. A pulse transmitter as defined in claim 3, characterized in this that said reactance is a condenser.

6. A pulse transmitter in accordance with claim 2, characterized in this that said networks are uniformly distributed along said line.

7. A pulse transmitter comprising a source of non-sinusoidal wave pulses, a transmitter of ultra short waves, a transmission line extending between said source and transmitter and having a folded portion, a reactance tube network across the terminals of said folded portion, said network including a phase shifting circuit and a vacuum tube, and a connection from a grid of said tube to a source of audio modulating voltage.

8. A pulse transmitter comprising a source of non-sinusoidal wave pulses, a utilization circuit, and a transmission line extending between said source and utilization circuit, a plurality of physically spaced adjustable line sections inserted in series at difierent locations along each wavelength of said line, a reactance tube network across the terminals of each adjustable line section corresponding to the junction points to said line, and a connection from the control electrodes of said reactance tube networks to a common source of modulating potential.

9. A pulse transmitter comprising a source of non-sinusoidal wave pulses, a utilization circuit, a transmission line extending between said source and utilization circuit and having a folded portion, a. reactance tube network across the terminals of said folded portion, said network including a phase shifting circuit and a vacuum tube, and a connection from a grid of said tube to a source of audio modulating voltage.

10. The method of operating a transmission system including a transmission medium, which comprises generating pulses of a substantially sion line extending between said, source and utilization circuit, a, circuit. providing a delay path for waves passing thereover connected between two spaced points on said line, a reactance tube network across the terminals of said circuit, said 7 network including a phase shifting circuit and a vacuum tube, and modulating'means coupled to an electrode of said tube.

WALTER VAN B. ROBERTS.

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