Nov. 5, 1946. w. VAN B. ROBERTS 2,410,748 PULSE TRANSMITTER Filed Aug. 1, 1942 . .gvs %\QEYSBQ m .NNKN N, .\8E5: 7 [Q 1,.\3R3 QMg9v5é2@EsQE» QE G mog?bog .Mm r E. ‘E Ev. T/, RR.nim gumuA:.ii mm gm c. 95%, c,cmcm M k \ m‘: ,. .98 Q‘s.Lk0usm, \ ail0wz ?zis. . 328E 35m53.o. u ‘ M 0 .. 2,410,748 Patented Nov. 5, 1946 UNITED STATES PATENT OFFICE" I PULSE TRANSMITTER. Walter van B. Roberts, Princeton, N. J., asslgnor to Radio Corporation of America, a corporation of Delaware Application August 1, 1942, Serial No. 453,170 11 Claims. This invention relates to improvements in pulse transmission systems. An object of the present invention is to provide an improved method of and apparatus for modu lating the timing of successive pulses in a, pulse type transmitter. ‘ Another object is to modulate the timing either from a. phase or frequency standpointof non sinusoidal waves without varying the timing of (Cl. 250-'—17) - waves traveling along the line will su?er attenu ation as well as variations of velocity of propaga tion. To avoid this undesired attenuation,- it is proposed in accordance with the invention to in troduce a. time delay between the arrival of waves at the phase shifting portion of the react ance 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 the generator of said waves. 10 described with reference to the accompanying A more speci?c object is to provide a modulat drawing, of which: , ing system which includes a source of constant, Fig, 1 shows, by way of example only, one em frequency waves, a non-re?ecting load, a line bodiment of the present invention; and‘ connected between the source and the load, and Fig. 2 shows, graphically, the timing variation ' reactance tube network means connected across 15 of pulses traveling along the system shown in the line and arranged to control the timing of arrival of waves at the load, with means for com- . pensating for attenuation of the waves by circuits of the reactance tube network means. Fig.1. , . p ' In Fig. 1, there is shown a pulse transmitter vsystem which includes a blocking oscillator l adapted to- generate relatively widely spaced An exposition of the principles underlying the 20 \pulses of constant amplitude and frequency, 8 present invention will now be given: ‘It is known which are fed into a concentric transmission line to employ reactance tube circuits which include ‘ 2 for subsequent utilization by ‘a transmitter 4 a multi-electrode vacuum tube having a condens er connected between, the anode and the con and antenna 5. In series with the line 2 and forming part thereof there are provided loops or trol grid and a resistor connected between the 25 adjustable length folded portions 3, 3, and an control grid and the cathode of the tube. A vari other line 2'. The folded portions 3 are shown able reactance can thus be obtained across the , in the form of lecher wire lines with adjustable anode and cathode which constitute, in effect, sliders, by way of example. _,The transmitter 4 terminals for the circuit. It is known that such is adapted to convert energy pulses received from a combination behaves with respect to a sinus 30 line 2 into corresponding pulses of ultra high fre oidal voltage applied to the aforesaid terminals quency waves and to radiate these waves from. like a combination of capacity'and resistance antenna 5. A number of identical reactance vac whose magnitudes may be varied by varying the uum tube circuits l2 are connected across the biasing potential of the control grid of the tube. terminals 9 and II of the folded portions 3 and I have found, however, that this behaviour is not 35 the outer conductor of the transmission line. ‘limited to sinusoidal ‘waves and that such a re Each of these networks comprises a. phase shift actance tube system behaves like a ‘combination ing circuit which includes capacity 6 and resistor of capacity and resistance with respectto waves l in series, and by-pass condenser 8. One arma of any shape whatsoever impressed upon the net ture of condenser 6 is connected to terminal 9 work terminals. A similar result is reached for 40 while the other armature of this condenser is’ . other reactance tube systems employing phase connected to the control grid of- the reactance shifting elements of other natures than the ca tube intimately associated therewith.‘ The re pacity-resistance combination which is discussed ' sistor 7 and by-pass condenser 8 are connected above by way of illustration. 1 in series between the ground lead of the cathode Inasmuch as the reactance tube network de 45 and the control grid. This phase shifting net scribed behaves like a combination of capacity ‘ work produces a voltage across resistor 1 ‘as a and resistance, it is now proposed in accordance result of voltage at-terminal 9 of foldedfline pori with the invention to connect a sumcient num tion 3. The anode [0 of the reactance tube is ber of such reactance tube networks across a connected,v to the other terminal ll of the folded transmission line to effectively ‘control the ve-. 50 part 3 so that anode current produced by the locity of propagation of waves along said line by ' aforesaid grid voltage occurs earlier with respect varying the effective distributed shunt capacity ' to the arrival of a traveling pulse the longer the across the line. However, since each of these folded part 3 of the line. The result of this is networks introduces‘ a resistance component as the anode current pulse may be analyzed well as a capacity component across the line, 55 that into not only a wattless or ‘energy-less compo . - ' 2,416,748 invention will be achieved so long as the effective nent which acts to retard or advance the pulse along the line, but also an energy component which increases the energy of the traveling pulse at point H sufficiently to offset the abstraction of energy from the pulseas it passes point 9 by the dissipative circuit 6, T. If the length of , ' 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.‘ the folded portion 3 is too ‘short, the traveling pulse will ‘suffer a net loss of energy in passing the system from point 9 to point H, while‘ if the In the‘drawing, direct current energizing voltage - pulse will be increased in passing through the plied by means of a shunt feed choke coil, while folded portion 3 is too long, the energy of the 10' for the anodes of the tubes has been shown sup a blocking condenser forms the alternating cur system_- Preferably, the length'of the folded por tion 3 should be adjusted to permit the pulse to. rent connection between anode and line. Other arrangements may, of course, be substituted for energizing the various tube electrodeswith direct pass-without change of energy. Where‘short" pulses are dealt with, each reactance tube network l2hproduces‘a certain displacement of the voltages. ’ . ' q The term “non-sinusoidal" used in the ap traveling pulse with respect to its normal‘ posi- ' , pended claims is intended to' designate any shape tion, and any number of networks may be'con pulse otherathan a continuous sinusoidal wave. nected across the line at will. However, the in What is claimed is: vention is not limited to such pulses and in case 20 1. In a transmission system, a source of non waves having shapes more nearly sinusoidal are sinusoidal wave pulses, a transmission line con employed, it is preferable to connect a consid nected to said source for feeding said pulses to a ‘ erable number of reactance networks (for ex . load, means for relatively displacing the positions ample ten or twelve, uniformly spaced) per wave of said pulses on said line comprising a phase. length measured along the line, In this way, the a shifting circuit shunted across said line, a vacuum . line behaves to the operating frequency as though tube excited from said phase shifting circuit, and its capacity were uniformly distributed. Three a connection from the output of said tube to said identical networks are shown‘ in Fig. l of the line at a'point displaced along said line- from the drawing, but it will be realized that the. actual point of connection of said phase shifting circuit, number employed will depend uponthe length 30 whereby the energy component of anode current of the line and the amountpf modulation‘ de sired. f fed into said lines reduces the energylosses of said waves traveling along said line while the energy . The grid potential for each of. the reactance tubes is obtained from lead “extending to a v‘ lessccmponent acts effectively‘to shift the po’si-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 - e ngle source of modulating voltage which might, - ,forjexample, be audio frequency. In this case, the pulses arriving at the‘transmitter 4 will be ' phase modulated in accordance with audio volt age. Howevenit is well known that the audio I ‘voltage may be suitably-predistorted so that the pulses arriving attransmitter 4 are frequency physically spaced adjustable line sections inserted 40 in series at different locations along said line, a modulated with respect to the original voltage. prior todistortion. v Fig. ' each adjustable line section corresponding to the . 2 represents-along the'upper line‘ A the a. reactance tube network across the terminals of ' junction points to said line, and a connection from - series of constant amplitudehconstant frequency 45 the control electrodes of said reactance tube net pulses impressed by the vblocking oscillator l on the left hand end of transmission line 2. Along the line B, directly beneath, are shown the pulses arriving’ at transmitter‘ 4. It should be noted that these pulses on line Bare of unchanged 50 amplitude but that their spacing is altered as works to a common source of audio frequency modulating potential. 3. A pulse transmitter comprising a source of substantially ‘rectangular wave pulses, a trans mitter, a- line connection between said source and . said transmitter, a plurality of lecher wire lines inserted in series with said line at different loca tions along said line, a slider for each lecher wire line for adjusting the e?ective length thereof, a ing oscillator, yet their momentary phase or fre quency of arrival is alternately greater and less 55 reactance tube network connected across the junction points of each lecher wire with said line, - than that of the blocking oscillator. In the low . each of said networks including a vacuum tube _ est line C of Fig. 2 are shown the pulses of ultra‘ , illustrated so that while the average frequency of arrival is the same as the frequency of the block - short waves'radiated from antenna 5, which pulses _ are substantially identical in position and length having a grid, an anode and a cathode,‘ a react ance connected between the grid of each tube but occur with variable. frequency determined by 60 and that junction point of its associated lecher wire line nearest'said source, a resistance con the frequency of the pulses shown in the line 13 immediately above. ’ ' ' . - : ‘It will be appreciated that by the use of, the necting said reactance to the cathode through a. , by-pass capacity, a connection from the anode of each tube to the other junction point of its asso present invention, it is not necessary to modulate the operation of the blocking oscillator in any 65 ciated lecher wire line which is nearest the trans mitter, and a connection from the grid of each respect to obtain a modulation of‘the pulses, as tube to a common source of modulating voltage, _ajresult of which; the construction of such an oscillator is greatly‘simpli?ed. Furthermore, in ' whereby the energy component of anode current fed into said line by said first source reduces the view of this advantage ~' of ‘ the invention, the blocking oscillator. may be operated under crystal 70 energy lossesof the waves traveling along the line. control for improved stability. . 4. A pulse transmitter comprising a source of It will also be realized. that the phase shifting pulses, a utilization circuit, a line connected be circuit connectedv across'the' transmission line 2 ' tween said source and utilization circuit, and. a ' at point 9, for example, can take other speci?c forms than that illustrated. Thevobject of the 76 reactance tube network connected to spaced 2,410,748 points on said line and having a source of modu 9. A pulse transmitter comprising a source of lating voltage connected thereto for varying the relative ‘timing of the pulses along said line, said non-sinusoidal wave pulses, a utilization circuit, a transmission line extending between said source and utilization circuit and having a folded por tion, a. reactance tube network across the ter minals of said folded portion, said network in-‘ cluding a phase shifting circuit and a vacuum tube, and a connection from a grid of said tube network including a phase shifting circuit and a vacuum tube. f. 5. A pulse transmitter as de?ned in claim 3, characterized in this that said reactance is a con denser. ’ 6. A pulse transmitter in accordance with claim 2, characterized in this that said networks 10 to a source of audio modulating voltage. 10. The method of operating a transmission are uniformly distributed alongr said line. " system including a transmission medium, which 7. A pulse transmitter comprising a source of comprises generating pulses of a substantially non-sinusoidal wave pulses, a transmitter of ‘constant frequency, transmitting said pulses over ultra short waves, a transmission line extending said transmission medium, affecting said medium between said source and transmitter and having 15 at a plurality of spaced points in accordance with a folded portion, a reactance tube network across signal modulation to thereby vary the velocity the terminals of said folded portion, said network including a phase shifting circuit and a vacuum of propagation of said pulses through said me dium, and simultaneously increasing the energy 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 of the pulses traveling over said medium. 11. A transmitter comprising a source of non sinusoidal waves, a. utilization circuit, a transmis . sion line extending between said, source and uti 20 lization circuit, a, circuit. providing a delay path source and utilization circuit, a plurality of phys for waves passing thereover connected between ically spaced adjustable line sections inserted in 25 two spaced points on said line, a reactance tube series at di?erent locations along each wave network across the terminals of said circuit, said length of said line, a reactance tube network 7 network including a phase shifting circuit and a across the terminals of each adjustable line sec vacuum tube, and modulating'means coupled to tion corresponding to the junction points to said an electrode of said tube. ' line, and a connection from the control elec trodes of said reactance tube networks to a com mon source of modulating potential. 30 WALTER VAN B. ROBERTS.