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Nov. 5, 1946.
Filed Aug. 1, 1942
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Patented Nov. 5, 1946
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. ,
' 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.
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
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
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
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
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.
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
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
control for improved stability. .
4. A pulse transmitter comprising a source of
It will also be realized. that the phase shifting
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
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.
5. A pulse transmitter as de?ned in claim 3,
characterized in this that said reactance is a con
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
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.
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