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Патент USA US2104915

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Jan. 11, 1938.
B_ _1_ THOMPSON
2,104,915
TUNED OSC ILLATOR C IRCUIT
Filed Sept. 29, 1954
(434,677)’
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INVENTOR
dJ. 7/1’0 P 0N
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BY W
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ma,
ATTORNEY
Patented Jan. 11, 1938
2,104,915
TUNED OSCÍLLATOR UIRCUET
`Browder J. Thompson, Summit, N. J., assigner
to Radio Corporation of America, a corpora
tion of Delaware
Application September 29, 1934, Serial No. 746,124
12 Claims.
This invention relates uo a new form of short
wave tuned oscillatory circuit which is character
ized by extremely low loss.
The customary tuned circuits used on wave
5 lengths of several meters and less comprise par
allel or concentric lines having distributed con
stants, and small circuits having lumped induct
ance and capacitance. Of these, only the concen
Y tric lines give high impedance, since the radiation,
lll eddy current, and stray dielectric losses of the
other circuits are usually high. Concentric. lines
have the disadvantage of requiring a conductor at
least one-quarter o1" a wave length long.
Ú
It has been proposed to provide a tuned circuit
1*" consisting oi two copper hemispheres supported
on a copper rod with flanges on the hemispheres
forming a timing capacity, while the supporting
rod forms the inductance. Such an arrangement,
however, introduces considerable loss in the cir
co cuit, because of the high external electrostatic
ñeld set up. For the same reason, the tuning is
affected by stray capacitances.
The present invention provides a highly eñîl
cient tuned oscillatory circuit having lsubstantially
no external magnetic or electric iielcl, and this is
achieved by the use of inner and outer conductors,
the surface ci the outer conductor being substan
tially continuous electrically so that there is no
external magnetic or electric ?eld, and the inner
:A C) conductor being connected to the external ele
ments ci the circuit by means of one or more leads
l
extending through the outer conductor.
Al
though it is appreciated that there are some losses
produced by the connecting leads, the losses con
sist principally of resistance losses of the inner
conductors and can be made to be very low. One
advantage of the present invention lies in the sub
stantial freedom of the circuit from the effects oi
stray tuning due to movements of dielectrics and
40 conductors near the surface.
The invention is described in more detail in
connection with the accompanying drawing,
wherein Figs. 1-3 illustrate different preferred
embodiments of the invention.
Fig. l shows a cross section of a tuning circuit
comprising a continuous hollow sphere I, prefer
ably copper, enclosing two- rods 2, 3 with the in
ner ends terminating in discs ll, 5 in the center to
form a tuning capacity, the length of rod between
50 discs 4, 5 and the surface of sphere l serving as
the tuning inductance. Leads 6 are brought out
of the tuning circuit through holes in the sphere.
These leads can be tapped oil anywhere along the
rods to match any external impedance.
Fig. 2 shows another embodiment which com
prises a metallic cylinder l, preferably copper or
brass, enclosing copper rods 8, 9 terminating in
discs ll, 5 to form the inductance and capacitance
respectively, as in Fig. l. Rod 8 is herein shown
threaded at the end to permit variation in the Ul
capacity between the discs d, 5, merely by a turn
of the tuning knob Iß. This arrangement is
simpler to construct than the spherical arrange
ment of Fig. l, and possesses all of the advantages
oi the latter.
in Fig. 3 is shown an arrangement which, in
effect, is one-half oi that of Fig. 2, with the lead
lí brought out from the end of the support rod
E2. The plate i3 at the free end of the rod l2
provides one terminal oi a capacitance whose
15
other terminal is the outer surface oi the cylinder.
The value of this capacitance may be adjusted by
varying the length of rod l2. This embodiment
has a considerable advantage in mounting, as the
circuit can be placed directly on the ground plate
of the apparatus.
Water cooling of the inner conductor l2 may be
provided, if desired, by making the conductor hol
low and causing a iiow of cooling iiuid through it
by means oi an internal tube. Since, at high fre
quencies, the skin effect causes practically all the
current to flow near the surface of the conductor,
it will be readily understood that the resistance
would not be appreciably increased by removing
material from the interior of the conductor. For ‘
the same reason, very little loss is introduced by
the cooling fluid. If mercury is employed for the
cooling, little or no loss will be introduced due to
it comparatively low resistance.
Another advantage of the present invention,
besides that or“ very low loss, is that the improved
oscillatory circuits enable tuned circuits to be
constructed for very short wave lengths of the
order of one meter and less, while still providing
appreciable lumped capacity, since the induct
ance can be made very low.
Although the arrangements illustrated in the
drawing are preferred and have been shown to
be symmetrical, it should be understood that the
enclosing surface need not have any symmetrical
shape or be a surface of revolution in order to
practice the invention; nor is it necessary that
the inner conductors be axially located or the
condenser be substantially in the center. Lack ï
of symmetry o1", or small openings in, the outer
surface have no serious adverse eiîect, and, elec
trically, are not greatly inferior to any ci the
idealized structures illustrated. The essential
thing is that the outer surface be substantially
2.
2,104,915
continuous electrically, so that there is no ex
7. A high frequency tuned oscillatory circuit
ternalrmagnetic or electric field.
comprising a substantially continuous metallic
What is claimed is:
surface enclosing an inductance in the form of
two metallic rods and a capacitor in the form of a
pair of separated metallic plates, one end of each
rod electrically terminating at one of the plates
and the other end at the enclosing surface, and
means for adjusting the length of one of the rods
n l. An ultra high frequency tuned Voscillatory
circuit comprising a container in the form of a
metallic surface of revolution, a lumped capaci
tor substantially in the center of said surface of
revolution, and connected to said surface by in
ductance in the form'of support rods, and a lead
within said'surface of revolution connected to
the outer'surface of each of said support rods
between the> ends thereof and extending there
from externally of and through said surface of
within saidv surface for varying the distance be~
tween said plates, and a'lead connected to the 10
outer surface of each of said support rods and
extending externally of and through said sur
face:
revolution, said leads being physically separated
15
from each other.
.
8. An ultra-high frequency tuned oscillatory
~
2. An 'ultra high frequency oscillatory circuit »
i comprising a substantiallyrenclosed metallic sur
substantially continuous
metallic
surface,
a
lumped' capacitor substantially inthe center of
said surface and connected to said'surface by
faceV of revolution, a capacitor comprising two
separated plates substantially in the center of.
20 said enclosed surface of revolution, a metallic'`
supporting rod devoid of concentrated reactance
directly connecting each of said plates to said
circuit comprising a container in the form of a 15
inductances in the form of Vsupport rods, and a
lead' within said container connected to the outer
surface of each of said support rods between the
ends thereof and extending therefrom externally
surface, said rods forming an inductance which, of and through said container, said leads being
taken together with the plates of said capacitor, physically
Vseparated from each other.
25 comprise the oscillator circuit, the adjacent ends
9. A high frequency tuned oscillatory circuit 25
of said rods being separated substantially by the
distance between said plates, and leads coupled ' comprising a container in the form of a substan
tially continuous metallic surface, a lumped ca
to the outer surface of said rods and extending pacitor within said surface, and a pair o-f in
substantially perpendicular thereto and through ductance elements in the form of linear conduc
30. said surface of revolution.
tors devoid of concentrated reactance directly 30
3. A high frequency tuned oscillatory circuit in connecting
saidr capacitor to said surface, and a
accordance with claim 2, characterized in this lead within said container connected to the outer
that said enclosed surface of revolution is'V a
sphere.
4. An ultra high frequency oscillatory circuit
comprising a substantially enclosed cylinder, a
capacitor comprising two separated plates» sub
stantially in the center of said enclosed cylinder,
a metallic supporting rod devoid of concentrated
reactance directly connecting each of said plates
to a wall of said enclosure, said rods forming an
ductance which, taken together with the plates
of said capa itor, comprise the oscillatory circuit,
the adjacenî ends of said rods being separated
V45 substantially by the distance between said plates,
surface of each of said support rods between the
ends thereof and extending externally of and
through said container.
l0. A highV frequency tuned oscillatory circuit
comprising a container in the form of a sub
stantially continuous metallic surface, a lumped
capacitor within said surface, a pair of induc
tance elements in the form of linear conduc 40
tors devoid of concentrated reactance directly
connecting said capacitor- to said surface, and a
lead conductively coupled to the outer surface
of each of said inductance elements extending
and leads coupled to said rods and extending ~ from within said container externally of said os
substantially perpendicular thereto and through
said cylinder.
5. An ultra high frequency oscillatory circuit
50 comprising a substantially enclosed metallic sur
face of revolution, a capacitor comprisingrtwo
plates substantially in the center of said enclosed
surface of revolution, a metallic supportingV rod
for each plate of said capacitor connecting the
55 plate to the surface, said rods forming an in
ductance which, taken togetl'ier‘with the plates of
said capacitor comprise the oscillatory circuit,
means located externally of said surface for ad
justing one of said support rods with respect to
60 the other, for Varying the capacity betweenr said
plates, and leads coupled to said rods and ex
tending substantially perpendicular thereto and
through said surface of revolution.
6. An ultra high frequency tuned'oscillatory
65 circuit comprising a container in the form of a
metallic surface of revolution, a lumped capacitor
substantially in the center of said surface of
revolution and connected to said surface by'in
ductance'in the form of sup-port rods, and leads
70 extending from said support rods externally1 of
said surface of revolution, said leads being ad
justable over the lengths of said rods.
cillatoryV circuit, and substantially >at a right
>angle to its associated inductance elements.Y
11. A high frequency tuned oscillatory circuit
comprising a container in the form of a substan-
tially continuous metallic surface, a lumped ‘ca
pacitor within said surface and connected to said
surface by inductance in the form of two sup
port rods arranged substantially inthe same
straight line, and leads conductively coupled toV
the outer'surface of said support rods‘and extend
ing externally of said surface Yat substantially a
right angle to said support rods.
12. A. high frequency tuned oscillatory circuit
comprising a substantially continuous metallic
surface enclosing an inductance in the form of 60
two metallic rods, and a capacitor in the form of
a¿ pair of separated metallic plates, one end of
each rod electrically terminating at one of the `
plates and the other end at the enclosing sur
face, means for adjustingthe length of Vone of 65
said rods within said surface for varying the dis
tance between said plates, and leads adjustable
over the lengths of said rods and extending'there
from externally of said metallicsurface.
BRQWDER J. THOMPSON.
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