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July 21946@
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Filed .n_n. 2s. 1943
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Robert L. Harvey m
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Patented ¿Joly 9,„1946__
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PATENT
^ AUNITED STATES
OFFICE ~
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INSULATING. -AND DIELECTRIC MATERIAL
Robert L. Harvey. Princeton, N. J.. lssignor to
Radio Corporation of
of Delaware
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America. a con»- cration""""` "
Application January 29, Masern! no. 413.931
1 lliialn‘i- (Cl. S60-41)
l
,
My present invention relates to insulating and
dielectric materials for radio currents and has for
its general object to provide an improved insulat-~
Accordingly. a speciflc-obiect of my invention '
ing and dielectric material having lßertain unique
properties which render it especially suitable. for
use in electrical apparatus of the type designed '
t0 handle currents of ultra-high-frequencies', in
cluding so~called “centimeter waves”. l
My invention will be described in connection
with the accompanying drawing wherein the sin- '
glefigure comprises a group of comparative curves
showing how the Q
.
_
is to provide an improved insulating and dielec
tric material> for currents of radio frequencies,
and one which shall exhibit a ilat “Q” or. alter- >
natively. a rising "Q” with an increase in frequency. and this, too. at frequencies of upwards
of nve million cycles (5 megacycles) per second.
A'Another and important object of my present
invention is to achieve the aforesaid highly de
airable and unique characteristics in a material
having satisfactory heat resisting properties.
(QT-_“
'
2
tuned circuits in a desired manner. with fre»
fluency;
reactan
The foregoing and other objects are achieved
resistance
- of certain materials changes with frequency.
It is known to those skilled in the art to which
my invention appertains that the Q of the usual
insulating materials. including the common ther~
in accordance with my invention by the addition,
to moldable types of insulating compounds. prior
to the molding operation, of a metal of low spe
cific resistance. such for example. as copper or
silver.' in o. finely divided state. The speciilcl re
mo«plastic and thermo-setting resins. decreases
with an increase in frequency. Thus. as shown
by the curve which is designated "A” in _the ac
companying chart, polystyrene (or "styroi," as it
is sometimes called) exhibits a Q which decreases 25
from a high value of approximately 6,000 at fre
quencies _of the order of l rncgacycle to a value of
In m1571118 my invention into eil'ect I prefer to
employ polystyrene as the basic insulating ingre
dient because of its relatively high "Q" value.
though I may employ other thermoplastic or
thermosetting insulating materials. such for ex
ample as the phenol aldehyde, urea. ‘aldehyde and.
less than 2.000 when subjected to frequencies in
furfural resins, and to use copper particles of,
'x the 60G-1.000 megacycie range.
sa?. 300 mesh as the metallic mier. The mixing
80
It is also known that if two dielectric materials.
_may be carried out with' the insulating material
:such. for example, as polystyrene and Asilica. di
either in the powder or liquid form.
'
oxide (see- curve “B”). are mixed together, the
As shown by curve C of the drawing, the ad
¿ resulting compound will possess a Q lower than
dition of» substantially 10% by weight of copper
- either of its constituents at any given frequency
I and. like _its separate constituents. will exhibit >a 35
j decrease in Q with an increase in frequency.
There are numerous applications in radio and
' analogous communication systems of> the type
utilizing ultra-high-frequencies for an insulating
particles to polystyrene results in a moldabie non
conductive compound which exhibits a suhstan- .
tially constant Q over a frequency range of from.
say. 5 to 400 megacycles. In order to achieve a Q ~~
which increases with frequency I employ a greater
Percentage of powdered metal.` Thus, referring to
or dielectric material which will exhibit a con- 40l curve D.‘I have -found that the addition of 35 %.
etant Q or a rising Q. with an increase in freby weight. of powdered copper to polystyrene re
quency. By way of example: in a transmission
sults in a compound which exhibits o. uniformly
line wherein losœs normally increase with fr@
Q in the 5 to 400 megacycle band. Curves
_ quency due to redistribution of the current il. e..
E and F' show that over the same frequency range
"skin efiect”) _a material having 'a Q which in 45. o. somewhat lower Q, but one which nevertheless
creases with frequency could bc employed as
dielectric and/or insulating material to compen
sate for such losses. A material which exhibits
inflatQorarisingQ.withanincreaseinfreé'V
increases with frequency, is achieved when the
percentage of copper in- the compound is ln
creased to 50% and 70% respectively.
I have found that the addition of the powdered
quen'cy can also be used to advantage. either 5° lr'netal to the conventional insulating materials in
alone or in combination with other materials, as
creases the usable temperature range of such
the dielectric medium' in electric capacitors .of
materials. Thus, in the case of polystyrene the
various types and ratings._ By way of example.
usable temperature range is increased from 75°
-auch capacitors could be used in installations
Cito, say. 90° C.
'
wherein it is desired-to vary the selectivity ofthe
As a result ci' my work with these dielectric
/
/
8,403,657
consisting ot polystyrene and distributed there~
compounds over a. iride frequency range I have
reason to believe that the slope oi' the curves C,
through a ñneiy divided meta! selected from the
group consisting of _copper and silver in the proportion of from 10 percent to 35 percent by weight
o! the polystyrene. said medium exhibiting n
ratio o! œactance to resistance within the fre
D. E and F xemaìn substantially the same as indi-A
cated m the drawing at irequencies of the order
of several thousand megacycies._ but owingto the
possibility of error in making the necessary :new
_'urement; at these frequencies with present day
` npparatus and technique. I _have omitted such -
representation from the drawing.
_
I claim: '
_
'_
quency range o! from 5 megacycies per second to
1.000 megacycles per second which has a. value
at least. as great at the higher of said frequencies
„_ as at the lower of said frequencies.
‘
An eiearioai insulating and dielectric medium
ROBERT L HARVEY.
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