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Патент USA US2408930

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ÚCÍ- 8, 1945-
A. M. GuREwlTscH
FILTERING ARRANGEMENT
2,408,927
Filed July so, 1942
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Inventor;
Y Anaiole M. Gur‘ewitsch,
Hf?. A‘Ltcarn @n
2,408,927
Patented Oct. 8, 1946
UNITED STATES PATENT OFFICE
2,408,927
FILTERING ARRANGEMENT
Anatole M. Gurewitsch, Schenectady, N. Y., as
sìgnor to General Electric Company, a corpo
ration of New York
Application July 30, i942, serial-No. 452,946
5 Claims.
(c1. 17a-_44)
l
This invention relates to an electrical filtering
arrangement especially adapted for use at ultra
2
glass cylinders 20 and 2l sealed between them.
The part l1 provides a terminal for the grid l2,
and a terminal for the anode is provided by a
cylindrical enlargement 23 which is welded or
soldered against the upper surface of the part
the design of radio circuits and like apparatus
I6.
to provide means for effectively separating the
The cathode I3 is provided at its lower extrem
direct current and alternating current paths.
ity with a flange 25 which parallels the under
At the lower frequencies, such as the frequencies
surface of the part I8 but which is separated
commonly used in radio broadcasting, this sep
from that part by an insulating spacer 21 (e. g.
aration may be accomplished by the use of choke 10 a mica washer). With this arrangement the
coils and condensers, properly arranged. How
part I8 has a high frequency connection with the
ever,V at higher frequencies, especially at fre
cathode through the capacity existing between
quencies corresponding to wave lengths on the
this part and the flange 25 but is effectively in
high frequencies.
As is well known, it is frequently necessary in
order of a few centimeters, the conventional ar
sulated from the cathode as far as direct current
rangements fail to produce the desired results 15 is concerned. Separate direct-current connec
and it is necessary to resort to more complex ex
tions are made to the cathode by means of lead
pedients including specially designed ñlters.
The present invention is ‘principally concerned
with the provision of an improved form of ultra
high frequency ñlter which is characterized by
simplicity and compactness of structure and
which is well adapted for use at even the shortest
wave lengths.
Briefly, the invention makes use of a multiply
in wires 29 secured to the under surface of the
part 25 and terminally connected to prongs 3l
which depend from the base of the discharge
tube. Additional prongs 33 and lead-in wires 34
are provided for the purpose of supplying heat
ing current to a coiled filament 35 arranged '
within the cathode cylinder I3 so that the emis
sive part of the filament can be maintained at
folded coaxial transmission line arrangement 25 an elevated temperature by this means.
In the arrangement of Fig. 1 the tube l0 is
providing a plurality of quarter wave filter sec
seated in a socket or adaptor 31 having acces
tions in series. In order to obtain a band-block
sible terminals 38 to which appropriate con-fr
characteristic the various sections may be made
of different lengths so that each corresponds to
nections may be made. The socket 31 is itself
a quarter wave length at some particular fre 30 >supported by the combination of a ?xed ring 40
and a split locking ring 4l, the ring 40 being
quency within the selected frequency range.
secured to the inner surface of an elongated
The features of the invention desired to be
cylinder sleeve 44 having certain further func
protected herein are pointed out in the appended
tions Which will be explained at a later point.
claims. The invention itself, together with its
The oscillating circuits employed in connection
further objects and advantages, may best be un
with the discharge tube l0 are provided by the
derstood by reference to the following descrip- y
combination oi a series of three concentric tu
tion taken in connection with the drawing in
which Fig. 1 is a longitudinal sectional view of
bular conductors 48, 49 and 58. The outer con
ductor 48 has a high frequency connection with
a high frequency oscillator embodying one of my
improved filter arrangements; Fig. 2 is avpartial
section of the discharge tube which is represent
ed in less detail in the assembly of Fig. 1, and
Fig. 3 is a diagrammatic view useful in explain
>ing the operation of the construction of Fig, l.
Referring particularly to Fig. 1 there is shown
an ultra-high frequency oscillator having a
40 the cathode of the tube l0 through a ring of
contact fingers 53 which bear upon the surface of
the tube part I8. Similarly, the cylindrical con
ductor 48 has a symmetrical connection with the
grid of the tube through spring contact fingers
5.5 which bear upon the grid terminal l1. Final
ly, a high frequency connection between the in
three-electrode discharge tube l0 as its central
ner tubular conductor 50 and the anode of the
element. As appears more clearly in Fig. 2, this
tube l0 is provided by pressing the extremity
tube comprises a cylindrical anode ll, a grid l2
of the conductor over a tapered adaptor 51 which
50
and a cylindrical cathode I3 having its emissive
is fitted snugly onto the anode terminal and
part in the form of a flat disk surface I4 which
which bears contact lingers 51’ adapted to en
faces the grid |12. The envelope within which
gagethe disk I6. The tubular conductor 50 is
these electrodes are enclosed comprises a series
insulated from the adaptor 51 with respect to
of three circular metal parts I6, l1 and I8 which 55 direct currents by the interposition between
are supported in mutually spaced relation by
2,408,927
3
their juxtaposed surfaces of a mica sleeve 58.
It will be seen, however, that the capacity which
exists through the mica assures that the con
ductive parts in question are effectively directly
connected as far as high frequency currents are
concerned.
With the arrangement speciñed, the space be
tween the conductors 4B and 49 forms in effect
a transmission line section which may be ad
justed as to length to provide a resonant tank
having a resonant frequency appropriately re
lated to the desired frequency of operation of
the oscillator. This adjustment may be accom
plished by the use of an annular plug orcontact
ring 6G having two sets of contact ñngers El and
62 which respectively bear upon the opposed
surfaces of the tubular conductors `llß‘and Q9.
Actuating rods 54 which extend out through a
to the main structure of the oscillator and is
operated at ground potential, so that no diñiculty
exists with reference to the D.-C. connections
to this element. On the other hand, mutually
insulated connections must be made to both the
anode l! and the cathode I3.
The anode terminal is insulated from the
grounded structure by the mica spacer 58, and
positive potential is applied to it by the use of a
conductor l2 connecting with the adaptor 51 and
extending outwardly through an insulating block
'5... at the end of the oscillator structure. an ex
ternaily accessible terminal for this arrange
ment being indicated at l5. Due to the gap pro
vided‘between the tubular conductor 50 and the
adaptor 5l by the spacer 58 there is some tend
Yency for coupling to exist between the otherwise
compietely enclosed high frequency system and
the direct current conductor T2 and its associ
ated circuits. In _order to avoid objectionable
effects attributable to this cause, it is expedient
to provide filtering means in the formrof hollow
A similar tunable transmission line section iS
` provided between the grid and anode by the com
metal sîeeves i8 and 78 ñtted on the conductor l2
bination of the tubular conductors 49 and 50.
The resonant frequency of the tank circuit thus
and each providing a reentrant discontinuity with
respect to currents ilowing along this conductor~
provided between‘the grid and anode is adjust
able, as in the case of the grid-to-'cathode cir
Filtering means of the type specified are known
`er se and are not intended to be claimed herein
except as embodied in an improved arrangement
to be described at a later point. Their usefulness
cuit, by means of a slidable contact ring or plunger
l(53,' having Vexternally accessible actuating rods 69.
Assuming the application of appropriate’direot
‘
l'J
depends in part upon'the consideration that the
current potentials to the various electrodes of
the‘turbe iii-_, oscillations may be obtained by
conductor "i2 and the surrounding tube 5i) form a
coaxial transmission line to which the propagation
provided‘and by arranging for a properfeed back
The passage of such energy along the line may
properly adjusting 4the two tunable tank circuits
of high frequency energy is necessarily conñned.
coupling between thesencircuits. The principles
be alternatively viewed as attributable to high
which govern the operation of an` oscillator of
this kind arel fully described in
frequency currents flowing over` the opposed sur
faces of the coaxial conductors orto the propaga
tion of waves in the space between the conduc
`
rial No. 448,205, nieu
of Richard C. Jensen
assigned to _the General Electric Company, a
corporation of New York.
In
40
tors. Taking the latter viewpoint, it may be'said
that the discontinuities provided by the sleeves
'I8 and l@ tend to block the propagated waves
quired that the inner and> outer lines betuned
by reflecting them
operating frequency, such tuning being obtained
For complete blocking or reflection‘to 'occur
at a particular frequency, the optimum condi
tion is that in which the length of the blocking
by adjusting each` line so that its length corre
sponds approximately to an odd number (e. g. l,
3, 5, etc.) of quarter wave lengths at the> fre
quency to which it is being tuned. Feedback
may in some instances be provided Asolely’by the
inter-electrode capacity of the tube l i) butin most
>`cases it is found preferable to employ a probe o1*
loop (not shown in Fig. l) extending betweenj the
inner and outer transmission line sections for pro
viding more positive coupling between them.
, jOn the assumption that the concentric con
sleeve is a quartel` wave length (or an odd num
ber of quarter wave lengths) at `such, frequency
and in which the impedance “seen”l at the right
hand end of the sleeve is infinite. The latter con
dition is fulfilled `by the reentrant'sleeve con
struction illustrated in Fig. 1 since the resonant
quarter wave section enclosed by each sleeve actu
ally represents an inñnite impedance (at ‘ the
resonant frequency) in series withy the section
55 formed between the outer surface of the sleeve
ductors ¿58, 49, 5G and the connectedmetallic
parts` provide a Vcomplete conductive enclosure,
it would appear that high frequency energy de
andthe surrounding conductor. It is also de
sirable that the difference in diameter between
each sleeve and the conductor 'l2 be relatively
veloped within the enclosure `should be
great and that the spacing between the sleeve
confined and that no high frequency coupling 60 and the surrounding conductor 5l be small. By
between the oscillating system and external
making the sleeves 78 and 'I9 of different lengths
agencies should exist.
However, such an as
sumption ignores the presence of the insulating
spacers 2l (Fig. 2) and 58 (Fig. l). These spacers,
which are required to permit the establishment
of D.-C. potential differences between the vari
ous electrodes of the tube lû, represent leakage
gaps in an otherwise continuous metallic struc
and by using as many such sleeves as are needed,
a considerable band of frequencies may be blocked
so that unwanted coupling is prevented regard
oscillator is operated.
.
,
A generally Vsimilarproblem with respectto
high frequency coupling exists in connection with
the means employed'for supplying heating _cur
high frequency energy and other disadvantageous 70 rent (either D.-C. or 6o cycle'A.-C.) tothe cath
effects. For this reason it is necessary to provide
ode of the tube iin These means include the
ture and may permit uncontrolled radiation of
socket terminal 38', which. is assumed to be con
filtering means in association with the D.-,C. and
low frequency A.-C. connections’of the tube.Y
nected to the cathode filament, and a conductor
The grid i4 of
the tube is connected directly 75 85 having a connection with this terminal (the
other cathode connections do not appear in Fig.
4desired to operate the oscillator at one frequency
_,only, all the filter sections may be made of identi
cal length, that is to'say, of a length correspond
>1,_but are indicated diagrammatically in Fig. 3).
.The `conductor 88 extends through an opening 81
formed in a transverse wall part> 88 which other
wise4 completely encloses the space within which
>ing to a quarter wave length at the frequency
in question. On the other hand. where a range
of operating frequencies is to be employed, the
various iiltering sections are preferably made of
different lengths as shown, so that the arrange
the socket end of the tube 4|) is positioned. At
one vend it is supported in an insulating bushingv
>90,' and at vthe other end is provided with an ex
ternally accessible terminal 9| mounted in an
insulating wall part‘92. Objectionable high fre
quency coupling is to be anticipated in connec
tion with this arrangement becausev of the pos
sible- propagation of high frequency- energy
through the gap provided by the cathode spacer
21 (Fig. 2), through the glass seals of the tube
ment as a whole provides a band-stop filter.
The operation of the invention may be 4further
lo explained
by reference to the diagrammatic rep
resentation of Fig. 3 in which elements which
can be readily identified with parts previously de
scribed in connection with Figs. 1 and 2 are des
ignated by similar numerals differentiated by
„ |íJ,.through the opening Si' and along the con
priming.
l
yAs has been previously explained, the oscil
ductor 86.
VThis problem may, of course, be dealt with by
a filtering arrangement identical with that em
lating system is made up of the discharge tube
I8’ and the two resonant circuits which are re
ployed inV connection with the anode, that is, by
spectively provided between thenconduct’orsrl'ß'
the use of several reentrant quarter wave iilters
arranged sequentially in axial alignment. How
ever, while the use of such an arrangement in
connection with the anode does not tend ma
terially to increase the space requirements of
the oscillator, the same consideration does not
apply in connection with the cathode; that is
to say, the use of two or more quarter wave ñlters
arranged in end-to-end relation in connection
with the cathode terminal would obviously greatly
extend the length of the structure as a whole.
In accordanceV with my invention this dif
ficulty is avoided by the use of a folded conductor
arrangement in which a number of quarter wave
filter sections are provided in a concentric rela
and 49’ and the conductors 49’ and 50’. Feed
back is provided (in part) by means of a conduc
tive probe ||8 which is mounted on the tuning
ring 6G' and which extends through an axial slot
cut in the tubular conductor A9'. An output ar
25 rangement for the high frequency energy de
veloped is illustrated as comprising a coupling
loop H6 which extends into the space between
the conductors 49’ and 50’ and which is made
externally accessible by means of a concentric
30
conductor transmission line comprising a metal
tube H8 and a coaxial wire |20.
Direct current terminal connections for the
electrodes of the tube I8’ are indicated at 12’ and
86', cathode bias being provided by a resistor | |5
tionship. This arrangement includes in the first 35 connected in series with the cathode. The con
instance a conductive element 93 which surrounds
siderations which require the use of filtering ar
the conductor 86 and which for a short portion
rangements in association with these connections
of its length forms with the conductor a coaxial
arise from the presence of the condensers |2| and
transmission line along which high frequency
|22, the first set representing the by-pass capac
energy passing through the opening 8l tends to
ity provided by the insulating washer 21 (Fig. 2)
be propagated. To block the ñow of such energy
and the second set representing the capacity pro
a reentrant quarter wave discontinuity is pro
vided by the mica insert 58 (Fig. 1). As has
vided by mounting upon the conductor 86 a me
been previously indicated, these spacers repre
tallic sleeve 94 which is open at one end and
sent gaps through which undesirable high fre
which is of materially larger diameter than the
quency coupling may occur. As far as the anode
conductor. The length of the sleeve 94 is made
conductor 12' is concerned such coupling is pre
such as to correspond closely to one or more
vented by the inclusion of the filtering elements
odd quarter wave lengths at a selected frequency
18’ and 19’. In connection with the cathode
Within the expected operating range of the oscil
supply conductor 86’ a similar function is per
50
lator. In series with this "arrangement there is
formed by the concentrically arranged ñlters 96’
provided a second reentrant quarter wave filter
to 10|’. Accordingly, no substantial coupling be
ing section provided by a tubular conductor 91,
tween the high frequency oscillator and the ex
which may be looked upon as a reversely bent
ternal circuits is permitted.
extension of the conductor 93. This is surround
While the invention has been described by ref
55
ed by a tubular conductor 98 which bears a re
erence to a particular embodiment it will be un
versely bent part |08 adapted to provide a still
derstood that numerous modifications may be
further reentrant discontinuity in the path of
made by those skilled in the art without depart
wave propagation. A sleeve |0| fitted into the
ing from the invention. I, therefore, aim in the
cylinder 44 decreases the dimensions of the free
appended claims to cover all such equivalent var
60
space about the conductive part lüû. A metallic
iations as come Within the true spirit and scope
washer |03 which closely surrounds the extrem
of the foregoing disclosure. In the claims, wher
ity of the conductor 86 serves to support the as
ever the term “quarter wave” is employed it is
sociated tubular elements 98 and |80 and closes
to be understood as applying either to a single
one end of the inner conductor. For supporting
quarter wave or to any odd number of quarter
65
this structure and for securing it to the remain
waves.
ing structure of the oscillator, use is made of a
clamping ring ||0 which abuts against a narrow
flange I|| provided on the outer surface of the
part d4 and which has a screw-threaded engage
ment with the part 43 as indicated at ||2.
As a result of the Aarrangement described, the
What I claim as new and desire to secure by
Letters Patent of the United States is:
1. A filter comprising a plurality of successively
telescoped coaxial conductors connected to pro
vide a plurality of quarter wave discontinuities
in series,` adjacent ones of said conductors being
only possible path for the escape of high fre
insulated from each other for unidirectional
quency energy through the left hand extremity
currents.
of the apparatus of Fig. 1 is by series passage
2. A band-stop filter for frequencies within a
through the various filter sections. Where it is 75
7
@A085927
given- range comprising a plurality of successively
telescoped concentric conductors *connected to
provide a number of filtering sections in lseries,
'adjacent ones of said conductors being insulated
from each other for unidirectional currentsy each
of said sections having a length corresponding to
a quarter wave length at some frequency within
the given range, and the various sections being
of diiîerent diameters whereby each represents a
comprising, a high frequency ñlter including a
plurality of telescoped conductors arranged to
provide ‘a multiple reversed path for‘electromag
netic waves tending to pass through the ñlter,
each reversed section of the filter comprising a
reentrant discontinuity effective to block passage
of waves of a particular wave length, and adja
cent ones of said conductors being insulated from
each other for unidirectional currents.
5. In combination, a high frequency system, a
3. In» an- arrangement for decoupling the power 10
conductor for supplying current to a. pait of said
leads to an ultra high frequency space resonant
system, and a high frequency filter associated
system, a high frequency ñlter including a plu
with said conductor, said ñlter comprising a con
rality of telescoped conductors of varying diam
ductive tube surrounding said conductor and de
eters connected to provide a number of filtering
sections in series, each of said sections comprising 16 fining with it a'coaxial transmission line, means
on said conductor for providing a quarter wave
a reentrant quarter wave discontinuity in the
discontinuity with respect'to the others.
l path of propagation of the waves desired to be
discontinuity in saidrline, and further conductive
filtered, and adjacent ones of said conductors
being insulated from each other for unidirectional
means concentrically surrounding said tube and
insulated therefrom at the frequency of `said cur
currents.
4. A device for decoupling the power leads to
an ultra high frequency space resonant system
20 rent for providing a, second quarter wave discon
tinuity serially related to the first.
ANATOLE M. GUREWITS CH.
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