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Патент USA US2129293

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Sept. 6, 1938.
Filed March 25‘, 19:57 '
Patented Sept.
nsNn-rsss mmfilz?znmt or wave '
Rudolf Weber, Berlin, Germany, assignor
funken Gesellschait fiir- Drahtlose Telegraphic
m. 11.11., Berlin, Germany, a corporation oi’ Ger
Application March 25, 1931, Serial No. 132,901
In Germany March 12, 1936
3 Claims.
(01. 178-44)
The practical ‘demand arises occasionally to ' S3 are closed, while switch Si is opened. The
make the band width of receivers changeable in
circuit in this condition is shown in Fig. 3. Con
side wide limits say, between 1 and 15 k. c. This densers C3 and 04 as well as the resistances WI
demand will be made, for instance, if in airplane and W2 are thus rendered inoperative, while
5 ‘receiver apparatus a change is made from beam condensers Cl and 02 no longer operate as cou
direction ?nding to the so-called impulse type” pling condensers, but are merely included in the
- of direction ?nding. In this'latter instance, the oscillation circuits and avoid detuning, for in
impulses, in rectangular shape, must be faith
the switch position shown in Fig. 3, each oscilla
fully reproduced in the Braun tube so that a tion circuit Ct—L contains an additional con‘
1° wide-band must be received.
denser, namely, the coupling condenser Cl and 10
When a change to such a wide band is made, C2, respectively. In the circuit illustrated in Fig.
detuning oi' the oscillation circuits is inevitable. , 3 the coupling between the oscillation circuits is
Hence, the condition of untuning would have to effected only by condenser C and it is so loose
be corrected by the addition of condensers or that the ensuingband width is limited. But in
' coils.
However, switches carrying radio fre
lieu of this coupling also any other coupling could
quency energy are undesirable because of addi
be employed.
tional damping and the requisite shielding.
Now, the invention discloses 'a circuit arrange
ment in which thesedrawbacks are avoided by
of similar, tunable circuits, each including an in- '
reason that the switches carry no radio frequency
‘energy or practically so. In one switch'position,
ductance, a variable condenser, a resistance and
a. pair or ?xed condensers all connected-in series
two paralleled series arrangements of condensers,
in the order named, a series coupling condenser
connected between. high potential'ends of said
inductances, a conductive connection between the
low potential ends of said inductances, switch 25
mechanism. individually associated with each
tunable circuit for short circuiting the resistance
What I claim is:
1. A band-pass ?lter network comprising a pair
all of like capacity, serve as a coupler capacity
being common'to the oscillation circuits, whereas
‘25 in the other switch position one of these con
densers, to avoid detuning, is separately con
nected in each or the two oscillation circuits
and another suitable coupling is chosen.
The invention shall be explained in more detail
30 in what 1ollows_and with reference to the accom
panying drawing wherein:
and one of the ?xed-condensers when in closed
position, and other switch mechanism conjointly
associated with both tu'nabl'e circuits and con 80
.nected between the respective junctions of the
, Fig. 1 shows the circuit organization of_ the in
short circuited resistance and?xed condenser,
whereby the frequency band to be transmitted
Fig. 2 shows the circuit connections obtained
35 when the switches are in the positions illustrated
in Fig. 1 whereby transmission of a wide fre
quency band is effected,‘ and Fig. 3 shows the cir
cuit connections obtained when the switches are
in the positions opposite to those illustrated in
40 Fig. l whereby-the transmission of a narrow fre
quency band is e?ected.
may be selectively varied within wide limits with
out altering the tuning of the circuit, upon open
ing the ?rst switch mechanism and closing the
second switch mechanism, and ‘vice’ versa.‘
. 2. A band-pass ?lter network comprising a
pair of similar oscillation circuits, each compris
ing a variable condenser, an inductance, a re
sistance and two equal capacities, all connected
Referring'to Fig. 1, there are shown a pair of
coupled tuned circuits Cz-L.
in a closed circuit, a coupling condenser con
nected between the high potential ends of the
In one of ,the
switching positions, only the switch Si is closed
two inductances, a conductive connection be- '
tween the low potential ends of said inductances' 45
45 so that the four similar condensers CI-Cl con
jointly actlike a single condenser C1 of the size‘ a switch connected between low potential ends
' of the individual condensers as shown in Fig. 2.
' The coupling in this connection is'very close, for
which reason, to minimize crevasing or the pro-‘
'50 duction of a double peaked resonance curve,
damping resistances WI and W2 are included in,
the circuit. ‘The coupling insured by condenser
C, Fig. l, is only very loose contrasted with the
coupling due to C1.
7 58 In the other switch position, switches s: mg
of the two circuits, between the common termi
nals of the resistance and one of the two equal
capacities in each circuit, and a switch in each‘
circuit shunting said resistance and seldom of
the two equal capacities, the arrangement being
such that upon operation of the ?rst switch to
closed position and with the two last mentioned
switches in open position the circuits are ad
lusted to ‘pass a wide band of frequencies, while
the closing of the two last mentioned switches ' coupling condenser and'said parallel coupling
and the opening of the ?rst switch adjusts the ‘ capacity being of such magnitudes that the cir
circuits to pass a narrow band of frequencies. in cuits are closely coupled to pass a wide frequency
each case the oscillation circuits being tuned to band, and means for converting said network
_ to one capable of passing a narrow frequency
substantially the same resonant frequency.
3. A band-pass ?lter network comprising a band comprising a ?rst switching mechanism for
causing the plurality of ?xed condensers to be
pair of tunable circuits, each includingan in
ductance and a variable condenser, 15. series cou
pling condenser connected between the high po
10 tential ends 01’ said inductances, a conductive
connection between the low potential ends of
said inductances, a plurality of ?xed condensers
common to said pair of tunable circuits and serv
ing as a parallel coupling capacity, said series
come ine?’ective as a parallel coupling capacity
and a second switching mechanism individual to
each tunable circuit for short circuiting certain 10
01 the ?xed condensers and switching into said
tunable circuits others of said ?xed condensers.
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