US2434474A - Circuit arrangement for ultra short waves - Google Patents

Description

jam i3? 394g. l Q S'TRUTT 2,434,474

CIRCUIT ARRANGEMENT FOR ULTRA SHORT WAVES Filed March 25, 1943 \o 70 F/L.

v l HiAr//VG SUP/3L Y IN V EN TOR.

Patented Jan. 13, 1948 CIRCUIT ARRANGEMEN T FOR ULTRA SHORT WAVES Maximiliaan Julius Otto Strutt,

Eindhoven,

Netherlands, assignor to Hartford National Bank & Trust Co., Hartford, Conn., as trustee Application March 23, 1943, Serial No. 480,197 In the Netherlands January 28, 1941 Section 1, Public Law 690, August 8, 1946 Patent expires January 28, 1961 4 Claims. (Cl. Z50-20) This invention relates to a circuit arrangement for ultra-short waves which comprises a resonant circuit mainly consisting of two parallel conductors, for instance a tunable Lecher-wire syst-ern, and an electron discharge tube which may serve for amplifying, mixing or detecting purposes.

More particularly, in mixing circuit arrangements for the reception of ultra-short waves, it is often advantageous to connect the cathode of the electron discharge tube to a point of a resonant circuit which is not earthed for high frequency. In such a circuit, however, disturbances occur when the cathode of the said electron discharge tube is indirectly heated by means of a filament which is fed from a supply earthed for high frequency, the said disturbances being audible as crackling or humming noises after detection of the high frequency oscillations.

One of the objects of the invention is to provide means by which the said disturbances, due to the high frequency voltage set up between the lament and the cathode of the electron discharge tube, can be avoided in a simple manner in arrangements of the kind referred to above.

To this end, according to the invention, the supply conductors for the filament between a point earthed for high frequency and the point of the resonant circuit connected to the cathode of the electron discharge tube are tightly coupled throughout their length for high frequency currents to the part of the resonant circuit conductors located between the two points in such manner that between the cathode and the lament of the tube there occur at least substantially no alternating voltages having a frequency whose order of magnitude corresponds to the natural frequency of the resonant circuit.

The said close coupling for high frequency currents can be realized by arranging for the supply conductors between the said points cf the resonant circuit, with the interposition of insulating material, to extend along the surface of the reso nant circuit conductors, which may be shaped as a band, or within the tubular resonant circuit conductors, thus establishing a capacitative coupling between the supply and resonant circuit conductors and avoiding the appearance of disturbing high frequency voltages between corresponding points of the conductors.

In another suitable form of construction of the circuit, according to the invention, at least one of the supply conductors is constituted by one or by both resonant circuit conductors or by a part thereof.

reference to the accompanying drawing representing, by way of example, a particularly suitable form of construction of a push-pull mixing circuit according thereto.

The circuit represented in the drawing com nected triode systems produce the local oscillations, to which end the control grid circuits comprise a Lecher-wire system 8 which can be tuned by means of an earthed bridge 25, the anode cir- Y cuits including a resonant circuit 9 and the cath- The invention will be more fully explained by ode circuit comprising a tunable Lecher-wire system I0, I0', I0", all of which circuits are tuned to the frequency of the local oscillations.

Between the two diode anodes is interposed a resonant circuit II which is tuned to the frequency of the incoming oscillations supplied to this circuit through the intermediary 0f a coupling coil l2.

The anodes of the triode systems are connected through a resistance 2| to the positive terminalv of a source of anode voltage (not represented) whose negative terminal may be earthed.

The cathodes B, I of the two triode systems 2, 3 are connected respectively to the ends of the resonant circuit constituted by the parallel conductors I and I0' and the bridge ID", the centre of the bridge I0" for tuning the circuit being connected to earth thrcugh the series connection ofV a resonant circuit I4 tuned to the intermediate frequency and a network I5 which serves to produce a suitable diode bias and consists of the parallel connection of a resistance and a condenser.

In the circuit illustrated, the cathodes '6 and I of the tube I convey alternating voltages having the frequency of the local oscillations with respect to earth so that, if the cathodes are indirectly heated by laments I6, I'I connected to an earthed supply, alternating voltages also occur between each of the two cathodes and the associated lament, which voltages cause. unde-l` sirable disturbances, as has already been said'-v above.

According to one aspect of the invention, the occurrence of these disturbances in the circuit illustrated is avoided by supplying the heating Voltage Egi, in the case under review an alternating voltage, to the laments IB, Il through conductors coupled to the resonant circuit conductors between the point I8 of the resonant circuit I0, i8', l0" earthed for local oscillations and the ends of this circuit which are connected to the cathodes. For this purpose, one end of each lament I6, I 1 is directly connected to the associated cathode 6, I respectively and through the intermediary ofthe resonant circuitconductorsv i0, l respectively themselves and the point I8 of the bridge l0" to the junction terminal I9 for the heating voltage, which terminal is earthed for high frequency, whereas the other end ofv eachfilament is connected to the junction terminal through conductors 2|, 2|' respectively insulatingly arranged within the tubular resonant circuit conductors I0, I 0' respectively and aleadl in point 22 located similarly to point i'of'the tubular bridge piece l0".

a choke 23 constituting a, high impedance to inf termediate frequency oscillations.

By supplying the heating current to the filaments in the manner set out above, the: occur rence of alternating voltages having a frequency whose order of magnitudecorresponds to the natural frequency of. the. resonant circuit isV avoided withcertainty between cathode vand lament, thus removing the cause of the said disturbances.

What I claim is:

1. A circuit for ultra short waves, more particularly a mixing circuit, comprising a resonant circuit which includes twor parallel conductors.

andan electron discharge tube having a filament, an indirectly heatedcathode connected to a point on the resonant circuit whichis not earthed for.

between the cathode andithe filament of` the* tube there appear at least substantially noalternating voltages having a frequency whose orderof magnitude corresponds to the natural frequency of the resonant circuit.

2. A circuit for ultra short waves, as claimedy in claim 1, in which said resonant circuit comprises tubular conductors and one or both supplyv conductors between thesaid points of theresonant circuit are provided withinV saidtubularu con--H ductors.

3. A frequency mixer comprising` a pair'of` oscillator electrode structures each including an;

indirectly heated cathode, a filament therefor, a:

grid and an anode, all located in a single evacuated envelope, a diode anode cooperating with.

each cathodeand also located in'said envelope; tuned circuits coupled. betweenk corresponding, electrodes of said structures' and tuned to: the frequency of the locally produced oscillations, said. cathode tuned circuit comprising-a pair of par.-

allel tubular conductors one end of which isshunted by atubularconductor,,and the other.

Thesupply conductor: connected to the junction terminal I9 includes;

end of which is connected to said cathodes, one terminal of each filament being connected directly to its cathode, the other terminal of each filament being connected to a supply lead extending through the interior. of that tubular conductor which is associated with its cathode, a connection from the center point of said shunting tubular conductor to one terminal of an alternating current filament supply, a condenser connecting said last terminal to ground for radio frequency energy, and a connection from the other terminal of said filament supply to the supply leads in the interiors of said pair of tubular conductors, a tuned circuit coupled between said diode anodes and tuned to the frequency of the input waves, and a circuit tuned to the difference of the frequency of the locally produced oscillations and the frequency of the input waves, said last circuit being located between the cathode tuned circuit and the diode anode tuned circuit.

4. A frequency mixer comprising a pair of oscillator electrode structures each including an indirectly heated cathode, a filament therefor, a grid andan anode, a diode anode cooperating with each cathode, tuned circuits coupled between corresponding electrodes of said structures and tuned to the frequency of the locally produced oscillations, said cathode tuned circuit comprising a pair of parallel tubular conductors one end of which is shunted by a tubular conductor, and the other end of which is connected to said cathodes, one terminal of each lament being connected directly to its cathode, the other terminal of each filament being connected to a supply lead extending through the interior of that tubular conductor which is associated with itsV cathode, a connection from the center point of said shunting tubular conductor to one terminal of an alternating current .filament supply, a condenser connecting said last terminal to ground for radio frequency energy, and a connection from the other terminal of said filament supply to the supply leads in the interiors of said pair of tubular conductors; a tuned circuit coupled between said diode anodes and tuned to the frequency of the input waves, and a circuit tuned to the sum or difference frequency of the locally produced oscillations and the'frequency of the input waves, said last circuit being coupled to the center point of said shunting tubular conductor.

MAXIMILIAAN JULIUS OTTO STRUTT.

REFERENCES CITED The following references are `of record in theV file of this patent:

UNITED STATES PATENTS Number Name Date 2,097,514 Chaffee Nov. 2, 1937 2,236,004 MacLean Mar. 25, 1941V 2,272,062 George Feb. 3, 1942: 2,285,372 Strutt et al June 2, 1942 FOREIGN PATENTS Number Country Date 557,163" Great Britain Nov. 8,1943'

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