US2479537A - Detector-oscillator circuit for ultra high frequency receivers - Google Patents

Description

Aug. 16, 1949. G. w. FYLER 2,479,537

- DETECTOR-OSCILLATOR CIRCUIT FOR ULTRA HIGH FREQUENCY RECEIVERS Filed Dec. 30, 1942 Inventor: George W. F5 ler',

Patented Aug. 16:, 1949 l UNITED DETECTOR-OSCILLATOR CIRCUIT FOR ULTRA; filGHiiEREQUENfi i 'George'fW. Fyl er, "Stratforgl, Conn, assignor to General"Electriv'eompany, a corporation of New-York 'An licai onpceem er so. ia42 -,s..e i stamina My invention relates to circuits ior ultra hig vantages thereof, ,m ay best .be un erstood by frequency receivers and it has forits object to referencejtothelfellowing ti'e'scr i-ptiori taken in vprovide an improved frequencyconversion circuit connect' n with the accompanyin drawing, in .for such receivers. whichulifig. 1 is va partially di'agramrnatic per- My invention relates more particularlyzto de- H5 spective viewI lfepresentin the frequency cantector-oscillator circuits for ultra high frequency version circuits fora receiverof the su'p erheterowaves in Which transmission lines are ,used as giyn e typeemhodying my inventiojri; ennu g. 2

.part of the tunQdcimuits of the ospillator and .ijs acr'ossesectionalvievv'takenla r 'gthlinei fl detector. In] such detector-oscillator e'ircuits, it in the q slirectio ieft earr s. is desirable that all direct coupling .between the 10 .Re'fer ing to the drawing, I have Shown ajtr'ansultrahigh frequency input, circuitvan d, the tank mission time; f! to supplyinputsignals from any circuitof the local oscillator be avoigiegi in order cle'siralole.source'suchasanantenhato the'input that no voltage ofhthe oscillatorirequency lee c cuit oflcorivcrter'ii. Local oscillations are induced ,in the'antennagircuit of the receiverio supplied by means of oscillator 12 and, are mixed cause currentsof this frequency to f 1o vv in these ,15 .with thet input radio frequency signals in concircuitswith consequent increased powe drain v erter l l'joprovide, intheusual mannehfeuron the .oscillator, as well as.undesiredraqiatign .rents .ihth'e.anodeicircuitjofflthe converter I I, of of oscillator signals. It is des irahleililgetvisethat the desiredintermediate frequencies; which curno voltage of t s a ,ire uens J coup es a .ae a tth r m win i p ir t into the oscillatory circuit 0f thei qscillato tp goemediatefrequency transformer 1 13. The 1 1 7-- cause an undesired loading efiect of the trents from the secondary of transformer [Bina y circuit with resultant loss;in ultirnate sep ,he plied,.by ,means of leacl'll to sub equent It is an object of ny-inventmn toprovid stagesiofiwlthef receiver whichf rnay' coinprise one or more amplifiers for thei riterme' ate ire.- high frequency, receiveriniwhicha I -gs quency c urr.e'n i' s,'a' detector; signaKairiplificatiQn r nsmission line "conductors ll iicfi qp t at? i e e' fi l t matcly, -a tili 'tion Q Q ""h the oscillatory circuit for the oscillatpr. and the as, a loudsneakljl Thesii tt ilpo st the input circuit for the convetter. Qreceiverfcirmiits may tater any cles v ed "y pe "receiverforultrahigh freguen cyra o. ave 1 Another object of my invention -is,to provide arenotshowilfinithe.draiiv' g1 an m ved e qs l t 2 i 1 aw n m te e e e e el e ea -t i l 4 t fifitfi e ivee b fis lwi now: tm INplwhich a S n l an sien in ds conn e ed ta 4 .535 :fln i 3W i e il hof ew tween the local oscillatorandthe conventerand s ion apparatusf, an as ned to the assig eeof is adjustable: b eemknhmeaasi r s n te at both the frequency of the ioc wsci llator and the frequency of, the input radio waves.

A further feature of any invention is: the ,ern-

iployment of a singlepair of transmissionfline gated conductors in conjunction with a .-first.-e1ectr ,0n [to ground at ,oscillation,frequencies by a -,by:p ass discharge device as asourceofiocaloscillfitiuns, a capacitor. iTheoscillatorcircuitsj2 ,;,are; similar the conductors being connected in parallel i to .tothosehes ihedt in said; copendingg anp icat c s p y n-p a oscillations t t e; controlteleca afp -pitis t-an i-ie ectto itd c ir eedcyice 1,5

trode of the first dev efan i c nl1 nctiontwith hav na-aneanqde t firiatcathqde ilandiaicontml a pair of electron disc1 1a r g:e devicesas .ayireelectrode l8. ,Tll seliscli arge;.device-l-5;is.,inonnted quency conversion circuit, the pan; piconductors .45 :in;the usual, manner -on acha-ssiszzn whichiacts being connected te e t elv to t contro el craszaifigndu iiiveziplane ,fflrmingi-an .equipotential trodes of the pair of devices tosupplyzzthcreto suriace fi 3ed.;at ground-potential .for. radiozf rein-ph s s a o mth lo a sc 1 tquen w currents. {Ehe ontroL electrode 18 of ut- -ph .i nals from t adio; .r,equency d vices!5;is; ouplediby.meansioftcapacito -vzl to input circuits. I 50 .a,transmissioniilineifi .comprising.a,1.pair of: par- :The features of my invention .which,I;-belive t0 allelarods or eoncluctorsv23 .andi 24. substantially be novel are set forth with particularitylin; the equally spaced,- from -plane.- 20,=,andl. asmall adie- .appendedwclaims. My invention, itselfixhnWever, tance, thereabovaas.shownaatEigez.

both as touiitsuorganization andzmethodsot-top- *:The,-.1ine:;22..-,and ,planeaazfl.thusszformlat-tuned .eration, together with?furmeraobjccts.eandtad- 455 oscillatorytor.tankcircuitinithecircuit between cathode l1 and control electrode |8, one side of said circuit being grounded for alternating currents. The line 22 is short-circuited by means of conductor I9 at the end connected to the control electrode l8 and is open-circuited at the other end, and a variable capacitor 25 is provided between the short-circuited end and the plane 20 for adjusting the electrical length of the oscillator transmission line oscillatory circuit. Resistor 26 is provided between cathode l1 and control electrode 18 to function as the usual grid leak resistor. The oscillator anode I6 is connected to ground through the small by-pass capacitor 21 to form an oscillator circuit as described in my above-mentioned copending application. Operating potential is supplied to the oscillator anode from the usual source, indicated on the drawin by the conductor bearing the legend +13 and the negative terminal of which may be grounded. Anode l6 may be connected to this source through radio frequency choke coil 28 and inductance 29 is connected between cathode H and ground and serves as a cathode choke to control the uniformity of oscillations over the band through which the oscillator l2 operates. The value of inductance 29 is selected so that oscillator l2 may be tuned over its entire range of frequencies by adjustment of capacitor 25 and that an adequate and uniform voltage is supplied to the converter ii. If the value is too small, it may cause the oscillations to stop, Whereas if it is too large, it may cause the oscillator to super-regenerate. In either case, uniformity of oscillation obviously is lost.

Radio frequency input signals being supplied from the antenna of the receiver over transmission line It are coupled to the transmission line 22 by means of the inductive loop 30, which loop preferably is balanced capacitively to ground or electrostatically shielded to prevent unbalanced coupling with the conductors of transmission line 22. By this means, any direct coupling between the oscillator circuit and the radio frequency input circuits is avoided so that the oscillator voltages are prevented from appearing in the antenna circuit to cause large currents of oscillation frequencies to appear in this circuit and cause radiation therefrom. A balanced inductive coupling likewise prevents radio frequenc signal currents from appearing in the oscillator tank circuit, with corresponding loss in signal energy.

The open ends of the conductors of the transmission line 22 are connected respectively to the control electrodes 3| and 32 of the pair of electron discharge devices 33 and 34 in the circuit of the converter The conductors 23 and 24 of line 22 are short-circuited at a point intermediate the open end and short-circuited end by means of an adjustable slider, or any other similar short-circuiting element, 35. By adjustment of the position of slider 35, the length of line 22 between slider 35 and the electrodes 3| and 32 may be adjusted for resonance at the frequency of the input radio frequency signals.

In the circuits of the converter the anodes 36 and 31 of the devices 33 and 34 respectively are connected serially with the primary winding 40 of intermediate frequency transformer l3 to supply currents of intermediate frequency thereto. In order that currents of radio frequency do not appear in the primary winding 40, condenser 4| is connected between the anodes 36 and 31 and is selected to have a value such that, at the frequency of the input signals, it series resonates with the inductance of the leads connecting it to the anodes, thus acting as a short-circuit for these signals and preventing their appearance in the primary winding. Operating potential for the anodes 36 and 31 is supplied from the usual potential source indicated in the drawing by the conductor bearing the legend +3 and by-pass capacitor 43 is connected between the lower terminal of winding 40 and ground to prevent the flow of intermediate frequenc currents to the potential source.

The cathodes 44 and 45 of the discharge devices 33 and 34 are connected together and are grounded to the chassis 20 by as short a lead as possible, the cathode preferably being connected to the tube base inside the respective tube and the base being grounded to the chassis in order to keep the degeneration in the input circuit of the converter II to a minimum value. At ultra high frequencies, degenerative loading of the grids of the devices 33 and 34 of the converter may occur due to the self-inductance of the cathode-to-cathode lead. Since this degeneration increases the input conductance of the converter and consequently reduces the signa1potential at the grids, this lead is made as short as possible.

Resistor 41 is connected between slider 35 and ground to provide a path for unidirectional currents from grids 3| and 32 to ground and its value is so selected that with the correct oscillator voltage amplitude the resulting bias on grids 3| and 32 maintains these grids substantially at the cutoff voltages of the devices 33 and 34. Alternatively, a cathode biasing resistance and capacitance combination may be used.

Primary winding 40 and secondary winding 5|] of intermediate frequency transformer |3 are shown as possessing an adjustable inductnace determined by the position of the tuning cores or slugs 5| and 52. The positions of the slugs are adjusted so that the inductances of these windings are tuned to parallel resonance with the distributed capacity of the windings and circuit at the desired intermediate frequency. In this manner the winding 40 serves as an oscillator circuit for the converter I tuned to the intermediate frequency and the winding 50 serves as a tuned in put circuit for subsequent stages of the receiver.

In the operation of the frequency conversion circuit described, radio frequency input signals are inductively coupled to the input circuit of the converter II by means of the loop 30 located between conductors 23 and 24 between slider 35 and the control electrodes of the converter discharge devices. Slider 35 is so adjusted that the length of line 22 between the slider 35 and the control electrodes is tuned for resonance Whereby the input signals are impressed upon the control electrodes 3| and 32 with opposite phase so that the line 22 serves as an out-of-phase pushpull input circuit line for the converter. The dotted lines 60 and El represent the voltage distribution along conductors 23 and 24- for Voltages of the frequency of the input signals and illustrate the manner in which thes voltages appear with maximum intensity and opposite phase upon the electrodes 3| and 32.

By means of variable capacitor 25, the electrical length of the connection between control electrode l8 of the oscillator and control electrodes 3| and 32 of the converter is adjusted for resonance at the frequency of the oscillations. The dotted line 62 represents the voltage distribution along the tuned transmission line including the conductors 23 and 24 for voltages of answer.

the.'frequency: of thelocali scil1at0r="|.2.;1 Asiindicated', this tuned line is one-half wave lengtlrin length at; thefrequency ofthe localoscillator, so that the oscillator voltage appears withmaximumintensity and in like phase relation upon the converter control: electrodes 31 and, 32.. The inductance 29 makes it possible to tune the oscillator'yl2' over its entire range of frequency with good uniformity of the oscillator voltage supplied? to-the convertenthe magnitude of the excitation voltage supplied to the converter being controlled by themagnitude: of the Voltage +3..

Due to the fact that the oscil1atorcurrentis in-phase in conductors. 23,, Hand the antenna coupling is. effective only for out-of-phase currents in. the same two conductors, no oscillator voltage is induced in the antenna circuit. Thus, by careful design of these circuits, there should belittle or no coupling between the circuits.v In this manner the same pair of conductors 23; and: 24, since, they are in. the oscillatory circuit of the oscillator |2,.form means for supplying oscillation voltages to the control electrodes 3|, and 32 of the converter in-phase and because of their inductive coupling with the antenna circuit function as an out-of-phase push-pull transmission line for the radio frequency input signals. These circuits are tunable independently, the radio frequency input circuit being tuned by means of adjustment of slider 35 and the oscillatory circuit of the oscillator by means of the variable capacitor connected between the oscillator grid circuit. and ground. By proper selection of the value of resistance 4'! and the potential applied to the anode Hi, theoscillator may be made to produce automatically the correct converter bias.

The circuit of the converter ll operates in the usual manner to produce in the anode circuits of the devices 33 and 34 currents having a frequency which is the difference between the frequency of the radio input signals and that of the oscillation signals on the local oscillator [2. The anodes of these devices are connected to the intermediate frequency transformer to impress intermediate frequency voltage across the primary of that transformer. Degenerative loading of the control electrodes of the converter, which degeneration normally is caused by self-inductance of the cathode leads and the grid to plate capacity of the devices, is reduced to a minimum by providing a short common cathode connection and by providing capacitor 4| to maintain the anodes of the devices substantially at :the same potential for the radio signal frequency. By the symmetry of the circuit this must be zero radio frequency potential. This capacity series resonates with the inductance of the anode leads at the signal frequency so that the anode is at ground potential at this frequency. Therefore, an important object of the capacitor 4| is to prevent radio frequency signal voltage from appearing on the anode of the converter tubes thereby preventing any degenerative effect through the grid to plate capacity of these devices. The connections between the primary of the intermediate frequency transformer I3 and the anodes 36 and 3! are made as short as possible to keep at a minimum any linkage with the radio frequency and oscillation frequency fields existing in the vicinity, which linkage would increase undesirably the radio frequency potentials supplied to the intermediate frequency transformer.

While I have shown a particular embodiment of my invention, it will of course be understood that I do not wish to be limited thereto since vamousifmndiflcationsimay be made, and-I ,COlT-r template; by the: appended claims to cover any such; modifications as. fall within. the true spirit,

and: scopeiof my. invention.

What lclaiin as new anddesire to. secureby LettersPatent oftheUnited States is:

1. In an ultrahigh frequency'receiving apparatus,..a source of ultra. high frequency signal w-aves;..a-loc.al oscillator havingv a pair of input, electrodes; a-push-pull converter comprising a pair of electron discharge devices each having. an anode, a cathode and a controlelectrode, a transmission line comprising a pair of parallel conductors, aconductive plane of fixed potential substantially equally spaced from said conductors, one. end of each of said conductors being coupled to. one of said input electrodes and said plane. being connected to: the other of said input electrodes,..whereby said line and said plane. form a tuned-input circuit for said oscillator, and the. other end of each of said conductors respectively being'connected to one of said control electrodes, means. inductively coupling said source of signal waves tosaid. line, whereby said line forms an. input circuitfor said converter, means for tuning saidv oscillator input circuit thereby to impress oscillations of ilke phase on said control electrodes, and means for tuning said converter input circuit thereby to impress said waves on said control electrodesin opposite phase.

2. In a receiver for ultra high frequency waves, a push-pull converter having a pair of control: electrodes, a transmission line connected in loop circuit between said control electrodes, means ineluding. said transmission line for impressing said ultraphigh frequency waves uponsaid control electrodes. in opposite phase relation, a local oscillator including an input. circuit, and means. including said transmission line for tuning said input circuit to a desired frequency and impressing the generated oscillations upon said pair of control electrodes in like phase relation.

3. In a receiver for high frequency signal waves, a source of signal waves, an oscillator having a control electrode, a push-pull converter having a pair of control electrodes, and a transmission line comprising a pair of conductors, each of said conductors being connected at one of its ends to the control electrode of said oscillator and each of said conductors being connected at its other end to a respective one of said pair of control electrodes, adjustable means for tuning a portion of said transmission line to the frequency of said signal waves, means including said transmission line for impressing signal waves from said source upon said pair of control electrodes in opposite phase relation, and means for tuning said transmission line between the ends thereof to the fre quency of said oscillations thereby to sustain said oscillations on said line and to impress said oscillations upon said pair of control electrodes in like phase relation.

4. In a high frequency radio receiver the combination of a source of signal waves, a source of local oscillations comprising an electron discharge device having a cathode and a control electrode, a resonant circuit connected between said cathode and control electrode and comprising a pair of parallel conductors each having one end coupled to said control electrode, a conductive plane of fixed potential in spaced relation with said conductors and connected to said cathode, and means connected between said conductors and said plane for tuning said resonant circuit to sustain said oscillations at a desired frequency, a push-pull converter having a pair of control electrodes connected respectively to the other ends of said pair of conductors thereby to receive said oscillations in like phase relation, adjustable means for timing a portion of said line between said pair of control electrodes and an intermediate point on said line to the frequency of said waves, and means for inductively coupling said source of waves to said tuned portion of said line thereby to impress said waves upon said pair of control electrodes in opposite phase relation.

5. In an ultra high frequency receiving apparatus, a source of ultra high frequency signal waves, a transmission line comprising a pair of substantially parallel conductors connected together at one end and open-circuited at the other end, a source of local oscillations including an electron discharge device having a control electrode coupled to the connected ends of said conductors, a push-pull converter including a pair of electron discharge devices each having a control electrode coupled to one of said conductors at the open-circuited end of said transmission line, means for adjusting the electrical length of said line between the ends thereof for resonance at the frequency of said oscillations thereby to sustain said oscillations and to impress said oscillations upon said converter control electrodes in like phase relation, means for short-circuiting said conductors at a point intermediate th ends thereof thereby to adjust the electrical length of a portion of said line between said converter control electrodes and said short-circuiting means for resonance at the frequency of said waves, and means inductively coupling said source of waves to said portion of said line thereby to impress said waves upon said converter control electrodes in opposite phase relation.

6. In an ultra high frequency receiving apparatus a source of ultra high frequency signal waves, a source of loca1 oscillations including a control electrode, a push-pull converter having a pair of control electrodes, a pair of substantially parallel Lecher wires each having one end connected to one of said pair of control electrodes and its other end connected to said local oscillator control electrode, means for short-circuitin said wires at a point spaced from each of said pair of control electrodes by a quarter wave length at the frequency of said signal waves, means inductively coupling said source of signal waves to said wires thereby to impress said waves upon said pair of control electrodes in opposing phase relation, and means for adjusting the electrical lengths of said wires between said pair of control electrodes and said oscillator control electrode to approximately one-half wave length at the frequency of said local oscillations thereby to maintain said oscillations and to impress said oscillations upon said pair of control electrodes in like phase relation.

GEORGE W. FYLER.

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

UNITED STATES PATENTS Number Name Date 2,011,943 Lindenblad Aug. 20, 1935 2,106,776 lrevor et a1 Feb. 1, 1938 2,216,964 Stepp Oct. 8, 1940 2,285,372 Strutt et al June 2, 1942

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