US2011942A - Ultra short wave receiver - Google Patents

Description

Aug. 20, 1935. R. w. GEORGE I ULTRA SHORT WAVE RECEIVER Filed Jarl. 16, 1952 INVENTOR R.W.GEORGE BY A ATTORNEY Patented Aug. 20, 19354 i UNITED LSTATES:

a r l o f f ULTRA SHORT WA E RECEIVER Ralph W. George, Riverhead N. assignor to' Radio Corporation of America, a corporation of Delaware f I Application JanuarylG 1932, Serial.No; 587,109 i V ams, (cram-20 This invention relates toradio receiving circuits I and has especial reference to such ofthes dcir cuits which-are c apable of receiving ultrashort waves. 7 v V The development 0f suitable apparatus for re-' ceiving signals from transmitters operating on low wave lengths has been attendedin the past with certain difficulties, one of the most prominent of which has been the difficulty of adjusting thefrequency 'of the receiver-so e'xactlyjthat the oscillations received from the transmitter, when beating-with the locally generated oscillations, produce a steady audio note. It is well known in the art that'the usual present day methods used for receiving continuous'wave signals, i.- e., the

audible "beat note system, are impractical for the reception of signals having ultra high frequencies *Suchas a f quency oft-he order. of 400 megacycles per second. a a I 7 invention is to overcome the-aforementioned. difli culty, and this is accomplishedby producing-a short; wavereceiver which is capable of receiving signals over a widerange of ultrahigh frequencies with high efficiencyand reliability; I

A further object of "thepresentinvention'is. to

fed into a translating device. The ultra nightmquency oscillator istuned to the incoming signal frequency plus or minus: a desired intermediate frequency, which intermediate frequency is then amplified and detected by a supen'regenerative detector-amplifier"circuit. r

;The use of 'an intermediate frequency f output from the Barkhausen-Kurz or Gill-Morrell type oscillator in this invention has beenfound to prac tically'eliminate the microphone tube noises-which are almost always present in the usualaudio out put of such detectors.

One feature of this finventionis the summary antenna tuning circuit for elirninating undesirable signals. g I Anotherfeature is the tuning means provided in the ultra high frequency'oscillator circuit for controlling the resonant period of the first detectoroircuit. v

A still furtherfeature resides in the'super-re generative circuit'which dispenses with a'se'parate low frequency quenchingoscillator:

Accordinglm'one'of the objects of the present o Other objects, featuresv and advantageslwill appear in the subsequent detailed description. It

*ArENr-j orie l will be noted, however, that some of the features 7 are useful in other fields thanthat of shortwave receptiong- I I The accompanying Referring to-the'drawing-there is shown a simple-"bi-polar antenna system i, I, connected through condensers 2, 2'to the grid 3 and plate 4 of an ultra high' frequency oscillator circuit 5.

Attached to the antenna wires in the manner shown in the drawing is a tunedantenna circuit 6 for eliminating undesirable frequencies. This circuit includes a tunable condenser '17. Th'efin-f dividual wires of circuit 6 areeach approximately v drawing illustrates a com plete ultrashort wav'e receiving systeinembodye mg the principles ofthis inventionff a quarter-wavelength long and, together, form l5. Thepinductance -of these wires taken. with the'capacity of condenser lform a parallel res onant circuit which is'tuned-to the frequency of the incoming signal waves; Asis-well known, such a parallel tuned circuit pre'sents' infinite impedance to the incoming signals and much less impedance to the undesired signal frequencies.v V

Condensers 2*,- Zfare blocking condensers which a U shaped circuit grounded at its center point V I 7 20 I act to prevent the batteries 9 and it the respective gridandplate-potentiometer circuits from grounding through the antenna tuned circuit 6; These condensers may also'be utilized to assist in controlling the degree of'coupli'n'g between the antenna and the high frequency oscillator detec-. I

tor circuitfi. H g v i The electron discharge tube circuitfi comprises an ultra high frequency oscillator of thew'ell known Barkhausen-Kurz or. GillaMorrell type which acts in the present invention'both as an oscillator and detector. ;The grid Zllandplate efof the; tube aresupplied with suitable potentials by batteries 9 and III in theirrespectivepotentiome eter'circuits. Tunable condenser l is utilized forchanging the resonant period of; the first de tector circuit for heterodyning the incoming signal to any desired intermediate frequency.

The output of the ultra highfrequencyjcircuit is shownjcoupled by means of blocking condenser o l2 to'a'n intermediate frequency amplifier detector circuit or the super-regenerative type. 'It is to be understood, =of course, that, if desired; a transformer coupling arrangement maybe employed instead of the, capacity coupling l2 shown in the drawing; also; that the outputcircuit may 7 suitably be connected togthe plate'ins'tead, of the a grid in a very obvious manner. Connected'across the output circuit of the oscillator on one side of condenser I2 is a coupling impedance l3 for tuning the output to any frequency band. This coupling impedance may be a resistance, capacity or inductanceand may take any known form de: pending upon how wide a frequency band is desired in the output circuit. For example, if impedance coupling I3 is a resistance, as shown in the drawing, the output currents of the oscilla-' tor will have a wide frequency range. On the other hand, if impedance I3 is a parallel reso: nant tuned circuit, a very narrow frequency band output will result for very'obvious reasons,

Condensers l4 and I5 are by-pass condensers: for the intermediate frequency currents to prevent their passage into potentiometer battery circuits -9 and I0.

One form of intermediate 'frequency amplifier.

which has been used in this inventionwith excellent results is the super-regenerative circuit. The use of such circuitas a second detector makes the complete ultra high frequency receiver well adapted toportable use since its employment 'eliminatesa multi-tube intermediate frequency amplifier and possesses such desirablequalities as high sensitivity and ease of adjustment. Although any type of intermediate amplifier circuit may be used with the ultra short wave receiver described herein, the super-regenerative type of circuit is preferred. It is to beclearly understood, however, that the super-regenerative circuitspdescribed herein are n t limitedin their use to the oscillatory system shown' since they have been used with excellent results on long waves. The super-regenerative,receiving circuit shown in the figure is describedin my copending application Serial No. 589,392, filedJanuary 28, 1932, and is an improvement over thesuper-regenerative circuits described in W. VanB Roberts Patents Nos. 1,948,315 and 1,982,694, granted Februe ary 20, 1934 and December '4, 1934, respectively,

to which reference is made for a more complete understanding of the generalv operation of this,

type of circuit. This circuitinvolves the use of onejtube coupled to the input circuit to give regeneration and another tube,coupled;to the input circuit to give degeneration, each tube {functioning alternately, according tothe quenching frequency impressed on the cathodes.

The intermediate frequency currentjis fed to coil l6 whichislcoupled to IT, I8, in turn con nected to a pair of triodes I9 and of the indirect heater type. Circuit l1, l8 is tuned t0 the incoming intermediate frequency. The triodes l9 and 20 have connected to;thei r plate circuits a feed back coil 2| which is coupled to the grids of the-tubes. Condensers 32 and 33 are radio frequency by-pass condensers. A keying or low quenching frequency oscillator 22'is shown coupled to the'cathodes 23 of the tubesfor varying, at a predetermined frequencyythepotential of the cathodes with respect to the grids.

quency quenching currents have no detrimental eifect on the high frequency circuit.

Although this manner of coupling has been shown in connection with a two tube circuit it is to be clearly understood that it is not limited thereto, but may be applied to any super-regenerative circuit. 7 7

Referring nowto the operation of the circuit in detail, let us assume, for the purpose of illustration only, thatit' is desired to receive electromagnetic waves of a length of approximately onea half meter, corresponding to 600 megacycles. In

actual practice, wave lengths of the order of one centimeter may be received. 7 The incoming ultra high frequency signals are received over bi-polar antenna I, I, and passed to the high frequency oscillator circuit 5 through condensers 2, 2, the undesired low frequency signals being by-passed to ground through antenna tuned circuit 6. Ultra high/frequency oscillatorcircuit 5 is adjusted to give the desired intermediate frequency by means of tuning condenser ll, filament rheostat 34 and ,the plate. and the, rid Pot ntiometers 9 and lflrespectively. The intermediate frequencyobtained by the reaction of oscillator circuit 5 with the incoming signals is then passed throu h the condenser l 2 to the super-regenerative second detector amplifier, the coupling impedance I3 being adjusted to give thedesired frequency band. The supereregenerative second detector amplifier circuit may be adjusted, if desired, to receive currents of a frequency of 3 megacycles. In orderto, receive currents of this frequency'on the super-regenerative second detector, the first oscillator detector circuit 5 should be adjusted to oscillate at603 or 597 megacycles.v The ultra high frequency circuits are arranged to be sufficiently broad in frequency response to efficiently pass. a band several megacycles either side of the desired signal frequency, which, in this case, is 3 megacycles. v The output circuit, including cone denser l2 and coupling impedance I3, is arranged to efficiently pass the three megacycle intermediate frequency, with itsmodulation, Ultra high frequency. oscillator circuitj operates both as a detector and heterodyne oscillator, i. e., the circuit oscillates at 600:3 megacycles and also detects at the same frequency. The combination of the incoming signal waves at 600 mega cycles and the waves generated by;high frequency oscillator 5, namely, 600:3 megacycles, results in an output intermediate frequency of-3 megacycles across condenser, 8. This intermediate frequency is received in the super-regenerg ative circuit and amplified anddetected. The

audio frequency signals are then heard in the headphones. V

The embodiment of the invention illustrated and described herein has been selected merely'for the purpose of clearly setting forth the prin- 'ciplesinvolved. It will be apparent, however, that the invention is susceptible of being modified to meet different conditions encountered in its use and it is therefore, aimed to cover by the appended claims all modifications within the spirit and scope of the invention.

1. In combination in an ultra shortwave receiyingh'system, a bipolar antenna tuned to the incoming signal wave, an ultra high frequency detector heterodyning oscillator for producing an intermediate frequency, said oscillator comprising an electron discharge device having an anode,

' cathode and control electrode, and-'havingmeans for maintaining the contrcl electrode at a high positive potential relative to the cathode and anode, a pair of Lecher wires connected to said anode and control electrode, a tuning condenser connected across said Lecher wires, said antenna being coupled to said Lecher wires through blocking' condensers, an output circuit coupled to one of said Lecher wires, and an impedance in said output circuit for tuning the band of frequencies 7 in said output circuit.

2; In combination in an ultra short wave receiving'system, a bipolar antenna tuned to the incoming signal wave, an ultra high'frequency detector heterodyning oscillator for producing an intermediate irequ-en'cmsaid oscillator comprising an electron discharge device having an anode, cathode and control electrode, and having means for maintaining the control electrode at a high' positive potential relative to the cathode'and anode, a pair of Lecher wires connected to said coupled" to that one' ofsaid Lecher wires which is connected to the 'controlelectrode, a resistance in said output circuit for tuning the band of v frequencies, and a radio frequency by-pass condenser'in circuit with said resistance.

3. In combination inan ultra shortwave reoeiving system, a bipolar antenna tuned .to the incoming signal wave, an ultra high frequency detector heterodyning oscillator for producing an intermediate frequency, said oscillator comprising an electron discharge device having an anode,

cathode and control electrode, and having means for maintaining the control electrode at a high positive potential relative to the cathode, and

anode, a pair of Lecher wires connected to said anode and control electrode, a tuning condenser connected across said Lecher wires, saidantenna being coupled to said Lecher wires through blockcoupled to one of said Lecher wires.

R. W. GEORGE.

ing condensers, an output circuit comprising a I I super-regenerative amplifier detector circuit 0

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