US2460781A - Circuit for stabilizing frequencies of transmitter-receiver systems - Google Patents

Description

Feb. 1, 1949. CANTELO 2,460,781

CIRCUIT FOR STABILIZINGFREQUENGIES OF TRANSMITTER-RECEIVER SYSTEMS Filed Feb. 27, 1945 Fig .1 kaAcm/vca FREQUENCV Mam/Mme 03c. MULT/PL/ER POWER AF 6: J 01 7 M1 I V A1 FZEQUE/VC) FQEOUENCV oer 5/ CHANGE Ml/LT/PA/ER JC- AFC 7- f WWW af' u mm 1.5 c N667? AMA & p/sa AMP AR E52 RECEIVER A J F551 A a I FREQUENCY CHANGER Fig 2 REACTAA/CE Fksoutwcr M00 LATOA? 0 c. MULT/PL/Ek POWER AMP AF CV 01 r 4 M1 A1 40w FREQ FREQUENCY CHANGER FREQ. awn/v 5? E FREQUENCY A F C MUL 7' IPA/ER FREQUENCY INVENTOR CHANGER HERBERT/Z (AA/r510 BY Wi 5 Patented Feb. 1, 1949 GIRCUIT FOR STABILIZ'ING FREQUENCIES F TRANSMITTER-RECEIVER: SYSTEMS Herbert. Reginald Cantelc, WrittIe, England, assignor to Radio Gorporationofi. America, a orporation of Delaware Application February 27, 19185., Serial N0; 5735. 2.24;

In Great Britain October 7, 1943 Section 1, Public Law 690., August 8; .".946 Patentexpires October-7; 1963" This inventionrelates to frequency controlling and stabilizing means in radio apparatus. and the like, particularly in transmitter-receiver apparatus; that isradio apparatus and the like which may be used either as a transmitter or as. a re.-, ceiver. The invention is particularly suitable for use in such radio apparatus of the kind used forpoint-to-point operation on a common wave, and provides a means whereby the frequency of 18. Glaims- (01. 250- 6).

2: from Al isapplied'. These are the essential elements required for transmission.

Again! in both figures, AR represents a receiving aerial, A2 a. radio frequency amplifier to which. received energy: is applied, F03 a frequency changer inwhich received energy and a beat fre quency from F62 are mixed to produce an intermediate: frequency, IFA an intermediate frequency amplifier to which output from F033 is the oscillations generated in the apparatus when pp DLa -discriminator to-which amacting as a transmitter may be stabilized, and D- fi d intermediate f q y" s pp e d whereby the apparatus when acting as a receiver fr W ch e d eq y Signal s demay be maintained in tune with a remote transrived. A3 an audio frequen y amplifier, the O itter; in spite of some drift in thefrequency of put M r wh s pp i t y suita l utithe oscillatory energy transmitted by said translization devic (not shown). These are the estte sential. elements required for reception.

Though not exclusively applicable to angular II- fi r 0 r p nts a stabilized (for velocity modulated systems, the invention is pri example, Crystal fi Osc a on enerama-rily intended for such systems. tor, M2 a frequency multiplier in which the freh inventionprovides aisimple means for t, quency of oscillations from O2 is multiplied, F02 taining the control and stabilization of frea frequency ha t wh frequency mu tiquency or tuning as: t case may be; 1; any plied oscillations from MI and M2 are applied frequency within a band covered, or on any spot to p d a a r qu n y which s ppli d t wave within such hand, without recourse having frequency cha r F0 get e With the reto be had to a variable intermediate frequency; ceived' radio frequency'energy, e-p educe the in- According t t invention t widest termediate frequency already referred to, FCl' a pact a radio apparatus, or the like, adapted f r frequency changer to which oscillations from Ol use alternatively as a transmitter or as a reg and (in Fig. 1) oscillations from M2 or (in Fig. 2) eel-Yer, includes an oscillation generator and a beat frequency from F04 are mixed to produce means for automatically stabilizing the trans- F50; beat frequenfiyz M3 repremitter oscillation generator and modulating the gents frequency n- 13 1n W1110h the efrequency of oscillations produced th b in} quency of the oscillat ons generated in 02 is .cordance with Signing to be transmitted when multiplied or a harmomcselected, 03 1s a stable the apparatus is operating as a transmitter" or variable oscillation generator oflow frequency, in accordancewith drift in the frequency of re- F frequency changer? in which oscillations sewed signals when the apparatus s operating EIOIn O3 and frequency multiplied oscillations as a receiver. iroin are mixed to produce a beat frcquencl The invention is. illustrated in the drawing for These are essentia1e1e' whereof Fig.v 1 illustrates the firstv arrangement ments forstablhzmg mtermeqlate frequency of the invention, but is not the preferred ar- F mm e mngement and Fig 2 illustrates a preferred a} bilgzl 'lg thle frequency of the oscillations, gen r, rangemcntj Angular velocity modulation is as,- a g f i gim f f h sumedin both the systems illustrated. the, fig fi g 3312: A 1 z In both figures, OI represents an oscillation frequency may be ap d o IFA l ea generator the oscillations from which are to be eonsidering, first, the arrangement of Fig. 1, modulated, or a reactance. modulator r n r l the operation is as follows: valve winch 1S sub ected to control by, for e During transmission the frequency changer ample, audio irequencymgnals-AE from aiselirce FC'I' is excited from the output of the oscillator (not shown) and which serves: to; modulate the of and also from the output of the frequency genelfatcd' 0| ,1 Ml a frequency multiplier M2. Switch s is'on contact? and the ip ier to Whl-Qhv OSFIllBztlDD-S are difference frequencyiol. Mz o2 is extracted, and a d} phfier to which frequency used toexcite the intermediate frequency ammultiplied: modulated oscillations. are applied, plifier IFA and limiter-discriminator DL The and AT a transmitting aerialtoxwhich theoutput control valve CV and discriminator circuits DL of oscillations from of increases, issuch .as to tend to reduce and thus restore therfrequency of j oscillations from I oscillations of CI is made equal to 2 M2.02, and the mid-intermediate frequency will therefore: beM2.02. For the purpose of reception during which the power amplifier AI is switched off at switch SI, a portion of the output of the frequency multiplier Ml together with the output of the frequency multiplier M2. is used to excite the frequency changer F02, fromwhich the sum frequency (MI.OI+M2.02)' is extracted. This frequency is then mixed with the incoming'frequency in the frequency changer FC3 and the difference frequency extracted. Switch S isnow on the. receiver-contact R and the signal at this 'quency of oscillations from ojnusimilatlyjthe g sense of the. bias generated when thefre'quency the variable oscillator 03 is mixed with the out- .put frequency of themultiplier M3 in the frequency changer FCA from which, as may be convenient, the sum or, the difference of the two The nominal frequenc of .frequenc'ies may be extracted. This extracted freque'nc'y M3.0 2i03 is the reference frequency used for the stabilization of 01. Since the intermediate frequency and the frequency to which the discriminator is tuned are constant it can be seenthat for any value of the frequency of Ol,

difference;,-frequency islthenused to excite IFA.

If the receiver and the'distant transmitter. are exactly in tune'the diif'erence frequency at F03 willbe (MI.Ol -l-,M2.0Z).MI.OI 0r M202. Since this is the mid-frequency of the intermediate frequency amplifierIFA and limiter no frequency correcting bias will be generated by DL. If, however; the frequency of the incoming signal decreases, the difference frequency extracted from F03 will increase and therefore produce from discriminator DL a bias which will tend to decrease the frequency of oscillation of Ol, and therefore also of the frequency multiplier, MI. The frequency extracted from the frequency changer F03 thus tends to remain constant, even if the incoming signalshould drift in frequency. In systems employinga narrow deviation band itisespecially importantin'order to avoid distortion arising-in the detection of the signallby the discriminator and-its rectifier that the mean frequency applied to the discriminator should remain substantially constant. The circuit means provided perm'it this end-to be achieved.

, The simple scheme described does not readily lend itself to the second object of the invention viz., the stabilization of the transmitter oscillator at any frequency within its hand, as it provides only for frequency stabilization at one spot frequency of the transmitter oscillator. 'It is moreover subject to the disadvantage that theoutput circuit of the frequency changer FCI is tuned to the rsame frequency as-the'output circuit of the frequency multiplier M2. The outputcircuit of the frequencychanger F0] will therefore contain two components of the same frequency, one derived from the frequency changing action and one arising from direct amplification of the frequency M202. Since the limiter discriminator 'DL will respond to the larger of the two signals it is necessary to make the component due to direct amplification of M202 small in relationto .that due to frequency changing action, and this "may bea matter of some dificulty to arrange.

Accordingly the slightly more complicated circuit arrangement shown in Fig.2 is preferred. This incorporatesall the elements of Fig. 1 and the necessary additional elements. The frequency of a the stable variable oscillator 03, which isof low frequency, maybe determined either by an L. C. circuit or by a CR circuit. The range of ably chosen, a suitable harmonic of the crystal oscillator may be combined with a suitable Value of the frequency of the oscillator 03 to give a frequency which difiers from the frequency of the oscillator .Ol; by'aconstant amount equal to the intermediate frequency; Thus, for example; let it'be assumed that the intermediate frequency is 4 mc./s. and that the oscillator Cl is to be tunable over the range of 15 to 24 mc./s. Let it also be assumed that the frequency ofOZ is 1 mc./s. .and that the harmonic selector M3 permits the selection of harmonics from the 10th to the 18th. Assuming that the sum of the frequencies (03 +M3 .02) is extracted from F04 it can readily bev seen that the ,frequency range to becovered by-03 is from 1 to 2 mgr/s. Thus with O! at 15 mc. s., M3.02will.be10 mc./s., (M3.02+O3) will be 11 mc./s.; and tl'i edifference O'l (M3.02+O3) will be 4 mc./s. With Ol at 24 mc./s., M392 will be 18 mc./s., and 03 will be 2 mc./s., so that OI(M3.O2+O3)=24 (18+2)=4 mc./s. For some odd value of the frequency of Cl, say, 18.75 mc./ s., M302 willbe 13 Inc/s, and 03 will be 1.75

mc./s., sothat V 7 ol (M3.02+Q3) '='18.75-'(13+1.75) =4 mc./s.

V Alternatively, if continuous variation of O! is not required, but merely a selection of spot waves, 03 may be a crystal oscillator having a harmonic selector covering any ,desired number of harmonics. over 'a'ran'ge of the frequencies equal to the frequency of O2; ItWill thus act as a' Vernier to O2. 11f a. few spot waves only are required 03 andFCfi maybe omitted and the output of M3 be fed directly to PC I;

' The frequency multiplier M2 .is of fixed frequency, and selects a harmonic 'of 02 equal to the intermediate -frequency. .The frequency changer FCZ'istuned to avfrerq'ue'ncy (Ml.Ol+M2.02)

asin the case-of Fig. 1. 1 The frequency OI is not in-this circuit embodiment restricted in its relation-toM2.02.

' Since the frequency of O3 is small in relation to the harmonic frequency M3-LO2',-with which it is combined;a-smalrpercentage drift in 03 will represent a much smaller percentage drift in the combined frequency (03 +M3.02)and will therefore have negligible effect on the stability of the y te If. f 1 l I 1 An advantage of the system in both the-simple and preferred ar'rangemerits 'is that "the output of the frequency multiplier M2 may, by suitable switching, be used for the purpose of alignment *of the:intermediatc'frequency stages, without the use of an external source'of frequency; I ."WhatiS claimed-is":

1. A radio or like apparatus adapted for use estates alternatively as a trans lming bs'ci-ll" mission, a frequency "changer for p od-uc'ing an intermediate frequency frolii received 'sig'n-ljfriequency and oscillations derived from said oscillat tion generator, means for producing a ire quen'cy controlling potential variable in sign and magnitude in accordance with departures om a desired frequency of thefioutpu't from said gen- "orator, means ror rcducin' a second frequency controlling pdten'tial variable in and magni tude in "accordance with departures frdmthe frequency "of received signal frequency requisite to "maintain a desired mean frequenc o'fjsaid inter- "mediate frequency, "a frequency 'controlling'derice for said oscillation generator operable under control of said first frequency con-trolling potential to stabilize the frequency of said generator or underjcon't'rol of said second frequency controll lng potential to vary the frequency ofsaid generator, thereby to stabilize said intermediate frequency. I

2. Apparatus "as claimed in claiml, including a stabilized oscillation generator and a second frequency changer and wherein said first frequency controlling potential "is derived from a first frequency controlling beat frequency produced by mixing oscillations derived from both said gener'ators in said second frequency changer coupled thereto and to said first oscillation generator-Ln,

3. Apparatus as claimed in claim 1, includinga stabilized oscillator generator, a second frequency changer coupled thereto and to said "first oscillation generator, a coupling between said second frequency changer and said frequency changer and wherein said second frequency controlling potential is derived from said intermediate frequency "and wherein said intermediate frequency is produced by mixing a second frequency controlling beat frequency with said received signal frequency in said first frequency changer, said second frequency controlling beat frequency being produced by mixing oscillations derived from both said generators insaid second frequency changer.

4. A radio or like a paratus adapted foruse a'lternatively as a transmitter or as a "receiver apparatusis operating as "a transmitter, a second oscillation enerator, means for deriving a first automatic frequency controlling beat frequency from oscillations generated by both said generators, means for deriving a 'iirst automatic frequency controlling potential from said first automatic frequency controlling beat frequency and means for applying said potential to said first generator so as to maintain the frequency of oscillations generated thereby substantially constant, and, for use when said apparatus is operating as a receiver, said second oscillation generator, means for deriving a second automatic fre quency controlling beat frequency from oscilla tions generated by both said generators, means for deriving an intermediate frequency from said second automatic frequency controlling beat frequency and said received oscillatory energy, means for deriving a second automatic frequency controlling potential from said intermediate frequency, and means for applying said potential to saidffirst eeneiatorseas to vary the re-queasy of the oscillations generated thereby, by varying the frequency *of said second automatic frequency controlling beat frequency, ll'dmaliritji-n said intermediate frequency substantially con stant spite of drifts in the frequency of-said received os'cillat-oryenergy V L 5. ,A radiogor like 'apparatusadapted for use alteinativelyas a transmitter or s a recerver and having a first oscillation generator; means for modulating oscillations from "stiid generator in accordance with signals to be transmitted, means for transmitting modulated oscillations, and means for receiving oscillatory energy from a remote station includin for use when -said rap paratus' operating as a transmitter, a first stabilized. oscilia'tion generator, a second stabili'zed, variable, oscillation generator, :inefa'ns for deriving a stable beat frequency from oscillations enerated by both said stabilized oscillation generators, means for deriving a first automatie frequency controlling beat frequency from said stablebeat frequency and oscillations from said first generator, means for deriving a first automatic frequency controlling potential from said first automatic frequency controlling beat frequency, and means for applying said potential said first generator so as to maintain the firequency of oscillations generated thereby substantiallyaconstan-t, and, for use when said apparatus is operating as a receiver, said-firststabilized-oscilla-tion generator, means for deriving a second automatic frequency controlling beat frequency from oscillations generated by said first andfirst stabilized oscillation generatorsnieans for "deriving an intermediate frequency from said second automatic "frequency controlling beat frequency and said received oscillatory energy, means for deriving a second automatic frequency controlling the first beat frequency is derived from the mixii-1g of oscillations from the first generator without frequency multiplication with oscillations from said second generator.

7. Apparatus as claimed in claim 5, whercin the modulated"oscillations are subjected to frequency'inultiplicati'on before transmission "and the first automatic frequency controlling beat frequency is derived from the mixing of oscillations from thefirst generator without frequency multiplication with the stabilized beat frequency.

8. Apparatus as recited in claim 1 including a stabilized oscillation generator, 2. frequency increaser coupled therewith wherein oscillations produced by said stabilized oscillation generator are subject to frequency multiplication and harmonic selection, said first means comprising a frequency changer coupled to said first oscillation generator and said frequency increaser wherein oscillations from said first mentioned oscillation generator are mixed with oscillations from said frequency increaser for the production of energy of beat frequency from which said first frequency controlling potential is derived.

,9. ,Apparatus as recited inclaim 1 including a stabilizedoscillation generator, a first frequency oscillations are subject to frequency multiplication before transmission, a second frequency mulsaid second means for producing said second frequency controlling potential.

10'' Apparatus as recited in claim 1 including :a stabilized oscillation generator and a stabilized variable frequency oscillation generator, a frequency changer coupled with said last two generators for producing energy, of abeatfre'quency and of constant frequency, and wherein said first means includes a frequency changer coupled with said last named frequency changer and with said first oscillation generator for producing energy of :a second frequency controlling beat frequency from which said'first frequency controlling potential is derived. 7 V

'11. Apparatus as recited in claim 1 including a stabilized oscillation generator, a second fre- -quency changer coupled to said stabilized oscillation generator and to said first oscillation generator for deriving energy of frequency controlling beat frequency; and wherein said second means includes a coupling between said second frequency changer and said first frequency changer which is excited by received signals for producing energy of a second frequency controlling'beat frequency from which is derived said second frequency controlling potential.

'12 Apparatus as recited in claim 1 including a stabilized oscillation generator, a 'second' frequency changer coupled therewith and with said first named oscillation generator, a, frequency 'multiplier in each of said last two named cou- 'plings, and wherein said second named means includes a coupling between said second frequency changer and said first named frequency changer which is excited by;received signals for producing energy of a frequency controlling beat frequency from which said second mentioned fre-.

quency controlling potential is derived.

13. Apparatus as recited in'claim 1 including a source of signals and a coupling between. said source of signals and said frequency controlling device for modulating the oscillations generated bysaid first generator in accordance with signals.

- 14. ApDf ratus as recited in claim 1 wherein said 15. Apparatus as recited in claim 4 including a V f requencymultiplier coupled to said first oscilla- ,ticn generator in which multiplier the modulated automatic 11 19? cflupled to said second oscillator, said third means including a frequency changer coupled to said modulat'edoscillator and to said second frequency multiplier so that said first automatic frequency controlling beat frequency is derived by mixingoscillations from said second generator multiplied in frequency with oscillations from said first oscillation generator.

16. Apparatus as recited inclaim 4 including a frequency multiplier couple'd to said modulated oscillation generator, a frequency multiplier coupled to said second oscillation generator and wherein said means for deriving said second automatic frequency controlling beat frequency includes a frequencychanger coupled to both of said frequency multipliers. V

17. Apparatus as recited in-claim 5 including a frequency multiplier coupled to said modulated oscillation generator to subject the modulated oscillations to frequency multiplication before transmission, a second frequency multiplier coupled to said first stabilized oscillation generator, and wherein said fourth means includes a frequency changer coupled to said last mentioned frequency multiplier and to said second stabilized oscillation generator for deriving said first stabilized beat frequency.

18., Apparatus as recited in claim 5 wherein said means forderiving said second automatic frequency controlling 'beat'frequency includes a frequency changer and frequency multipliers coupling said first stabilized oscillation generator and said first oscillation generator to said frequency changer wherein isderived said second frequency controlling beat frequency. HERBERT REGINALD CANTELOH REFERENCES CITED Thefollowing references are of record in the file of this patent:

v UNITED STATES PATENTS Number f Name Date 2,228,815 Deerhake Jan. 14, 1941 2,276,008 1 Armstrong Mar. 10, 1942 2 ,317,547 McRae Apr. 27, 1943 1 2,333,719, Heroldv Nov. 9, 1943 2,363,835; Crosby Nov. 28, 1944 2,379,395 Ziegler et al. June 26, 1945 2,380,288 Bligh July 10, 1945 2,407,212 Tunick Sept. 3, 1946 2,408,791 Magnuski Oct. 8, 1946 2,408,826 Vogel Oct. 8, 1946 i FOREIGN'PATENTS- Number Country Date 551,472 I Great Britain Feb. 24, 1943

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