US 1342885 A
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PatentedJune 8, 1920.
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UNITED STATES PATENT OFFICE.
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IETHOD OF RECEIVING HIGH-FREQUENCY OSCILLATIOHS.
Specification of Letters Patent.
Application filed February 8, law. Serial No. 275,744.
To all whom it may concern:
Be it known that I, Enwm H. AnMs'rnoNo, a citizen of the United States, now residing in Paris, France, have invented certain new and useful Improvements in Methods of- Receiving Hi h-Frequency Oscillations, of which the fol owin 1s a specification.
This invention re ates to'a method of receiving transmitted'high frequency oscillations as in radio tele aphy or radio telephony and it is particularly effective when receiving damped or undamped waves of short wave len h. Another result achieved by the use of t is invention is that because of its selectivity the interference caused by undesirable signals, strays, and atmospherics is reatly reduced.
e particular difiiculties overcome by this'invention will be understood from the following explanation: It is well known that all detectors rapidl lose their sensitiveness as the stren h of t e received signals is decreased, an that when the strength of :the high frequency oscillations falls below a certam point the response of a detector becomes so feeble that it is impossible. to receive signals. The application of low frequency amplifiers assist somewhat up to a certain point,
ut theinherent noise in all low frequency amplifiers limits the extent to which low frequency amplification can be carried. It is alsowell known that the sensitiveness of a rectifier for weak signals ma be restored by the use of the heterod e prlnciple, but xthis is only a partial solution of the problem inasmuch as this method can be used only in certain cases.
A solution for the loss of sensitiveness of capacity which exists between the elements.
difliculty encpuntered in the abovemethod ofamplification; first, there is'a tendency of the amplifier system to oscillate as the frequency is increased, and secondly, it is impossible to make the amplifier operate well at more than one frequency without a variety of adjustments. The limit of the practical amplifier at present is about 100 meters and the range of wave lengths from 0-100 meters are unused at the present time because of the difiiculties of amplifying and detecting them. High frequency amplifiers have been constructed-to operate on wave lengths as low as 200 meters, but with only fair efiiciency.
The present invention discloses a method of indirect amplification and reception which operates independent of the frequency of the incoming oscillations and which, therefore, opens up the great ran e of wave lengths below 100 meters and maies possible, in fact, the use of waves of a few meters in length whereby radio communication by directed beams of energy becomes a practical apposition. The present invention may also used to great advantage on wave lengths from 300 to 1,000 meters with a considerable gain in selectivity and sensitiveness, as compared ,to any of the known methods.
This new method of reception consists in converting the frequency of the" incomin oscillations down to some predetermined and lower value of readily amplifiable high frequency current and passing the converted current into an amplifier whlch is adjusted to operate well at'this predetermined freuenc I After passing through the amplier, t ese oscillations are detected and indicatcd in the usilial manrgr. The (ilnterngdliate uency is aways a ve goo .an i iit i t beyond this requirement there is no oth r limitation as to what it shall be. The method of conversion preferred is the beat method known as the heterodyne principle, except that in the present system the beat frequency is always adjusted to a point above good audibility.
The process of convertin the incoming high frequency oscillations ownto the audible range ,may be carried out in several stages and each stage may be amplified by means of a multi-tube am lifier. e great advantage of this meth is that the effect Patented June 8, 1920.
of the output side of the amplifier upon the input side is eliminated as the frequencies are entirely different. As a consequence of this the limitation on amplification which has always been imposed by the tendcncy of the amplifier to 'oscil te is re-. moved, and exceedingly great amplifications become possible.
In the accompanying circuit diagrams; Figure 1 illustrates a simple diagrammatic adaption of 'theinvention, Figs. 2 and 3 illustrate in detail an arrangement of cir-' cuits and vacuum tubes whereby this new method of receiving may be accomplished. Fig. 4 illustrates a system in which the proces of conversion-and amplification is carried out in two stageswherebv certain advantages hereinafter explained are obtainable.
' systemof circuits and apparatus m A' separate heterodync 11 is shown coup ed to the circuit 9-10 and is used when receiving undamped waves. By means ofthis new method may be utilized as follows he incoming oscillations are combined in the circuit 2-3 with the oscillations generated locally by the source 6. The frequency-of the source 6 is adjusted to give a beat fre-- quency which is the predetermined freuency, to which the amplifier is adjusted.
he combined high frequency currents in 4 to a current of predetermined frequency. This converted current is applied to the amplifier 8 and amplified thereby. If the incoming oscillations are damped or modulated as in telephony, they are received directly by means'of the rectifier 9 and indicated by the telephones 10. If the inc-oming'oscillat-ions are undamped it is necessary to associate some auxiliary device such as the heterodyne 11 with the second detecting circuit 9-10.in the manner shown. The
rectifiers 4 and 9 are indicatedconventionally but they may be vacuum tubes or crystals or any other similar suitable device.
The choice of the rectifier depends on several considerations which are well known at thepresent time. The high frequency amplifier 8 may be any one of the several types which are well known and it may frequency amplifier 28 am lifies the amplifier 8 which is ad'usted we converted by means of a rectifier,
' quency of 1,000,000 is reduced.
cycles per secon be either resistance or inductance coupled. Where selectivity is required inductance coupling should be used and the circuits 'tuned by means of condensers.
I n Flg. 2 a source 12 of incoming oscillations is associated with the circuit 13--14 preferably tuned to the incoming oscilla--' tions; a vacuum tube oscillator-rectifier 16 in conjunction with the circuit 15-13- 14.-1617 forms a self-.heterodyne. A multi-tube high frequencyi'sistance cou led' amplifier 18 amplifies energy obtained by inductive couplin from the inductance 17. A detector 19 an telephones 20 detect and indicate the oscillations amplified by' the am lifier 18.-
P ig. 3 illustrates in detail the utilization of my method using a. tuned amplifier syscillations, and a vacuum tube recti system 2 223+-25 converts the combm oscillations of the incoming and those from the separate heterodyne 24. Thecircuit 26-27 is tuned to the converted combination of the two oscillations. A multi-tube hi h t.
ing energy heterodyned an detected by the tem wherein 21 is the source of incomuglotg vacuum tube system 29and indicated by the -tele hones 30.
1g. 4 illustrates the general a ment of circuits and apparatus in which the rinciple 'of f uency conversion and amp ification is emp oyed twice. The coil '31 represents the source ofthe incoming oscillations. 3 is a circuit tuned to tbs1 incoming oscillations; a separate hetero 32-33. A detector 35 rectifies the coinbined currents which are applied to the high frequency amplifier 38 and the amplified currents again combined with local oscillations from the source 40 and then applied to another high frequency amplifier 43 by means of the coupling 41- -42. The resultant energy is then detected and indicated by the detector 44-and the telephones 45. The operation of this system will be :understood from the following brief analysis:-Suppos e the incoming oscillations have a frequency of 10,000,000 cycles per second. The amplifiers 38 and 43 will be adjusted to frequencies which may be approximately 1,000,000 and 100,000 cycles r second respectively. By adjusting the quency of-the local source 34 to 11,000,000 and passing the combined high frequency current through the rectifier 35 a This frequency is then ampli ed by the amplifier 38 and combined with a second. locally roduced current from 40 which is adj to 1,100,000 cycles. This combine current is' converted by means of the rectifier 39 into a' current having a frequency of 100,000
and this new current is e 34 is .associated with the circuit each time.
amplified by the amplifier 43. The output of this amplifier is then detected and indicated by means of the rectifier 44 and telephone 45. There is no reason for limitin the process to two steps. If it is desire the 100,000 current out ut of 43 can be converted into 20,000 cyc es and again amplified before passing into the detector 44 and indicator 45. The number of stages of frequency conversion and amplification which may be-employed is almost unlimited if thefrcquency is lowered in small steps As already pointed out the great advantage of this amplification in stages is that it eliminates the reaction between the output and input sides of the amplifier and removes thereby the feature which has heretofore always placed a limit on the ampli fication which may be obtained.
It should be particularly noted that the reception of spark signals and telephonic speech is accomplished without the hissing or distorted tone which invariably results when the ordinary form of beat or heterodyne reception is employed. The reason for this is rather involved and in any case unnecessary as it is an easily demonstrated ex rimental fact.
1. The method of amplifying and receiving high frequency electrical oscillatory energy which comprises, combinin t e incoming energy with locally generated high frequency continuous oscillations of a frequency differing from said incoming energy by a third readily-amplifiable high frequency, converting the combined energy by suitable means to produce said readily-amplifiable high frequency oscillations, amplifying the said third high frequency oscillatlon's, and detecting and indicating the resulting amplified oscillations.
2. The method of amplifying and receiving high frequency electrical oscillatory energy which comprises, combining the incoming energy with locally generated high frequency continuous electrical oscillations of a frequency differing from said incoming energy by a third readily-amplifiable high frequency, rectifying the combined energy to produce said readl -amplifiable high frequency oscillations, amplifying the said third high frequency oscillations, and detecting and indicating the resulting amplified oscillations.
3. The method of amplifying and receiving high frequency damped .wave oscillatory electrical energy which comprises, combining the incoming energy with locall generated high frequency continuous e ectrical oscillations of a frequency differing from said incomin energy by a third readilgamplifiable high frequency, converting t e combined emggy by suitable means to produce said rea y-amplifiable high frequency oscillations, amplifying the said third high frequency oscillations and detecting and indicating the resulting amplified oscillations.
4. The method of amplifying and. receiving undamped wave high frequency electrica oscillatory energy which comprises combining the incoming energy with locally generated high frequency continuous electrical oscillations of a f uency differing from said incoming energy y a third readily-amplifiable high frequency, amplifying the said third high frequency oscillations, combining 4 said third high frequency electrical oscillations with locally generated high f uency oscillations at a frequency near to sai third high frequency, converting the said last combined energy to produce low frequency oscillations and indicating the resulting low frequency oscillations.
5. The method of indirectl amplifying high frequency electrical oscillatory energy which comprises combining said energy with high frequency continuous electrical oscillations of a freq energy by a third readily-amplifiable high frequency, converting the combined energy by suitable means to produce said readilyamplifiable high frequency'oscillations and uency differing from said amplifying said resulting readily-amplifiable hi h fre uency oscillations.
(i. The met 0d of amplifying and receiving electrical oscillatory energy of short wave length which comprises combinin the incoming energy with locally generated igh frequency continuous electrical oscillations of a frequency differing from said incoming v energy by a third high frequency within the range of 20,000 to 250,000 cycles per second, rectifying the combined energy to produce said oscillations of said third high frequency, amplifying the said third high frequency oscillations and detecting and indicating the resulting amplified oscillations.
7. The method of receiving and amplifying high frequency oscillations whereby the incoming energy is utilized to produce oscillations of a difierent locally predetermined high frequency which are then amplified and the resultant energy utilized to reduce oscillations of a second different, loca ly redetermined, high frequency, which are t en amplified, detected and indicated.
8. The method of receiving and amplifying high frequency currents whereby the in coming oscillations are combined with a second locally generated high. frequency oscillations, and the combination converted by suitable means to produce oscillations of a third high frequency, which are then amplified and the resulting ener combined with a fourth localliy generate oscillations an the combination wnverted high frequency by suitable means to produce oscillations of I 9. The method of receiving and multipredetermined and amplified before a stage amplifying high frequency oscillations combined with successively difierent locally 10 whereby the incoming ener 1s utilizedto generated oscillations and converted to" r0- roduee oscillations of a v ifierent locally uce the successive oscillations and w 'ch 5 predetermined high frequency, which are after the last stage of amplification are then p amplified and the resultant energy" detected and indlcated.
utilized to rodueesuccessive oscillations of high frequency, which are locally EDWIN H. ARMSTRONG.