E H.ARMSTRONG.
`
`METHOD or RECEIVING HIGH FREQUENCY OSCILLATIONS.
`APPLICATION FILED FEB. 8. 1919.
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`1,342,885.,
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`Patented June 8, 1920.
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`677974,
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`ATTORNEYS
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`UNITED sures PATENT OFFICE.
`
`EDWIN 11. Aairsraoxe, or unis, rnaxca.
`
`IETHOD OF RECEIVING HIGH-FREQUENCY OSCILLATIOKS.
`
`1,342,885.
`
`Specification of Letters Patent.
`
`Patented June 8, 1920,
`
`4
`
`Application filed February 8, 19}9. Serial No. 275,744.
`
`amplification; first, there isa tendency of
`the amplifier system to oscillate as the fre-
`quency is increased, and secondly, it is im-
`possible 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 me-
`ters are unused at the present time because
`of the difiiculties of amplifying and detect-
`ing them. High frequency amplifiers have
`been constructedto operate on wave lengths
`as low as 200 meters, but with only fair
`efliciency.
`The present invention discloses a method
`of indirect amplification and reception which
`operates independent of the frequency of
`the incoming oscillations and which, there-
`fore, 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 di-
`rected beams of energy becomes a practical
`pgoposition. 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 com-
`pared 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 which is adjusted
`to operate well atithis predetermined fre-
`uenc .
`: After passing through the ampli-
`er, t ese oscillations are detected and indi-
`catcd in the usual manner. The intermediate
`uency is always above good, audibility
`yond this requirement there is no other
`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 au-
`dible range ,may_ be carried out in several
`stages and each stage may be am lified by
`means of a‘ multi-tube am lifier.
`e great
`advantage of this math
`is that the effect
`
`70
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`1|
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`1“
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`To all whom it may concern: ~
`Be it known that I, Enwm H. Anusmoxc,
`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 ayspecification.
`-
`This invention re ates to‘a method of re-
`ceiving transmittedhigh frequency oscilla-
`tions as in radio telegraphy or radio teleph-
`ony and it is particularly effective when
`damped or undamped waves of ’
`receiving
`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
`thisinvention 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 de-
`creased, an that when the strength of :the
`high frequency oscillations falls below a cer-
`tainpoint the response of a detector becomes
`so feeble that it is impossible. to receive sig-
`nals. The application of low frequency am-
`‘lifiers assist somewhat up to a certain point,
`but the_inherent noise in all low frequency
`amplifiers limits the extent to which low fre-
`quency amplification can be carried.
`It is
`alsowell known that theysensitiveness of a
`rectifier for weak signals may be restored by
`the use of the heterodyne principle, butwthis
`is only a partial solution of‘ the problem in-
`_ asmuch as this method can be used only in
`certaincases.
`.
`A solution for the loss of sensitiveness of
`the detector for weak sifgnals lies in the
`amplification of the radio
`e iiencycurrents
`before applying them to the etector. ‘This
`been recognized for, some time and va-
`rious forms of multi-tube vacuum tube am-
`plifiers have been developed and success-
`fully employed in practice on certain ranges
`of wave lengths’. Because of the inherent
`capacity which_ exists between the elements.
`of vacuum tubes, this method of amplifica-
`tion becomes increasingly diflicult, as the fre-
`quency of the oscillations to be received in-
`crease. There_ are two principal points of
`difliculty enccunteied in the above.inet__hod of-
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`1,342,385
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`of the output side of the amplifier upon the
`input side is eliminated as the frequencies
`are entirely cliffereiit. As a consequence
`of this the limitation on amplification
`which has always been imposed b the tend-
`ency of the amplifier "to 'oscil ate is re-.
`moved, and exceedingly great amplifications
`- become possible.
`In the accompanying circuit diagrams;
`Figure 1 illustrates a simple diagrammatic
`adaption of "the invention, Figs. 2 and 3
`illustrate indetail 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 proc-
`es of conversion-and amplification is car-
`ried out in two stagesivlierebv ceitain ad-
`vantages hereinafter explained are obtain-
`‘ able.
`‘2o'
`Referring. now to Fig. 1; the source of
`the incoming oscillations_is represented by
`a coil 1. An inductancc__2 and -a capacity
`3 form a circuit preferably tuned to the
`incoming frequency. -A rectifier 4 in the
`circuit 3_——5 is a means for converting the
`combined currents of the incoming energy
`and the locally generated oscillations from
`the source 6. A coupling 5-7 serves to
`apply the converted oscillations to the high
`frequency amplifier 8 which is ad‘usted
`fre-'
`to amplify well at a predetermine
`quency; a detector 9 and telephones 10 serve
`to detect and indicate the resulting ener
`.
`- A’ separate heterodyne 11 is shown coup ed
`to the circuit 9-10 and is used when re-
`ceiving undamped waves. By means of.thisnew
`* systemof circuits and apparatus in
`method. may be utilized as follows :— he in-
`coming oscillations are combined in the cir-
`cuit 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 fre-
`uency, to which the amplifier is adjusted.
`he combined high frequency currents in
`2—i3'{£ie converted by means of a rectifierfl
`to a current of predetermined fre-
`4
`quency. 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 meansof the rectifier 9 and in-
`dicated by the telephones 10.
`If the incom-
`ingoscillat-ions are undamped it is neces-
`device‘ such ,
`sary to associate some auxiliary
`,
`as _the heterodyne 11 with the second detect-
`ing circuit 9—10.in the manner shown. The
`rectifiers 4 and 9 _are indicated. conven-
`tionally but they may be vacuum tubes or
`crystals or any other similar suitable device.
`The choice of the rectifier depends’ on sev-
`eral considerations which are well known
`at the- present time." The high frequency‘
`amplifier 8 may be any one‘ of the several
`types which are
`well known and it may
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`be either resistance or inductance coupled.
`Where selectivity is
`required inductance
`coupling should be used and the circuits
`means of condensers.
`-
`tuned by
`In Big. 2 a source 12 of incoming oscil- 70
`.
`lations is associated with the circuit 13——14
`preferably tuned to the incoming- oscilla--'
`tions; in vacuum tube oscillator-rectifier 16
`in conjunction with the circuit 15-13-—
`14--16-17 forms , Va
`self-heterodyne. A
`multi-tube high frequencyfésistance coigiled
`arréplifier 18 ampliffies enehrgy (obtaine by
`in uctive eouplin
`rom t e in uctance 1 .
`A detector 19 an telephones 20 detect and
`indicate the oscillations amplified by" the
`am lifier 18.
`‘
`’
`I4 ig. 3 illustrates in detail the utilization
`of my method using a. tuned amplifier sys-
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`75 "
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`tem wherein 21 is the source of inwm ’
`'
`cillations, and a vacuum tube recti
`system 22-23+-25. converts the combin
`olscillations of ltihe iggoming andrtiliose from
`tie separate
`ete
`yne 24.
`e-_circuit
`26-27 is tuned to the converted combination
`of _the two oscillations. A multi-tube hi h
`1:-
`' frequency amplifier 28 am lifies the
`ing energy heterodyned an detected by -the
`in 29'and indicated by the A
`vacuum tube syste
`tele hones 30.
`'
`.
`itg. £4 illusttiéatesdthe gegqral .a
`men‘ 0
`circui
`an
`appa
`us in w 1c
`the
`rinciple ‘of frequency conversion and
`amp ification is emp oyed twice. The coil
`'31 represents the source of: the incoming‘
`oscillations.
`3
`is a circuit tuned to
`the incoming oscillations.; a separate hete-_ A
`rodyne 34 is .associated with the circuit
`32—33. A detector 35 _rectifies the com-
`bined currents which are applied to the
`high frequency amplifier 38 and the ampli-
`fied currents again combined with local os-
`cillations from the source 40 and" then ap-
`plied to another high frequency amplifier
`A 43 by means of the coupling 41-42. The
`resultant energy is then detected and in-
`' dicated by the detector 44~and the telephones
`45. The operation of this system will be
`.-understood from the following brief anal-
`oscillations
`ysis:——Suppose
`the incoming
`have -a frequency’ of 10,000,000 cycles per
`second. The amplifiers 38 and 43 will be
`adjusted to frequencies which may be ap-
`proximately 1,000,000 and 100,000 cycles
`r
`second respectively. By adjusting the
`-
`quencyof-the local source 34 to 11,000,000
`and- passing the combined _high "frequency
`current -through the rectifier 35
`a fre-
`_ is fre-
`'. quency of 1,000,000 is
`reduced.
`quency is then ainpli ed by the amplifier
`38 and combined with a second. locally ro-
`to
`‘ duced current from 40 which is adj
`~» 1,100,000 cycles. This combined‘ current is
`converted‘ by means ‘of the rectifier 39 into
`' a frequency of 100,000
`a" current haviqg
`,
`cycles per secon , and this newvcurrent is
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`as
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`1,842,885
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`8 .
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`oscillations, amplifying the said third high
`'
`and in-
`frequency oscillations and detecting
`dicating the resulting amplified oscillations.
`_ 4. The method of amplifying and. receiv- -
`70
`mg undamped wave high frequency electri-
`ca oscillatory energy which comprises com-
`bining the incoming energy with locally gen-
`erated high frequency continuous electrical
`oscillations of a f
`uency differing from
`said incoming energy y a third readily-am-
`plifiable high frequency, amplifying the said
`combining»
`third high frequency oscillations,
`said third high frequency electrical ‘oscilla-
`tions with locally generated high f
`uency
`oscillations at a frequency near to sai
`third
`high frequency, converting the said last com-
`bined energy to produce low frequency os-
`cillations and indicating the resulting low
`frequency oscillations.
`5. The method of indirectly amplifying
`high frequency electrical oscil atory energy
`which comprises combining said energy with
`high frequency continuous electrical oscilla- _
`from said '
`tions of a frequency differing
`90
`energy by a third readily-amplifiable high
`frequency, converting the combined, energy
`by suitable means to produce said readily-
`amplifiable high frequencyoscillations and
`amplifying said resulting readily-amplifi- .
`95
`able high fre uency oscillations.
`(3. The met 0d of amplifying and receiv-
`ing 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
`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 fre-
`quency, amplifying the said third "high fre-
`quency oscillations and detecting and indi-
`cating the resulting amplified oscillations.
`7. The method of receiving and amplify-
`ing high frequency oscillations whereby the
`incoming energv is utilized to produce oscil-
`lations 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 re-
`determined, high frequency, which are t en
`amplified, detected and indicated.
`_8. The method of receiving and amplify-
`ing high frequency currents whereby the in-
`coming oscillations are combined with a sec-
`ond locally generated high. frequency oscil-
`lations, and the combination converted by
`suitable means to produce oscillations of a
`third high frequency, which are then ampli-
`fied and the resulting ener
`combined with
`a fourth locall generategy
`high frequency .
`oscillations an the combination wnve
`produce oscillations of
`by suitable means to
`afifth high frequency, which are then am-
`plified, detected and indicated.
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`amplified by the amplifier 43. The output
`of this amplifier is then detected and in-
`dicated by means of the rectifier 44 and
`telephone 45. There is no reason for lim-
`itin the process to two steps.
`If it is de-
`sire
`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 theifrcquency is lowered in small steps
`As already pointed out the great
`' each time.
`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 here-
`tofore 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 hetero-
`dyne reception is employed. The reason
`for this is rather involved and in any case
`unnecessary as it is an easily demonstrated
`ex
`rimental fact.
`]
`claim:
`1. The method of amplifying and receiv-
`ing high frequency electrical oscillatory
`energy which comprises, combinin
`the
`incoming energy with locally generated high
`frequency continuous oscillations of a fre-
`quency differing from said incoming energy
`by a third readily-amplifiable high fre-
`quency, converting the combined energy by
`suitable means to produce said readily-am-
`plifiable high frequency oscillations, ampli-
`fying the said third high frequency oscilla-
`tions, and detecting and indicating the re-
`sulting amplified oscillations.
`2. The method of amplifying and receiv-
`ing high frequency electrical oscillatory en-
`ergy which comprises, combining the incom-
`ing energy with locally generated high fre-
`quency continuous electrical oscillations of
`a frequency differing from said incoming
`energy by a third readily-ainplifiable high
`frequency, rectifyin the combined energy
`to produce said readi y-amplifiable high fre-
`quency oscillations, amplifying the said
`third high frequency oscillations, and de-
`tecting and indicating“ the resulting ampli-
`fied oscillations.
`’
`3. The‘ method of amplifying and receiv-
`ing high frequency damped .wave oscillatory
`electrical energy which comprises, combin-
`ing the incoming energy with locall gener-
`ated high frequency continuous e ectrical
`oscillations of a frequency differing from
`said incoming energy by a third readily-
`amplifiable high frequency, converting t e
`combined ens.‘-.1i;gy by suitable means to pro-
`duce said rea '_ y-amplifiable high frequency
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`E .
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`1,342,885
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`- 9. The method of ‘receiving and multi-
`4. stage amplifying high frequenc oscillations
`-- whereby the incoming ener
`y‘is utilized‘to
`produce oscillations of a V ifierent
`locally
`5 predetermined high frequency, which are
`_
`"amplified and the. resultant ‘energy
`utilized to roduce successive» oscillations of
`high frequency, which are locally
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`predetermined and amplified before being.
`combined with successively difierent locally
`generated oscillations and converted to‘
`ro-
`uce the successive oscillations and w "ch
`after the last stage of amplification are then
`— detected and indicated.
`.
`
`10
`
`EDWIN H. ARMSTRONG.
`
`5