US 1901642 A
Description (OCR text may contain errors)
March 14, 1933.
c. w. HANSELL 1,901,642
SIGNALING Filed Dec. 23, 1929 2 Sheets-Sheet 1 E AW l g & g WW!- INVENTOR CLkRENCE W. ANSELL ATTORNEY March 14, 1933. c. w. HANSELL 1,901,642
SIGNALING Filed Dec. 23, 1929 2. Sheets-Sheet 2 INVENTOR CLhRENCE 1!. HA SELL BY 7 ATTORNEY ii atented 14, 1933 near IPOBA'IION OF AMERICA, A CORPORATION OF DELAWARE SIGNALING Application filed December 23, 1929. Serial No. 416,053.
In my copending United States patent application Serial Number 230,438, filed November 2, 1927, I have disclosed a signaling system wherein signaling may be carried on 7 by phase shift of a carrier wave, signal transmission at one phase corresponding to, say, dots, and signals corresponding to another phase representing dashes. Absence of signal would, of course, indicate spacing. In this manner, signaling speed can be materially increased.
However, with such a system wherein a carrier wave is phase shift-ed according to signals to be transmitted, certain defects are present especially when it is attempted to signal at extremely short wave lengths. Not only is it more diliicult to maintain apparatus in synchronism, which apparatus is preferable for the operation of the system described in my copending application at higher frequencies; but in addition, certain phenomena often occur during the transmission of short waves which makes it unfeasible to signal by phase shift or by phase reversal. T hat is, it has been found that the length of path followed by the wave often fluctuates rapidly and this, of course, causes phase shifts in the received energy and precludes the possibilityof accuraate signaling by this method in many instances. 7
To overcome the foregoing difficulties and to make signaling by phase reversal possible at very short wave lengths is the main object of the present invention. In order to accomplish this object, modulating energy rather than carrier energy is phase shifted according to signals to be transmitted and then a carrier is modulated with the modulating energy. .The combined wave is subsequently transmitted to a receiver.
Where diiiiculties in obtaining synchronism are due to apparatus difliculties only, I modulate the amplitude of the carrier energy. In short wave transmission, however,
unequal fluctuations in carrier and side bands and selective fading make the use of amplitude modulation quite diflicult and often 1m possible. Under these circumstances fre- 0 quenoy modulation of the carrier energy is preferred. Thus, when frequency modulation is used, although the carrier may fi uctur ate in phase, the modulating energy, being of relatively lower frequency, islittle affected by the elements which cause phase reversal I of high frequency energy in the ether, and 7 hence the phase shifted modulating component of the transmitted Wave arrives at the receiver substantially as transmitted.
Preferably as is the case with the system described in my copending application,
translation is accomplished by the useof a locally generated wave of. energy ofa fre quency equal to the frequency of the phase displaced transmitted energy. .In my 00-" pending application crystals are resorted to nous energy; but, if it were attempted to'gencrate relatively low frequency energy," such as utilized inthe present scheme, with crystals, they would of necessity be of extremely largesize, difficult to obtain and expensive. Therefore,-rather than resort to crystals for controllingthe frequency of locally generated energy so as to conform with the phasev displaced modulated energy, I makense of PATENT OFFICE CLARENCE w. HANSELL, or roar :rnrrnnson, NEW YORK, ASSIGNOR To nAnIo con an electromechanical resonator other than a crystal to control the frequency of the locally generated energy. In a preferred form of my invention I utilize a tuning fork for electromechanical control, which is sufficiently accurate and inexpensive.
,As the frequency of themodulating wave I may vary, it is desirable that the wave locally erated at the receiver-be synchronized in frequency therewith andjto accomplish this by electromechanical.control is a further ob- I jcct of the present invention. J Briefly this is carried out "by varying a mechanical stress or a pull on the electromechanical -"vibrator whereby its fre uencyis altered in the cor rect direction. 8f course, in doing thisI also make use of a phenomenon that I have referred to in my copending application, namely, that when a'wave is phase reversed-180. degrees its second harmonic is not altered in phase.
fully. by utilizing. alternating potentials 180 degrees-apart derived by frequency doubling the demodulated signalwave at the receiver in connection w1th aloca'llygener- 65 v as a means for generating the local synchroated, frequency-doubled wave 90 degrees away from the waves separatedbyV18O degrees, a current flow can be obtained in a d1- rection such that it will indicate the phase shift caused by change in frequency of the locally generated wave relative tothe incoming demodulated wave. The current is then used to correct, by altering the stress on an electromechanical frequency controlling device, the'frequency of the locally generated wave so that it is maintained in synchronism with the incoming demodulated wave.
-* para'tus shown in Figure 1, and
Figure 3 is given to aid in the explanation of the operation of Figure 2. Turning to Figure 1, by means of keying apparatus 2, currents of opposite polarity are sent over a: land line 4 to a quick acting relay 6 which, by means of a double acting armature 10, controls the potential drop due to the flow of current through each of tie two halves of a resistance 8. This potential variation due to the relay acts differentially on the modulator tubes 14, 16, which, in turn, act to reverse'the phase of the output from transformer 12. The relay apparatus 6, leis more fully described and I claimed in my copending application Serial Number230,439
. filed November 2, 1927.
With the armature 10 in its mid, uncontacting position, no modulating energy appears in the out-put transformer 12coupled to electron discharge devices 14, 16 because of the symmetrical connection thereof. However, when, say, contact 10 moves in its upper position tube 14 draws a larger-current than tube 16 and allows modulating energy of one phase to appear in the secondary of trans former 12. In its lower position tube 16 drawsmore current than 14 and modulating energyfrom source'18 appears in-the output circuit 12 relatively phase reversed. Either of the phase reversed positions may be utilized to indicate dots or dashes and, when armature 10 is allowed to remain in its mid position, the absence of energy from local oscillator 18 in output circuit'12. will indi- 'cate a space.
Modulating energy, phase displaced according to signals tob-e transmitted, appearing in the secondary of transformer 12 is then fed into a modulator 20-supplied with I carrier energy from a source'22. The out-' i "put of modulator 20 is fed into a power ampli- I tier 24 and, radiated by a suitable antenna26.
It is to be understood, of course, that radia- I tion from antenna 26 may be made to be either a single side hand, both side bands or both side bands and the carrier. Or, any combination thereof as produced by amplitude modulation may be radiated as desired, the requisites necessary being either filters in the case where certain side bands are to be-suppressed, or in the case when the carrier is to be suppressed, a carrier suppression modulator may be used at 20. Or, if desired, a filter may be connected tothe output thereof for eliminating the carrier energy from the power amplifier 24. Preferably, for short wave transmission, the modulator 20 should react upon source22 to carry its frequency in accordance with the modulatingenergy from 12 in amanner similar to that shown in my Patent No. 1,787,979.
At the receiver (see Figure 2) a portion of the transmitted energy is collected upon an antenna 28, amplified by means of an amplifier 30, and demodulated by means of with the energy supplied by transformer 38 to tube 36, there will be a predominant flow of current in tube 36 which will cause armature 38 to move in one direction, applying currents of one polarity from source 40 to'a suitable translating or recording device 42; V
and, when the phase of the modulating component of the collected energy is reversed, tube 34wil1 predominate in the drawing of anode current, causing armature 38 to'be moved in a reversed direction, applying en ergy of'a different polarity to recording device 42. In the absence of signal'energy, the armature 38 will remain in itsmid position whereby the translating device 42 will indicatea space. v V
In order to obtain the necessarytranslating energy, of like frequency and constant phase 'rel'ative'tothe demodulated energy, at 38, a portion of the demodulated energy from the output of detector 32 is taken from a of a frequency doubler 48,which, because of the parallel connection of the anodes and the serial connection of the gridsof tubes 50, .52 comprising it, has appearing in the output side thereof a second harmonic of the demodulated energy. Despite phase reversals of the fundamental, the harmonic energy remains relatively constant in phase.
The energy of doubled frequency is fed through transformer fi l, lines 56, and transformer 58 to the serially connected or phase opposed anodes of electron discharge devices 60, 62 having their input circuits connected in parallel or cophasially. To the input circuits of tubes 60, 62 throughtransformer 4, is fed energy from frequency doubler 66 which is supplied with energy from a local generator of waves 68 arranged to generate as nearly as possible energy of a frequency equal to that of the demodulated received wave. r
By virtue of the foregoing connections, and by suitable adjustment of the taps onphase adjuster 44, with frequency doubler 66 sup plying energy of the same frequency as that supplied by frequency doubler 48, the instantaneous potentials applied to the anodes and control electrodes of tubes 60, 62 may be made as indicated in Figure 3 where E indicates control electrode potentials applied to tubes 60, 62 and E E indicate respectively anode potentials of tubes 60, 62.
WVith such an arrangement it will be seen that the unidirectional componentsof the currents appearing in the anode circuits 60,62 are identical. In the event that there is a relative change in frequency of the potentials applied to the input and output circuits of tub-es 60, 62, there will be a phaseshift of the control electrode potentials relative to the anode potentials of tubes 60, 62 which in turn will cause one or the other of the two tubes to draw a greater unidirectional component than the other. For a very complete discussion of the operation of this apparatus reference is made to my copending application Serial Number 230,214, filed November 1, 1927 on automatic tuning.
The foregoing principle is relied upon for correcting the frequency of the local generator of waves. The local generator 68 comprises a vacuum tube 70 regeneratively connected through electromagnets 72, 4 acting upon tuning fork 7 6 which, of course, controls the frequency of oscillation of source 68. By means of a permanent U magnet 78, having coils 80, 82 wound about each leg thereof, the pull on one leg of tuning fork 76 may be varied and hence the frequency of vibration of tuning fork 76 may be varied. Hence, by connecting coils 80, 82 in the anode circuits of tubes 60, 62 respectively, the pull of the magnet may be altered according tothe unidirectional flow of current in each tube. In this way, depending upon the phase shift caused by a change in frequency of the local oscillator relative to the demodulated signal Wave, the differential anode currents of tubes 60, 62 alters the pull on tuning fork 76 in a direction such that its frequency is pulled into step with the demodulated 4 wave. V
Many changes, of course, will readily suggest themselves to those skilledin .the art. For example, the input and output circuits of tubes 36, 34 and tubes 60, 62 may be reversed without altering the principles underlying my invention. It is, therefore, to be understood that the scope of this invention is to be limited not by what has been shown but solely by the breadth of the appended claims.
' Having thus described my'invention what l Iclaimis:
1. The method of signaling which includes transmitting carrier energy'modulated with signal phase displaced, low frequency energy, M collecting a portion of the transmitted car- (30 rier energy, synchronizing locally generated energy with the low frequency component of the collected energy by utilizing even nunii bered multiple harmonics of the energies to be synchronized and utilizing the synchro-" nized energy and the low frequency component for translation. Y
2. The methodof signaling which includes transmitting carrier energy modulatedy with signal phase displaced, low frequency energy, collecting a portion of the transmitted carrier energy, synchronizing locally generated energy with the low frequency component of I the collected energy by utilizing a harmonic q of the modulating energy that remains 00-" phasial regardless of phase displacements of the modulating energy and utilizing the low frequency energy and. synchronized energy for translation.
3. The method of signaling which includes transmitting carrier energy modulated with signal phase displaced, low frequencyenergy, collecting a portion ofthe transmitted-car: rier energy, synchronizing locally generated energy with the low frequency component of the collected energy by utilizing the second harmonic of the component and the locally generated energy, and translating the combined component and locally'generatedenergy. ,4. The method of translating signals-transmitted by phase reversing modulating energy which includes doubling the' frequency o'fa portion of receiveddemodulated energy, 'gen- .4 r crating energy locally, doubling the frequenl cy of a portion ofthe locally genera-ted'energy, synchronizing the received and locally generated energies by utilization of the dou-" bled frequencies, and'combining the phase, of thereceived demodulated energy'offun damental frequency with that of the local energy of fundamental frequency inorde'r f to detect phase reversalof the modulating component of the received energy. 5 1' 5. The method of signaling which includes generating carrier energy, modulating the carrier with relatively low frequency, signal phase displaced, energy, transmitting the resultant energy; collectin; a portion of the, transmitted energy, recti ying the'energy to obtain the signal phase'displaced component, locally generating energy of a frequency corresponding to the phase displaced component, utilizing the second harmonic of the component and the second harmonic of locally generated energy to synchronize the component and the local energy,combining the synchronized energies, and utilizing the .combinedenergies for translation.
6. In combination, means for transmitting carrier energymodulated with signal phase displaced low frequency energy; means for collecting a portion of the transmitted car- .rier energy, meansfor synchronizing locally generated energy with the low frequency component by. utilizing the same harmonic of the energies to be synchronized and means for translating'the combined locally generated energy and low frequency component.-
7. In comb-matron, means for transmitting carrier energy modulated with signal phase displaced low frequency energy; means for collecting a portion of the transmitted carrier energy, means for synchronizing locally generated energy with the low frequency component byutilizing that harmonic of the modulating energy that remains cophasial regardless of phase displacements of the modulating energy, means for combiningthe locally generated energy and the low frequency component and means for translating the combined energies.
- 3 8. In combination, means for transmitting carrier energy modulated withsignal phase displacedlow frequency energy; means for collecting a portion of the transmittedcarrier energy, means for synchronizing locally generated energy .with the low frequency.
componentby utilizing the second harmonic "of the componentand the locally generated energy and means forcombining and translating the locally generated energy and low frequency component.
.9. In areceiving system .for translating signals transmitted by phase reversingmodulating energy, means for doubling the frequency of a portion of received demodulated energy, means for generating energy locally, means forldoubling the frequency of a portion of the locally generated energy, means for synchronizing the 'receive'd' and locally generated, energi'es by combining the double frequencies, and means for combining-the received demodulated energy of fundamental frequency with that of the localenergy of fundamental frequency in. order 'todetect phase reversal of the modulating component ofthe received energy; I
10. In combination, means for generating carrier energy, means for modulating the carrier with relatively low .frequencysignal phase displaced energy, means for 'transmitting the resultant energy; means for collecting a portion .of the transmitted energy, means for rectifying the energy. to obtain the signal phase displaced component, means for locally generating energy of a frequencyfcorresponding to the phase displaced component, means for utilizing the second hare monic of the component and the second harmonic of locally generated energy to synchronize the component and the local energy, means for combining the synchronized energies, and means for utilizing the combined energies for translation.
11. The method of translating signals including a carrier on which phase reversed signalfrequencies have been'impressed by means of signal demodulating means and translating means comprising a pair of thermionic tubes which includes the steps of, collecting said'signal modulated" carrier, demodulatingsaid modulated carrier, applying demodulated energy to like electrodes of: said pair of electron emission tubes substantially in phase, applying locally generated synchronous energy todiiferent like electrodes of said tubes approximately in opposed phase,
andutilizing-the difference in the currents in the output circuits of said. tubes for produc ing indications characteristic of the signals impressed on said carrier 12. In a system for translating signals transmitted by phase reversal .of modulating energy on a'carrier, means for collecting said modulated f'carrier, signal demodulati'ng means connected with said collecting means, a pair of thermionic tubes, 7 means for connecting a pair of like electrodes in said tubes to the output circuit of said demodulating means, means for applying locally generated synchronous alternating current energy to another pair 10f electrodes in said pair of tubes in substantially opposed phase, and
translating means connected with the output I circuit of said tubes.
CLARENCE. W. HANsnLL.
CERTIFICATE OF CORRECTION.
Patent No. 1,901,642. March 14, 1933.
CLARENCE W. HANSELL.
It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 81, for "carry" read "vary"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.
Signed and sealed this 15th day of August, A. D. 1933.
M. J. Moore.
(Seal) Acting Commissioner of Patents,