US1882698A - Signaling by phase displacement - Google Patents

Description

Oct. 18, 1932. E. F. w. ALEXANDERSON 1,882,693

SIGNALING BY PHASE DISPLACEMENT Filed Dec. 9, 1927 F r F F 1 40 46 6 J48 T- 12 22 42 so "SW/Tc r "z 77/15 #0105750 RELHY w OSCILLATOR 3s INVENTOR ERNST EW. ALEXANDERSON AT RNEY Patented Oct. 18, 1932 UNITED STATES v PATENT ore-Ice 'nnusr r. W. ALnxANDnRsou, or SCHENECTADY, NEW Yonmnssrenon 'ro RADIO 'conronn'rron or AMERICA; A CORPORATION OF'DELAWARE SIGNALING BY PHASE DISPLACEMENT Application filed December 9, 1927. Serial No. 238,820.

This invention relates to signaling by phase displacement, and moreparticularly to multiplex signaling by phase reversal.

Code transmission utilizes three conditions ii for the elements representing an alphabetical letter, the usual conditions being either absence of signal, signal dot, or signal dash. Inasmuch as a dash is three times the time duration of a dot it isobvious thatsignaling speeds might be increased if a signal condition equivalent to a dash, but of the duration ofa dot, could be used, and this I propose to do by transmitting signal energies of different phase, and preferably of opposite phase.

It will be clear-that with this mode of signaling no space is needed between signal impulses representing either dot and dash, or dash and dot, for the phase reversal will itself evidence the change. In this way signaling speed may be further increased.

On reflection it will be realized that having made all signal impulses of equal length, and

having introduced phase reversal to discriminate between kinds of signal impulses, the spacing between successive dots or successive dashes may be omitted, and signal impulses of varying length commensurate with the numberof successive signal impulses of like character may be transmitted. To provide a method and means for signaling in accordance with foregoing discussion is one object of my invention.

A further object of my invention is to pro- I vide for multiplexing signals transmitted by phase reversal, which I do by transmitting at one frequency a plurality of messages each utilizingenergies 180 apartin phase, but (littering in phase relative to one another. Thus, in the case of a duplex transmitter the energies for two channels may be relatively in phase quadrature. In such case the resultant energy will be constant in frequency but will beradiatedin any of eight uniformly displaced phase positions, relative to the phase of an uninterrupted carrier of like frequency, and four components in quadrature will be utilized. for two channels of phase reversed signaling.

A source of energy such as an alternator or atube transmitter maybe utilized for trans mission by phase reversal simply by arrangingthe key to reverse the connections between the antenna circuit and the transmitter.

This, however, leads to the disadvantage that losses are introduced by reason of the repeated connection of the source to a resonant antenna circuit which is oscillating in opposed phase. The reversing key would close the circuit at a time ofmaximum shock, and then,before the system could begin to radiate in reversed phase .the'source of energy would have to overcome the oscillation in the antenna circuit and build it up anew in reversed phase. To obviate this defect is a still further object of my invention, which I accomplish by momentarily interrupting the energy supplied to the antenna, and mean while slightly detuning the antenna a pre determined amount for the appropriate time necessary to produce phase reversal of the energy therein. In this way, when the transmission energy is again applied to the antenna it is exactly in phase with the oscillations of the antenna. 1 More broadly expressed, the method includes shifting the phase of the energy in the resonant circuit through a desired phase displacement by detuning the resonant circuit a predetermined amount for the appropriate time necessary to produce the desired phase displacement. My invention is more completely described in the following specification, in which Figure 1 indicates the letter F in con tinental code; 1 c

Figure 2 represents the same letter with a phase reversed dot substituted for the dash; Figure 3 indicates the same letter with the spaces between dot and dash, and dash and dot. omitted; I

Figure 4 represents the same letter without spaces between signal impulses in any single alphabetical letter;

Figure 5 is a schematic wiring diagram for a simplex transmitter embodying my invention; and V Figure 6 is a schematic wiring diagram for a duplex transmitter embodying my invention. t

Figure 1 indicates the letter F, represented. in the continental code by dot, dot, dash, dot,

phase reversal has been indicated on the tapeby a depression below the line.

Just how the signals transmitted by phase reversal may be detected and suitably trans lated for this purpose is more fully disclosed in a copending application of Clarence W. Haisel, Serial No. 230,438, filed November 2, 192

l The spaces in Figure 1 serve the purpose of indicating the cessation and beginning anew of signal impulses. It is clear that in signaling by phase reversal the termination of a signalimpulse of one phase and the beginning of a signal impulse of opposite phase is inherently marked by the phase reversal, and therefore the spacing between dot and dash, or dash and dot, may be omitted, as has been indicated in Figure 3, thus shortening the time duration of the signal to five units. However, having signaling energy of opposite phase available for dots and dashes makes'it possible to again revert to dashes for representing a number of dots. A signal impulse in one phase may be sent for a length of time commensurate with a number of successive signal impulsesof like phase. This has been indicated inFigure 4, in which the time duration of the entire signal has'bee'n reduced to four time units. Actual signal speed will be increased even more than is here indicated, for many letters have a bigger percentage of dashes, and the saving is thereby augmented. Furthermore, at present, spaces several time units in length are used between letters, whereas with this system only a single time unit space is needed, just as is at present used between the dot and dash elements of a single letter. 7 I Attention is now directed to Figure 5, in which the antenna 2 is tuned by means of the inductances 4 and 6, and is energized from a suitable source 8. 7 As the reception of phase displaced signals. depends primarily upon synchronizing, it is desirable that the tran mitter be as nearly constant in frequency as possible, and therefore if the source is a vacuum tube source it preferably is controlled through a crystal drive, asindicated at 10. The source 8 is connected to the antenna circuit in direct phase by means of the conductors 12 and 14, and in reversed phase by means of the conductors 16 and 18. These are each provided with relay operated switches 22, 24, 26 and 28.

In practice the keying means will preferably be automatic, but for illustrationthere y switches 26 and 28 are opened. With the key contacting solely with the contact 36 the switches 26 and 28 are closed, whereas the switches 22 and 24 are opened. In the mid position of the key the switches are all closed,

, and the energy source is short circuited. Of

course the source either naturally has, or will be arranged to have, a sufficiently high internal reactance so that the short circuit will not be at all injurious, and will serve merely to take the output away from the antenna circuit.

'The antenna inductance 6 has connected across it the radio frequency circuit 40 of a magnetic amplifier 42. The direct current or saturating circuit of the amplifier is closed by means of a relay controlled switch 44. Means should be provided for adjusting the degree of detuning produced when the magnetic amplifier is made operative to detune the antenna circuit, and this has been most simply represented in the present instance by the variable battery tap 46, which may be adjusted to alter the degree of saturation produced when the switch 44 is closed, and by the tap 48 on the inductance 6, which varies the amount of inductance in parallel with which the magnetic amplifiercircuit is connected.

7 The key 30, when moved through mid position about pivot 32, contacts for an instant with a contact point 38, and this serves to actuate the relay 50 of the switch 44. For any predetermined degree of detuning produced by the magnetic amplifier there is a fixed appropriate time durationof detuning which will result in phase reversal of the energy in the antenna, relative to what it would be if the antenna circuit had not been detuned. Thus, if the amount of detuning is only one thousand cycles per second the proper time of closure for the switch 44 is one-two thousandth of a second. The relay 50 is any suitable form of time adjusted relay which, regardless of the length of time the key contacts with the segment 38, is merely tripped once for the exact time interval desired, say, the onetwo thousandth of a second.

If signals are transmitted in the nature of those shown in Figures 2 and 3 the relay 50 will have been tripped between successive dots or successive dashes, but this will not be of consequence because when an actual space is allowed between signal impulses the energy in the antenna attenuates to too negligible a value to result in losses when the circuit is again closed in like phase, rather than in reversed phase. This follows because the significance of a transmitted space is an absence of signal energy. However, I deem the type of signaling shown in Figure 4 to be preferable, and then the question does not arise at all, except for the spacing between letters and words, and there the same reasoning holds, thati's,the antenna energy reduces to zero, hence its phase does not matter.

In Figure 6 I have'indicated an arrangement which is very similar to that shown in Figure 5 except that provision is made for duplex transmission. In this case the energy source has been indicated as being a high frequency alternator 80, and energy is so tapped from the windings of the alter natorthat two component energies displaced 90 in phase are made available. These are fed simultaneously to the antenna circuit as shown, and are each independently keyed. The antenna circuit is arranged forindependent detuning by means of two circuit arrangements each quite similar to that shown in Figure 5.

A moments reflection will show, referring to one of the key positions for one of the phases as an arbitrary zero of phase, that a similar key position for the other energy alone will cause a 90? displacement in phase, and that a simultaneous positioning of both keys in the said position will cause a resultant antenna current which is displaced 45 in phase. The various combinations of key positions of the two keys will result in either no transmission, or transmission in any of eight phase positions spaced 45 apart. These may be assigned, at the ,receiver, to any desired code or characterizatiombut in the'present case it is most simply assumed that the components of the eight positions which lie along two axes inquadrature will be used for two signaling channelson each of which the signaling is tobe by phase reversal.

To explain in greater detail, key 30, being in contact with the fixed contact 34, there,

lay controlled switches 22 and 24 are closed. Key 30, also being in contact with the fixed contact 36, the relay controlledswitches 26 and 28 are closed. The four switches being closed, it follows that the corresponding phaseof the two phase radio frequency alternator is short circuited, hence there is no antenna energy of that phase. With the key 130 in the center position shown, the same conclusion applies to theenergy of the other phase, and consequently there is no antenna output at all. Now if the key 30 is moved onto the contact 34, and away from the contact '36-, the switches 22 and 24 remain closed, while the switches 26 and 28are opened, so that energy of one phase is fed from the terminals 1, 30f alternator 80 directly to the antenna. This, for the sake of. comparison, may be considered as the zero angle the opposite direction, so as to leave the contact 34,,andengage only the contact 36, then of the'pha-se. Ifnow the key 30 is moved in switches 22 and 24 are opened, while swiches 26 and 28'are closed, and energy is supplied from-the sameterminals and the same phase of the alternator" 80 to the antenna but through the crossed connections, so that the antenna energy is 180 degrees in phase away from what it was with the key on the contact 3' If the key 30 is left centered, and the key 130 is moved ontothe' contact 134, and away from the contact 136, the relay controlled switches 122 and 124 remain closed, while the relay controlled switches 126 and 128 are opened, so that energy is fed from the terminals 5, 7 of one phase of the two phase radio frequency alternator 80 directly to the antenna. This energy may be coinsidered as oocupying a degree phase relation. If the key ismoved in the opposite direction, leaving the contact 134, and engaging the contact 136, theswitches 122 and 124 are opened, 3 while the switches 126 and 128 are closed, and

energy is fed from the same terminal and the same phase of the alternator, but is cross connected to the antenna, so that the antenna energy is displaced 18 0 degrees in phase from what it is when the key is moved onto the contact 134. The resulting antenna energy may be considered as occupying a 270 degree phase position.

Now if the key 30 is moved onto the contact ito 34, and at the same time the key 130 is moved onto the-contact 134, energies are'fed to the antenna simultaneously in zero and 90 degree phase positions. These energies add to a resultant energyin a 45' degree phase posi tion, which is radiated. If the key 30 is engaged with the contact 36, and the key 130 with the contact 134, then energy is fed to the antenna in 90 degree and 180 degree phase positions, so that the resultingenergy lies in a degree phase position. If the key 30 is'engaged with the contact36, and the key 130 is engaged with the contact 136, then energy is fed to the antenna in degree and and 27 0 degree phase relationship, so that the resultant energy is radiated in a 225 degree phase position. And finally, if the key 30 is kept in contact with the fixed contact 34', and

the key 130 is moved to'engage the contact 136, then energies of zero and 270 degree i 225,.and315 degree phase positions, as they should, since such energy is radiated only upon simultaneous actuation of both the key 30 and the key 130. I

In addition to the advantages already pointed out it may be mentioned that the effective transmitting power of any single transmitter is doubled, because by sending positive and negative waves alternately it transmits almost continuously, rather than intermittently. The signals are relatively secret because the present types of receiving sets are unable to distinguish between positive and negative waves. The frequency spectrum required for the system is exceedingly small. Even for multiplexing the necessary frequency spectrum is not at all broadened, for the multiplex signals are all transmitted on a single frequency carrier. The load on the energy source is more nearly constant, and besides greater efiiciency and increased life, the more uniform loading of the transmitter makes it more readily possibleto attainv constant frequency transmission.

I claim: i

1. The method of shifting the phase of the energy in a resonant circuit through a desired phase displacement which includes detuning the resonant circuit a predetermined amount for the appropriate time necessary to produce the desired phase displacement.

2. The method of reversing the phase of the energy in a resonant circuit, without shock, which includes slightly detuning the circuit a predetermined amount for the appropriate time necessary to produce the desired phase reversal.

V 3. In phase reversal signaling method of reversing the phase of the energy transmitted through an antenna circuit which includes momentarily interrupting the energy supply to the antenna, meanwhile slightly detuning the antenna a predetermined amount for the appropriate time necessary to produce phase reversal of the energy. therein, and thereafter supplying energy of reversed phase to the antenna.

4. Means to shift the'phase of energy in a resonant circuit through a desired phase displacement comprising, the resonant circuit,

means to detune the resonant circuit a pre-,

determined amount, and means to make said detuning means operatlve to detune the circuit the appropriate time necessary to pro- .duce. the desired phase displacement.

5. A transmission system for signaling by phase reversal comprising a source of carrier energy, an antenna. circuit tuned to the frequency of the carrier energy, means to detune the antenna circuit a predetermined amount keying means for supplying energy from the source to the circuit in either of two opposed phases, and means responsive to a phase reversing change in said keying means for making the antenna detuning means operative the appropriate time necessary to produce phase reversal of the energy in the antenna.

6. In radio communication, the method of transmitting code signals from an antenna system which includes transmitting signal impulses in one radio frequency phase to represent dots, transmitting signal impulses of equal length in a different radio frequency phase to represent dashes, and shifting the phase of the energy in the antenna circuit through the necessary phase displacement by momentarily interrupting the energy supply to the antenna, and meanwhile slightly detuning the antenna. a predetermined amount for the appropriate time necessary to produce the desired phase displacement.

7 In radio communication, the method of transmitting code signals from an antenna system which includes shortening the length of the dashes to that of the dots, distinguishing therebetween by reversing the radio frequency phase of one relative to the other, only momentarily interrupting the energy supply to the antenna between the impulses representing dots and dashes, and meanwhile slightly detuning the antenna a predetermined amount of the appropriate time necessary to reverse the phase of the energy therein.

8. A radio communication system compris ing an antenna circuit, means tosupply signal impulses thereto in one radio frequency phase to represent dots, means tosupply signal impulses of equal length in a different radio frequency phase to represent dashes, and means to shift the phase ofthe energy in the antenna circuit through the desired phase displacement including means for momentarily interrupting the energy supply to the antenna, and means for simultaneously detuning the antenna a predetermined amount for the appropriate time necessary to produce the desired phase displacement.

9. A radio communication system comprising a source. of radio frequency carrier en ergy, an antenna circuit therefor, means to key said source to supply continuous wave signal impulses to theantenna, means to reverse the phase of the energy supplied to the antenna to distinguish between signal impulses representing dots and those representing dash-es, means to momentarily interrupt the energy supply to the antenna between dots and dashes, and means for simultaneously detuning the antenna a predetermined amount for the appropriate time necessary to produce phase reversal of the energy in the antenna. I

ERNST F. W. ALEXANDERSON.

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