US2446819A

US2446819A - Synchronized pulse communication system

Info

Publication number: US2446819A
Application number: US480823A
Authority: US
Inventors: George W Fyler
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1943-03-27
Filing date: 1943-03-27
Publication date: 1948-08-10
Anticipated expiration: 1965-08-10
Also published as: FR938839A

Description

Aug. 10, 1948.

e. w. FY-LER 2,446,819

SYNCHRONIZED PULSE COMMUNICATION SYSTEM Filed March 27', 1943 TRANSMITTER rms DELAY 86*" ozvlca TIMEDELAY DEVICE CONVERTER DETECTO AMPLIFIER LOC OSCILL 0R Inventor George W. Fyler,

y His Attorney.

Patented Aug. 10, 1948 2,446,819 SYNCHRO-N-IZED PULSE COMMUNICATION STEM George W. Fyler, Stratford', Conn assignor to General Electric Company, a corporation of New York Application March 27, 1943, SerialNo; 480,823

6' Claims. (01. 250--'-13') My invention relates to pulse systems of communication.

Pulse systems are advantageous for the. transmission of speech, music, and other forms of. intelligence, because the effect of extraneous electric fields, noise, etc., which may affect the receiving apparatus, may be reduced by rendering the receiving means inoperative during the intervals between pulses. Moreover, by width or frequency modulating the pulses of radio frequency carrier, limiting means may be employed to eliminate, or at least substantially reduce, the amount of noise voltage appearing on the received pulses. Moreover, for a given average power, it is possible to operate the transmitting oscillator electron discharge devices or tubes at high instantaneous powers and, consequently, high efiiciencies. It isv therefore, an object of my invention to provide a new and improved radio communication, system of the pulse type.

Another object of my invention is to. provide a new and improved method and'meansfor reception in which the effects of undesired impulses, extraneous influences, etc. are reduced or eliminated.

The utilization of pulse communication systems makes possible duplex or multiplex operation on one frequency whereby two or more different'conlversations or transmissions of signals may be conducted on one frequency at the same time without interference. It is another object of my invention to provide a new and improved system for duplex or multiplex operation.

It is still another object of my invention to provide a duplex or multiplex system in which im.- pulses may be transmitted only when no signal is being received.

Another object of my invention is to provide in duplex or multiplex systems, means for synchronizing the times of transmission of. the various transmitting means.

The novel features which I believe to-be characteristic of my invention are-set forth with particularity in the appended claims. Myinvention itself, however, both as to its organization method of operation together with further ob jects and advantages thereof may best be un'derstood by reference to the following description taken in connection with the accompanying draw ing in which Fig. 1 represents schematicallya circuit embodying the principlesof my invention; Fig. 2 shows a modified form ofreceiver which may be substituted for the receiver shown in Fig. 1; and Fig. 3 shows inblock form an adapta- 2 tion of the principles ofmy invention to a multipl'ex'system of radio communication;

In Fig; 1, thereis shown an embodiment of my invention permitting duplex or multiplex communication on a single band of frequencies. Means is provided whereby pulses are transmitted only during the intervals betweenreceived pulses.

At each'station in the system, there is provided a suitable" transmitter Eilfiand. a suitable receiver 5!;

The transmitter may comprise asawtoot'h wave generator 52, illustrated in the form of a multivibrator of the floating cathode type, may comprise electron discharge devices ll and l' 2 having anodesl3', M, control electrodes 15,16 and the cathodes", 18, respectively. A cathodebiasing resistor 19 is provided between the cathodes and ground. The capacitor is connected between the'anode 1-3 and the control electrode 16. A capacitor 8! and'a resistor 82 are connected in series between the anode l4 and ground; The control electrodes are connected to ground by suitable resistors 9T and 98. Anode potential is 16 to. become negative and the discharge device 12 is rendered non-conductive. Thecapacitor 8 tends to'become charged when the device 12 is non-conductive because of the high potential thenexisting on anode '14. The charge on capacitor 80, which accumulated during the preceding interval tends to leak off through the resistance. 98

and the control electrode 16. gradually becomes less negative and finally becomes sufiiciently lessnegative to permit the device 12 to conduct current. Such conduction causes currentto flow through the resistance 19' and drives the cathode l1 slightly more positive with respect to the control electrode 15 and thereby causes. a reduction of the anode current through the device 1 L The result is; an increase'in the positive potential on the anode 13' which drives the control electrode 16 of the device 74 slightly more positive toin-- crease the current through the discharge device 12. The current in the resistance 19. again increases. This increase continues until the discharge. device H is cut on". The condenser 8| of the sawtooth wave, the stored energy is released suddenly by the condenser 58 and the inductance 59 at a relatively high potential to the anode SI of the oscillator 62. lease provides a pulse of high intensity, short du- The sudden re=.

vices

88 and 89. relative widths of the positive and negative square condenser 8|. Thus, it may be considered that the transmitter is rendered inoperative when pulses are to be received or that the transmitter is rendered operative for the transmission of pulses only at predetermined times between the receipt of pulses from a remote transmitter.

In order to adjust the time interval between the positive and negative impulses impressed on the control electrode '15 there is provided means 93 comprising a, potentiometer type resistance connected between the control electrodes of the de- This causes variation of the blocks without appreciably changing the frequency. Ifthe repetition rate of pulses in the multivibrator '52 of the transmitter and the quench frequency of the receiver are chosen relaration, radio frequency energy which is trans;

mitted over the antenna 63 to the remote receiver. Suitable modulation means may be employed as indicated by the numeral 60. The amplitude of the sawtooth wave of plate current in the discharge device 5'! may be controlled or varied by the potential of a second control electrode I00 of the device 51. The discharge of the device 51 is dependent not only on the waves impressed thereon by means of the control electrode 56 but also by the potential of the second control electrode I 00. In this manner a simple modulator of the Heising type may be used for modulating the potential of the control electrode I00 in accordance with audio modulation frequencies. It is apparent that the pulse rate should be higher than the highest modulating frequency.

The lower portion of Fig. 1 illustrates a suitable periodically apertured receiver which may be of the super-regenerative type with a self-quench rate which is nearly the same as the repetition rate of the multi-vibrator. Signals received on the antenna 64 are reproduced by any desired means including a loudspeaker 65.

Means is rovided to synchronize the transmission and reception of pulses from any one station so that pulses are not transmitted during the period of reception of pulses. This means may comprise a suitable time delay device 86,

connected between the anode 06 of the detector 61 and the control element of the discharge device H of the sawtooth wave generator. A negative impulse appearing on the anode 66 of the detector is differentiated in a suitable filter 8! to remove audio components of the anode voltage and is impressed on the time delay circuit 85. The time delay circuit illustrated is in the form of a multivibrator, and includes

electron discharge devices

88 and 89. The differentiated pulses from the receiver are impressed on the control electrode 90 of device 83. Relatively square pulses appear in the anode circuit as indicated in the drawing. These pulses are'differentiated in suitable filter sections 9! and 92 and the sharp, differentiated pulses, the shape of which is indicated at the output of the filter sections, are impressed on the control electrode 15 of the discharge device ll in the sawtooth wave generator of the transmitter.

Inasmuch as the discharge device H is normally conducting, the appearance of positive pulses on the control electrode usually has no effect and the generator continues to generate sawtooth waves. However, the receipt of negative pulses drives the control electrode 15 sulficiently negative to cut off the discharge device H and interrupt the production of sawtooth Waves by causing discharge device (2 to discharge system'is appreciably increased. 1

tively-close together, as, for example, 1000 cycles per second and 990 cycles per second respectively, the receiver and transmitter will tend to pull into synchronism in such a manner that the local transmitter will emit pulses at a definite time during the intervals between the receipt of pulses from the distant stations. Of course, these frequencies should normally be higher than the highest modulating frequency, as previously pointed out above. Therefore these values are merely illustrative. For voice communication purposes, these frequencies might be at least 5,000 to 10,000 cycles per second to insure good intelligibility.

In order to adjust the repetition rate of the sawtooth wave generator 52, the resistances and 98 may be made variable. In a similar manner, in order to adjust the repetition rate of the multivibrator 86 in the time delay circuit associated with both the transmitter and the receiver, a resistance 94 of the variable type may be connected between the positive terminal of the source of potential 95' and a point on the potentiometer 93. The quench rate of the receiver may be adjusted to the desired frequency by providin a variable resistor 95 shunted by a suitable capacitance 99 in the grid-to-cathode circuit.

By proper choice of constants in the time delay circuits, the system automatically locks in such a way that the receiver synchronizes with the remote transmitter, and the local transmitter synchronizes with the local receiver by means of 50 the time delay device. The remote receiver locks in with the local transmitter and the remote transmitter then synchronizes or looks in with the remote receiver. a

The provision of the time delay circuits, and

the adjustment device or means 93, enables adtion of the system will take place because the transmitter in one station will synchronize the receiver at the distant station, the distant receiver will lock-in the distant transmitter and the local receiver will then lock in with the distant transmitter. In this way a double lock is provided which will insure proper operation of the system even if only one end of the system is working properly and, accordingly, the reliability of It has been stated that a superheterodyne type the each station including a control pulse generator, each of said pulse generators having substantially the same free-running repetition rate, a superregenerative receiver at each of said stations having a quench rate substantially equal to'said predetermined repetition rate, each of said receivers automatically synchronizing with the other of said transmitters, and adjustable time delay means at each of said stations responsive to recelved pulses at the same station for developing synchronizing pulses recurring at said repetition rate but delayed by a selectable time interval, and means for synchronizing the pulse generator at the same station with said delayed pulses, there'- by to insure that pulses are transmitted from each station only in the intervals between reception of pulses at the same station, said time delay intervals being adjusted to cause the transmitters and receivers at both said stations to be mutually locked in synchronism in a closed loop to operate at said repetition rate.

5. A pulse communication system comprising a plurality of variably spaced stations, a pulse transmitter at each station including a pulse generator, each said pulse generator having substantially .the same predetermined repetition rate, a periodically operative receiver at each station apertured at a rate substantially equal to 'said repetition rate, each said receiver being arranged to synchronize with any one of said transmitters, a multivibrator at each of said stations connected for synchronization by pulses received at the same station, each said multivibrators being connected to synchronize the local pulse generator with pulses received at the local receiver so that pulses are transmitted from any station only at discrete interval betweenireceived pulses, and means for varying the on-ofi ratio of said multivibrator thereby to var the time interval between received and transmitted pulses at any one station in accordance with the spacing between said stations.

6. In a pulse communication system including a pair of spaced stations. a pulse transmitterin each of said stations, a control pulse generator for causing each of said transmitters to radiate discrete pulses at the pulse frequency of said generator, each said generator being adapted to be synchronized for operation at a common pulse frequency, a pulse receiver in each of said stations, means for synchronizing each receiver with pulses from the transmitter at the other station and for rendering said receive operative only during short time intervals including said pulses, and adjustable time delay means controlled by received pulses from each receiver for impressing synchronizing pulses on the control pulse generator at the same station after a selectable time delay; "thereby to restrict radiation of pulses from each station to discrete intervals between reception of pulses at the same station, said time delays being adjusted to cause the transmitters and receivers at both said stations to be mutually locked in synchronism in a closed loop to operate at said common pulse frequency.

' GEORGE W. FYLER.

REFERENCES CITED The following references are of record fileof this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain May 22, 1930 in the Number Number