US2475609A - Sending and receiving signaling system - Google Patents

Description

Juiy 12, E949. B. B. GAULD SENDING AND RECEIVING SIGNALING SYSTEM Filed Jan. 16, 1945 710 n Z l 22 5 RAD) MODULATOR INTERMEDIATE MODULATOR AUDIO FREQUENCY DETECTOR FREQUENCY DETECTOR AMPLIFIER AMPLIFIER AMPLIFIER I I I OSCILLATOR I n I BEAT FREQUENCY fi \t OSCILLATOR I *"q I \IS AMPLIFIER BROWNLEE B.GAULD y v f Patented July 12, 1949 SENDING AND RECEIVING SIGNALING SYSTEM Brownlee B. Gauld, Brookline, Mass, assignor, by 'mesne assignments, to Raytheon Manufacturing Company, a corporation of Delaware Application January 16, 1945, Serial No. 573,085

Claims. (Cl. 177--386) The present invention relates to a signaling system and more particularly to a system for ranging with the use of wave energy in which a signal is transmitted and an echo received from an obstacle or reflecting surface on which the transmitted wave impinges. The present system may be usefully applied to sound ranging and depth sounding employing high frequencies near the upper limit of the sonic and in the supersonic range.

The present system is furthermore specifically concerned with the elimination of the differential drift in frequency between the oscillators used for reception and those used for transmission of the signal. In the present invention this is accomplished by using a beat frequency oscillator both in transmission and in reception, the oscillator providing a different frequency for transmission than for reception, the difference being definitely established either by the introduction of a small trimming condenser in the tuning circuit of the oscillator in transmission or in reception.

The advantage of the system as used in the present invention is that the beat frequency note remains independent of any drift in either of the oscillators used for sending and/or receiving since, apart from changes due to Doppler effect, the ultimate audio frequency signal used as a final indicator is uniquely determined by the frequency difference produced by the trimming condenser, for instance, in the beat frequency oscillator in changing over from sending to receiving, or vice versa.

The invention will be further described in the specification below when taken in connection 2 detector II on which the frequency of the oscillator I2 is impressed through a buffer stage l3. The blocks have legends indicating electrical circuits employing diode, triode, pentodeor other multiple element thermionic tubes arranged in the usual manner for providing the type of circuit designated in the drawing. The electrical output of the modulator detector is impressed with the drawing illustrating an embodiment of the invention which shows the invention set forth schematically in block diagram.

In the drawing, i represents a projector which may be used for underwater signaling for transmitting a beam of supersonic or ultra high frequency waves. This may be of any of the wellknown types such as electrodynamic, electromagnetic, magnetostrictive or piezoelectric construction. The projector may both transmit and receive or, if desired, separate projectors for transmission and reception may be used. The projector is energized over the line 2 which is connected to the two-position switch 3. The switch 3 may form one element of a gang switch 4 which includes the other individual switches 5, 6, l and 8. These switches, as illustrated in the drawing,

are shown in position for receiving. When the poles are thrown downward, they are in position for transmission.

In the drawing, as illustrated, the projector I in position for receiving is connected over the line 9 to the radiofrequency amplifier it which amplifies the signal picked up by the projector. The amplifier I0 is connected to the modulator upon the intermediate frequency amplifier 2 I, the output of which is impressed upon a second modulating detector 22 to which the beat frequency oscillator M is connected for producing an audio frequency signal which is the indicator in the circuit. The instant of reception may indicate a distance measurement, or direction indication, or both. The present invention is, however, more concerned with the means and methods of the production of the signal itself rather than the measurements obtained by it. This signal may be amplified in the audio amplifier i5.

The beat frequency oscillator may be adjustably tuned to the desired frequency through the tuning. condenser [6 which has connected across it a furthertuning element, such as trimming condenser ll, shown in the drawing as connected in circuit by means of the switch 6 in the position of transmission but not reception.

In the description above, it has been indicated that the position of the switch is shown for receiving a reflected signal. It is presumed that this signal was transmitted when the poles of all the individual switches of the gang switch 4 were in a downward position when the relay key I8 is depressed. This is diagrammatically shown as a plain key but it may be independently or automatically operated periodically by a cam or any other equivalent means. When the switches are in their downward position, the oscillator I2 and the beat frequency oscillator I 4 combine to produce the desired signaling frequency for energizing the projector. For this purpose the oscillator I2 is connected through the switch 8 to the modulator l9 to which, also the beat frequency oscillator I4 is connected. These frequencies combine or heterodyne to control and produce the resultant frequency which is amplified by the driver amplifier 20 and impressed upon the projector I through the switch 3. The projector may be keyed by switching to a sending position and then to a receiving position or it may be separately keyed during the interval that the gang switch is in sending position. This may be. accomplished in any wellknown fashion. The sending interval may be synchronized to occur during the interval when the key or switch I8 is depressed.

'Various combinations of frequencies may be used for the oscillator l2 and the beat frequency oscillator It. The result desired is to provide a frequency in the range in which the projector will most efiiciently operate. Assuming that this is inthe vicinity of 20,000 cycles, then the combination of the oscillator l2 and the beat frequency It will be arranged to produce such a frequency. If we assume the frequency of. the oscillator i2 is 80,000 cycles and that of the beat frequency oscillator 60,000 cycles on transmission, then the difference combination will produce a frequency of 20,000 cycles on transmission. An echo produced by this signal will then be received by the projector when the projector is connected for reception. The received echo signal will be the same 20,000 cycle note, modified by whatever Doppler effect may have been introduced by relative movements in the medium. In fact, the only shift from the predetermined beat note frequency will be caused by the Doppler eifect as the result of relative motion of the reflecting surface and the transmitting and receiving source. This note will be picked up by the radio frequency amplifier l0 and passed to the modulator detector H in which it will be combined with the frequency from the oscillator II. The output ofthe modulator detector will be passed to the intermediate frequency amplifier 2| and then to the second modulator detector 22 where it will be combined with the frequency from the beat frequency oscillator i4 whose frequency now has been slightly changed by the omission of the condenser i! in the tuning condenser circuit. The value of this change which is definitely determined by the capacities involved may be of the order of 500 cycles so that in receiving, the beat frequency oscillator-may be 60.500 cycles instead of 60,000 cycles, or 500 cycles higher. The intermediate frequency amplifier 2| will have a frequency of 60,000 cycles, the difference between 80,000 cycles introduced by the oscillator l2 and the 20,000 cycles from the signal picked up by the projector. Then the combination in the modulator detector 22 will produce the audio frequency beat note of 500 cycles subject to the effect of Doppler, which is the difference frequency in the beat oscillator between sending and receiving. In the arrangement described above, it will be seen that the frequency of the oscillator I2 need not be particularly stable other than, of course, that the resultant frequencies must be reasonably suitable for the circuits in which they function. If the projector is fairly broadly tuned and so also the other thermionic tube circuits, the oscillator I2 and the beat frequency oscillator need not be kept within closer limits than that necessary to keep the transmitting frequency within the range of the eflicient operation of the projector. In this way both the oscillator I2 and the beat frequency oscillator may drift considerably without affecting the efficient operation of the system.

Having now described my invention, I claim:

1. In a sending and receiving signaling system operating on the same wave frequency, in combination, means providing a heterodyne signaling frequency for transmission and reception including a beat frequency oscillator, switching means for connecting the beat frequency oscillator for sending or receiving including means establishing a different beat frequency of oscillation for sending than for receiving, and means operative in the receiving position for producing an indication having an oscillating frequency corresponding to the difference between the beat frequencies of said oscillator for sending and receiving.

naling frequency for transmission and reception including a beat frequency oscillator having means establishing a different beat frequency of oscillation for sending than for receiving, and a second oscillator having the same frequencies in sending and receiving, means for combining the heterodyne frequency of transmission with the first oscillator frequency of reception for producing an indication having an oscillating frequency corresponding to said difference between the beat frequency of sending and receiving.

3. In a sending and receiving signaling system operating on the same wave frequency, in combination, a projector, means for providing a heterodyne signaling frequency for said projector for sending comprising a beat frequency oscillator having means establishing a different beat frequency of oscillation for sending than for receiving and a fixed oscillator operatively connected therewith for establishing the transmitting signal frequency during sending, and operative during receiving to cooperate with signals of the transmitted signal frequency to reproduce the sending frequency of said beat frequency oscillator and means combining said reproduced frequency and'said beat frequency of oscillation for receiving to produce an indication having an oscillating frequency corresponding to the difference therebetween.

4. In a sending and receiving signaling system operating on the same wave frequency, in combination, a projector, means providing a heterodyne signaling frequency for said projector for sending comprising a fixed frequency oscillator and a beat frequency oscillator operatively connected to provide the sending frequency for the projector and switching means for switching said projector from sending to receiving including means for slightly changing the beat frequency of said beat frequency oscillator and means including said oscillators for producing an audio frequency corresponding tothe difference frequency of the beat frequency oscillator from sending to receiving position.

5. In a sending and receiving signaling system operating on the same wave frequency, in combination, a projector, a fixed frequency oscillator and a beat frequency oscillator, a receiving circuit, a power amplifying circuit, switching means operatively connecting said oscillators to said power amplifying circuit for energizing said projector and for connecting said oscillators to said receiving circuit for receiving the signal picked up by said projector, and means for providing said beating oscillator with a slightly different frequency in sending position from that in receiving position for producing an audio frequency corresponding to the difference frequency of the oscillator from sending position to receiving position.

BROWNLEE B. GAULD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Leyn May 5, 1942

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