US1830242A - Wobbled frequency superheterodyne system - Google Patents

Description

Nov. 3, 1931. R. H. RANGER' WOBBLED FREQUENCY SUPRHETERODYNE SYSTEM Filed March 22, 1929 WANN - HNI vwenoz RlcHARD Human meek m W m W Patentedl Nov. 3, 1931 RICHARD HOWLANI; RANGER, 0F NEWARK,

A COBRORATION 0F DELAWARE CORPORATION Ol' AHEBICA,

NEW JERSEY, ASSIGNOB TO RADIO wonnen niiaumwcr sUrEiiHErmionYNE sirsrmr application nica irma as, im. serial no. 349,075.

The present invention relates to radiontrans mitting andreceiving systems, and is particularly directed to transmitting and receiving systems of the heterodyne type.

Great interest has been taken recently in wobbled frequency transmission systems, and the present invention is particularly directed to the development ofa transmitting and receiving system, especially adapted to wobbled fiequency transmission, which merely means that the transmission of the radio wave from the transmitting station is continuallyvwobbled back and forth between two limiting frequencies to accomplish the signalling, or, in other Words, the wobble is the characteristie u on which the signalling is accomplishe Y In telephonic transmission, for example, the frequency may be wobbled between two wave lengths to a greater or lesser extent, and the usual receiver is set or adjusted to one side of the frequency shii't so that, as the frequency is wobbled back and forth, the' receiver will respond to a greater or a lesser extent as the frequency comes nearer or furtherfrom the frequency to which the receiver is set. i

A system of this type has been found to have certain drawbacks to be taken, which, for example, may be given by the following statement:

The wobbled frequency does not seem to carry through fading conditions as well as the more usual method of modulation, and this is robably due to the fact that there are less siii; bands which will carry through on one side or the other of the basic carrier when the other side is out, and another reason is,` that a wobbled frequency transmission is not readily adapted to heterodyne reception.

As a rincipal object of the present invention, I have, therefore, Sought'to develop a novel method and means by which the use of a' wobbled frequency transmission system may 'be taken advantage of to the fullest extent. so that the system may be readily applicable to heterodyne reception, such as is highly desirable in many instances.

As a further object of my invention, I have unless other steps are .ing sim le sought to develop a method and means by which it is possible to utilize a wobbled frequency transmission system in heterodyne reception in which it is unnecessary to maintain a constant frequency and phase relationship between the local wobbling oscillators of the transmitting and receiving systems.

As a further object of my invention, I have sought to develop a system wherein it is possible to utilize local oscillators in connection with wobbled frequency hetei-odyne receiving and transmitting systems in which the local oscillators at tne transmitter and receiver are spaced apart from each other by any predetermined and desirable values or amounts.

As a still further object of my invention, I have sought to develop a method and means by which the wobbled frequency heterodyne transmitting and receiving system may be readily adapted to multiplex transmission and reception, and in which the local oscil' latoi's oi the transmitter and receiver may be wobbled back and forth .between two limiting frequencies at a number of dilierent rates corresponding to the number of channels in-A eluded in the multiplex commumcation system. v

As a still further object of my invention, I have sought to develop a wobbled frequency transmission and reception System in which the detrimental elects of fading have been substantially overcome and avoided.

A still further object of my invention is o to provide a wobbled frequency transmitting 85 and receiving system which is simple in its construction and arrangement of parts, a system which is compact, easily operated, convenient to install, eicient in its use, substantially fool-proof, and which may be readily arranged and set up by merely makchanges to the already existing types o heterodyne transmitting and receiving systems.

l Stili other and ancillary objects of my invention will become apparent to those skilled in the art to which the invention relates by reading the following specification in connection with the accompanying drawings, wherein Fig. 1 thereof illustraiesdiagram- 100 matically one form which the invention may t assume, and Fig. 2 illustrates a suitable means by which the basic frequency of one oscillator muy be wobbled although stood that the above named illustrations are merely given by way of exam le, and that other forms of the invention wi at once suggest themselves to those skilled the art to which the invention has been directed.

For the purpIose of more clearl describing my invention, have chosen to i ustrate the same as applicable to certain frequency values which have been found to be'especially sui to the purposes and objects of the invention, but it should be borne in mind that other frequency values may readily be substituted for those given by way of illustration, and the invention should therefore be considered as basically covering all frequencies and not restricted to the specific examples illustrated. N ow referring articularly to Fig. 1 of the accompanying wings, let it be assumed, for example, that a thirty meter wave length,

t or a ten thousand kilocycle frequency is being used. As shown on the dra the transmitter 1 containing a local osc' tor generating the ten thousand kilocycle freq..ency muy then be wobbled back and forth troni this basic frequency uy any suitable and Icsired uniount, for example, `by an amount of fonihundred and fifty cycles or over a band nlne hundred cycles wide. As shown, this wobbling may be produced by means of a fort kilocycle wob ler 3. The wobbled carriedv may then be transmitted from any desired type of transmitting antenna sysem 5 and projected or directed out through the c ther as an ordinary radio wave. y

The wobhled carrier is then picked up by a receiviny an.enna system 7 of any desired and preferred type located at the receivin point. At the receiver, a normal type o lick-up system tuned, for example, to a f uency of ten thousand kilocycles and provi ed with one t or two stages ofr radio frequency amplification at this particular frequency, as has been illustrated by the tuning system and amplifying system 9.

For detection, a different form of de- .tector than 'is customarily used with the usual formi of superheterod e recei has been provided. I ave arran' tector 15 in combination with a local oscillator system 11 which is wobbled at a slightly differentrate than the incoming signal energy, and may 18 at a thirty-tive kilocyc e rate. For example, let it be su posed that the frequency of the local osc' ator 11 has been chosen as nine thousandeight hundred kilocycles, then, if neither the incoming signal en nor the local oscillator of nine thousand eig t hundred kilocycles were wobbled, this would produce, as an output of the detector system it is to be underted hundred has been shown, and this may this debe wobbled. for example, by a' wobbler 15 a superaudible frequency of two hundred kilocycles, which is equal to the difference between the carrier frequency from the transmitter system and the frequency of the local oscillator. Intermediate tuning of the system-in this case would be done at this two hundred kilocycle rate.

* However, let us now assume `that a wobbling action is to be produced upon the transmitted signal energy means of the fort?1 kilt cycle wobbler 3. he two hundred ki ocycle tuning will then be quite sharp and the nine uen However, it has been found that the wobb ed frequency will still come th h. Let it now be supposed, however, that local oscillator 11 nerating a frequen of nine thousand eig t hundred kilocycles is made to wobble to an amount equal to the nine hundred cycle shift of the transmitter but at a rate slightly dierent from the wob- 'ble rate of the incomin signal energy, for

example, at a rate of t irty-live kilocycles. The local wobble will, therefore, fall in and out of step `with the `incoming signal energyhat a rate of fve'thousand times a second.`

en the local wobble is in step with the received wobbled uency energy, the resultant beat in the intermediate frequency will bestead or, in other words, two hundred kilocyc es exactly, and therefore the intermediate frequency amplifier system 17 has been shown, for the purpose of a concrete illustration, as being set sharply to this two hundred kilocycle tone.

However, when the local oscillator is out of phase with the incoming wobble, the intermediate frequencyl and forth at a very igh rate, namelv, forty kilocycles, and over an eighteen hundred cycle band, and, at this time, the intermediate frequency tunin prevents the intermediate frequency ampli er from picking up ener to any considerableor observableextent, an at any rate, the pick-upis considerably less than when the two wo blers are in step so that the net result will be that the intermediate frequency will respond mo@ eectively a number of times r second corresponding to the frequency difference in the two wobblers, which wasassumed in4 this case to be five thousand cycles. n

The detection of this intermediate frequency takes place in the second detector system cycles will shift in this wobbled will be wobbling back 19, which may be of any well known type,

and will therefore give a five thousand cycle for wobbler 3,

give the diferent rate outputs so that the system may easil be multiplexed. For example, the wob g rates may be respectively at the rate of forty thousand cycles as above thirty-nine thousand cycles for wobbler 3a and thirty-eight thousand cycles for wobbler 3b, presupposing that there are to be three channels in the multiplex system. Then the nal outputs of the second detector system 19, appearing in the output circuit 21, will be respectively five thousand cycles, four thousand cycles, and three thousand cycles, which ma then, by the aid of well known and suitab y designed filter systems such as filters 23, 23a and 23b tuned to 5000, 4000, and 3000 cycles respectively, be arranged to filter the independent signals for actuating several out ut systems.

a means of wob ling the basic frequency of an oscillator such as, for example, the 10,000 kilocycle oscillator 1 of th'e transmitter, or the 9,800 kilocycle oscillator 11 of the receiver, one of several methods may be used. For example, a magnetic amplifier circuit. such as is used in the Alexanderson alternator equipment, and -which is well known in the art, may be used. Such a magnetic amplifier consists of a high frequency winding, and a low frequency control winding, as has been illustrated by Fig. 2 of the accompanying drwii f h i dm y 2 o t e accompanying wings, the usulilg type of vacuum tube oscillator 23, having the usual plate, grid land filament members 25, 27 and 29 respectively, may be connected as an oscillator according to the eral fashion disclosed by U. S. Patent to fr artle No. 1,356,763, and in the circuit thereo 1s included an inductance 31 connected between the late and grid members of a vacuum tube. he inductance is shunted b a capacity element 35. In such a type osci lator, the lament member of the vacuum tube should be connected to any predetermined and suitable point on the inductance 31 connecting the plate and grid members of the vacuum tube.

As has been shown in connection with Fig. 2 of the drawings, the inductance 31 is divided so that a portion 33 thereof surrounds a magnetic cone 37 of a magnetic modulating system. .Also carried by the core 37 and wound inside of the winding 33 is preferably arranged a second winding 39 which is differentially wound with respect to the outside winding 33, so that each half of the inner winding has noV direct inductive action on the other, but the control winding is capable of saturating the iron core about which both windings are placed, and thus serve to reduce materially the inductance eifect in the high frequency winding, which, in the case illustrated, is the winding 33 fo a portion of the oscillator circuit of the oscillator 23.

As has been shown by Fig. 2, plate potential is applied to theplate of the oscillator 23 from a source +B through a choke coil 41 to block high frequency` direct current source. or simplicity of illustration, a source of filament current for the filament 29 has not been shown, although the same may consist of the usual filament battery or alternating current supplied .through any desired type of available resistor.

In addition to the method herein shown for wobbling a basic frequency, recourse may be had to a system of the general type disclosed by copending application of Clarence W. Hansell, Serial N o. 264,102, liled March 23, 1928, in which two master tuned circuits of different periods are provided, and coupg to each of these two circuits is accomplished Iin an alternate manner.

On very high frequencies, it is impossibpp" to get a good frequency shift suitable f r wobbling the basic carrier by merel chan ing-the plate potential on the osci ator 1n a cyflical manner so as to periodically 'wobble the output thereof. Likewise, when using screen gri tubes, the voltage impressed u on the screen grid of the tube may be varie to cause a similar frequency shift.

For the purpose of transmittin simultanecurrents from the ously on two completely difrent wave lengths so as to promote further effectiveness through fading conditions, a complete duplicate of thel operation may be made on two or more separate and independent transmission systems. This means that when a signal is desired to be sent out, the transmitter equency will be wobbled on eachof the separate transmitters by the same wobbler control so that the wobbles will be exac l in phase. This may easily be accomplishe by' arranging -a single wobblerso as to control simultaneously a plurality of transmitting stations. For receiving urposes, a similar iluuliber of receivers will e set up, and simar wobliler is arranged to control the frequency shift of the local oscillators on each of the receivers so that these also will be exactly invphase. The final outputs from each of the receivers will then tween the wobblers at the transmitting and receiving stations which will ybe exactly in phase and may be combined just as they are, and utilized in the manner above disclosed for the single transmitting and receiving sys- 120 tems. As an illustration of the general type of transmitting and receiving'systems which may be provided for transmitting and 'receiving over a plurality of separate and individual communication channels so as to 125 avoid fading effects,

reference may herein be made to copendmg applications filed jointy by Harold H. Beverage and Harold O. eterson, on March 15th, 1928, as Serial Numbers 261,736, 261,737, 261,738, covering 130 to the separate transmitters, the same produce beat notes berespectively, a system for combining rectified currents, an antenna switcher system, wherein a plurality of separate antenna systems are cychcally used to energize the same receiver, i and a system wherein individual beat notes have been combined. The above namedatpplications have been merely referred tov y wa of example and not 1n a hmiting and other modincations will at once LA; 10 themselves to those skilled in the art to w i ch the invention has been directed.

Having now `described my invention, what I claim and desire to secure by Letters Patent is the following:

1. In a signalling system, a transmitting station, means for producin a carrier freuency for transmission an means for independently wobbling the said carrier fre uency of the said transmitter between pre- $0 etermined frequency values at a plurality of different predetermined rates corregon ing innumber to the independent sign trans- 2. In a multiplex communication system, a transmitting station, means for generating a carrier frequenc for transmission from said station, means or impressing a plurality of dierent signals upon said transmitter and modulating said transmitter thereby, and means forwobbling the carrier frequency of said transmitter at a plurality of dierent rates corresponding in number to the number of different signals impressed upon said transmitter. d

3. In a multiplex communication system having the transmitted carrier frequency wobbled at a plurality of different rates corresponding in number to the number of separate signal channels forming the multiplex system, a receiving system, an oscillator at said receiver of a frequency different from the carrier frequency transmitted, means for wobbling said receiver oscillator at a rate different from each wobble rate of the incoming carrier, and a plurality of receivers for receiving signals produced by the hetero- 'dyne action of: said receiver wobbled frequency and said incoming wobbled frequency ener. v 50 4. system for transmitting and receiving energy which includes a transmitting station, means for wobbling the carrier freuency of the said transmitter between preetermined frequency values at a predetermined rate, means for receivin the wobbled frequency energy transmitte from said transmitting system, an oscillator at the receiving station of a uency different from that of the said transmitting station, means for wobblingthe frequency of said receivin oscillator at said receiver by an amount equa to the wobble of the said transmitting station and at a rate dierent from that of said transmitting station, means for producing as beat notes of a frequency equal to the difference between the wobble rates of thesaid local oscillators of the said transmitter and the' receiver and means forutilizing the resultant amp 'fied energy of said beat notes.

5. A system for transmitting and receiving energy which includes a transmitting station, means for wobbling thecarrier freuency of the said transmitterbetween preetermined frequency values at a predetermined rate, means for receivin the wobbled frequency energy. transmit transmitting system, an oscillator at the reeeiving' station of a frequency removed from the transmitter carrier by a predetermined amount,V means for wobbling the frequency of said receiving oscillator at said receiver by an amount equal to the wobble of the said transmitting 'station and at a rate different from `he wobble rate of said transmitting station, and means for receiving the si rnals from said produced by the heterodyning action o said a two wobbled frequencies.`

6. In a multiplex communication system,

`the method of heterodyne transmission and reception of radio frequency energy which includes generating a carrier frequency at a transmitting station, wobbling the said carrier over a redetermined frequency band, controlling e rate of wobble of said trans mitter carrier at a plurality of predetermined and chosen rates, receiving the wobbled transmitted carrier, generating at the receiver a local frequency dilferent from that of the locally generated carrier of the transmitter, wobbling the locally generated frequency of the receiver over a frequency band equal to that of the wobble of the transmitted carrier, producing from the incoming and locally generated frequencies beat notes of a frequency empiial to the difference between the various wob le rates of the transmitterand receiver, amplifying the resultant beat notes,

and utilizing the said amplified beat notes for producing indications of a plurality "of transmitted signals. n l

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7. The method of heterodyne transmission and reception of radio frequency. energy ma multiplex communication system which in:

cludes generating a carrier frequency at a transmitting station, wobbling the said carrier over a redetermined frequency band, controlling e rate of wobble of said trans mitter carrier at a plurality of predetermined chosen rates, receiv` said wobbled transmitted carrier, generating at the receiver a local frequenc diiferentfrom that of the locally generate carrier of the transmitter, wobbling the locally generated fre quency of the receiver over a frequency band y equal in width to that of the wobble of the transmitted carrier, producing a heterodyne action at the receiver between the received and locally generated wobbled uency energy, and converting the hete yne beat notes into a plurality of different signals.

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8. The method of heterodyne transmission and reception of radio frequency energy which includes generating a carrier frequency at a transmitting station, wobbling the said carrier over a predetermined frequency band, controlling the rate of wobble of said transmitter carrier at a predetermined chosen rate, receiving said wobbled transmitted carrier, generating at the re 1 ceiver a, local frequency different from the generated carrier of the transmitter, wobbling the locally generated frequenc of the receiver over a frequency band equal 1n width to the wobble of the transmitted carrier, controlling! the rate of wobble of the locally generated frequency at the receiver at a rate different from that of the wobble rate of the transmitter. producing beat notes of a frequency equal to the difference between the wobble rates of the transmitter and receiver, amnlifyimgr the resultant beat notes, and utilizing the said amplified beat notes for producing indications of the transmitted signal energy.

9. In a multiplex communication system,

the method of transmission of radio frequency energy which includes generating a carrier frequency at a transmitting station, wobbling the said carrier over a predetermined frequency band.` controlling the rate of wobble of said transmitter carrier at a plurality of predetermined and chosen rates corresponding in number to the number of signals transmitted simultaneously.

3.5 RICHARD I-IOWLAND RN GER.

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