US1604140A - Multifrequency oscillator - Google Patents

Description

. H. A. AFFEL MULTIFREQUENCY OSCILLATOR Filed Sept. 19. 1924 A TTORNE Y Patented oei. ze, 192e.

lUNITE!) SiATiFiS HERMAN A. AFFEL, I' MAFLEWOOD,'NEV JERSEY, ASSIGNOR TO AIVEBIICAI TELE- PHONE'ANDTELEGRAPH COMPANY, A CORPORATION OF NEW' YORK;

MULTIFREQUENCY OSCILLATR.

Applic'atonfiled September 19, 1924. Serial No. 738,698.

'This invention relates to oscillation generators, and more particularly to an oscillation generator capable of producing a plurality, of frequencies. V

While multi-frequency generators l have 'been produced heretofore, such generators h'ave, for the most part, been of the type in 'which lthev various frequencies generated are related toeach otheras harmonics of a comnl n'ionfundam'ental. It is an object of the 'present invention toproduce a multi-frequencygenerator in which the various frequencies produced 'may be related in anonharmonic' manner and yet may be definitely iscont'rolled by a principal frequency. Another object of the invention is to produce 4an oscillatingA circuit including a complete oscillating path in which the frequency changes 'from point to' point in the path a lplurality lof times. Another object of the invention is to produce an oscillating circuit in which a high degree of stability is attained. 'Still another object of the invention is to producean oscillating circuit in which, ,y y

' less than the Vdifference :between the frequencies f f1 and f2, and "consequently, `the cuni yby theadjustment of a single timing element, a plurality 'of diderent frequencies may all be simultaneously changed.

These objects and other objects of the in- 4`fvention are attained by the"arrangenients disclosed, which are fullyA set forth in the following description and illustratedin the accompanying draw'ing,"li`igures l and 2 of Vwhich are circuit :diagrams showingmtwo modifications Voff/the inyenticn. l

Referring to Fig. l,"Mand`M designate, respectively, f the'balanced type having their input circuits connected' to frequency sources f1 and f2,"re'spective`ly. Y Owing to the balanced connections of the modulators, the'fr'equen'cies .pfff and f2 appliedtd the two modulators will be suppressed in the output circuit'an'dwill net betransmitted. 'The output `circuit of 'the modulator M- is connectedv tothe input circuit of the" modulator throughtwo parallel branches, oneincluding the tuned selective circuit S1 and the `other including a A*lowfpass filterSa. The output `('zircuit of the modulator M is connected with the input filter S2`liayin'g its cut-off point' so located as to pass the frequencies flj and f2.

The circuit arrangement above described constitutes a generator of oscillations and at Adifferent points inthe' circuit four di iferent two vacuum tube modulators circuit of the modulator l/ through a band lgenerated frequencies may be taltenf dif.

For this purpose, ahigh pass 'filter Sli'and a low pass lter S3 are connectedito they output circuit of the modulator M, anda high pass filter S2 anda low pass filter Sjareconnected to the outputl circuit4 of themodulator vtuned circuit, these yoscillations will beimto the unmodulatedV carrier f1.

pressed upo'n the 'modulator-lifts beat with t the carrier frequency f1, thereby producing sum and difference frequencies )f1-Ht and /L'l-a, as well as a frequency `corresponding The frequency f1 is suppressed by reason of the bal ance of the modulator circuit and the diff-@v ence frequency fl-a is 'suppl-@Seed by; 'the band filter S2 as this frequency falls below its lower cut-.off point. The frequency ct is frequency f l-l-c vpasses through the baud filter S2 and is rimpressed upon the modulator fM".l VThe frequency /f'l-l-ct 'beats-with the frequency f2 to produce sum and difference frequencies. lf b bextakeii as the difference betweent f1 and f2, the e'lipression ffl-o may be substituted for the'frequency f2. `The the difference frequencywill be b-a. l'The uninodulated component corresponding to frequency f2 is suppressed bythe: balanced circuit of the modulator. `Y The low pass vlillter S3 in the output circuit has its cut-off point below the frequency a, and if the fijequencies f1 and y, are Vso chosen that?) is greater' than a and Zi-q is less than ci, lthe difference frequency bi-ct produced'by the modulator M in its outpi'it'circuit will be lwith'the carrierlfreque'ncy f1, a sum 1frequency .fl-{#{bla} and a ldifference "frequency f1-(b-a) are produced. The difference frequency falls below the lower cutoff point of the band filter S2 but the sum frequency fl-i-(-a) falls between the cutoff points f1 and f2 of said filter, so that the sum frequency only is transmitted. The sum frequency in turn is impressed upon the modulator. M, thereby beating with the frequency f2 to produce a sum frequency 2f1+2ba and a difference frequency a. The sum frequency is suppressed as it falls above the upper cut-off point of the filter S3 and is too high to be passed to the tuned circuit S1. The difference frequency a, however, passes through the tuned circuit S1 and starts the cycle of operations above described anew. u It will be seen that in the complete oscillating circuit the frequency is changed four times and that the four frequencies thus produced need not bear a harmonic relation to each other. The primary frequency ct is independent of the frequencies f, and f2 supplied to the modulators and is determined only by the tuning of the selective circuit S1. Consequently, the frequencies f, and 'f2 may vary within limits from time to time without producing any change in the primary frequency a. The otherv three frequencies generated, namely, ffl-a, b-e and fl-l-(b-e) are all functions of the primary frequency a but need not be harmonics thereof. In the assumed case, the generated frequency b-a is less than a and the other two generated frequencies are greater. It will also be noted that the energy must be transmitted twice over the same path in order to complete one cycle of the action. The various frequencies transmitted during the different operations of the cycle are indicated by the schematic diagram shown in Fig. 1 in the interior of the main circuit layout.

Another characteristic of the arrangement disclosed is that all four of the frequencies generated may be changed (within limits) by merely adjusting the tuned circuit S1. Y

This follows from the fact that the frequencies f1+a, -a and fl-i-(b-a) are all functions of the primary frequency a, and since the frequency a is independent of the frequencies f, and f2 and is determined only by the tuning of the selective circuit S1, it follows at once that all Afour of the frequencies generated will depend upon the tuning of the circuit S1.

The four frequencies generated may be readily taken off from the oscillating system by means of combinations of high pass and low pass filters as indicated in the diagram. Since only the frequencies a and b-(r appear in the output circuit of the modulator M, these two frequencies may be taken off through high pass filter S1', and low pass filter Sa', respectively, thesefilters being connected in branches leading from the output circuit of the modulator M. The lower cutoff point of the high pass filter and 'the upper cut-off point of the low pass filter should be brought as close to each other as is consstent with selectivity and the two frequencies representing these cut-off points should be intermediate between the normal values of frequencies a and b-a, so as to allow for any change in the frequencies due to adjustments of the tuned circuit S,. Y The vfrequencies fl-l-q and ffl-(bwa) appear only in the output circuit of the modulator M and can be taken off through the high pass filter S2 and low pass filter S4, respectively, these kfilters being connected in branches associated with the output circuit of the modulator M. Here again the lower cut-off frequency of the filter S2 and the upper cut-off frequency of the filter S4 should be as close together as is consistent with the proper selectivity and t" the two cut-off frequencies should also be located intermediate between the normal values of fla-a and ffl-(bua) to permit of a desired amount of change in the frequencies by changing` the tuning of the circuit S1.

A modified arrangement is shown in Fig. 2, in which a tuned circuit selective of the frequency b-q is substituted for the low pass filter Also, instead of the band lilter S2 of Fig. l, a pair of branches including tuned circuits S2 and S4, selective of frequencies fl-l-q and f1-{-(-a), respectively, are used.

The operation will be similar to that described in connection with Fig. l but it will be noted that in this arrangement, if .the selective circuits S2, S3 and S4 are sharply tuned, the generator will tend to be more stable. This follows from the fact that each one of the four frequencies generated depends upon the setting of four dilere'nt tuned circuits selective of four different frequencies. For example, the primary frequency a depends not only upon the setting of the selective circuit Sl but upon the setting of the other three selective circuits S2, S3 and S4 as well. Similarly, the other three frequencies likewise mutually depend upon all four tuned circuits.

It will be obvious that the general principles hereindisclosed may be embodied in many other organizations widely dierent from those illustrated without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

l. In a multi-frequency oscillation generator, a closed path in which the oscillations flow, means to determine a primary frequency in said path, and means to produce a plurality of changes in frequency as the energy flows over said path, the frequencies resulting from such frequency changes not being related to the primary frequency as harmonics thereof.

ino

2. In a multi-frequency generator, a closed path through which the vgenerated frequencies iow, means in said path to determine a primary frequency, and means in said path to produce successive changes in the fre quency, the final change being a change to the primary frequency, and a complete cycle of changes involving a transmission of energy more than once about said path.

3. In a multi-frequency generator, a closed path over which the frequencies generated flow, means in said path to determine a primary frequency, means in said path to step upl the frequency, and means in said path to step down the frequency, the successive frequency changes thus produced beingso related that the energy Will flow a plurality of times about said path in order to complete a cycle.

4. In a multi-frequency generator, a closed path over which the frequencies generated flow, means in said path to determine a primary frequency, means in said path to combine said primary frequency With an auxiliary frequency to produce a sum frequency, and means in said path to combine said sum frequency with another auxiliary frequency to produce a difference frequency, whereby a plurality of said frequency changes occur as the energy traverses said path.

5. In a multi-frequency generator, a closed path over which the frequencies generated flow, means in said path to determine a primary frequency, means in said path to combine said primary frequency With an auxiliary frequency to -produce a sum frequency, and means in said path to combine said sum frequency With another auxiliary frequency to produce a dierence frequency, whereby a plurality of said frequency changes occur as the energy traverses said path, the last frequency change being a change to the primary frequency, said auxiliary frequencies being so related to each other that the energy will flow over said path a plurality of times in order to complete a cycle.

6. In ya multi-frequency oscillator, a closed path over which the oscillations generated flow. a pair of frequency changing and translating devices in said path, a plurality of selective branches in each portion of the path connecting the output of one translating device to the input of the successive translating device, one of the selective devices in one of the branches of one of said portions of said path determining one of the frequencies generated independently of the selective devices in other branches.

7. In a multi-frequency oscillator, a closed path over Which the oscillations generated flow, a pair of frequency changing and translating devices in said path, a plurality of selective branches in each portion of the path connecting the output of one translating device to the input of the successive translating device, one of the selective devices in one of the branches of one of said portions of said path determining one of the frequencies generated independently of the selective devices in other branches, said selective device determining all the other frequencies circulating in said path.

In testimony whereof, I have signed my name to this specification this 18th day of September, 1924.

HERMAN A. AFFEL.

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