US2246184A - Single side band transmitter - Google Patents

Description

June 17, 1941'. H. o. PETERSON SINGLE SIDE BAND TRANSMITTER Filed oct.- 22, 1958 MQUSQW Patented June 17, 1941 UNi-TEDv "STAT SINGLE SIDE BAND TRANSMITTER Harold v0. Peterson,Y Riverhead, N. Y.,4assgnor to Radio Corporation of America, a corporation of Delaware Application october 22, 193s, serial No. 236,389 6 Claims. (ci. 17e-171.5)

In the past single side band systems have been l used to advantagaespecially in the transmission of telephony In order to produce "the single side band type of modulation it has beenv customary to use a modulator which inherently produces -two sets of side bands andthen filter olf onesetof side bands. This is more or less difficult because the two sets of side bands vare so close together in the frequency spectrum.- It is the object. of this invention-to make this process of signal side band signaling easier. This is accomplished by producing in a novel manner a carrier and side band widely separated in frequency from the Voltages used in producing the same and other produced components thereby eliminating or simplifying the means necessary for separating a carrier and one side band from the other side band. v

Inv describing my invention, reference will be made to the drawing, wherein? Figure 1 is a graphicrepresentation of the a ternating voltages, signal voltages, and so A'forth in my novel method of and means for producing single sideband modulation; v

Figure 2 is a schematic showing of a signalling system arranged in accordance with'my invention. 'Y

Referring now to Figure 1, at C'I have shown a voltage wave of carrier wave frequency, and at A a modulation frequency, both being in a frequency spectrum which starts 'at zeroffrequency.

The frequency of C may be any desired frequency above the highest modulating potential lfrequency. The two frequencies A and Cl are now assumed to be supplied to a current limiter with the amplitude of the voltage of lfrequency C greater than the amplitude of thev modulating potentials at frequency A. In the output `of the limiter an additional new frequency S will appear at a frequency which is equal to C plus the difference between frequencies C and A. Freforth. C-l-(C-A) is S in the graphic representation of Figure 1. The variations in amplitude of S, it is believed, are accompanied by opposite variations in a component not considered here,

in order thatthe total output remains constant. The lfphase relations of S andnCand 2C have been disregarded in the graphic representation of Figure 1 and' to some extent in the description Ithatfollows, because here we are 'primarily interested in the positions in the frequency spectrum of C, 2C, and S. f

This carrier 2C and single .side band S are readily selected from the other frequencies, because they are so farremoved from theother components of material amplitude. These frequencies as they stand, yprovided the carrier is of.. suflicient amplitude and properly related in phase to the sidebandS for the use to which it is put, may be used for transmission or may be impressed on additional vcarrier waves to produce outputs wherein new carriersand side bands are widely separated from other .output frequencies so that .theymay be readily selectedby economical filter systems.

In Figure2 I have :shown by block diagram a single side `band transmitter in which the prin-,- ciple. involved in this invention is utilized. .In Figure 2, l is a rmicrophone having itsoutput connected with the primary winding P of a transf former 3 and a source of potential ,2., The secondary winding S of 3 supplies modulating potentials to an amplifier 4, in turn connected with a current limiter 6. These elements. supply the voltagesrrepresented .by A in Figure 1. .Wave energy from a source 5 is also supplied to the limiter 6. This voltage is2represented by C in Figure 1,v and in practice is madeconsiderably stronger than the amplitude of the modulating potentials supplied to 6 from amplifier 4. In the output of 6 the components described above, C, S,

2C, 3C, and so forth, are present and the filter connected with the output of limiter 6 selects from said output the frequencies 2C and S. These frequencies may be used directly from Vthe output of 'l for signalling purposes, if desired.

If the carrier 2C is not of proper amplitude, a new carrier may be supplied, or 2C may be augmented. Voltages for this purpose are derived from source 5 by a phase adjuster l5, a voltage doubler I6, and an amplitude regulator Il', these voltages being supplied to the selective circuit I or the output thereof. The side band S and augmented carrier 2C may now be used for signalling purposes, if desired.

If the frequency of 2C is not as high as desired, an additional modulator 8 may be supplied by voltages S and 2C, and also by a new carrier from a generator or carrier wave source 9. The output of modulator 8 will include the the output of I on oscillations from a source I2;

In each of these modulator outputsthe carrier and side bands to be selected areA Widely sep- *combination of, a source of signal voltages, a

arated from other components Aandare readily'- `filtered out. The final output'may be amplified,

if necessary, in amplifier I3 and supplied to a radiation system I4 or a line 20.

What is claimed is:

aziaii greater than the highest signal frequency', a source of modulating voltages of lesser amplitude than said first voltages, a limiter coupled to both sources, a filter circuit, tuned to pass a band of frequencies including twice the frequency of the rst voltage minus the frequency of the second voltage, coupled to said limiter, and a frequency doubler 'coupling said r'st source to said filter circuit. 4

4. In a single side band signalling system, the

source Vofwplt-age of a, frequency greater than the frequency of the highest signal voltage, and of -greater'amplitude than the amplitude of the peak `signal voltagefa'limiter coupled to both of said sources, a 'l'ter'circuit tuned to pass a band of frequencies including twice the frequency of the 1. The method of producing a carrer'an'd si'de band. energy widely separated inthe'frequency spectrum from the. said A'carrier and othercom.- ponents of the combination which Aincludes the stepsIof,-. combining voltage. of carrier frequency Withr'ncdulating voltages,.said carrier frequency voltage being considerably greater in amplitude than the modulating voltages,.limiting theamplitude ofthe voltages as .combined to a consta'nt value, to .thereby produce a rst vcomponent havingetwicethe frequency of thecarrier. vol-tage Y j and a second component having a frequency equal ;to the. frequency. ,of the carrier voltage, plusthe carrier voltage minusthe modulating voltage,andof. an amplitude .which varies in accordance with variations the amplitude of the modulating voltages, `and .doubling the frequency ing twicethe frequency. of the-carrier voltage and a ysecond component havingza frequency equal to, the frequency. -of the carrier voltage, l .plus the carrier voltage minus the signal voltage.,fand of. an amplitude which varies in accordance with variations inthe amplitude of the signal voltages, ''I- augmenting the-amplitude of-.saidlrst component andi modulating anew, carrier in 4accordance with said augmented Afirst component and'said second component.

3. inra Singh. Side band signalling system, the

combinationof'a source of voltages of a frequency second voltage minus the frequency of the signal voltages 4coupled to said limiter, a utilization circuitfcoupl-ed Withsaid filter circuit, and means for impressing ori-said utilization circuit voltages of a frequency equal -to 'twicethe frequency ofthe Second .voltaee- 5. In asin-gie side -bandVsig-nalling system, the combination of, :a source/olf signallingvoltages, a source` of lvoltage of a frequency greater than the highestsignal frequency, and of greater amplitudegthan the amplitude of the signalling voltages, a limiter coupled to4 both of Isaid sources, a filter circuit tuned Yftrojpass, .a Aband of frequencies including 4twice the frequency Vof `the secondvoltage minus the frequency of the signalling voltages, -a modulator coupled withA said filter. circuit,

' a source ofoscillations Aof'carrier wave frequency coupled vto said modulator, and phase adusting means for 'impressingon said modulator voltages of a frequency equal to twice the frequency of the lsecond `voltage and of, a phase 'to laugment I the amplitudes of said voltages of twicelthe v4fref quency of said second voltage.l

. ,In a :single side bandsignalli-ng system the combination of, asonrce ofvoltagepf a frequency greater than the highest signal frequency, a

TVV1: sourceof tsignalvoltages of llesser amplitude than said first voltage, a current limiter coupled to both sources, a lter circuit tuned to pass a bandl of frequencies `including twice the frequency of the firstpvoltage minus ythe frequency of the Asignal Vlage'ua mlfdlllato 3f. `Smm@ .0f Glell. vfirequency wavescoupled With-,said modulator, means for `impressing .the output .ofysaidlter on said modulator and a .phase adjuster, 'a frequency doubler; andV mi 'amplitude regulator in casca-de coupling; saiidlfirst ysource of vol-tage -to :said modu later toiimpress thereon voltagescf :double the frequency 4lofthe voltages-of said irst source and of fai-phase vto fai'd the voltages of4 twice the-frequency-"of the vltag'esfof source'supi plied @by saifdfllterv '-to 'said modulator.

Y HA'RLDO. PETERSON.

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