US1988609A - Synchronizing system - Google Patents

Synchronizing system Download PDF

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Publication number
US1988609A
US1988609A US552179A US55217931A US1988609A US 1988609 A US1988609 A US 1988609A US 552179 A US552179 A US 552179A US 55217931 A US55217931 A US 55217931A US 1988609 A US1988609 A US 1988609A
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Prior art keywords
frequency
oscillator
circuit
wave
tube
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Expired - Lifetime
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US552179A
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English (en)
Inventor
Reeves Alec Harley
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AT&T Corp
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Western Electric Co Inc
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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
    • H03L7/00—Automatic control of frequency or phase; Synchronisation
    • H03L7/02—Automatic control of frequency or phase; Synchronisation using a frequency discriminator comprising a passive frequency-determining element

Definitions

  • An object of the invention is to provide an arrangement whereby a constant frequency difference may be maintained between two oscillators remote fromeach other.
  • Another object of the invention is to provide a variable reactance without mechanical control.
  • an arrangement in which the effective reactance of a network is varied in accord- .15 ance with the variation of an associated impedance, said impedance being located in said ,network or in another network coupled thereto.
  • the variable impedance may be the space discharge path of a vacuum tube, impedance variation being obtained by varying the biasing potential.
  • a predetermined relation between the frequencies of two or more oscillators may be obtained by controlling the conditions of oscillations of one or more oscillators, independently of the conditions of oscillation of one or more 01' the remaining oscillators.
  • a high frequency signaling system comprising two oscillators, one at a transmitting station and the other at a receiving station. A portion of the output from the transmitting oscillator is transmit ed to the receiving station where two tuned circuits with overlapping resonance curves act differentially on a variable impedance. When the currents in the tuned circuits are not equal, variations in the impedance modify the tuning of the receiving oscillator,.thus keeping the frequency of the two oscillators difierent from each other by a substantially constant amount.
  • Fig. 1 shows a circuit arrangement in which an inductance is adapted to vary depending on the variations of a resistance
  • Fig. 2 shows an arrangement of the invention in which an inductance is-adapted to vary as a function of the variations of the biasing potential applied to the grid or. control element of a three element vacuum tube;
  • Fig. 3 shows a slight variation of Fig. 2
  • Fig. 4 shows an improved frequency multiplier device of the invention involving the principle illustrated by Fig. 3;
  • Fig. 5 shows a frequency divider device of the invention based on the same principle as the 5 multiplier of Fig. 4;
  • Fig. 6 shows an arrangement for synchronizing a local oscillator to the average frequency of a ource whose frequency is varying;
  • Fig. 7 shows a resonance curve
  • Fig. 8 illustrates the application ofan automatic gain control arrangement
  • Fig. 9 illustrates an alternative way of using a receiver embodying features of the invention.
  • Fig. 10 illustrates a circuit which is effectively a combination of the circuits of Figs. 6 and 8, that is, an adaptation of the circuit of Fig. 6 to include the automatic gain control arrangement of Fig. 8.
  • Fig. 1 discloses a network comprising inductances L1 and L2 and a resistance R1 in series and having terminals A and B.
  • Shunting inductance L2 is a resistance R: whose variation will modify the inductance between the termi-' nals A and B. This will appear from the consideration of the total impedance of the circuit which is given by the following equation:
  • resistance R changes the total effective reactance of the circuit. If the resistance R: be replaced by a three-electrode 35 vacuum tube T as shown in Fig. 2 and if the platev impedance of this tube be varied by changing the grid bias, for example, the effective in'ductance of the whole circuit from A to B would be changed and therefore if a condenser C is provided in parallel between A and B as shown in Fig. 2 the resonance frequency of the circuit thus formed will be changed in accordance with variation of the biasing potential of the vacuum tube. It should be noted that the above method of controlling reactance by means of a vacuum tube is not limited to its use in conjunction with resonant or anti-resonant circuits, but the application to resonant circuits is merely given for illustrative purposes.
  • FIG. 3 A modification of the arrangement of Fig. 2 is shown in Fig. 3.
  • the inductance L2 instead of being in series with the main inductance is coupled to it to a degree less than and the frequency of the wave total eifective inductance will also vary.
  • the resistance component of the total impedance will also be changed to some extent, but in the practical application of this device, this resistance variation is unimportant in its effect.
  • the coupling between the two coils may be performed by means of either an air core or of a core of magnetic material.
  • Fig. 4 shows an application of a non-mechanical reactance control in a frequency multiplier system
  • S represents a standard of low frequency such'as a tuning-fork, or a magnetostriction, oscillator. Supposing that it is desired to obtain in the output of the frequency multiplier a frequency corresponding to a high harmonic of the standard frequency, for instance, the harmonic corresponding to the low frequency when multiplied by 8192.
  • an oscillator 1 of any well known type, is adjusted to a frequency within two or three per cent of the desired harmonic and its output frequency is divided by 8192 by means of an aperiodic frequency divider diagrammatically indicated by F which may be, for example, like the one disclosed in British Patent No. 296,827, both the frequency divider output and the output of the standard low frequency source being connected to the grid of a rectifier tube 2.
  • the voltage drop across the plate resistance R of rectifier 2 is used as the grid bias of the low impedance control tube 3 which has a plate coil D coupled to the oscillatory circuit of oscillator 1.
  • the operation of the frequency multiplier system will now be apparent.
  • the voltage drop across resistance R will vary from a small to a high value, at the beat frequency between the outputs of divider F and standard oscillator S. Let us consider a fewcycles of the wave from oscillator S during which the output wave of divider F lags behind that of oscillator S. If the frequency of the wave from oscillator 1, for any reason, becomes slightly greater thanthe required harmonic of the wave from oscillator S, then the two low frequency voltages on the grid of tube 2 will have a smaller phase difference than before, which will cause the voltage drop across R to increase.
  • control tube 3 The resulting increase in the plate resistance of control tube 3 will cause the coil D to have less shunting eifect than before on the inductance with which it is coupled so as to effectively increase such inductance and cause the frequency of oscillator 1 to be lowered, i. e., the two low frequency outputs will tend to become 90 apart as before.
  • a frequency divider of the invention adapted to be used in measuring a relatively high frequency.
  • the device operates on the same principle as the multiplier of Fig. 4 although in a reverse manner.
  • the frequency to be measured is applied to the grid of the screened grid tube E.
  • This tube amplifies the unknown frequency and at the same time prevents back coupling on to the source of this frequency.
  • Oscillator l and control tube 3 are of the same design as the similarly identified element in Fig. 4.
  • the oscillator output is however now appliedto the harmonic generator M.
  • the wave from oscillator '1 is in the region of 1 megacycle, that is, the limit of the working frequency of the aperiodic divider.
  • the circuits of M and 1 are adjusted so that a particular harmonic, for example the twentieth, is at a frequency within 2 or 3% of the frequency to be measured.
  • the output of devices M and of E are applied together to the rectifier tube 2 which is of the' same design as the similarly identified tube in Fig. 4 and performs a similar function.
  • the action of the device is to synchronize automatically the frequency of the wave from oscillator 1 (which is of the order to be measured by the aperiodic frequency divider) so that a particular known harmonic of that frequency has exactly the same frequency as that to be measured, in other words,
  • a method which may conveniently be used in a short wave single side band receiver is to transmit a small amount of ordinary carrier frequency as well as an inverted single side band.
  • the speech side band is displaced upwards by 1000 cycles as well as being inverted, the resulting beat frequencies at the receiver give ordinary straight speech, in other words the present single side. band receiver acts as a receiving it performs its normalfunctions.
  • the screened grid amplifier tube 4 (Fig. 6) has the control grid connected to the source of frequency which is to be used as a synchronizing signal (i. e. the partially suppressed carrier of the distant station, stepped down to intermediate frequency).
  • the circuit is arranged so that if, for any reason, the beat note between the local oscillator and the synchronizing signal departs from the desired value the resulting inequality in outputs of H and K gives a voltage difference between 9 and 10 in such a direction as to cause the resulting change in impedance of L to change the frequency of 5 torestore the original beat frequency.
  • the high value resistances N and P and condenser Q are added to give the required time constant to the frequency changing device.
  • This time constant is adjusted to such a value that "when the synchronizing signal disappears for its maximum length of time the local oscillator B can never drift more than the allowable number of cycles from its desired frequency.
  • the output at the frequency required is then taken at point- Fig. 8 illustrates an arrangement somewhat analogous to that of Fig. 6 but provided with au- The frequency ofthe wave from oscillator 5 is adjusted.
  • the signals (waves from distant transmitter and local oscillator) are applied on the input of rectifier 6 as in Fig. 6, and we will consider below what happens when the signals change in amplitude as may occur under fading conditions.
  • a change of amplitude will change the output of the rectifier tube 6 which after amplification in the amplifier LFP is applied through a transformerTRtoihegrids of a balanced detector,
  • Fig. 9 is a block schematic diagram of the receiving equipment of a high frequency signaling system embodying features of the present invention.
  • This system is a high frequency signaling system of the single side band partly suppressed carrier type.
  • FIG 14 is a device on which is applied odyne receiver which may, for instance, be with-' in the range of 500 to 503 kilocycles for one received speech side band.
  • the output of '14 is applied to a frequency changer FG, the output of which (within the range 20 to 23 kilocycles) is applied to a repeater 15 followed by a filter 16 of pass range equal to 20 to 23 kilocycles.
  • the output of the filter 16 is applied to a balanced demodulator BDM associated with a local carrier oscillator COSC adapted to give a frequency of 20 kilocycles.
  • the original signals, for instance, speech are restored in the terminal output equipment S0.
  • a synchronized oscillator SOSC of say 520 kilocycles is associated. with the frequency changer FG and with a gain control and rectifying device GR similar to device of Fig. 8 which is associated with an oscillator 080 of 16 kilocycles and with a repeater 17 whose output passes through low frequency tuned circuits LF andthence to a balanced detector BD.
  • the balanced detector BD and the gain control device GR are associated through a gain control lead 18.
  • the output of the balanced detector ED is applied to a reactance control device RCC which adjusts the synchronized oscillator 3080, through a synchronizing lead 19.
  • the grid bias of the rectifier giving the beat note is obtained from the average voltage drop in two resist-ances associated with .a balanced detector.
  • the above mentioned grid bias depends only on the amplitude of the received signals and not on its frequency. The increased bias lowers the gain of the detector when the signal amplitude increases so that the resulting beat frequency voltage is substantially constant within wide limits of signal voltage.
  • the synchronized oscillator has its frequency shifted about 20 kilocycles away from the frequency of the incoming, partly suppressed, carrier frequency and acts as a beating oscillator; the resulting side band (on the 20 kilocycle range) is then put through a filter having sharp cut off on each side of the received side band.
  • An ordinary stable oscillator at the required frequency (about 20 kilocycles) is then used to re-supply the carrier frequency into a balanced demodulator.
  • Fig. 10 illustrates what amounts, effectively, to a combination of the features illustrated in Figs. 6 and 8.
  • the lettering is the same as that which has been used in said Figs. 6 and 8, these indicating the functions of the respective elements in such a way as, with the like physical arrangement of elements in the figure, to obviate the necessity of explaining the figure in detail.
  • Fig. 10 is a reproduction of Fig. 8 to include the circuit and structure anterior to the 76 combining device 6, this inclusion therefore cov ering tubes 4 and 5 and their immediately associated circuits.
  • the output circuit of tubeL of Fig. 8 has been connected to the oscillator 5 of Fig. 6, which it controls, this connection being shown exactly as in Fig. 6.
  • Fig. 10 differs from the circuit of Fig. 6 substantially only in the addition of the gain control feature of Fig. 8, Fig. 10 therefore disclosing both the gain control feature of Fig. 8
  • the present invention may be embodied'in widely different structures and is particularly useful in high frequency communication systems particularly in those of the carrier suppressed or partly suppressed types.
  • filter circuits may be employed having overlapping attenuation curves.
  • a greater degree of control of the fre quency range over which synchronizing occurs is possible. For instance,.by employing low pass filters of which the attenuation curves slope in opposite directions, synchronizing will occur over the width of the frequency band included within the two slopes, and in general, this band can be made wider than that included within the two resonance peaks shown in Fig. 7.
  • a high frequency signaling system comprising a controlling wave source and a controlled oscillator, a resonant frequency determining circuit in said controlled oscillator, means for combining the outputs of said wave source and oscillator to obtain a beat frequency, two circuits having overlapping resonance curves each in energy flow relation with said combining means,
  • means comprising a variable shunt circuit whereby the differential current from said two circuits act differentially upon a variable tuning impedance in the frequency determining circuit of the controlled oscillator in such a manner that the frequency of the wave from said controlled oscillator when varied relatively to that of the wave from said controlling wave source is modified to compensatorily restore the initial frequency relation between currents from said wave source and oscillator, and means comprising a series resistance and a shunt condenser in the input path of said variable shunt circuit whereby the tuning of the controlled oscillator varies as a function of the average frequency of the wave from the controlling wave source over a given interval of time.
  • a high frequency signaling system comprising a controlling wave source and a controlled oscillator, a resonant frequency determining circuit in said controlled oscillator, means for combining the outputs of said wave source and oscillator to obtain a beat frequency, two circuits having overlapping resonance curves each in energy flow relation with said combining means,
  • a high frequency signaling system comprising a controlling wave source and a controlled oscillator, a resonant frequency determining circuit in said controlled oscillator, means for combining the output of said wave source and oscillator to obtain abeat frequency, two circuits having overlapping resonance curves each in energy flow relation with said combining means, meanswhereby the differential currents in said two circuits act differentially upon a variable impedance in the frequency determining circuit of the controlled oscillator in such a manner that the frequency of the wave from said controlled oscillator when varied relatively to that of the wave from said controlling wave source is modilied to compensatorily restore the initial frequency relation between currents from said wave source and oscillator and a gain control means directly associated with said last mentioned means tor rendering the frequency control function of the system substantially immune from the eflects of amplitude variations of the waves received from the controlling oscillator.

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  • Noise Elimination (AREA)
  • Channel Selection Circuits, Automatic Tuning Circuits (AREA)
  • Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
US552179A 1930-08-01 1931-07-21 Synchronizing system Expired - Lifetime US1988609A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB23216/30A GB360891A (en) 1930-08-01 1930-08-01 Electrical frequency control systems

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US1988609A true US1988609A (en) 1935-01-22

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US (1) US1988609A (it)
DE (1) DE603793C (it)
FR (1) FR722059A (it)
GB (1) GB360891A (it)
NL (1) NL35814C (it)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2425657A (en) * 1941-04-17 1947-08-12 Rca Corp Short-wave apparatus
US2436946A (en) * 1941-04-10 1948-03-02 Virgil A Hamilton Capacity-type phonograph pickup
US2438425A (en) * 1942-11-26 1948-03-23 Rca Corp Computing device
US2513428A (en) * 1947-10-20 1950-07-04 Philco Corp Superregenerator

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102707106B (zh) * 2012-05-18 2014-08-20 宁波伟吉电力科技有限公司 电力次谐波数字信号源

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2436946A (en) * 1941-04-10 1948-03-02 Virgil A Hamilton Capacity-type phonograph pickup
US2425657A (en) * 1941-04-17 1947-08-12 Rca Corp Short-wave apparatus
US2438425A (en) * 1942-11-26 1948-03-23 Rca Corp Computing device
US2513428A (en) * 1947-10-20 1950-07-04 Philco Corp Superregenerator

Also Published As

Publication number Publication date
GB360891A (en) 1931-11-02
FR722059A (fr) 1932-03-11
DE603793C (de) 1934-10-11
NL35814C (it)

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