US2165517A - Oscillation generator - Google Patents

Oscillation generator Download PDF

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Publication number
US2165517A
US2165517A US216212A US21621238A US2165517A US 2165517 A US2165517 A US 2165517A US 216212 A US216212 A US 216212A US 21621238 A US21621238 A US 21621238A US 2165517 A US2165517 A US 2165517A
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United States
Prior art keywords
frequency
phase shift
network
networks
reactance
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Expired - Lifetime
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US216212A
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English (en)
Inventor
George H Stevenson
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AT&T Corp
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Bell Telephone Laboratories Inc
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Publication date
Priority to NL62295D priority Critical patent/NL62295C/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US216212A priority patent/US2165517A/en
Priority to GB15707/39A priority patent/GB529291A/en
Priority to FR856963D priority patent/FR856963A/fr
Application granted granted Critical
Publication of US2165517A publication Critical patent/US2165517A/en
Priority to ES177007A priority patent/ES177007A1/es
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/30—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator
    • H03B5/32—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator being a piezoelectric resonator
    • H03B5/34—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element being electromechanical resonator being a piezoelectric resonator active element in amplifier being vacuum tube

Definitions

  • This invention relates to vacuum tube oscilla- 'ent of the internal resistances of the vacuum tubes tion generators and more particularly to the staand the resulting oscillations are therefore stable bilization of the oscillation frequency of such in frequency. generators against variation with changing ex- In the preferred forms of the invention one citation voltages.
  • Objects of the invention are of the phase shifting networks is made to have to improve the frequency stability of vacuum tube a very rapid frequency variation of the phase shift feedback oscillators; to diminish the effect of at the 90-degree point and the other networks are the internal capacities of the vacuum tubes upon designed to provide slowly varying phase shifts.
  • the rapid phase shift charcathode temperature in many types of vacuum acteristic is preferably obtained by the use of a tube oscillators are known to have their origin piezoelectric quartz crystal as one of the react- 15 in the resulting variation of the internal resistances of the network, as described in detail hereances of the vacuum tube. In order that these inafter.
  • the vacuum tubes each produce fixed invention is shown schematically in Fig. 1.
  • the several by R1 and R2, respectively, the source having a phase shifting networks are each designed to voltage E1.
  • the coupling network consists of a produce stable phase shifts of 90 degrees at the 1r section, each branch of which includes only assigned oscillation frequency and are combined pure reactance elements.
  • the configurations of 50 in such manner as to provide a total phase shift the branches are not illustrated and, for the of'zero in the closed loop circuit, thereby estabpresent, may be left undetermined, but it is aslishing a necessary condition for self-oscillation. sumed that they are such as to permit the im Because of the character of the coupling netpedances of the shunt branches to take the same works, the zero phase shift condition is independvalue, 7'X, at an assigned frequency and for the 55 series branch impedance to take the value +7'X at the same frequency.
  • the output voltage E2 across resistance R2 has the value given by the equation E R1R2+X
  • the two voltages are in quadrature and the quadrature phase relationship is obviously independent of the values of R1 and R2.
  • the output voltage lags 90 degrees behind the input voltage. Reversing the signs of all three reactances reverses the phase of the output voltage causing it to lead the input voltage by 90 degrees.
  • Figs. 2 and 3 Simple forms of phase shifting networks are shown in Figs. 2 and 3, the former having a positive series reactance provided by an inductance and the latter a negative series reactance provided by a capacity.
  • the two shunt branches in each network are alike and, therefore, have equal reactances at all frequencies.
  • the network of Fig. 2 produces a lagging output voltage and that of Fig. 3 produces a leading output voltage.
  • the quadrature relationship is produced in each case at the frequency of the resonance of the series branch with a single one of the shunt branches.
  • the networks should, preferably, be of such character that a quadrature phase shift in either direction is produced at not more than one frequency.
  • Figs. 4 An example of such modification is shown in Fig. 4 wherein the series branch comprises a series resonant circuit L1C1 shunted by a capacity Co and the shunt branches comprise similar antiresonant circuits L2C2.
  • the series branch is proportioned to have a positive or inductive reactance in the neighborhood of the assigned frequency and the shunt branches are proportioned to have negative reactances at this frequency.
  • the frequency variations of the two reactances are shown by the curves of Fig.
  • the series branch exhibits a resonance at a frequency f2 and an anti-resonance at a higher frequency is and has a positive reactance in the intervening range.
  • the shunt branch reactance is negative or capacitive above the anti-resonance frequency f1 which preferably lies well below the resonance of the series branch.
  • the frequency for a lagging phase shift of 90 degrees must necessarily lie in the interval between f2 and f3 and is determined by the equality of X1 and X2, as indicated at 7% in the figure.
  • the particular value of this frequency may be varied by adjustment of the shunt capacities C2 or of the series capacity Co.
  • a second frequency of phase quadrature exists below the anti-resonance frequency of the shunt branches, but in this case the phase shift is in the opposite direction,
  • one of the shunt inductances in Fig. 3 may be replaced by a three-element combination like the series branch of Fig. 4.
  • the three-element combination L1C1Co in Fig. 4 will be recognized as corresponding in configuration to the equivalent impedance network of a piezoelectric quartz crystal. Accordingly, a piezoelectric crystal may be used in this position.
  • the effect of substituting the crystal is to make the frequency range in which the branch has an inductive reactance extremely small and to provide an extremely rapid variation of the phase shift with frequency in this range.
  • the impedance measured at the input terminals of the phase shifting network is purely resistive at the frequency of phase quadrature and has the value X +R2.
  • a second network not necessarily similar but having a quadrature phase shift at the same frequency, may therefore be inserted ahead of the network shown without either affecting the phase shift of the other at the common frequency of phase quadrature.
  • the two networks may produce phase shifts in opposite senses if desired.
  • the oscillator circuit shown in Fig. 6 comprises two vacuum tubes IB and II coupled in tandem by reactance networks l2 and I3 to form a closed feedback loop.
  • Network I3 which is the principal frequency determining unit is of the general type shown in Fig. 4', the series branch being constituted by a quartz piezoelectric crystal CX and the two shunt branches by similar parallel combinations of inductances L2 and capacities C2.
  • the shunt branches of network [3 are proportioned to be anti-resonant at a frequency well below the crystal resonance.
  • Network !2 coupling the input of tube II to the output of tube In is generally similar to that shown in Fig.
  • Tubes l0 and H are preferably of screen grid types to avoid any. effects from internal feedback.
  • a common source l4 provides plate and screen current for both tubes and a separate source l5 provides a negative bias for the grid of tube II.
  • the remaining elements of the circuit comprise blocking and by-pass condensers which should be large enough to have negligibly small impedances at the operating frequency.
  • the shunt inductances in the two networks serve to provide conductive paths for the grid and plate currents of the tubes.
  • each of the two vacuum tubes produces a fixed phase shift of 180 degrees, together they contribute zero total phase shift in the closed loop.
  • Thenetwork l3 produces a lagging phase shift of 90 degrees at a frequency for which the crystal CX has a positive reactance equal in magnitude to the negative reactance of either of the twoequal shunt branches. At this frequency, the phase shift is independent of the values of the terminal resistances constituted by the plate circuit of tube H and the grid circuit of tube H).
  • the network 5?. must produce a leading phase shift of 90 degrees.
  • each shunt branch has an inductive reactance equal to the reactance of the series branch capacity at the oscillation frequency.
  • the anti-resonance frequencies of the shunt branches must be higher than the oscillation frequency, but preferably should be lower than the second harmonic of this frequency.
  • the circuit of Fig. 6 can oscillate only at the frequency determined by the quadrature phase shifts of the two networks and, since the phase quadrature in each case is independent of the tube resistances, the oscillation frequency is stable.
  • Each network is provided with shunt capacities at both ends in which the grid and plate capacities of the tubes may be included. The stability is, therefore, unaffected by the presence of the tube capacities. Furthermore, the effect of the shunt capacities is to diminish the impedance presented to the tubes by the networks at harmonics of the oscillation frequency and thereby to reduce harmful modulation effects.
  • the impedance of the crystal CX imparts to the phase shift characteristic of network l3 a very rapid frequency variation at the oscillation frequency which has the effect of increasing the stability of the system.
  • Network 12 is characterized by a slow variation of the phase shift in the neighborhood of the oscillation frequency. This has the advantage of making the adjustment of the system non-critical.
  • the principal frequency determining network I3 is modified to permit the use of a shunt connected crystal and the compensating network I2 is suitably mod fied to take account of the change.
  • a high resistance i6 is provided to act as a grid leak path for tube iii.
  • the network i3 is basically similar to the type shown in Fig. 3. At the operating frequency the crystal CX has an inductive or positive reactance equal to the negative reactance of the series branch capacity C4 and the other shunt branch L202 is proportioned to have the same inductive reactance as the crystal at this frequency.
  • the network produces a leading quadrature phase shift and the compensating network [2 must, therefore, produce a lagging quadrature phase shift in order. that oscillation may take place.
  • the shunt inductances in network l2 are made large enough to be anti-resonant with the shunt capacities at a frequency well below the oscillation frequency and the series capacity C is likewise made large enough to have a negligible impedance.
  • the tubes are then in effect coupled solely through the shunt capacities which, in combination with the high internal resistance of screen grid tube ii], produce a substantially con stant lagging phase shift of degrees. It is desirable that the shunt coils have low dissipation and that the grid of tube II have a sufiiciently great negative bias to prevent any grid current being drawn.
  • the shunt capacities C3 should be fairly large and, while this may result in a considerable attenuation of the voltage. the gain of the two tubes is usually sufficient to ensure adequate feedback. Modifications of this type of shunt reactance coupling are obvious.
  • the required ISO-degree phase shift is produced by means of two quadrature phase-shift networks connected in tandem, each proportioned to provide a phaseshift of 90 degrees in the same direction at the oscillation frequency. It has already been pointed out that two or more of the quadrature phase shift networks maybe connected in tandem, provided that all produce the quadrature phase shift at the same frequency.
  • Network i3 which includes the piezoelectric crystal CX, is the principal frequency controlling network. Both this network and the compensating network l2 are of the general type represented by Fig. 2.
  • the function of the compensating network in this case is to supplement the phase shift of network I3 so that together they compensate the 180-degree phase shft of the vacuum tube at the oscillation frequency. Plate current is supplied to the tube through a shunt inductance II. This inductance may be made large enough so that its admittance is negligible or its effect may be compensated for by an appropriate adjustment of the adjacent shunt condenser in network [2.
  • a single tube having a negative amplification constant may be used.
  • a stabilized oscillator circuit employing such a tube is shown in Fig. 9.
  • the tube I8 includes, in addition to the usual anode, an auxiliary or space charge anode 20 located between the control grid and the cathode.
  • the output circuit is connected between the auxiliary anode and the cathode. The action of a positive voltage superimposed on the bias voltage of the control grid is to rob the auxiliary anode of some of the electrons that would otherwise go to it and thereby to diminish the auxiliary anode current.
  • Plate batteries l4 and I9 and grid bias battery 15 may be adjusted to give suitable voltages for the realization of the effect in substantial degree.
  • an unbiased diode 2! may be connected across the tube input as shown. This serves to provide the amplitude limiting action on the oscillation currents which is usually produced by the current flow in the amplifier grid path.
  • the external network comprises two quadrature phase-shift networks l2 and 63, which produce phase shifts in opposite directions, respectively.
  • Network I2 is of the type shown in Fig. 3 and the principal frequency controlling network 13 is of the type shown in' Fig. 2, modified to substitute a piezoelectric crystal OX for the series inductance.
  • the feedback network may be further proportioned so that not only does each component network produce a stable phase shift of 90 degrees, but also that all of the branches of the two networks have reactances of the same magnitude at the oscillation frequency. In that case, the central impedance combination L02 becomes infinite at the oscillation frequency and these elements may therefore be omitted without affecting the operation of the system.
  • the feedback network 22 comprises a series branch including a crystal GK and a series capacity 02, a shunt branch constituted by a second capacity equal to the series branch capacity, and a second shunt branch ineluding an inductance L such as to have a reactance equal to that of either of the two condensers at the operating frequency.
  • a series branch including a crystal GK and a series capacity 02
  • a shunt branch constituted by a second capacity equal to the series branch capacity
  • a second shunt branch ineluding an inductance L such as to have a reactance equal to that of either of the two condensers at the operating frequency.
  • the phase quadrature networks used in the systems of the invention are characterized by the properties of their image parameters.
  • the image impedance of the network at either pair of its terminals is equal to the square root of the product of the open circuit and short circuit impedances measured at these terminals and the image transfer constant is equal to the hyperbolic arc-tangent of the square root of the ratio of the short circuit impedance to the open circuit impedance.
  • the image impedance is found to be a real quantity of value X at the assigned frequency and the transfer constant to be the hyperbolic arc-tangent of an infinitely great pure imaginary quantity.
  • the real character of the image impedance corresponds to a purely resistive character and indicates that the frequency for which the reactances have the special values lies within a transmissien band of the network.
  • the value and character of the image transfer constant shows that it represents a simple phase shift of degrees without any accompanying attenuation.
  • the networks are thus characterized by having image phase shifts of 90 degrees at frequencies within transmission bands or for which the image impedances are pure resistances. In the circuits of the invention, the networks operate at the frequency thus determined, for which the quadrature phase shifts are stable.
  • phase shifting networks shown in the drawings which include piezoelectric crystal elements are all characterized by a very narrow transmission band in the frequency range where the crystal reactance is inductive.
  • a vacuum tube oscillator circuit comprising amplifying means, a transmission path coupling the output and the input terminals of the amplifying means to form a closed feedback loop, and a plurality of reactance networks included in the feedback loop, each of said networks being proportioned to produce at a common assigned frequency a phase shift of 90 degrees which is stable with respect to variations of the network terminating impedances, and the networks together with the amplifying means producing a total phase shift in the feedback loop which is zero at the common assigned frequency.
  • a common tube oscillator circuit comprising amplifying means, a transmission path coupling the output and the input terminals of the amplifying means to form a closed feedback loop, and a plurality of reactance networks included in the feedback loop, each of said networks being proportioned to produce at a common assigned frequency a phase shift of 90 degrees which is stable with respect to variations of the network terminating impedances, one of said networks being also proportioned to produce a phase shift which varies rapidly with frequency at the assigned frequency, the others being proportioned to produce slowly varying phase shifts, and the networks together with the amplifying means producing a total phase shift in the feedback loop which is zero at the common assigned frequency.
  • a vacuum tube oscillator circuit comprising amplifying means, a transmission path coupling the output and the input terminals of the ampli fying means to form a closed feedback loop, and a plurality of reactance networks included in the feedbackloop, each of said networks having an image phase shift equal to 90 degrees at a commcn assigned frequency for which its image impedances are real and finite, and the networks together with the amplifying means producing a total phase shift in the feedback loop which is zero at the common assigned frequency.
  • a vacuum tube oscillator circuit comprising amplifying means, a transmission path coupling the output and the input terminals of the amplifying means to form a closed feedback loop, and a plurality of reactance networks included in the feedback loop, each of said networks having an image phase shift equal to 90 degrees at a common assigned frequency lying within a transmission band of the network, one of said networks being proportioned to have a narrow transmission band in which the assigned frequency is included whereby its phase shift varies rapidly with frequency at the assigned frequency, the other networks being proportioned to have phase shifts which vary slowly with frequency, and the networks together with the amplifying means producing a total phase shift in the feedback loop which is zero at the assigned frequency.
  • a vacuum tube oscillator circuit comprising amplifying means, a transmission path coupling the output and the input terminals of the amplifying means to form a closed feedback loop, and a pair of reactance networks included in the feedback loop, one of said networks having an image phase shift of 90 degrees at an assigned frequency lying within a narrow transmission band whereby its phase shift is stable with respect to variations of its terminating impedances at the assigned frequency but varies rapidly with frequency, the other of said networks being proportioned to produce a phase shift which is substantially 90 degrees at the assigned frequency and which varies slowly with frequency, and the two networks together with the amplifying means producing a total phase shift in the feedback loop which is zero at the assigned frequency.
  • a vacuum tube oscillator circuit comprising amplifying means producing a 90-degree phase shift at an assigned operating frequency, a transmission path coupling the output and input terminals of said amplifying means to form a closed feedback loop, and a reactance network included in said transmission path, said network being sense from the phase shift of said amplifier,v
  • a vacuum tube oscillator circuit comprising a two-stage vacuum tube amplifier, a 'reactance network coupling the stages of said amplifier in tandem, a feedback path coupling the output and the input of said amplifier to form a closed transmission loop, and a second reactance network included in said feedback path, said first network being proportioned to provide a phase shift which is substantially 90 degrees at an assigned operating frequency and which varies SlOWly with frequency, said second network comprising two shunt branches and a series branch in ladder configuration, the reactances of branches being proportioned with respect to each other to produce a stable phase shift of degrees in the opposite direction from the phase shift of said first network at said operating frequency, whereby the total phase shift in the closed transmission loop is zero at the said operating frequency independently of the resistances of the amplifier input and output circuits.
  • a vacuum tube oscillator circuit in accordance with claim 7 in which the shunt branches of said second network have equal reactances of like sign at the operating frequency and the series branch has a reactance of the same magnitude but of opposite sign at said frequency, and are proportioned to make the phase shift vary rapidly with frequency.
  • a vacuum tube oscillator circuit in accordance with claim '7 in which one of the branches of said second network is constituted by a piezoelectric crystal.
  • a vacuum tube oscillator circuit comprising an amplifying vacuum tube, a feedback path coupling the output and the input terminals of said tube to form a closed transmission loop, and a pair of reactance networks included in said tandem in said feedback path, each of said networks being proportioned to have an image phase shift of 90 degrees at an assigned oscillation frequency for which the image impedances of the two networks are pure resistances, wherebythe quadrature phase shifts of the networks are independent of the internal resistances of the vacuui'n tube, and the two networks together with the vacuum'tube producing a total phase shift in the closed loop which is zero at thesaid oscillation frequency.
  • a vacuum tube oscillator in accordance with claim 10 which the said vacuum tube produces a zero phase shift between its input and output voltages and in which the said networks produce quadrature phase shifts in opposite directions at the oscillation frequency.
  • a vacuum tube oscillator comprising vacuum tube amplifying means having zero phase shift, a feedback path coupling the output and input terminals of said amplifying means to form a closed transmission loop, and a four-terminal reactance network included in said network, said network comprising a pair of series impedance elements constituted respectively by a piezoelectric crystal and a capacity connected in series, a second capacity connected in shunt at the outer terminal of said crystal and an inductance connected in shunt at the outer terminal of said first-mentioned capacity, all of said elements being proportioned to have reactances of equal magnitudes at an assigned oscillation frequency, the reactance of said crystal being inductive at said frequency.

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  • Oscillators With Electromechanical Resonators (AREA)
US216212A 1938-06-28 1938-06-28 Oscillation generator Expired - Lifetime US2165517A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
NL62295D NL62295C (enrdf_load_html_response) 1938-06-28
US216212A US2165517A (en) 1938-06-28 1938-06-28 Oscillation generator
GB15707/39A GB529291A (en) 1938-06-28 1939-05-26 Oscillation generators
FR856963D FR856963A (fr) 1938-06-28 1939-06-28 Oscillateurs électriques perfectionnés
ES177007A ES177007A1 (es) 1938-06-28 1947-02-28 Mejors en sistemas de transmisión telefónica en dos sentidos

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US216212A US2165517A (en) 1938-06-28 1938-06-28 Oscillation generator

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US2165517A true US2165517A (en) 1939-07-11

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US216212A Expired - Lifetime US2165517A (en) 1938-06-28 1938-06-28 Oscillation generator

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ES (1) ES177007A1 (enrdf_load_html_response)
FR (1) FR856963A (enrdf_load_html_response)
GB (1) GB529291A (enrdf_load_html_response)
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2451858A (en) * 1945-01-26 1948-10-19 Gen Electric Controlled frequency oscillator
US2498759A (en) * 1947-03-24 1950-02-28 Rca Corp Wide band oscillator and modulator
US2586167A (en) * 1945-07-03 1952-02-19 Us Navy Oscillator
US2683810A (en) * 1949-03-30 1954-07-13 Marconi Wireless Telegraph Co Piezoelectric crystal oscillator
US2981899A (en) * 1958-08-12 1961-04-25 Hahnel Alwin Frequency divider

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1116280B (de) * 1959-12-15 1961-11-02 Standard Elektrik Lorenz Ag Frequenzstabilisierungsschaltung fuer Oszillatoren

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2451858A (en) * 1945-01-26 1948-10-19 Gen Electric Controlled frequency oscillator
US2586167A (en) * 1945-07-03 1952-02-19 Us Navy Oscillator
US2498759A (en) * 1947-03-24 1950-02-28 Rca Corp Wide band oscillator and modulator
US2683810A (en) * 1949-03-30 1954-07-13 Marconi Wireless Telegraph Co Piezoelectric crystal oscillator
US2981899A (en) * 1958-08-12 1961-04-25 Hahnel Alwin Frequency divider

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FR856963A (fr) 1940-08-19
GB529291A (en) 1940-11-18
ES177007A1 (es) 1947-04-16
NL62295C (enrdf_load_html_response)

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