US1979994A - Oscillation generation - Google Patents

Description

Nov. 6, 1934. H. o. PETERSON OSG ILLATION GENERATION Filed May 27, 1931 44 AMPl/F/ Hw- I JECO/VD OETECTaQ u AMPl/FIEQ JMPl/F'IEK Flt 762 Ill All "I vvvyr UIPI/f INVENTOR H.0.PETER on BY W ATTORNEY Patented Nov. 6, I934 UNlTED STA OSOILLATION GENERATION tion of Delaware Application May 27, 1931, Serial No. 540,314

9 Claims.

This invention relates to the generation of high frequency oscillations and is especially directed towards new and useful piezo-electric crystal controlled oscillation generators.

It has been proposed, heretofore, to control the frequency of oscillations generated with a three electrode electron discharge device by means of a piezo-electric crystal. In practice I have found that such tubes have shown extreme reluctance m in producing oscillations, and accordingly, it is an object of my present invention to overcome the hesitancy of such a system to oscillate. In order to do so I make use of tubes having high interelectrode impedance such as the tetrode or screen grid tubes whereby oscillation generation is facilitated. Moreover, the use of such tu es or devices insures greater output for a given amount of radio frequency voltage impressed upon the frequency controlling crystal, thereby offering the advantage that the crystal need not be worked as hard as heretofore required which often times resulted in destruction of the crystal because of its high amplitude of mechanical vibration.

Another object of my present invention is to provide an oscillator whose only resonant fre quency control means shall be a piezo-electric crystal as a result of which frequency stability is enhanced by virtue of the fact that there are no tuned circuits associated with the oscillator which will have an effect upon the crystal frequency.

Still another object of my present invention is to provide an oscillation generator of the regenerative type using a tube having more than three electrodes wherein feed back shall occur solely through a piezo-electric crystal, the input circuit of the oscillator being made preferably aperiodic whereby the frequency of oscillations generated in the output circuit of the oscillator shall substantially always be determined by the frequency of only the crystal and may bear, if desired, a harmonic relation in frequency to the frequency of operation of the crystal.

Still further objects of my present invention are to provide modifications of the oscillators de- 9 scribed briefly hereinabove, such as an oscillator having an electron discharge device of the multigrid type, the grid associated with the input circuit being connected aperiodically to the cathode, the device having resonant means associated with another grid; and, broadly resonant means for feeding back energy from the anode to the aperiodic input circuit whereby high frequency oscillations are sustained in the resonant means associated with one of the grids. This resonant means in the grid circuit may, of course, take the form of a tunable circuit and, the feed back may be established through a piezo-electric crystal.

As a further modification I provide in accordance with my present invention, a tunable circuit associated with the anode and cathode of an electron discharge device oscillator, the frequency of oscillations being determined by a piezo-electric crystal connected between the grid adjacent the anode, or a grid maintained at a relatively high positive potential, and the cathode of the electron discharge device oscillator.

As required by law, my present invention is defined with particularity in the appended claims. However, it may best be understood both as to its structural organization and mode of operation by referring to the accompanying drawing, wherein,

Figure 1 illustrates an improved crystal oscillator, according to my present invention, incorporated within a transmitting arrangement,

Figure 2 illustrates another form of oscillator showing its application in a superheterodyne receiver, and,

Figure 3 illustrates still another form of my presentinvention.

Turning to Figure 1, the electron discharge device 2 preferably of the screen grid or tetrode type has an aperiodic input circuit comprising resistance 4 connected between grid 6 and cathode 8 illustrated as being of the heater type. Grid 6 is, of course, the normal control grid adjacent the cathode and is suitably polarized by the current flow through resistance l. An aperiodic output circuit is connected between the anode 10 and cathode 8 and it comprises a resistance 12 in series with a suitable source of anode polarizing potential 14 as well as resistance 16 connected between resistance 12 and the cathode. By the use of a connection 18, variably tapped to resistance 16, a suitable positive biasing potential may be applied to the screen grid or electrode 20 adjacent anode 10. The screen grid is by-passed to ground for radio frequency currents by the action of suitable condenser 22.

By virtue of screen grid electrode 20 intermediate grid 6 and anode 10 there is very little possibility of feed back through the tube, and, in order to introduce feed back to cause generation at a desired frequency of oscillation, I connect resonant means preferably in the form of a piezo-electric crystal 24 between the anode 10 and control electrode 6 or, in other words, between the aperiodic input and output circuits.

Upon the application of suitable potentials to the various electrodes of the tube 2, crystal 24 becomes excited as a result of which currents corresponding to a natural frequency of the crystal fiow through the input circuit 4 causing large voltage variations across the output resistance 12. For frequencies other than a natural frequency of the crystal, there will be no appreciable current fiow through resistor 4 as a result of which, at other frequencies, there will be no output from electron discharge device oscillator 2.

The foregoing oscillator circuit will be found to oscillate readily and in a very stable fashion. It offers the advantage that inasmuch as there are no tuned circuits associated therewith other than the crystal or its equivalent, for example, a sharply tuned resonant circuit, any crystal or circuit having a frequency within any desired limits, may be caused to oscillate in the described circuit. Moreover, in the modification illustrated which is preferred because of the lack of tuned circuits, the frequency of oscillation more closely approaches the true frequency of the crystal for, as already indicated to some extent, there are no tuned circuits acting to influence the frequency of oscillation of the crystal.

Output energy may be taken from the output circuit of electron discharge device 2 through a suitable blocking condenser 26 acting to vary the potential on a control grid 28 of electron discharge device amplifier 30. Control grid 28 is biased by the action of a suitable condenser and resistance arrangement 32. Moreover, tube 30 may be of the screen grid type having a suitable screen grid 34 polarized by the action of a resistance 36 connecting it to the anode potential lead 38. In the anode lead there is placed a further output resistor 40 which may if desired be replaced by a tuned circuit and output energy from resistor 40 may be fed in suitable fashion to a further amplifier and modulator tube 42.

By varying the potential on the screen grid 41 of amplifier tube 42, modulation of the high frequency oscillations in the tunable output circuit 44 of tube 42 may be accomplished. To vary the potential on screen'grid 4i and hence modulate the oscillations appearing in output circuit 44, a resistor 46 is connected in series with the screen grid biasing source 48 and, in shunt with the series combination of resistance 46 and source 48 there is placed an electron discharge device 50 supplied with modulating potentials from, for example, a transformer 52. As a result, variations in current through resistance 46 will vary the potential on screen grid 41 thereby producing modulation in energy appearing in the output circuit 44.

Of course, any other suitable modulating arrangement may be used such as, for example, the Heising scheme or, either the plate voltage or grid voltage of amplifier tube 42 may be varied in a manner similar to that given for screen grid 41. Modulated output energy from tunable circuit 44 is then fed to a suitable power amplifier 54 in turn energizing an antenna 56' in order to propagate the modulated energy to a receiving station.

The electron discharge device oscillator 2 of Figure 2 is identical with that shown in Figure 1 with the exception that a tunable circuit 58 comprising an inductance coil shunted by a variable condenser is placed in series with the polarizing lead 18 for supplying biasing potential to the electrode 20 adjacent the anode 10. By suitably tuning circuit 58 to a harmonic of crystal 24the amplitude of that harmonic of crystal 24 corresponding to the tuning of, tunable; circuit 58 is increased. This harmonic energy may be taken directly from tunable circuit 58 by coupling thereto a coil 60 and the harmonic energy may be amplified by a suitable amplifier 62 and combined in a first detector 64 with amplified radio frequency energy initially derived from antenna 66 and amplified by a suitable high frequency amplifier 68. The output of the first detector 64, which, as is well known in the art, is of an intermediate frequency, may be further amplified and then detected in a suitable detector '70 whose output may be supplied to an amplifier and then to a translating device such as ear phones 72 in order to translate a transmitted signal.

If desired, energy from electron discharge device oscillatcr 2 may be taken, by means of transmission lines '74, from the aperiodic output circuit and in particular from output resistor 12. Energy of any desired frequency generated by the oscillator may be filtered out by the use of a suitable filter '76 and utilized in any suitable fashion as found desirable such as in a receiving systern or, for example, used as the carrier for some transmitter.

As a further modification of my present invention, utilizing a multi-grid tube for the generation of oscillations, the resonant means or tuned circuit 58 of Figure 2 may be replaced by a piezoelectric crystal '78 as shown in Figure 3, and, in order to apply screen grid potential to the electrode 20 adjacent the anode of plate 10, the crystal 78 is shunted by a choke coil 80 suitably grounded for high frequency potentials by the action of condenser 83. Moreover, the plate or anode circuit need not be aperiodic, but between the anode l0 and cathode 8 there may be connected as shown, resonant means in the form of a tunable circuit 82 from which, as indicated, output energy may be taken and utilized as found desirable.

For best operation of the arrangement shown in Figure 3, the plate circuit 82 should be tuned to substantially the natural frequency of the crystal '78 or to a frequency slightly higher than a natural frequency of the crystal 78. The tuning of circuit 82 should, therefore, correspond to the natural fundamental frequency of crystal '78 or, to any desired harmonic thereof.

The circuit shown in Figure 3 is claimed in my divisional application, Serial Number 621,416, filed in the United States Patent Oifice on July 8, 1932.

Various modifications of my present invention will, of course, readily suggest themselves to those skilled in the art. Consequently, my present invention is not to be considered limited in any way by the modifications shown but is to be given a scope commensurate to that indicated by the appended claims.

Having thus described my invention, what I claim is:

1. In a system for generating oscillations, an electron discharge device having an anode, a cathode, a control electrode adjacent said cathode, and another electrode intermediate said control electrode and said anode, an aperiodic input circuit connected between said control electrode and cathode, an aperiodic circuit connected between said anode and cathode, a tuned circuit having inductance and capacity connected between said electrode intermediate said control electrode and anode, and said cathode, and, a, piezo-electric crystal connectedv between said anode and said control electrode.

2. In a system, for, generating oscillations, an electron discharge device having an anode, a

cathode, a control electrode adjacent said cathode, and another electrode intermediate said control electrode and said anode, an aperiodic input circuit connected between said control electrode and cathode, an aperiodic circuit connected between said anode and cathode, a tuned circuit connected between said electrode, intermediate said control electrode and anode, and said cathode, and, a connection from said anode to said control electrode for establishing feed back from said anode circuit to said aperiodic input circuit.

3. In a system for generating high frequency oscillations, an electron discharge device having an anode, a cathode, and a plurality of grids intermediate said anode and said cathode, an aperiodic high frequency input circuit connected between one of said control electrodes and said cathode, a resonant circuit connected between said other control electrode and said cathode, means for maintaining the control electrode to which said resonant circuit is connected to a potential positive relative to the control electrode connected to said cathode through said aperiodic circuit, means for polarizing said anode to a positive potential, and, means for establishing feed back from said anode to said aperiodic circuit.

4. In a system for generating high frequency oscillations, an electron discharge device having an anode, a cathode, and a plurality of grids intermediate said anode and said cathode, an aperiodic high frequency input circuit connected between one of said grids and said cathode, a resonant circuit connected between another grid and said cathode, means for maintaining the grid to which said resonant circuit is connected to a potential positive relative to the grid connected to said cathode through said aperiodic circuit, means for polarizing said anode to a positive potential, and, a piezo-electric crystal connected between said anode and said aperiodic input circuit for establishing feed back from said anode to said input circuit.

5. In an oscillation generating system, an electron discharge device having an anode, a cathode, a screen grid adjacent said anode, and a control grid adjacent said cathode, a circuit connecting the grid adjacent said cathode and said cathode, a piezo-electric crystal coupling said anode to said grid adjacent said cathode, a tunable circuit connected between the grid adjacent said anode and said cathode, and, a circuit connecting said anode and said cathode.

6. In combination, a vacuum tube having an anode, a cathode, a grid adjacent the cathode, and a screen grid, circuits interconnecting said anode and cathode and said grid adjacent said cathode and said cathode, a piezoelectric crystal connected between said anode and grid adjacent said cathode, and a circuit tuned to a harmonic of a natural frequency of said piezo-electric crystal connected between said screen grid and cathode.

7. Apparatus as claimed in the preceding claim characterized by the fact that the circuit between said grid adjacent said cathode and said cathode includes a resistor, and by the fact that the circuit connected between said anode and cathode includes a resistor.

8. An oscillation generator comprising a tube having an anode a cathode a control grid and a screen grid, a circuit connected between said control grid and cathode for subjecting said control grid to a suitable operating potential with respect to said cathode, a high frequency circuit connected between said anode and said cathode, a piezo-electric crystal coupling said anode to said control grid, and, a resonant circuit connected between said screen grid and cathode, said resonant circuit being tuned to a harmonic frequency relative to a fundamental frequency of said piezo-electric crystal.

9. An oscillation generator comprising a tube having an anode a cathode a control grid and a screen grid, a circuit connected between said control grid and cathode for subjecting said control grid to a suitable operating potential with respect to said cathode, a resonant circuit connected between said screen grid and cathode, a high frequency circuit connected between said anode and cathode, a piezo-electric crystal coupling said anode to said control grid, and means for deriving harmonic frequency energy relative to a fundamental frequency of said piezo-electric crystal from said circuit connected between said anode and cathode.

HAROLD OLAF PETERSON.

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