US1980581A - Crystal controlled oscillator - Google Patents

Description

Nov. 13, 1934.

DE WlTT R. GODDARD 1,980,581

CRYSTAL CONTROLLED OSCILLATOR Original Filed June 4. 19'" xii/WWO? 78 wimp/m (SM/ML INVENTOR DE wm DDARD ATLI'ORNEY Patented Nov. 13, 1934 warren STATES CRYSTAL CGNTROLLED OSCILLATOR De Witt R. Goddard, Riverhead, N. Y; assignor to Radio Corporation of America, a corporation of Delaware Original application June 4, 1931, Serial No.

Divided and this application July 8,

1932, Serial No. 621,415. In Great Britain May 2 Claims.

This case is a divisional application of my copending application, Serial Number 542,091, filed June 4, 1931, and in general covers the arrangements illustrated in Figures 3 and 5 of '5 the referred to copending application.

, four electrode and five electrode tubes together with appropriate circuits and a crystal for frequency controlling the oscillations produced by the tetrodes or pentodes used. The ready production of the oscillations according to my present invention, may be attributed to a large degree to the fact that the tubes used have a very high interelectrode impedance and consequently have much higher amplification giving rise to good generating action.

Another object of my present invention is to provide a crystal controlled oscillation generator wherein a two electrode crystal shall be placed between the grids of an electron discharge device.

Still a further object of my present invention is to provide oscillators which shall be crystal controlled and in which the frequency of oscillation is more nearly that of the crystal than has been possible heretofore. To do so, according to the present invention, use is made of impedances preferably in the form of resistances which shall have no independent resonant characteristics of their own.

Other objects as well as advantages of the present invention will become apparent as the description thereof proceeds which will be given with the aid of the accompanying drawing, wherein Figure 1 illustrates an improved crystal controlled oscillation generator according to my present invention utilizing a screen grid electron discharge device, and,

Figure 2 illustrates a modification utilizing a pentode or five electrode tube.

In the oscillator shown in Figure l, the crystal 2 is connected between the screen grid 20 and the grid 4 adjacent the cathode 6 of the tetrode 8. The grid 4 is maintained at a suitable bias by the action of a resistance 50 connected between the grid 4 and cathode 6; and, grid 20 is maintained at a suitable potential by tapping it through an impedance preferably in the form of a resistance 52 to a potentiometer 54. which also supplies anode potential to the anode 12 through the output impedance here shown in the form of a resistance 56.

The oscillator described in connection with Figure 1. has the advantage of having no tuned circuits, and, will, therefore, operate when any crystal having a frequency within practical limits is inserted in the circuit. The circuit, of course, will not oscillate when the crystal is removed. Moreover, as there is no tuned circuit to get out of adjustment and effect the frequency of the crystal, the oscillations produced by the circuits will always be at a value closer to a true frequency of the crystal than is the case where tuned circuits are used in combination with the crystal controlled electron discharge device oscillator.

Another circuit for generating high frequency oscillations utilizing an electron discharge device of the pentode type and using the crystal for frequency control is shown in Figure 2. The piezo-electric crystal 2 is here shown as connected between the grid 20 adjacent the anode 12 and the grid intermediate the space charge grid 58 and the screen grid 20. The grid 60 is maintained at a suitable potential by the a ction of grid leak resistor 50, and, the screen grid is maintained at a suitable potential by tapping it through conductor 21 to a potentiometer 64. The space charge grid 58 is preferably tapped to a potentiometer 66 such that the space charge grid is maintained a few volts positive with respect to ground or with respect to the potential of cathode 6. The anode to cathode circuit is completed through an impedance preferably in the form of a resistance 68 and potentiometer 54.

Output energy from the oscillator may be taken through transmission lines '70 and blocking condensers 18 to any suitable utilization circuit.

Various modifications of the present invention will, of course, readily suggest themselves to those skilled in the art. Accordingly, the present invention is not to be limited by the exact circuits illustrated, but is to be given the full width and scope indicated by the appended claims.

Having thus described my invention, what I claim is:

1. An oscillation generator comprising an electron discharge device having an anode, a cathode, a grid adjacent said anode, a grid adjacent said cathode, and a grid intermediate said grids; a single piezo-electric crystal connected between the grid adjacent said anode and said intermediate grid, a non-inductive resistance connected between said intermediate grid and said cathode, a non-inductive resistance connected between said anode and said cathode from which high frequency undulatory electric currents may be derived, and means for subjecting. the grid.

adjacent said cathode to a suitable operating potential with respect to said cathode,

2. In combination, an electron discharge de-' adapted to supply high frequency oscillatory energy at'a frequency fixed by said piezo-electric crystal. 1

DE WI'I'T R. GODDARD.

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