US2027448A

US2027448A - Crystal controlled oscillator

Info

Publication number: US2027448A
Application number: US176877A
Authority: US
Inventors: Harold O Peterson
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1927-03-21
Filing date: 1927-03-21
Publication date: 1936-01-14
Anticipated expiration: 1953-01-14

Description

Jan. 14, 1936. 1- Q PETERSQN ZJUZYAA-g CRYSTAL CONTROLLED OSCILLATOR Filed-March 21, 1927 WWHHIMB I INVENTOR ,22 n o. PETERSON EF WA Q/MW ORNEY Patented Jan. 14, 1936 UNETE TATES 2,022,4 lii ATENT or ies Harold (l. Fetersen, Riverhead, N. Y., assignor to Radio {Zorn-oration of America, a corporation of Belaware Application March 21, 1927, Serial No. 176,87?

9 Claims.

This invention relates to the piezo electric art and deals more specifically with a piezo electric crystal controlled oscillator.

It has been found that certain piezo electric crystals when out in accordance with the specifications noW well known relative to the preparation of such crystals, are set into oscillation only with great difiiculty.

It is, therefore, an object of this invention to devise a circuit which is more forceful in causing a piezo-electric crystal to oscillate.

It has also been found that the degree of control exercised by a. crystal upon an oscillating circuit is an inverse function of the amount of regeneration necessary to make the crystal oscillate.

It is, therefore, a further object of this invention to devise a crystal controlled oscillation circuit arranged for minimum regeneration.

These and other objects of the invention will be apparent readily to those skilled in the art from the following description taken in connection with the accompanying drawing in which:

Figure l is a diagrammatic sketch showing one embodiment of my invention.

Figures 2 to 5 inclusive are diagrammatic views showing modified forms of the invention.

Referring in detail to Figure l, a vacuum tube l0 having the usual filament, grid and plate is provided with the usual A, B and C batteries as shown. A choke coil H is connected in the plate circuit of the tube Ill. The input or grid-filament circuit of the tube II] is tuned by means of the inductance l2 and variable condenser l3. A neutralizing variable condenser i5 is connected between the plate and the resonant circuit 52-53. The piezo-electric crystal I6 is connected in parallel with the variable condenser I5 between the resonant circuit |2l3 and the plate of the vacuum tube. l4 indicates an additional balancing variable condenser to enable the circuit to be balanced in case the capacity of the crystal l6 plus the capacity of the condenser I5 is so much greater than the internal plate to grid capacity of the tube, that the circuit would oscillate as an ordinary tube oscillator, for adjustments of the resonant circuit l2l3 at frequencies other than the natural periods of the crystal. The condenser I5 is chosen of as small capacity as possible to obtain the balanced effect, for the reason that the balancing or unbalancing coupling should be made through the crystal I6.

The operation of the circuit is as follows:

When the vacuum tube I0 is energized and the circuit l2-l3 is properly tuned the system goes into oscillation at a frequency substantially equal to the mechanical frequency of vibration of the crystal, and the frequency of oscillations generated remains substantially constant for a considerable variation in the electrical constants of the circuit.

Referring to Figure 2 the vacuum tube it provided with the usual filament, grid, and plate and also the usual A, B and C batteries, has the coil it in the plate filament circuit. The B battery is connected between the positive terminal of the filament and the mid-point of the coil ll. A neutralizing variable condenser is is connected between the coil H and the negative terminal of the filament. tube It] is provided with the usual coil l2 and con denser l3. -A second neutralizing or balancing variable condenser it is connected between the plate and grid of the tube It as shown. Connected between the grid of the tube and the coil l l is the crystal {6 which is by-passed by a variable condenser ll.

Figure 3 shows a vacuum tube it having a plate circuit tuned by the coil l l and the variable condenser ll. tween the negative terminal of the filament and the mid-point of the coil H. A neutralizing variable condenser 55 is connected between the filament of the tube l9 and the coil 5! in a manner similar to the modification shown in Figure 2. The second neutralizing or balancing variable condenser M is connected between the plate and grid of the tube E0. The input circuit of the vacuum tube l9 comprises the coil l2 connected between the grid and filament. A balancing variable condenser a is connected between the filament and grid and the piezo electric crystal is shunted across said last mentioned variable condenser l5a.

Referring to Figure 4. the vacuum tube l0 having the usual filament, grid and plate and also the usual A, B and C battery connected as shown is provided with the coil H in the plate circuit. The input circuit of the vacuum tube ID comprises the coil i2 and the variable condenser l3 connected as shown. A variable condenser M in series with a coil l2a is connected between the plate and the negative terminal of the filament. Similarly a neutralizing variable condenser l5 and a coil I2b are connected in series between the negative terminal of the filament and the plate of the vacuum tube. The piezo electric crystal I6 is shunted across the variable condenser I5.

It has been found that when the plate poten- The input circuit of the vacuum The B battery is connected be- 2.13

tial is first applied exceedingly high voltages are developed across the plates of the crystal and in order to protect the crystal, I have provided the arrangement shown in Figure 5 which is the same circuit as shown in Figure 1 having in addition the gap or lightning arrester 20 across the input circuit and also the gap or lightning arrester 2! connected across the plates of the piezo-electric crystal ii. I have also found it desirable to include the high resistance 22 in the gap 2 I, which resistance is of the order of magnitude or 50,000 ohms.

I claim as my invention:

1. The combination of a vacuum tube oscillation generator having a filament, grid and plate. a first means to augment the inherent capacity between said plate and said grid, auxiliary means to neutralize said augmented capacity, and piezo electric means connected in parallel with a portion of said last mentioned means.

2. An oscillation generator comprising the combination of a tube having an anode, a cathode and a grid, a coil connected at an intermediate point to said cathode and at one end to said grid, a variable condenser comiecting the other end of said coil to said anode, a coil connected between said anode and cathode, a variable condenser connected across said anode and grid, and a two electrode piezo-electric crystal connected in shunt to said first mentioned condenser.

3. An oscillation generator comprising the combination of an electron discharge device having an anode, a cathode and a grid, a circuit comprising a condenser and an inductance coil connected between said grid and cathode, a second inductance coil, one terminal of said second coil being connected to said anode and an intermediate point on said second coil being connected to said cathode, a variable condenser connecting the other end of said second coil to said grid and a two electrode piezo-electric crystal connected in shunt to said last mentioned variable condenser.

4. Apparatus as claimed in the preceding claim characterized by the fact that there is provided in shunt to said grid and anode a variable con denser and that there is connected between said cathode and one terminal of said piezo-electric crystal an additional variable condenser.

5. An oscillation generator comprising the combination of an electron discharge device having an anode, a cathode and a grid, high frequency circuits interconnecting said anode, grid and cathode electrodes, a two electrode piezoelectric crystal connected to a pair of said electrodes for frequency stabilizing the frequency of oscillations generated by said device and, a two electrode spark gap connected across said piezo electric crystal.

6. Apparatus as claimed in the preceding claim characterized by the fact that in series with said spark gap there is connected a resistance.

7. In a crystal controlled oscillator, comprising a vacuum tube having cathode, grid and plate electrodes, an output oscillatory circuit connected between said plate and grid electrodes, a connection from said cathode to an intermediate point on said oscillatory circuit and a piezo electric control crystal and a variable compensating condenser being inserted in the lead from said output circuit to said grid electrode.

8. In a high frequency oscillator, comprising a vacuum tube having filament, grid and plate electrodes, an output circuit connected between said grid and said plate electrode, a connection from said filament to a tap point on said output circuit, and a compensating condenser and an electromechanical oscillating control device connected in the lead from said grid electrode to said output circuit.

9. In a high frequency oscillator, comprising a vacuum tube having filament, grid and plate electrodes, an output circuit connected between said grid and said plate electrode, a connection from said filament to a tap on said output circuit, and a compensating condenser and a piezo electric control device connected in the lead from said grid electrode to said output circuit.

HAROLD O PETERSON.