US2398502A - Oscillation generation - Google Patents

Description

April 16, 1946.

H. L. MORRISON OSCILLATION GENERATION Fild Feb. 5, 1944 INVENTOR HOWQBZJZ orrson ATTORN EY Patented Apr. 16, 1946 OSCILLATION GENERATION Howard Larue Morrison, Merchantville, N. as-

signor to Radio Corporation of America, a corporation of Delaware Application February 5, 1944, Serial No. 521,191

Claims.

The present invention relates to high frequency oscillation generation circuits employing multigrid vacuum tubes.

Broadly stated, the invention comprises a pushpull oscillator utilizing a pair of screen grid vacuum tube electrode structures capable of eflicient- 1y generating oscillations in the 300 megacycle region. In order to provide feed back between the output and input electrodes of the tube, there is provided a folded back one-half wavelength two-conductor line, one of whose conductors couples together the input and output electrodes of one electrode structure, while the other parallel conductor couples together the input and output electrodes of the other electrode structure. The length (half wave) of the conductors assures the desired phase reversal in the voltage at one end relative to the other.

A more detailed description follows in conjunction with a drawing, whose single figure illustrates one embodiment of the invention. Although the drawing illustrates a dual beam tetrode power tube having a pair of screen grid electrode structures within a single envelope, it should be understood that the principles of the invention are applicable to any screen grid tube.

Referring to the drawing, there is shown a push-pull oscillation generator comprising a pushpull beam power amplifier tube it of the RCA 832 type. This tube is a heater-cathode type containing in one envelope two beam power units each including a cathode, an input grid, a screen grid and an anode, as shown. The input grids are shielded from the output anodes by the screen ids, and the terminals for these electrodes extend from opposite sides. of the envelope. This particular type of tube (RCA 832) is designed for use primarily as a power amplifier for ultra high frequency energy, but has been adapted in the circuit herein illustrated to function as an oscillator in the range of 300 megacycles.

The anodes are connected to one end of a tuned parallel conductor system H which is shorted at the other end by a bridge member whose midpoint is connected to a source of anode polarizing potential B+. A slider l2, which is a short-circuiting member adjustable in position over the lengths of the conductors of, anode line circuit ll, serves to tune the anode circuit.

Connected to the input grids is a folded-back parallel conductor line l3, which is electrically one-half wavelength long at the operating frequency. One end of this line is connected to the input grids while theother end is free and brought back to the Vicinity of the tube envelope in order to couple the free ends of the conductors of the line capacitively to the anodes. It should be noted that each conductor of line it which i coupled at one end to an input grid of one beam power unit is capacitively coupled at its other end to the anode of the same beam power unit. Because of the particular length of the lin I3 (one-half wavelength) there is a. phase reversal in voltage at one end relative to the other which satisfies the requirement that the grid voltage be out-ofphase relative to the'anode voltage of the same electrode structure for the condition of oscillation,

The line l3 thus provides feed back externally of the vacuum tube structure. The desired amount of feed back coupling between the anodes and. the free ends of grid line I3 located adjacent the envelope of tube [0 is obtained by suitably adjusting the distance between these free ends and tube l8. If the grid line I3 is too long physically to satisfy any rigid requirement of compactness, then this line may be shortened physically but have the same one-half wave electrical length by connecting a small variable capacitor across the free ends.

A pair of grid leak resistors l 4 are connected to points of low potential on the grid conductors of line [3, thus'eliminating the need for radio frequency choke coils. Because of the particular location of these resistors, there is no radio frequency power wasted in them.

The oscillator of the present invention described above and utilizing an RCA-832 dual tetrode beam power, was able in one experimental embodiment to deliver five watts of power at 320 megacycles. In this embodiment, the lines I l and I3 were each a pair of copper rods. The tube and circuit lends itself to compactness, and the physical size of the equipment can be still further reduced by shortening the physical length of the anode line by means of a simple two-plate air condenser across the conductors thereof near the anode electrode terminals.

What is claimed is:

1. An oscillation generator comprising a vacuum tube having within an envelope a cathode for supplying an electron stream, a first grid, a

screen grid and an anode, said screen grid shielding said first grid from said anode, an output tuned circuit coupled to said anode, a feed back circuit comprising a conductor one-half wavelength long connected at one end to said first grid and folded so that its other end is outside and adjacent said envelope at thelocation of said anode and capacitively coupled to said anode solely by virtue of the space between said last end of said line and said anode.

2. A push-pull oscillation generator comprising a pair of electrode structures each including a control grid and an anode, a two-conductor line which is one-half wavelength long electricall and connected at one end to said control grids and capacitively coupled at the other end to said anodes primarily by virtue, of the spacing between said anodes and said last end of the line, said line being folded back on itself and so arranged that each conductor thereof which is connected at one end to the control grid of one electrode structure is folded back so that its other end is adjacent the anode of the same electrode structure for capacitive coupling thereto, and an output tuned circuit coupled to said anodes.

3. A push-pull oscillation generator comprising a dual electrode structure within a single envelope, each of said electrode structures including a control grid and an anode having terminals extending from opposite sides of the envelope, an

anode tuned circuit coupled to said anodes, and

a feed back circuit comprising .a two-conductor line one-half wavelength long electrically, said line being connected at one end to said control grids and folded so that the other end is adjacent said anodes but outside said envelope and capacitively coupled to said anodes for operation of said generator by virtue of the spacing between said anodes and said last end of the line.

4. A push-pull oscillation generator comprising a dual multi-grid electrode structure within a single envelope, each of said electrode structures including a-control grid and an anode having terminals extending from opposite sides of the envelope, and a screen grid for shielding the control grid from the anode, an anode tuned parallel conductor circuit coupled to said anodes, and a feed back circuit comprising a two-conductor line onehalf wavelength long electrically, said line being connected at one end to said control grids and folded so that the other end is adjacent said anodes but outside said envelope and capacitively coupled to said anodes for operation of said generator primarily by virtue of the space" between said anodes and the last end of the line, each conductor of said line having its free end capacitively coupled to the anode of the same electrode structure to whose control grid its other end is connected. I

5. A push-pull oscillation generator comprising a dual multi-grid, electrode structure within a single envelope, each of said electrode structures including a cathode for producing a stream of electrons, a control grid and an anode having terminals extending from opposite sides of the envelope, and a screen grid shielding the control grid from the anode, an anode tuned parallel conductor circuit coupled to said anodes, and a feed back circuit comprising a two-conductor line onehalf wavelength long electrically, said line being connected at one end to said control grids and folded so that the other end is adjacent'to said anodes but outside said envelope and capacitively coupled to said anodes for operation of said generator primarily byrvirtue of the space between said anodes and last end of the line, each conductor of said line having its free end capacitively coupled to the anode of the same electrode structure to Whose control grid its other end is connected, and separate grid leak resistors connected between points of low potential on the two conductors of said line and the cathodes of said electrode structures. 1

6. A push-pull oscillation generator comprising a pair of multi-grid electrode structures each including a cathode for producing an electron stream, a control grid, an anode, and a screen grid shielding the control grid from the anode, a twoconductor line one-half wavelength long electrically connected at one end to said control grids and capacitively coupled at the other end to said anodes primarily by virtue of th spacing between said anodes and said last end of the line, said line being folded back on itself and so arranged that each conductor thereof which is connected at one end to a control grid of one electrode structure has its other end adjacent the anode of the same electrode structure, a, grid leak resistor for each conductor of said line connected between a point of low potential on the conductor and the cathode of that electrode structure to which the said conductor is connected, and an output tuned circuit coupled to said anodes.

V '7. A push-pull oscillation generator comprising a pair of multi-grid electrode structures, each including a control grid, an anode, and a screen grid shielding the control grid from the anode, a two-conductor line having such electrical length that potentials of opposite instantaneous polarities appear at opposite ends thereof, said line being connected at one end to said control grids and capacitively coupled at the other end to said anodes primarily by virtue of the spacing between said anodes and said last end of the line, said line being folded back on itself and so arranged that the conductor which is connected at one end to the control grid of one electrode structure has its other end adjacent the anode of the same electrode structure.

8. Push-pull electron discharge device apparatus comprising a pair of multi-grid electrode, structures each including a control grid, an anode, and a screen grid shielding said control grid from the anode, a two-conductor line one-half wave- 7 length long electrically connected at one end to said control grids and capacitively coupled at the other end to said anodes primarily by virtue of the spacing between said anodes and said last end of the line, said line being folded back on itself and so arranged that each conductor thereof which is connected at one end to the control grid of one electrode structure has its other end adjacent the anode of the same electrode structure.

9. Push-pull electron discharge device apparatus comprising a pair of multi-grid electrode structures, each including a control grid, an anode, and a screen grid shielding said control grid from the anode, a two-conductor line having such electrical length that potentials of opposite instantaneous polarities appear at opposite ends thereof, said line being connected at one end to said control grids and capacitively coupled at the other end to said anodes primarily by virtue of the spacing between said anodes and said last end of the line, said line being folded back on itself and so arranged that the conductor which is connected at one end to the control grid of one electrode structure has its other end adjacent the anode of the same electrode structure.

10. An oscillation generator comprising a vacuum tube having within an envelope a cathode for producing an electron stream, a first grid, and an anode, a feed back circuit comprising a conductor having such electrical length that potentials of opposite instantaneou polarities appear at opposite ends thereof, said conductor being connected at one end to said first grid and folded so that its other end is outside and adjacent said envelope at the location of said anode and capacitively coupled to said anode primarily by virtue of the space between said last end of the line and said anode.

HOWARD LARUE MORRISON.

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