US3909658A

US3909658A - Wide band grid circuit coaxial tube

Info

Publication number: US3909658A
Application number: US463342A
Authority: US
Inventors: Elston H Swanson
Original assignee: INSTR FOR INDUSTRY
Current assignee: INSTR FOR INDUSTRY; INSTRUMENTS FOR INDUSTRY
Priority date: 1974-04-23
Filing date: 1974-04-23
Publication date: 1975-09-30
Anticipated expiration: 1992-09-30

Abstract

This invention relates to utilizing tubes having a coaxial base in a non-coaxial circuit and more particularly, to a grid line structure, including a trough, constructed to have effect as a coaxial line having shunt discontinuities distributed in the form of tubes.

Description

United States Patent nl):

Swanson [54| WIDE BAND GRID CIRCUIT COAXIAL TUBE |75] Inventor: Elston H. Swanson` Locust Vnllcy` Instruments for Industry` Farmingdnlc, N Y

[2:1 Filed; Apr. 23, i974 |2| Appl. NQ; 463.342

[73| Assignee:

[52] U.S. Cl. i SI5/39; 3310/54; 331/97; `31N/IUI [5|] Inl. HLI 7/46; HUlJ l9/8() |58] Field 0f Search .A 3l5/39L330/54133l/97. 331/98. lOl

156| References Cited UNITED STATES PATENTS 211191597 |l/l952 Mlyncznk 331/98 i451 Sept. 30, 1975 1627578 2/1953 Klein 331/98 1763.783 9/1956 Lorenzen et ul 331/98 3,133,253 5/1964 Luder 315/39 X 3.495,183 2/1970 DmlnduulultisV 33(1/54 3.718,869 2/I973 Gcrluck ISI/IUI Prz'fmlry l:`.\'an1il1er-S;ixfield Chatmon, Jr. Afmrney, Agent, orv Firm-Nolte and Nolte [57| ABSTRACT This invention relatos to utilizing tubes having i Conxiul baise in :i non-c0axiz1l circuit and more particularly, t0 u grid line structure. including a trough, Constructed to have effect as n Coaxial line having shunt discontinuities distributed in the forni of tubes.

I0 Claims, 4 Drawing Figures Sheet 1 of 2 U.S. Patent sept. 30,1975

WIDE BAND GRID CIRCUIT COAXIAL TUBE DESCRIPTION OF THE INVENTION This invention relates to a wide band grit circuit coristructed to have effect as a coaxial line thereby reducing the inductance of the grid line strip connecting the grids.

Typically, tubes having a coaxial terminal structure exhibit lower lead inductance from the tube elements to the external terminals, than do similar tubes having wire pin type terminals. However, to gain the advantage of the minimized inductance typified by the coaxial tubes, a coaxial circuit arrangement was necessary. The necessitating reason for a coaxial circuit is due to the fact that the cathode protrudes from within the grid structure. Further, for a grounded cathode circuit arrangement, the cathode is returned to effective or chassis ground potential, while the grid is at signal potential. The long lead necessary to return the cathode to ground usually contributes such additional inductance to the circuit arrangement that it is virtually impossible to use such tubes for broadband amplifier applications, as for example in a distributed amplifier.

It is an object of this invention, therefore, to provide a non-coaxial circuit grid line so constructed as to have effect as a coaxial line.

It is a further object of this invention, to provide a grid line structure for coaxial tubes such that reduced lead inductance is obtained.

lt is a still further object of this invention to provide a coaxial tube wide band coaxial grid circuit suited for use in broadband amplifier applications.

A still further object of this invention is to provide a grounded cathode coaxial tube having a non-coaxial grid circuit.

SUMMARY OF THE INVENTION The invention comprises a trough cover of any convenient shape or size over the base(s) of a coaxial tube(s). The trough is connected to a desired potential such as chassis ground, and to the cathode of the coaxial tube(s) thereby placing the cathode at the desired potential. The grid(s) of the coaxial tube(s) protrudes from the tube and extend into thc trough and is coupled to the control signal by means of a grid line inductor disposed within and isolated from the trough. The grid line inductor provides thereby a shielded grid control signal to the tube(s). ln this manner, the surrounding trough serves to reduce the effective inductance of the grid line, thus enabling higher cutoff frequency Capabilities of the line. Further the grounded trough not only 'serves to reduce the effective inductance ofthe grid line, but provides a low inductance ground lead for the cathode. Thus, the grid line structure, including the trough, may be considered to be a form of coaxial line,

having shunt discontinuities distributed in the form of tubes.

ln order that the invention will be more clearly understood, it will now be described in greater detail with reference to the accompanying drawings. in which:

FIG. I is an exploded view of a coaxial tube utilizing the trough structure according to the invention;

FIG. 2 is a cutaway drawing of a coaxial tube as illustrated in FIG. I;

0 grid collet 4A, a dielectric support 5, a grid line inductor 6, a screen bypass capacitor 7, a spacer 8, a ceramic chimney 9, a cathode ring 10, a control grid ring 1l, a screen grid ring 12 and ari anode contact 13. A rectangular trough I4 of plated copper having a hole 16 formed therein is fastened to the cathode collet 4A. The cathode collet 4A is so fastened to the trough 14 for example by soldering or welding, that electrical connection is made therebetween. Further, the cathode collet 4 is connected over the hole in the trough 4 thereby allowing for the insertion of the filament collet l, which when inserted protrudes into the cathode collet 4.

Insulating spacers 2 and bracket l5 are provided to insulate filament collet l from the trough I4, when supportably mounted thereto by suitable means, such as screws. Grid collet 4 has a larger diameter than the cathode collet 3 and is mounted to a dielectric support S, such as epoxy glass, such that the grid collet 4 forms ari outer sleeve over the cathode collet 3. The dielectric support 5 insulates the grid from the chassis I7. In this manner, both the cathode collet 3 and the grid collet 4 are disposed in the trough 14. The trough l4 is connected to the chassis by any suitable means, such as screws. thereby electrically coupling the cathode collet 3 to the chassis ground potential. A grid line inductor 6 is connected to the grid collet(s) 4 for coupling a control signal thereto.

The grid line inductor 6 is so connected to the grid(s) that it is within, but is not electrically connected to, the trough I4 and is shielded thereby. Thus by so constructing the grid(s) circuit to effectively include the trough I4 as a shield, a virtual coaxial line is formed having a shunt discontinuity(ies )distributed in the form of a tube(s). The surrounding trough serves to reduce the effective inductance of the grid line, while the chassis connection to the trough-cathode provides a low iriductance ground return lead for the cathode. It can further be seen by reference to FIG. 1 that a grid circuit structure according to the invention is most advantageous in a multitube (wide band amplifier) circuit having grounded cathodes and requiring low grid line inductance. FIG. l Shows the tube base and grid line structure for two tubes, i.e., the tube base structure explained in accordance with FIG. l comprising cathode collet 3A, grid collet 4A, insulating spacers 2, support bracket l5, filament collet I, a dielectric support (5) and the tube chassis I7, the second tube (or multitube) base grid line comprises a similar structure and is illustrated by cathode collet 3B and grid collet 4B of the second tube.

FIG. 2 is a cutaway drawing of a coaxial tube having a grid circuit and chassis connected cathode as described with reference to FIG. I. As can be seen, the cathode collet (22) is connected to the trough 20 and is placed over the filament collet 2l. The trough has a hole 27 formed therein to allow the insertion of the filament collet 2l into the cathode collet 22. The trough is connected to the chassis 19 by suitable means, such as screws, through mounting holes 28, The grid collet 23 protrudes within the trough 20 over the cathode collet 22 and is mounted to an insulating dielectric support 24. A screen bypass capacitor 18 forms part of the upper portion of the tube 25 and is connected to the chassis 19 and trough 20 by means of mounting holes 28. A grid line inductor 29 is connected to the grid(s) thereby providing a control signal path. In this manner, the grid line 29 is shielded within the grounded trough 20 and the chassis 19. Since the operation and construction of a coaxial tube is well known in the prior art, a detailed description of such has herein been omitted.

FIG, 3 shows a circuit diagram ofa distributed amplifier. Since the operating principals of such amplifiers are well known, a detailed description will not be herein repeated. Basically, however, it can be seen that the grid line consists of the chokes L14 to L22 and L24 to L31, along witli the capacitances from grid to ground. The amplifier is connected in two modules, the upper one terminating in tube V8, the output from which is fed via C10 and L32 into V16, and from there to the output terminal. In this regard, and with reference to FIG. 1 also, it should be recognized that when multiple tubes are used in a distributed amplifier circuit, the high frequency performance of the amplifier is limited by such things as the inductance ofthe cathode, grid and plate structure. This invention, by means of the non-coaxial grid circuit, including the trough, substantially reduces the inductance of the grid line inductor strip 6. Further, by constructing a rectangular trough 14 over the bases of the tubes 4A, 4B of the distributed amplifier, the grid line inductor strip 6 is effectively electrically shielded. The

cathode collets

3A, 3B are connected to the bottom of the trough 14 and the trough is connected to the chassis 17, thus placing the cathodes at the chassis (ground) potential. Generally, long leads are necessary to return the cathodes to ground, thus adding unwanted inductance and limiting the high frequency performance of the amplifier. However, the invention, by means of the chassis grounded trough 14 eliminates the need for long leads and thus further improves the high frequency performance of the amplifier.

FIG. 3B shows a partial structure view of a distributed amplifier circuit having grid line L14 to L16 as is shown in electrical circuit diagram 3A. Only the grid line structure according to the invention is shown. It is to be understood that such structure would be continued for all the amplifying stages of the distributed amplificr.

Whereas the present invention has been described with respect to specific embodiments thereof, it will be understood that various changes and modifications will be suggested to one skilled in the art, and it is intended to encompass such changes and modifications as fall within the scope of the appended claims.

What is claimed is:

l. A coaxial tube assembly comprising;

a chassis;

a substantially rectangular trough electrically connected to said chassis;

a coaxial tube mounted to said chassis having a grid,

cathode and anode wherein said cathode is electrically connected to said trough; and

a grid line substantially located within said trough and electrically connected to said grid. 2. A plurality of coaxial tube assemblies as described in claim l, wherein: 5 each has a grid which protrudes into the trough and is electrically insulated therefrom; and

each has a cathode which protrudes from within the grid and is connected to the trough.

3. A plurality of coaxial tube assemblies comprising:

a chassis;

a substantially rectangular trough electrically connected to said chassis and having a plurality of holes formed therein;

coaxial tubes supportably mounted to said chassis, each having a heater filament, a cathode collet, a grid collet and an anode, wherein said heater filaments protrude into said cathode through one of said holes, each of said cathode collets is connected to said trough around each of said holes and protrudes from within each of said grid collets; and each of said grid collets protrudes into said trough; and

a grid line substantially laying within the trough and electrically connected to said grid.

4. A wide bank non-coaxial distributed amplifier circuit assembly comprising:

a chassis;

a substantially rectangular trough electrically connected to said chassis;

a distributed amplifier of coaxial tubes having an anode, a grid collet and a cathode collet wherein the cathode collets are electrically connected to said trough; and

a grid line substantially within said trough and electrically connected to the grids.

5. A wide band non-coaxial distributed amplifier circuit assembly as described in claim 4, wherein;

the grid protrudes into said trough and is electrically insulated therefrom; and

the cathode collet protrudes from within the grid and is connected to the trough.

6. A circuit element for use with coaxial tubes comprising a first conductive element having at least one cathode collet mounted thereon and electrically connected thereto, said first conductive element being connectable to a reference potential and having means for securing said rst conductive element to an electrically conductive structural element, said first conductive element being substantially rectangularly configured to define with such an electrically conductive structural element a passageway within which said cathode collet is disposed which passageway constitutes means for confining and shielding a grid current carrying conductor.

7.. A circuit element as claimed in claim 6 wherein said first conductive element is trough shaped and said at least one cathode collet is secured to a base of said conductive element.

8. A circuit element as claimed in claim 6 wherein said first conductive element defines aperture means adjacent said cathode collet for the insertion of the cathode heating element.

9. An assembly of coaxial tubes each tube comprising a grid collet, a cathode collet and a heater element; a substantially rectangularly shaped electrical conductor element to which the cathode collet of each tube is electrically connected, said electrical conductor elesaid electrical conductor element constituting shielding means for said grid signal Carrying Conductor means.

l0. An assembly as claimed in claim 9 wherein said electrical conductor element is trough shaped having sides and a base, said structural element is secured to said sides to define said passage means and said cathode collets are secured to the base of said electrical conductor element.

k =k Ik

Claims

1. A coaxial tube assembly comprising: a chassis; a substantially rectangular trough electrically connected to said chassis; a coaxial tube mounted to said chassis having a grid, cathode and anode wherein said cathode is electrically connected to said trough; and a grid line substantially located within said trough and electrically connected to said grid.

2. A plurality of coaxial tube assemblies as described in claim 1, wherein: each has a grid which protrudes into the trough and is electrically insulated therefrom; and each has a cathode which protrudes from within the grid and is connected to the trough.

3. A plurality of coaxial tube assemblies comprising: a chassis; a substantially rectangular trough electrically connected to said chassis and having a plurality of holes formed therein; coaxial tubes supportably mounted to said chassis, each having a heater filament, a cathode collet, a grid collet and an anode, wherein said heater filaments protrude into said cathode through one of said holes, each of said cathode collets is connected to said trough around each of said holes and protrudes from within each of said grid collets; and each of said grid collets protrudes into said trough; and a grid line substantially laying within the trough and electrically connected to said grid.

4. A wide bank non-coaxial distributed amplifier circuit assembly comprising: a chassis; a suBstantially rectangular trough electrically connected to said chassis; a distributed amplifier of coaxial tubes having an anode, a grid collet and a cathode collet wherein the cathode collets are electrically connected to said trough; and a grid line substantially within said trough and electrically connected to the grids.

5. A wide band non-coaxial distributed amplifier circuit assembly as described in claim 4, wherein: the grid protrudes into said trough and is electrically insulated therefrom; and the cathode collet protrudes from within the grid and is connected to the trough.

6. A circuit element for use with coaxial tubes comprising a first conductive element having at least one cathode collet mounted thereon and electrically connected thereto, said first conductive element being connectable to a reference potential and having means for securing said first conductive element to an electrically conductive structural element, said first conductive element being substantially rectangularly configured to define with such an electrically conductive structural element a passageway within which said cathode collet is disposed which passageway constitutes means for confining and shielding a grid current carrying conductor.

7. A circuit element as claimed in claim 6 wherein said first conductive element is trough shaped and said at least one cathode collet is secured to a base of said conductive element.

9. An assembly of coaxial tubes each tube comprising a grid collet, a cathode collet and a heater element; a substantially rectangularly shaped electrical conductor element to which the cathode collet of each tube is electrically connected, said electrical conductor element being connectable to a reference potential, means physically connecting said conductor element to a structural element of said tubes and defining therewith passage means, said cathode collets being disposed within said passage means, the grid collet of each tube extending into said passage means in coaxial relationship with associated ones of said cathode collets, and grid signal carrying conductor means disposed within said passage means and connected to said grid collets, said electrical conductor element constituting shielding means for said grid signal carrying conductor means.

10. An assembly as claimed in claim 9 wherein said electrical conductor element is trough shaped having sides and a base, said structural element is secured to said sides to define said passage means and said cathode collets are secured to the base of said electrical conductor element.