US2526399A - Output connection for ultra high frequency devices - Google Patents

Description

Oct. 17, 1950 E. c. OKRESS EI'AL 2,526,399

OUTPUT CONNECTION FOR ULTRA HIGH FREQUENCY DEVICES Filed Dec. 23, 194: I

\ M 51 sa w a4 18 40 19.1 43 4 2 I 43 INVENTORS ATTOR N EY Patented Oct. 17, 1950 OUTPUT CONNECTION FOR ULTRA HIGH FREQUENCY DEVICES Ernest C. Okress, Montclair, and Leonhard W.

Holmboe, East Orange, N. J assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 23, 1943, Serial No. 515,346 (01. 17s 44) 5 Claims.

This invention relates to ultra high frequency devices, and more especially to output connections for such devices as magnetrons and the like.

One difficulty encountered in the output connections of the prior art has been the electrical breakdown'in the connection. It is usual for magnetrons and other high frequency devices to each provide an output connection which presents an outwardly extending exposed output lead the inner part of which is within the vacuum of the magnetron, saidlead being sealed by means of a surrounding glass sleeve closed at its outer end. The exposed outer end of the lead attaches to the center rod of a coaxial line, in the prior art, by a resilient fingered friction coupling. The assembly thus made is apt to be imperfect since the glassing cannot readily be made ideal electrically. Also the frictional contact member frequently makes poor contact with the lead, especially in view of the small diameter of such lead. In part, as a result of these conditions of prior art structures, suchadverse effects as brush discharge, excessive sparking, cracked glass, loss of vacuum, and so forth, occur.

Broadly considered, therefore, the present input connection which can be relied upon to assure good electrical conductivity and avoid conditions likely to result in injury to the glassing of the lead Wire.

Furthermore, an object of the invention is to provide an output connection which includes a transformer as part thereof.

A further object of the invention is to arrange for the releasable joining of the coaxial line to the magnetron with a resilient plug-in assembly from which the glassing is protected.

Still further objects of the invention will appear to those skilled in the art to which it appertains, as the description progresses, both by 'direct recitation thereof and by implication from the context.

Referring to the accompanying drawing in which'like numerals Ofreference indicate similar parts throughout the several views:

.Figure 1 is a longitudinal section of an output connection in accordance with the present invention;

Figure 2 is a cross-section thereof. as on line Figure 3 is a elevational view partially broken 2 J- away showing amodified construction oftransformer section; and

Figure 4 is a longitudinal sectional view similar to Figure 1, showing a further modified construction of parts.

In the specific embodiment of the invention illustrated in said drawing, the reference numeral iii designates the ultra high frequency generator, here shown as a'magnetron having cathode ll, anode l2 and resonator cavities l3 therein as usual'.- The output connection includes a conductive base or thimble. H, as of copper, which threads into the anode and opens into one of said cavities. After the thimble is positioned, ,it is soldered in place to make it vacuum tightp Said thimble provides a central passage I6 longitudinally therethrough which is continued at the outer end of'the thimble by the hollow interior of an axially alined tube I'l soldered thereon. Said tube is of appropriate material, such as an alloy sold in the trade under the name of Kovar, which willform an appropriate seal with glass, and at its outer end said tube is closed by a glass seal l8. Also sealed by said glass seal I8 is a central metallic lead l9 coaxial within the tube and thimble and having a loop 20 within the cavity I3 from which the thimble projects. The outer end of the lead l9 projects through the glass seal l8, and it is to this projecting end that the output connection is made for power transmission from the ultra high frequency device. The glass seal, by sealing with respect to both said lead and tube, maintains the vacuum within the passage l6 and within the magnetron.

The said thimble also provides a flange 2| thereon next its outer end, this flange havinga forwardly facing circular groove 22 therein and a screw threaded periphery. ,Said groove receives the rear end of a coupling collar 23 sealed therein, said collar having a circumferential shoulder 24 in the proximity of said rear end upon which a clamping ring 25 will seat. The clamping ring is internally threaded toscrew onto the threaded periphery of the thimble flange thereby retaining the collar seated in said groove and co-axially disposed with respect to the thimble, tube, passage and lead. The collar is hollow and considerably larger than the tube thereby providing a generous annular space .therebetween. Projecting into this'space is the rear end ofa section 26 of an outer tubular portion of acoaxial line. The forward end of the collar is flanged inwardly and soldered, as at 21, to said section 26 for obtaining electrical continuity conductor 31.

thereat as well as fixed and coaxial mounting of the collar upon said section.

Heretofore it has been general practice to provide a detachable connection to the projecting lead [9 from a central conductor in the coaxial line section therearound. The necessarily small diameter of the lead has been a contributing cause for poor contact in such detachable connection. Improper shaping of the end of the glass seal has been a cause contributing to breakdown. Long length of exposure of the lead between the glass seal and the connection has resulted in creation of brush discharge at high power output. For these and other reasons, we find it undesirable to employ a detachable connection exposed to the seal upon the small lead at its exit from the glass seal.

According to the showing of Figure 1, a transformer section 28 is applied permanently on the projecting end of the lead. The contact will be very snug and substantially the full length of the projecting end and said transformer section may be brought at its rear end into close proximity to the glass seal. Basing cement 29 or other material may then be applied in the crevice between the transformer end and the glass. By virtue of this construction, sparking and brush discharge are entirely avoided and causes for breakdown eliminated.

With further reference to Fig. 1, the transformer section is shown as a cylindrical barlike structure appropriately 'socketed at 3G to snugly receive lead 19, said lead I9 havin a quarter wave-length transformer 31 at a specific position in the line so as to present to the gen- "erator a specific impedance or'desirable operating condition. Behind the transformer 1ooking'into the line a very low standing wave ratio "is maintained. The transformer maybe formed a as an enlargement 3| as shown in Fig. 1, or as a recession 31* as shown in Fig. 3, depending upon the character of the total impedance which the generator is to see in order to work at the desired operating region with respect to the applied fields. Beyond the transformer represented by enlargement 3| or recession am the diameter of the next contiguous portion 32 is substantially the same as at the socketed end,

and then at the outermost part is reduced at 33 and end tapered at 34 to constitute a plugin portion, for which purpose that end of the section is longitudinally slit at 35. This plugin portion comprisin the reduced and tapered parts 33, 34, is constructed for insertion in and frictional contact with the wall of a socket 315 provided for the purpose in the contiguous end of a coaxial line center conductor 31 the diameter of which is the same as'the general rodlike part of the transformer to form a virtual surface continuation thereof. Resiliency of the plug-in part of the transformer section permits removal and insertion with respect to the center The outer conductor38 of this continuation coaxial line section has the same diameter as the outer conductor 26 of the transformer section of which it may be an integral or separable part. As shown, the outer conductors are separable and mechanically coupled.

The particular coupling shown for the outer conductors of the separable coupling comprises sleeves 39, 40 soldered or otherwise secured to the end margins of thesections and each projecting beyond said sections and abutting at their proximate ends preferably with a tapered engagement. At the outside of the sleeves are flanges 4|, 42 one of which, as 4| is rearward of the forward edge of the sleeve with which it is formed, and the other, 42, of which projects correspondingly toward the first so as to engage the same and interlock therewith. Clamping plates 43 overlie these flanges, said plates being shown square, and screws 44 engage between the plates next the corners thereof to clamp them toward each other and thereby clamp the flanges, sleeves and conductor sections together. Figure 3 illustrates the outer conductor as integrally formed in the region around the plug-in connection of the inner conductor.

While in Figure 1 the transformer is illustrated as enlargement 3| on the inner conductor and is shown in Fig. 3 as a recession 3W, both in the non-evacuated part of the line, equivalent transformer effect may be obtained by applying transformer means to the evacuated line, and this modification is included in the showing of Figure 3. In that View base or thimble l4 next the end which screws into the magnetron provides a cylindrical passage H5 for the lead l9 next to the loop 20 thereof. This passage It expands abruptly into a larger cylindrical passage lfi next to the outer part of the thimble and of a diameter equal to that of the Kovar tube IT. A cylindrical neck 3| projects into this enlarged cylindrical passage H3 and constitutes the transformer section which establishes the desired input impedance and consequently operating condition for the generator. Such an arrangement removes the necessity for establishing a high standing wave ratio in the line in order to present the proper input impedance to the generator.

The showing of Figure 4 presents a modification in lead-in and plug-in construction. Since the transformer is incorporated as part of the thimble, a removable transformer section as shown in Figure 1 is not applied at the outer end of the lead, but the continuation coaxial line is applied directly thereto. Accordingly, in Figure 4 the outer tubular coaxial line conductor 38 is applied directly to the coupling collar 23 which is juxtaposed to the nipple. Toward the outer end of the lead where glassed in glass seal l8 the lead has a gradual flaring portion 45 so that beyond the glassing the lead will have an outside diameter equal to that of the central conductor 31' of the coaxial line. The end of the projecting lead is socketed at 46 to receive the split reduced plug-in portion 41 of the central conductor of the coaxial line. This structure obtains a large surface contact between the wall of the socket and the plugin portion 4'! and also protects the glassing from injury consequential upon any possible arcing at the plug-in junction.

The transformer geometry, referred to in the output device of Figure 4, can be readily determined from cold impedance measurements and four terminal network theory once a desirable operating point is chosen on the circle diagram of the generator. A circle diagram is one containing power output, applied voltage and frequency as a function of the SWR (V) and phase angle with reference to some point in the line to which the generator is connected.

The construction disclosed herein, reference being made specifically to Fig. 4 for brevity although with change of reference numerals it is equally applicable to Fig. 1, is for purposes of achieving the desired operating point for the micro-wave generator or magnetron and an approximately matched line with conductor ratios so arranged as to obtain a maximum energy transfer, at a minimum electric gradient in the coaxial line exposed to air. The impedance for the desired operating point is established across a plane transverse to the loop and at the end of the thimble within the magnetron, and established by virtue of a fixed transformer, which in Fig. 4 is at 3l The energy is therefore propagated in vacuum in the region between coaxial conductors I1 and I9 and through the glass seal l8 into the air or other medium of the output coaxial line by benefit of tapered section 45 and outer conductor 38'. The purpose of the tapered section is to increase the center conductor diameter as quickly as possible but without introducing disruptive continuities to the energy transfer.

The outer conductor H of the vacuum section of the coaxial line is electrically shorted at its forward extremity (the end farthest from the magnetron) by virtue of a half wave folded line. The folded line is the gap spacing on both sides of the wall of tube 38 from beneath the shoulder in coupling collar 23 down and around the end of the conductor tube 38 and then up to the afore-v mentioned forward extremity of coaxial tube 11'. This folded line is all in a single medium, which in this showing is air, since that part of the device outside of conductor I7 is not evacuated. The folded line is, however, directly opposite or girdles the evacuated region within conductor H. By the construction shown, the high impedance established at the lower end of tube wall 28' is reflected through the characteristic impedance of line I1, 38', as a very low impedance at the forward-extremity or transverse plane of collar 23, since the low impedance at the said forward plane establishes a virtual radio frequency short thereacross.

Confining the transformer, as in Fig. 4, within the vacuum avoids the necessity of tolerating the standing wave ratio requisite thereat, in the air between the tapered line conductor 45 and outer conductor 38' and accompanying possible breakdown because of excessively high electrical intensities due to the standing wave pattern in the line. The transformer used in this form of the invention is a predetermined fixed impedance transforming section which permits the generator to operate into a chosen impedance which may require a high standing wave ratio due to resonant characteristic in the coupling device, and this would be undesirable if accomplished in a line exposed to air.

We claim:

1. An output connection for ultra high frequency devices comprising a lead, a coaxial tube around a part of said lead, a glass seal between said lead and tube vacuum sealing the region in said tube at the rear of said glass seal, a rodlike means of greater diameter than said lead secured thereon forward of and in proximity to said glass seal, and a filler interposed between said glass seal and said rod-like m an aid rodlike means having its forward end constituting one member of a plug-in connection and presenting greater circumference than the circumference of said lead.

2. An output connection for ultra high frequency devices comprising a hollow thimble adapted to be evacuated with said device, a center lead passing through said hollow thimble, means sealing the thimble and lead, and a transformer within the evacuated portion of said thimble;

,3. An output connection for ultra high frequency devices comprising 'a hollow thimble adapted to be evacuated with said device, a center lead passing through said hollow thimble, means sealing the thimble and lead, and a transformer outside the evacuated portion of said thimble.

4. An output connection for evacuated ultra high frequency devices, comprising a coaxial line from said device, said line having inner and outer conductors of which the inner conductor has one end which protrudes into said device, means vacuum sealing an evacuated region around a portion of said inner'conductor next said device, said inner conductor having exterior line connection past said sealing means, and 'a transformer in the line confined entirely within said evacuated region.

5. An output connection for evacuated ultra high frequency devices to an output line, comprising a vacuum sealed evacuated enclosure having a relatively small-diameter inner, conductor therethrough, the said enclosure including an outer conductor as part thereof, an inner conductor exterior to said enclosure of several times greater diameter than the said small-diameter inner conductor'and constituting a continuation thereof, the outer end of said greater-diameter inner conductor providing a releasable plug-in connection with said output line and having meansfor overcoming brush discharge and the like next the vacuum seal of said small-diameter inner conductor, and a transformer interposed between the generator and said plug-in connection and retained as a permanent and fixed part with the generator.

ERNEST C. OKRESS. LEONHARD W. HOLMBOE.

. REFERENCES CITED The following references are of record in the file of this patent:,'

. UNITED STATES PATENTS Number Name Date 1,928,408 Clavier Sept. 26, 1933 2,125,597 White'et al Aug. 2, 1938 2,127,408 Kaar Aug. 16, 1938 2,129,713 Southworth Sept. 13, 1938 2,304,186 Litton Dec. 8, 1942 2,309,966 Litton Feb. 2, 1943 2,311,520 Clifford Feb. 16, 1943 2,311,658 Hansen et al. Feb. 23, 1943 2,332,952 'Iischer et al. Oct. 26, 1943 2,351,895 Allerding June 20, 1944 2,414,785 I Harrison et al. Jan. 21, 1947 2,424,002 Sloan July 15, 1947 2,429,243 Snow et al. Oct. 21, 1947

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