US2414084A - Tunable resonator and oscillator - Google Patents

Description

Jan. 14, 1947. ow 2,414,084

TUNABLE RESONATOR AND OSCILLATOR Filed May 11, 1943 3 Sheets-Sheet l INl/ENTOR AE. BOWEN 8V ,4 T TORNE V Jain. I4 1947.

A. E. BOWEN TUNABLE RESONATOR AND OSCILLATOR Filed May 11, 1943 3 Sheets-Sheet 2 //v l ENTOR 4 AE. BOWEN By 14, 1947. BOWEN TUNABLE RESONATOR AND OSCILLATOR Filed May 11, 1943 5 Sheets-Sheet 3 //v vs/v TOR A. E. BOWEN I BY W M A T TORNEV Patented Jan. 11.1947:

after with reference to Et STATES PATENT OFFlC 2,414,084 v TUNABLE RESONATOR AND oscniLA'roR' Arnold E. Bowen, Red Bank, N. J., ,assignor to Bell Telephone of New York Application May 11, 1943, Serial No. 486,579

This invention relates to resonators and oscillators and, as to oscillators, particularly those of the magnetron variety with a segmented anode.

An object of the invention is to provide adjustable tuning for a resonator or oscillator.

Another object is to minimize losses by uncontrolled radiation from a high frequency oscillator particularly where the oscillator has adjustable tuning.

A feature of the invention resides in the manner of merging a segmented anode with a concentric transmission line structure.

Another feature is a combination of a segmented anode inside a vacuum envelope with a tuning adjustment outside the envelope.

A further feature of the invention is a halfwave resonator formed of a combination of a segmented anode with aconcentric linetuner, the resonator having short-circuited ends to prevent undesired radiations.

The invention is described in detail hereinthe accompanying drawings in which:

Fig. 1 i a perspective view, partly broken away, showing one form of magnetron oscillator embodying the invention;

Fig. 2 is a cross-sectional view in a vertical plane through the line 2-2 in Fig. 1;

Fig. 3 shows another embodiment of themvention;

Fig. 3A is a fragmentary view showing a modification of the structure of Fig. 3;

Fig. 4 shows still another embodiment of the invention; and I Fig. 5 is a cross-sectional view of the structure of Fig. 4 in a vertical plane through the line 5-5 in Fig. 4. I

In Fig. 1 there is shown within a vacuumtight envelope ID, a conductive cylindrical anode II which is slotted from one end to form a plurality of segments, such as I2, I 3,, I4 and I5. All the segments are conductively connected together or short-circuited at'one end by the body of the anode II. In Fig. 1 the short-circuited end appears at the right. At the open end, which is at the left in the figure, alternate segments including I2 and I4 are cut shorter than the others and are conductively joined together by a ring or yoke I*6 which may be shapedas shown, somewhat in the physical form of an internal gear with cut-away portions providing clearance for the remaining anode segments including the segments I3 and I5. as appears in cross-sectional view in Fig. 2. The latter group of segments are conductively connected together by a second supports 24 2 Claims. (Cl. 250-275) ring I'I. spaced apart from the ring I8, as shown. The ring I! requires no clearance spaces as the group of segments including I2 and I4 do not extend as far as the ring II. A Lecher pair I8, I9 is shown connected to the rings I6 and I I. The individual wires I8 and I9 of the Lecher pair may be sealed through the envelope I0 and the pair may be provided with a short-circuiting movable bridge 20 and any suitable mechanical adjusting means, represented here by a bent rod 2| with an insulating handle 22.

The cathode may be an axial filament 23 attached to supports 24 and 25. The envelope I I) may include a suitable press 26 for mounting the and 25 as well as an anode support 21. In well-known manner the supports 24, 25 and 21 may serve a leading-out conductors for the respective filament and anodeterminalsx Any suitable cathode heating means, such as a battery 28, may be provided, together with a source of anode potential such as a battery 29. Windings .30 and 3| may be provided, preferably external to the envelope II), to set up a suitable magnetic field inside the anode II. As is customary in this art, the axis of the magnetic field may be slightly tilted with respect to the axis of the anode II in order to impart a helical motion to electrons within the anode so that the electron motion is progressive along the axis.

In the operation of the arrangement of Figs. 1 and 2, electrons are emitted by the cathode 23 and constrained to circulate in the vicinity of the anode segments in manner well-known in the art, with result that high frequency oscillations in the slots becircuiting connection across the Lecher pair to constitute theother end of the half-wave resonator. It is found that electromagnetic waves can form standing wave patterns in the resonator as so constructed, with voltage nodes at the shortcircuited ends and with a voltage antinode appearing between adjacent anode segments over a portion of the anode II between the ring I6 and the right-hand end of the anode. The resonant frequency of the. system may be adjusted by moving the bridge along the wires I l and I! by manipulating the handle 22. As brought, out in Fig. 1, the electronic portion or the magnetron structure is situated inside the envelope whereas the adjustable portion oi the tuning element is located outside the envelope where adjustment is accomplished without the mechanical complication of any linkage'extending through the envelope.

In the arrangement of Fig. 3, the anode II and the rings I6 and I! connected to alternate anode segments are the same as in the arrange-' ment of Fig. i. The Lecher system in this case, however, is in the form of a concentric transmission line having an outer conductor 50 conductively attached to the ring l6 and an inner conductor 5| conductively attached to the ring I]. An annular slidable tuning member 52 is provided in the space between the conductors 50 and 5|. The member 52 may be adjusted in position by means of rods 33 and 34 attached thereto and provided with insulating handles 35 and 36. The vacuum-tight envelope may be arranged in any suitable manner so as to enclose the anode and leave the concentric line partially outside the vacuum space to permit the tuning adjustment to be efiected outside the envelope as in Fig. 1. Fig. 3 shows the envelope in three sections. The righthand section 31 is sealed to the right-hand side of the ring I6 in Fig. 3. A middle section 38 is inserted between the rings l5 and I1 and the lefthand section 39 is sealed to the left-hand side of the ring l1. The filament 23, which is axially 7 located as in Fig. 1, may be shorter than the anode II, as shown in Fig. 3, in order to limit the thermionic emission to the region where the electric field is the strongest, that is, the left-hand half to two-thirds, or so, of the anode, constituting a voltage antinode. ment is shown attached to a leading-out conductor 40 which is sealed through the envelope section 39. An insulating spacer 4|, such as a mica disc, may be employed for centering the conductor 40. The other end of the filament may be attached to a conductor "which is in turn conductively connected to a tension maintaining spring 43, which latter is connected to a leadingout conductor 44' that may be sealed through the section 31 of the envelope. A second insulating spacer 45 may be employed between the filament 23 and the spring 43 to center the conductor 42. The filament may be heated by means of the battery 28 as in the arrangement of Fig. 1 and the anode battery 29 may be connected to the outer conductor 50 of the concentric line outside the envelope, which is in conductive connection with the anode through the ring I6. A solenoid 30 may be provided to set up the desired magnetic field inside the anode The operation of the system of Fig. 3 is essentially the same as in the case of the arrangement of Figs. 1 and 2, the tuning being accomplished by manipulating the handles and 35 to adjust the position of the annular tuning member 52.

In the arrangements so far described, the anode is preferably designed to be approximately a quarter wave-length long, the Lecher system then comprising an additional quarter wave-length to make up the desired half wave-length for the combined structure. If desired, however, the anode as a unit may be made to operate substan-- tially as a half wave-length resonator. In this case the system may still be tuned by means of the exterior Lecher system, although the range of tuning is generally reduced. Fig. 3A shows a way in which the structure oi Fig. 3 may be mod- One end of the filaified so as to permit the anode to operate substantially as a halt-wave resonator. For this purpose there is attached to the left-hand surface or the ring I6 a short length of hollow tubular conductor 54 The conductor 54 has an inner diameter a little greater than the outer diameter or the anode II to afford a clearance between the conductor 54 and the segments such as I3 and I5 attached to the ring IT. The conductor 54 partly closes the space between the rings l6 and I! but leaves an annular gap through which electromagnetic waves reaching the rings l8 and I1 from the anode may enter into the space between the concentric conductors and 5|. A considerable capacity is provided between the conductor 54 and the segments such as i3 and i5, this capacity serving as a partial short-circuit between the two sets of anode segments at the left-hand end of the anode II in Fig. 3A.- The presence of the substantial short-circuit tends to make the anode operate as a halt-wave resonator by determining a voltage node at this point. The resonator is coupled to the adjustable tuning device through the annular space above described between the conductor 54 and the ring H. The annular tuning member 52 will in this case be adjusted to a position approximately a halt wave-length distance from the left-hand end of the anode. A certain amount of variation in the resonant frequency oi the system as a whole may be obtained by adjusting the position of the element 52 although, as above mentioned, the tuning range will generally not be as great as in the case where the anode serves approximately as a quarter wave-length section as in the arrangement of Figs. 1' and 2.

Fig. 4 shows an alternative construction in which the envelope is in a single section 55. The inner conductor 5| of the concentric transmission line is connected directly to alternate segments of the anode by means 01! a plurality of straight rods or wires 60 which pass through the envelope 55 and may be soldered to the conductor 5| outside the envelope. The outer conductor 50 is connected to the remaining segments oi the anode by bent rods or wires 5| which also pass through the envelope and may be soldered to the conductor 50 outside the envelope. The concentric line is in efiect passed through the envelope by means of the plurality of rods or wires and 6 A sectional view of the rods and their attachment to the anode segments is shown in Fig. 5. Instead of the filamentary cathode of Figs. 1 and 3, an indirectly heated cathode 23' of any suitable known construction is shown in the arrange ment of Fig. 4. The indirectly heated cathode may be inserted from one end of the envelope as shown and has the advantage that it is more easily centered than the filament and does not require spring tension. The thermionicaliy active portion of the cathode 23' may be confined to the region in the strongest portion of the electric field, by applying a suitable coating in that region.

Couplings for picking up the generated electromagnetic waves and means for conveying the waves to an antenna or ay other suitable utilization circuit or device may be provided in conventional manner. For clarity in the drawings, such output coupling means have been omitted. but these will be readily supplied by anyone versed in the ultra-high frequency art.

What is claimed is:

1. A resonator comprising a segmented anode, each segment of which has a free end at one and the same end of the anode and all of which'seg-' ments are conductively connected together at the other end by the body portion of the anode; a pair of conductive means joining together the free ends of alternate segments into two insulated groups, respectively, and a concentric transmission line, the inner and outer conductors of which are connected respectviely to said conductive Joining means.

2. A magnetron oscillator comprising a vacuum-tight envelope containing working electrodes including a segmented anode, the segments of which anode are all conduotlvely connected togather at one end. and tree at the other, a concentric line section located outside said envelope and having a closed end adjustable by means of a slidable short-circuiting conductor and having the opposite end open-circuited, means conductively connecting the free ends of the anode segments into-'two groups, said groups being insulated from each other, and means conductively connecting thesaid groups 0! segments with the respective terminals of the open circuited end of said concentric line section.

ARN-OLD E. BOWEN.

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