Jan. 14, 1947. A_ E, BowEN 2,414,084 TUNABLE RESONATOR AND OSCILLATOR Filed May 11, 1943 3 Sheets-Sheet l INl/ENTOR AE. BOWEN 8V ‘WM ,4 T TORNE V Jain. I4? 1947. A. E. BOWEN 2,414,084 TUNABLE RESONATOR AND OSCILLATOR Filed May 11, 1943 3 Sheets-Sheet 2 17a.3 4 I. //v l/ENTOR 4 AE. BOWEN By 14, 1947. A, E, BOWEN 2,414,084 TUNABLE RESONATOR AND OSCILLATOR Filed May 11,, 1943 5 Sheets-Sheet 3 \ \\ //v vs/v TOR - I A. E. BOWEN BY WA TM TORNEV Patented Jan. 11.1947: " ‘I 2,414,084 1 / ; UmEt " STATES‘ ‘PATENT OFFlC E . - _ 2,414,084 _ . v TUNABLE RESONATOR AND oscniLA'roR' Arnold E. Bowen,‘ Red Bank, N. J., ,assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application May 11, 1943, Serial No. 486,579 2 Claims.‘ (Cl. 250-275) This invention relates to resonators and oscil ' lators and, as to oscillators, particularly those of the magnetron variety‘ with a segmented anode. 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 An object of the invention is to provide adjust extend as far as the ring II. A Lecher pair I8, able tuning for a resonator or oscillator. I9 is shown connected to the rings I6 and I ‘I. Another object is to minimize losses by uncon The individual wires I8 and I9 of the Lecher pair trolled radiation from a high frequency oscillator may be sealed through the envelope I0 and the particularly where the oscillator has adjustable tuning. pair may be provided with a short-circuiting A feature of the invention resides in the man 10 movable bridge 20 and any suitable mechanical adjusting means, represented here by a bent rod ner of merging a segmented anode with a con 2| with an insulating handle 22. centric transmission line structure. The cathode may be an axial ?lament 23 at Another feature is a combination of a seg tached to supports 24 and 25. The envelope I I) mented anode inside a vacuum envelope with a may include a suitable press 26 for mounting the tuning adjustment outside the envelope. 15 supports 24 and 25 as well as an anode support A further feature of the invention is a half 21. In well-known manner the supports 24, 25 wave resonator formed of a combination of a and 21 may serve as leading-out conductors for segmented anode with a‘concentric linetuner, the the respective ?lament and anodeterminalsx resonator having short-circuited ends to prevent Any suitable cathode heating means, such as undesired radiations. ' ' ' 20 a battery 28, may be provided, together with a The invention is described in detail herein source of anode potential such as a battery 29. after with reference to the accompanying draw Windings .30 and 3| may be provided, preferably ings in which: , external to the envelope II), to set up a suitable Fig. 1 is a perspective view, partly broken away, showing one form of magnetron ‘oscillator em ~25 magnetic ?eld inside the anode II. As is cus tomary in this art, the axis of the magnetic ?eld bodying the invention; may be slightly tilted with respect to the axis Fig. 2 is a cross-sectional view in a vertical of the anode II in order to impart a helical mo plane through the line 2-—2 in Fig. 1; tion to electrons within the anode so that the Fig.v 3 shows another embodiment of them electron motion is progressive along the axis. vention; . In the operation of the arrangement of Figs. 1 Fig. 3A is a fragmentary view showing a modi? 30 and 2, electrons are emitted by the cathode 23 cation of the structure of Fig. 3; . and constrained to circulate in the vicinity of Fig. 4 shows still another embodiment of the the anode segments in manner well-known in the invention; and I art, with result that high frequency oscillations Fig. 5 is a cross-sectional view of the structure of Fig. 4 in a vertical plane through the line 35 are produced in the anode and in the slots be- ' tween the anode segments. The segmented 5-—5 in Fig. 4. I anode structure is merged physically and elec-‘ In Fig. 1 there is shown within a vacuum- ' trically into the Lecher pair I8, I9 by means of tight envelope ID, a conductive cylindrical anode the rings I6 and I1. The combined system is II which is slotted from one end to form a plu rality of segments, such as I2, I 3,, I4 and I5. All 40 found to constitute a half-wave resonator having short-eircuited ends. The right-hand end por the segments are conductively connected together tion of the anode I I, which is conductively joined or short-circuited at'one end by the body of the to all the anode segments, constitutes a short anode II. In Fig. 1 the short-circuited end ap circuiting connection at that end of the anode pears at the right. At the open end, which is as shown in Fig. 1. The bridge 20 forms a short at the left in the ?gure, alternate segments = circuiting connection across the Lecher pair to including I2 and I4 are cut shorter than the constitute theother end of the half-wave reso others and are conductively joined together by a nator. It is found that electromagnetic waves ring or yoke I*6 which may be shapedas shown, can form standing wave patterns in the resonator somewhat in the physical form of an internal gear with cut-away portions providing clearance 50 as so constructed, with voltage nodes at the short circuited ends and with a voltage antinode ap for the remaining anode segments including the pearing between adjacent anode segments over segments I3 and I5. as appears in cross-sectional a portion of the anode II between the ring I6 viewv in Fig. 2. The latter group of segments are conductively connected together by a second 55 and the right-hand end of the anode. The reso nant frequency of the. system may be adjusted 2,414,064 4 out in Fig. 1, the electronic portion or the mag i?ed so as to permit the anode to operate sub stantially as a halt-wave ‘resonator. For this purpose there is attached to the left-hand surface netron structure is situated inside the envelope 10 whereas the adjustable portion oi the tuning element is located outside the envelope where 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 by moving the bridge :0 along the wires I l and I! by manipulating the handle 22. As brought, or the ring I6 a short length of hollow tubular adjustment is accomplished without the mechani cal complication of any linkage'extending through - conductor 54 and the segments such as I3 and I5 the envelope. In the arrangement of Fig. 3, the anode II and the rings I6 and I‘! connected to alternate _ closes the space between the rings l6 and I‘! but anode segments are the same as in the arrange-' the anode may enter into the space between the concentric conductors 50 and 5|. A considerable i‘. ‘ attached to the ring IT. The conductor 54 partly leaves an annular gap through which electromag netic waves reaching the/rings l8 and I1 from ment of Fig. i. The Lecher system in this case, however, is in the form of a concentric transmis sion line having an outer conductor 50 conduc tively attached to the ring l6 and an inner con ductor 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 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 sub stantial 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 tun leave the concentric line partially outside the vac 25 ing member 52 will in this case be adjusted to a uum space to permit the tuning adjustment to be position approximately a halt wave-length dis e?ected outside the envelope as in Fig. 1. Fig. tance from the‘ left-hand end of the anode. A 3 shows the envelope in three sections. The right certain amount of variation in the resonant fre hand section 31 is sealed to the right-hand side quency oi the system as a whole may be obtained of the ring I6 in Fig. 3. A middle section 38 is 30 by adjusting the position of the element 52 al inserted between the rings l5 and I1 and the left though, as above mentioned, the tuning range hand section 39 is sealed to the left-hand side will generally not be as great as in the case where of the ring l1. The ?lament 23, which is axially 7 located as in Fig. 1, may be shorter than the an ode II, as shown in Fig. 3, in order to limit the thermionic emission to the region where the elec tric ?eld is the strongest, that is, the left-hand half to two-thirds, or so, of the anode, consti tuting a voltage antinode. One end of the ?la- ‘ ment is shown attached to a leading-out conduc 40 tor 40 which is sealed through the envelope sec tion 39. An insulating spacer 4|, such as a mica disc, may be employed for centering the conductor 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| out side the envelope. The outer conductor, 50 is 40. The other end of the ?lament may be at connected to the remaining segments oi the anode tached to a conductor "which is in turn con 45 by bent rods or wires 5| which also pass through ductively connected to a tension maintaining the envelope and may be soldered to the con spring 43, which latter is connected to a leading ductor 50 outside the envelope. The concentric out conductor 44' that may be sealed through the line is in e?ect passed through the envelope by section 31 of the envelope. A second insulating means of the plurality of rods or wires 60 and spacer 45 may be employed between the ?lament 6 | . A sectional view of the rods and their attach 23 and the spring 43 to center the conductor 42. ment to the anode segments is shown in Fig. 5. The ?lament may be heated by means of the bat Instead of the ?lamentary cathode of Figs. 1 and tery 28 as in the arrangement of Fig. 1 and the 3, an indirectly heated cathode 23' of any suit anode battery 29 may be connected to the outer able known construction is shown in the arrange; conductor 50 of the concentric line outside the envelope, which is in conductive connection with 55 ment of Fig. 4. The indirectly heated cathode may be inserted from one end of the envelope as the anode || through the ring I6. A solenoid 30’ may be provided to set up the desired magnetic shown and has the advantage that it is more easily centered than the ?lament and does not ?eld inside the anode ||. ' The operation of the system of Fig. 3 is essen require spring tension. The thermionicaliy ac tially the same as in the case of the arrangement 60 tive portion of the cathode 23' may be con?ned of Figs. 1 and 2, the tuning being accomplished to the region 65 in the strongest portion of the by manipulating the ‘handles 35 and 35 to adjust electric ?eld, by applying a suitable coating in the position of the annular tuning member 52. that region. , In the arrangements so far described, the anode Couplings for picking up the generated electro is preferably designed to be approximately a quar 65 magnetic waves and means for conveying the ter wave-length long, the Lecher system then waves to an antenna or ay other suitable utiliza comprising an additional quarter wave-length to tion circuit or device may be provided in conven make up the desired half wave-length for the combined structure. If desired, however, the an ' tional manner. For clarity in the drawings, such output coupling means have been omitted. but ode as a unit may be made to operate substan~~ 70 these will be readily supplied by anyone versed tially as a half wave-length resonator. In this in the ultra-high frequency art. case the system vmay still be tuned by means of What is claimed is: the exterior Lecher system, although the range 1. A resonator comprising a segmented anode, of tuning is generally reduced. Fig. 3A shows a each segment of which has a free end at one and way in which the structure oi Fig. 3 may be mod 75 8,414,084 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 = 6 . gather at one end. and tree at the other, a con centric 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 conduc tively connecting the free ends of the anode seg ments into-'two groups, said groups being insu lated from each other, and‘ means conductively Joining means. ' 2. A magnetron oscillator comprising a vacu 10 connecting the‘said groups 0! segments with the respective terminals of the open circuited end um-tight envelope containing working electrodes of said concentric line section. including a segmented anode, the segments of free ends of alternate segments into two insulated groups, respectively, and a concentric transmis sion line, the inner and outer conductors of which are connected respectviely to said conductive which anode are all conduotlvely connected to ARN-OLD E. BOWEN. '