JPH0453062B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a crossed electromagnetic field amplification tube for amplifying millimeter wave frequencies (EHF) over a wide band.

BACKGROUND ART The conventional ability to generate EHF power is limited by a number of factors. The power is narrow bandwidth (1-2G) using coupled cavity tubes (1-2kw).
Hz). 18.0~26.5 and
Helical traveling wave tubes are currently under development in an effort to provide power output in the 26.5-40.0 GHz frequency range. Other limitations on the types of tubes suitable for generating power in the above frequency ranges are the physical size, weight, and wide power delivery requirements for these tubes. A recognized need in the field of microwave amplifier tubes is for amplifier tubes capable of efficient broadband operation at high power levels at millimeter wavelengths. The problem was that microwave tubes were relatively small at millimeter wavelengths and thus limited in power.

OBJECTIVES It is therefore an object of the present invention to provide a new type of high power microwave amplifier tube that provides high power amplification over a wide frequency range at EHF frequencies.

SUMMARY OF THE INVENTION The foregoing problems are overcome and other objects and advantages are achieved by the millimeter wave amplifier tube of the present invention.

The amplifier tube of the present invention, useful for high power operation at millimeter waves, has a large number of anode segments to keep the power and electron flow density within limits. Thanks to its large number of anode segments, an amplifier tube can increase the cathode diameter many times compared to conventional tubes. Thus, a significant increase in average power potential output can be achieved. High average power and high gain are achieved with the axially continuous anode structure. The interleaved slot anode structure usable at millimeter wave frequencies is particularly suitable for the configuration of a continuation of π mode rings coupled together by circular TE ₀₁ mode lines. The amplifier tube structure is
It has a circular TE ₀₁ coaxial waveguide core with a cathode surrounded by an outer wall surface that is directly coupled to the anode segment. This cathode is of the cold cathode secondary emission type and has a much larger electron emitting surface than that of a normal tube. The coupling of the TE ₀₁ driver to the anode segment is inherently tight, favoring broadband, moderate power density operation. The anode structure has structural and power consumption advantages. The continuous connection of amplifier stages provides size and weight advantages both for the amplifier tubes and for the magnets. Due to the unique anode structure and increased cathode size, amplifier tubes
It is expected that it can be used effectively up to 90GHz.

Amplifier tubes are capable of significantly higher efficiencies. Amplifier tubes are also characterized by relatively low operating voltages, commercial simplicity, high reliability, and excellent phase stability.

The amplifier tube is a crossed electromagnetic field device using a secondary electron emitting cathode and a re-entering electron beam. The space charges are phase focused into spokes by the RF waves in the interaction region. In the preferred embodiment, four interactive slow wave circuits are used in series to provide an amplification stage. Each slow wave circuit is coupled to a periodic core filter. The coupling between the periodic core filter and the interactive slow wave circuit is provided by a slot at the base of the slow wave circuit. The coupling between each slow wave circuit at the anode and the core filter is tight, thus solving many of the retention problems. The power generation density in the anode circuit is low, solving the problems of the power consumption density and electron emission density limitations of the cathode. The anode slow wave circuit is coupled to the TE ₀₁ waveguide. Tight coupling of the slow wave anode circuit solves the mode control problem by providing single mode propagation in the axial direction. Tight coupling lowers the electrode generation density in the anode circuit, reducing power consumption and electron emission density problems. Tight coupling facilitates improved overall bandwidth. The multiple slot circuit elements in each anode slow wave circuit allow the gain to be maintained. The core filter section is driven in TE ₀₁ mode and the energy travels axially to one of the slow wave circuits and then radially through this slow wave circuit to the interaction region where the RF power is amplified. can get. The amplified power is routed radially through the slow wave circuit again to the core filter region where it travels preferentially axially to the next slow wave circuit at the anode where the RF power is amplified. , and such amplification takes place in each subsequent section until the power reaches the coaxial output of the tube.

The crossed field amplifier tube includes a two-dimensional cylindrical array of anode circuits for high power crossed field operation at millimeter waves. The electric field between the cylindrical anode and the surrounding cylindrical cathode is radial, and the magnetic field is axial in the space between the anode and cathode.
The power flow in the amplifier tube is along the direction of the magnetic field (perpendicular to the EXB motion of the electrons). Power flows axially within the cylindrical anode along a cylindrical TE ₀₁ waveguide. The waveguide section includes an attenuation element for mode control,
It is equipped with filter elements to control overall gain, bandwidth, and stability. The amplifier tube is Radaxtron due to the axial and radial flow of power in this tube.
It is named.

The input signal is fed to one end of the TE ₀₁ mode coaxial line. A magnetic field is generated at a slot in the outer conductor of the coaxial line and enters the interaction region where it interacts with the electron cloud provided by the cylindrical cathode. The outer conductor of the coaxial line is provided with a ring of longitudinal slots of alternating length. Each length of the slots resonates with their resonant frequency which approximately defines the passband of the amplifier tube. At frequencies near and between its two resonant frequencies, the slot is a very good RF radiation tube into the interaction region.
The π-mode RF field is amplified in the interaction region and sent back through the slot to propagate axially downstream through the tube to the slot in the next ring. A filter section within the coaxial line of the tube preferentially routes the amplified RF to the next ring slot rather than returning it toward the source. Impedance changes within the active tube also cause preferential transmission to the next amplifying section along the tube.

An effective magnetic design using permanent magnets with alternating polarity in connected sections of the anode slow-wave structure can be used to reduce the effects that would otherwise be critical for such large anode arrays. It reduces leakage magnetic flux and enables an effective lightweight permanent magnet design.
The arrangement for providing a longitudinal magnetic field uses samarium-cobalt magnets at the cathode, with iron pieces between each magnet to provide a magnetic flux path. The polarity of the magnets in adjacent cathodes are reversed, so that each iron piece presents an N-S magnet at its longitudinal end.

The amplifier tube uses a secondary emission cold cathode, such as a gold-magnesium oxide cathode, which provides good starting characteristics with a secondary emission ratio of 2.7 and a low crossover voltage of about 20 volts.

The crossed electromagnetic field amplifier tube of the present invention typically has a 35G
16% bandwidth and 12db at center frequency of Hz
It produces a peak power of 300 kilowatts at an average power of 3000 watts with a gain of .

[Explanation of Examples] The present invention will be explained in detail based on examples.

FIG. 1 shows a tube 10 of the invention in an isometric view with a partial section taken along an oblique cut through its axis of symmetry 11. FIG. This tube has an input microwave transition section 12 which converts the power into the tube from the TE ₁₀ mode in the waveguide 13 to the TE ₀₁ mode in this transition section 12 . A second transition section 14 at the output end of the tube converts the electromagnetic energy at the output of the tube from the TE ₀₁ mode to the TE ₁₀ mode, allowing power to propagate from the tube to the waveguide 15 . The center conductor 16 has end portions 16', 16'' thereof forming part of the transition sections 12, 14, respectively. The axis of the center conductor 16 coincides with the axis 11 of the tube and the center conductor 16 are coaxial with their outer conductors 17', 17'' surrounding their tapered portions 18', 18'', respectively. A central portion 19 of conductor 16 is concentric with the slot anode 20. Anode 20
This and conductors 17' and 17'' are respectively area 2.
It has an inner diameter equal to the inner diameter of the conductors 17', 17'' which are in contact and electrically connected at 1', 21''. The outer conductors 17', 17'' and 20 are generally made of copper and are connected at regions 21', 21'' by silver brazing. Center conductor 16 is made of a conductive core material 22, typically copper. Core material 22 is shown within cutout 23 in FIG. The core material 22 includes
Attenuates the electric field in the center conductor 16, thus
In order to suppress modes other than the desired TE ₀₁ mode that does not have an electric field on the surface of the center conductor 16,
An electrically damping layer 24, typically a carbonaceous layer, is coated. Layer 24 is lossy at the microwave frequencies at which the tube operates.

The ends 25', 25'' of the outer conductors 17', 17'' are brazed to the transition parts 12, 14, respectively. Each waveguide 13, 15 has a window (not shown) that allows microwave energy to pass through the waveguide and also allows the area between the inner conductor 16 and the outer conductor to pass through the waveguide. 26, as well as alumina or beryllia porcelain insulators 35, 36, magnetic structures 31,
33, 34, and a vacuum seal for the tube comprising a volume 26' surrounded by conductors 17', 17''.

A periodic core filter 27 is provided in the region between the slotted outer conductor 20 and the central portion 19 of the inner conductor 16.
, which includes circumferential slots 28 axially spaced from each other. The material of the filter 27 may be alumina or beryllia, and the material of the filter 27 may be alumina or beryllia.
is met. Alternatively, filter 27 may be a conductive metal attached to center conductor 16 and spaced from anode 20. The axial spacing of the circumferential slots 28 corresponds to the axial spacing of each ring 52 of the slots 29, 30 of the cylindrical outer conductor 20 shown in the isometric view of FIG. The short slots 29 alternate with the long slots 30, forming four circumferential rings 52 of equally spaced slots 29,30. Slot 29, 30
extends in the direction of the axis 11 and passes through the radial thickness 20' of the outer conductor 20. slot 2
9 and 30 are symmetrical in the longitudinal direction with respect to each circumferential line 36. The spacing between each circumferential line 36 is equal and coincident with the longitudinal center 28' of the circumferential slot 28 of the filter 27. The widths of the slots 29 and 30 in the circumferential direction are equal.

The magnetic circuit 31 consists of iron disks 32 and samarium-cobalt disk permanent magnets 3 that sandwich these disks.
5 and iron end pieces 33, 34, all of which are transverse to the axis 11. magnetic circuit 31, magnet 35, disk 32 and end piece 33,
34 each have a hole centered on axis 11 and are brazed together to form a single unit. The magnetic structure 31 includes magnetic end pieces 33, 34.
and outer conductors 17', 1, respectively.
7″ respectively brazed magnetic insulators 60,
61. Magnetic leg 32 and magnet 35 include a circular hole centered on axis 11 and spaced from central outer conductor 20 . tube 10
Provision for the application of a negative voltage to the cathode 41 of is provided by an electrical connector 37 attached to the conductive magnetic structure 31. Magnetic structure 31
The electrical conductivity of the magnetic structure 31 is improved by applying a conductive coating, such as copper or silver, to the components of the magnetic structure 31 prior to brazing.

Enlarged views of the iron disk 32, permanent magnet 35, and central outer conductor 20 are shown along cutting lines 3-3 and 4 in FIG.
3 and 4 for the regions respectively surrounded by -4. The isometric view of FIG. 3 shows the isometric cut 3- through the shorter slot 29.
3 is shown in much more detail than in FIG. 5 and 6 correspond to FIGS. 3 and 4, respectively, and show the cutting portions 3-3 and 4-4 in transverse section, respectively. The magnet 35 is seen to be slightly further away from the slot conductor 20 than the iron disk 32. The cathode 41 is applied to the inner cylindrical surface of the magnetic disk 35, leaving a radially protruding portion of the disk that acts as a cathode end shield 32'. The magnetic disks 35 are magnetized so that both sides of each magnetic disk have north and south poles.
The north and south poles of adjacent magnetic discs 35 are arranged oppositely, as shown in FIGS. Therefore, magnetic fields of the same polarity can be applied. In the case illustrated in FIG. 3, the south poles of the magnets 35', 35'' are adjacent to the iron disk 32''. For the next axially spaced iron disc 32, the north poles of the magnets on either side of it would be adjacent to this disc. Third
The illustrated magnet 35' has a cathode 41 and slots 29, 3.
0 and the anode 42 consisting of the outer conductor 20 generates a magnetic field in the direction of the directional arrow 39 in the interaction region 40 . Preferably, the cathode 41 is a layer of secondary electron emitting material. A suitable material is a thin layer of gold-magnesium oxide which exhibits good starting characteristics with a secondary electron emission ratio of 2.7 and a low crossover voltage of about 20 volts. Another suitable material is
It is a gallium arsenide with a secondary electron emission rate of 3.5 and a low crossover voltage of about 20 volts. Hot cathodes can also be used, which has the advantage of not requiring high input power to produce secondary electron emission, but has the disadvantage of requiring a more complex support structure. ing.

The magnetic field generated by the magnet 35'' in the interaction region 43 is in the direction of the directional arrow 44. The interaction space 43 exists between the cathode 45 and the slots 29, 30 of the anode 42.

Now referring to FIG. 1, the electromagnetic input TE ₁₀ mode power in the waveguide 13 is
is converted to TE ₀₁ mode. This RF (radio frequency) energy propagates through the space 50 between the outer conductor 17' and the inner conductor 18' and the outer conductor 2.
0 and the central portion 19 of the inner conductor 16
1, at which point the electromagnetic wave impinges on the tapered filter 27 between these two conductors. The electromagnetic energy is transferred to slots 29, 3 in the first row of slots 31.
0 to the first interaction region 40 where the RF energy interacts with the electrons emitted by the cathode 41. In the interaction region 40, the interaction between the electrons reaching the slot portion of the anode 42 from the cathode 41 and the electromagnetic field causes the electrons to bundle into a spoke-like shape.

RF energy coupled through slots 29, 30 creates a π mode field for electronic interaction. Each single slot operates close to its resonant frequency for frequencies within the amplifier tube's passband and can therefore be simulated by a tuned series LC circuit. Since the slots 29 and 30 have different lengths, the equivalent circuits of two adjacent slots are two LC circuits connected in series that resonate at different frequencies. This series LC
The circuit can be thought of as being coupled at each end by a one-eighth wavelength line to a short circuit provided by the cathode.

The interaction of the electromagnetic waves in the interaction region 40 with the spoke electron beams causes an amplification of the electromagnetic energy in the interaction region 40, and the electromagnetic energy is transferred from the region 26'' and the filter 27 through the slots 29, 30 of the ring 52'. The energy returning to the propagation region 51 is preferentially transferred to the next ring 5 at the anode 20.
2" slot to the next interaction region. The amplified energy passing through the slot in ring 52" also preferentially moves axially to the right into the next two interaction regions (the third (not shown in the figure), where this power is amplified in the same way. The interaction region 4 passes through the region 53 between the iron disc 32 and the slotted cylinder 20.
The electromagnetic energy from 0 to the interaction region 43 is not amplified because the polarity of the magnetic field, indicated by the directional arrow 44, is opposite to the directional polarity of the magnetic field 39 in the previous interaction region 40. however,
Electromagnetic energy that is amplified in region 40 and then passes through a slot in ring 52' and enters interaction region 43 through a slot in ring 52'' is of the appropriate phase to be amplified in interaction region 43. Amplification. The process continues in the remaining two interaction regions, and finally the energy leaving the last interaction region through the slot in row 34 fills the space between the outer electrical conductor 17' and the inner conductor 18''. It propagates through the transition section 14, from where it exits the tube. The direction of the amplified RF energy is preferentially provided by the periodic core filter 27, whose slot 28 and tapered portion 28'' extend axially to the right in the region 53 to the tube conductors 17'', 1.
The output transition section 14 provides a preferred direction of energy transfer to the coaxial output section 26 within section 2.
6 is converted into a TE ₁₀ mode that can be transmitted by _the output waveguide 15.

In summary, the crossed field amplifier tube comprises a two-dimensional cylindrical array of anode circuits for high power crossed field operation at millimeter waves. Cross field amplifier tube 10 includes two RF slow wave structures, a slot anode 20 and a periodic core filter 27.
The electric field between the cylindrical anode and the surrounding cylindrical cathode is radial, and the magnetic field is axial in the space between the anode and cathode. The slotted RF array 52 of the anode 20 is located in the interaction space 40.
RF electromagnetic field, cathode 41 and anode 20 generated by a negative voltage applied between terminal 37 and anode 20
It is designed to couple to an electronic spoke formed between cathode 41 and anode 20 under the influence of a radial electric field between and an axial magnetic field. Power flows axially within the cylindrical anode along a cylindrical TE ₀₁ waveguide. The RF slow wave structure of core filter 27 slows down the RF waves in the core filter, thereby increasing the amount of RF energy transmitted through slotted RF ring 52 of anode 20. Periodic core filter 27 increases the coupling impedance of millimeter wave slotted circuit ring 52 over a wide band. Dielectric core filter 27 also serves as a large microwave window for transmitting high RF power.

The waveguide is equipped with attenuation elements for mode control and filter elements to control overall gain, bandwidth, and stability. Copper center conductor 22
is provided with a lossy coating 23, which lossy material 23 attenuates any longitudinal or circumferential electric field, thereby inhibiting the TE ₀₁ from operating in other modes. Limit operation to mode.

The anode slow wave circuit is coupled directly to the TE ₀₁ waveguide. Tight coupling results in lower power generation density in the anode circuit, which reduces dissipation and electron emission density problems. Furthermore, mode control is enhanced. Tight coupling facilitates improvements in overall bandwidth. The large number of circuit elements in each anode slow wave circuit allows the gain to be maintained. Because of the axial flow of power in the amplifier tube, it is called axial CFA.

Next, an example of an embodiment of the present invention will be shown.

(1) A plurality of iron disks, a plurality of magnetic disks having north and south poles on opposite sides of each disk, each disk having a hole in its center and the axes of the holes aligned with each other. each of said iron disks and magnetic disks arranged alternately with each other to form a cylindrical body of the disk; and the cylindrical body of said disk. the polarity of the magnetic field of each magnetic disk being reversed with respect to the nearest magnetic disk in the axial direction of a plurality of opposite polarities in the region proximate to the plane of the hole of each one of said magnetic disks; A magnetic structure for obtaining an axial magnetic field, comprising: a cylindrical body of the disk described above that provides a magnetic field.

(2) The magnetic structure according to paragraph (1), wherein the diameter of the hole in each of the magnetic disks is larger than the diameter of the hole in each of the iron disks.

(3) The magnetic structure according to item (1), wherein at least two or more of the plurality of iron disks are connected to each other by an iron cylinder around the circumference of these disks.

(4) an electrically conductive first cylinder having a wall, said first cylinder having at least one ring, and electromagnetic energy on one side of said cylinder passing through said cylinder wall; A microwave slow-wave circuit comprising: each of said rings having a plurality of slots passing through said wall surface that can reach the other side of said first cylindrical body.

5. The circuit of claim 4, wherein the first cylindrical body includes a plurality of axially spaced rings along its axis.

(6) The circuit of paragraph (4), wherein said plurality of slots in each said ring alternate in length.

(7) said first cylindrical body comprising a plurality of rings spaced axially from one another along its axis, and said plurality of slots in each said ring alternating in length; The circuit described in paragraph (4).

(8) second and third conductive cylinders surrounding and spaced apart from the first cylinder, and generating π-mode electromagnetic energy between the first and third cylinders; The above first and second
The circuit according to paragraph (7), further comprising: TE ₀₁ mode electromagnetic energy between the cylinders.

(9) a periodic core filter between said first and second cylindrical bodies, and said filter comprising an annular groove corresponding in axial position to the axial spacing of said ring;
The circuit according to paragraph (8), further comprising:

Although the present invention has been described above with reference to embodiments, it will be apparent to those skilled in the art that other embodiments may be used within the scope of the present invention.

[Brief explanation of the drawing]

FIG. 1 is an isometric view, partially in section, of a crossed electromagnetic field amplification tube of the present invention. FIG. 2 is an isometric view of the anode of the amplifier tube showing the ring of slots. 3 and 4 are enlarged views of the isometric view of FIG. 1 of the area defined by boundary lines 3-3 and 4-4, respectively. Figures 5 and 6 show the boundary line 3-
FIG. 2 is an enlarged view of the area defined by 3 and 4-4 in a direction transverse to the cut plane shown in FIG. 1; In these figures, 10 is an amplifier tube, 12 is an input microwave transition section, 13 is a waveguide, 14 is an output microwave transition section, 15 is a waveguide, 16 is a center (inner) conductor, 17', 17 ″ is the outer conductor, 2
0 is the slot anode, 22 is the conductive core material, 23
27 is a periodic core filter (slow wave structure), 28 is a circumferential slot, 29 and 30 are slots, 31 is a magnetic circuit (magnetic structure), 32 is an iron disk, and 33 and 34 are iron ends. The piece 35 is a disk permanent magnet, 40 and 43 are mutual areas, 41 and 45 are cathodes, 42 is an anode, and 52 is a ring.

Claims (1)

Claims: 1. A coaxial input portion, a coaxial output portion, an inner conductor and an outer conductor, the outer conductor including at least one axially extending and circumferentially spaced slot. a coaxial line having one slot ring; and a cylindrical line surrounding and spaced from each of said slot rings and forming a cylindrical interaction area between each cathode and its corresponding slot ring. a cathode; a magnetic structure for providing a periodically reversing axial magnetic field in the interaction region in each of the slot rings; means for applying a voltage between the cathode and the outer conductor of the coaxial line; A cross electromagnetic field amplification tube consisting of a microwave filter placed between the inner and outer conductors of a coaxial line. 2. The amplifier tube according to claim 1, wherein every other slot of the ring has a different length. 3. The longer length of the slot resonates at a frequency at the lower end of the amplification frequency bandwidth of the tube, and the shorter length of the slot resonates at a frequency at the upper end of the amplification frequency bandwidth of the tube. The amplifier tube according to claim 2, which resonates. 4. The magnetic structure includes: a plurality of iron disks; and a plurality of magnetic disks each having an N pole and an S pole on opposing surfaces, each of the iron disks and magnetic disks having a A hole is provided at the center of the plate, the axes of the holes coincide with each other, and the iron disks and magnetic disks are arranged alternately to form a cylindrical body, and the polarity of the magnetic field of each magnetic disk is the cylinder is inverted with respect to the nearest magnetic disc, the cylinder generating a plurality of axially directed magnetic fields of opposite polarity in regions proximate to the face of each hole in the magnetic disc; The amplifier tube according to claim 1, which generates: 5. The amplifier tube according to claim 4, wherein the diameter of each hole in the magnetic disk is larger than the diameter of each hole in the iron disk. 6. The amplifier tube according to claim 4, wherein the cylindrical cathode has a secondary electron emitting material on the surface of the magnetic disk located in each hole of the magnetic disk. 7. The microwave filter has a periodic core filter consisting of a second cylindrical body that substantially occupies the space between the outer conductor and the inner conductor of the coaxial line, and the second cylindrical body is arranged to 2. The amplifier tube of claim 1, further comprising a circumferential groove adjacent to and axially aligned with each of the slot rings. 8. Claim 7, wherein the second cylindrical body is a conductive metal attached to the inner conductor of the coaxial line and spaced from the outer conductor of the coaxial line.
Amplification tube as described in section. 9. The amplifier tube according to claim 7, wherein the second cylindrical body is made of an insulating material. 10. The amplifier tube of claim 9, wherein the insulating material is selected from the group consisting of alumina and beryllia. 11. The amplifier tube of claim 7, wherein the insulating material substantially fills the space between the inner and outer conductors. 12. The amplifier tube of claim 7, wherein the second cylindrical body is axially tapered at the end facing the coaxial input section. 13. The amplifier tube of claim 1, wherein the inner conductor of the coaxial line is coated with an electrically lossy material. 14. The amplifier tube of claim 13, wherein the covering material covers at least an axial portion of the inner conductor where amplification takes place in an axially corresponding interaction region. 15 a first rectangular waveguide; and a first micro waveguide connected between the first waveguide and the coaxial input section to convert a TE ₁₀ mode in the waveguide to a TE ₀₁ mode in the coaxial input section. a second rectangular waveguide; a second rectangular waveguide connected between the second waveguide and the coaxial output section to convert a TE ₀₁ mode in the coaxial output section to a TE ₁₀ mode in the second waveguide; a second microwave transition section for converting into , wherein the cylindrical interaction region between the coaxial input section and the coaxial output section has a TE ₀₁ mode;
An amplifier tube according to claim 1.