CN217158105U - Weak reflection type folded waveguide slow wave structure - Google Patents
Weak reflection type folded waveguide slow wave structure Download PDFInfo
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- CN217158105U CN217158105U CN202220969338.8U CN202220969338U CN217158105U CN 217158105 U CN217158105 U CN 217158105U CN 202220969338 U CN202220969338 U CN 202220969338U CN 217158105 U CN217158105 U CN 217158105U
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Abstract
The utility model discloses a folding waveguide slow wave structure of weak reflection-type, including straight waveguide section and the district of buckling straight waveguide section with be equipped with impedance matching district between the district of buckling, so that be used for straight waveguide section with impedance matching between the region of buckling connects. Because the impedance matching section is introduced into the middle weak reflection type folding slow wave structure, the good impedance matching is realized, and the slow wave structure has good radio frequency transmission characteristic; meanwhile, compared with the conventional folded waveguide and the eccentric arc folded waveguide slow wave structure with the same physical size, the scheme of the utility model has excellent reflection performance; and compare with the folding waveguide of the conventional of the same physical dimension, the utility model discloses compare coupling impedance with the folding waveguide of conventional and obviously promote, based on the utility model discloses a travelling wave tube will have physical performance advantages such as bigger output, higher interaction efficiency, lower oscillation risk.
Description
Technical Field
The utility model relates to a microwave vacuum electron technical field, especially a folding waveguide slow wave structure of weak reflection-type.
Background
The traveling wave tube based on the vacuum electronics principle has wide application prospects in the fields of radar detection, broadband satellite communication, electronic countermeasure and the like, has the characteristics of high output power, wide frequency band, high efficiency and the like compared with an amplifier based on the solid electronics principle, and can meet the requirements of most of high-power electromagnetic emission systems at present. Generally, a traveling wave tube is mainly composed of a slow wave structure (slow wave line), an electron gun, a magnetic focusing system, an energy input and output coupling structure, and a voltage reduction collection stage. The slow wave structure is a core component of the traveling wave tube, is a main field for transduction of electron beams and electromagnetic waves, and can directly determine performance of the device through physical characteristics.
In the microwave frequency range, the common slow-wave structure mainly includes two major types, i.e., a helical structure and a coupled cavity structure. The helical line slow wave structure has the advantages of working bandwidth, low synchronous voltage, high interaction efficiency and the like, but the processing of the helical line slow wave structure in millimeter wave and terahertz wave bands is difficult due to the size common degree effect; the coupling cavity slow wave structure is an all-metal cavity structure, has high coupling impedance, can contain large power and has good heat dissipation, but has narrow working bandwidth, so that the application of the coupling cavity slow wave structure in a broadband scene is limited. The folded waveguide slow wave structure has the advantages of wide frequency band, easiness in processing and the like, and is widely applied to the design of millimeter wave and terahertz traveling wave tubes. However, the longitudinal electric field intensity of the folded waveguide slow-wave structure in the electron beam channel is weak, so that the coupling impedance of the conventional folded waveguide slow-wave structure is low, and further, the output power of the traveling-wave tube based on the conventional folded waveguide slow-wave structure is limited, and the electronic efficiency of the device is low. In order to further improve the coupling impedance of the folded waveguide slow wave structure, the ridge-loaded folded waveguide, the eccentric arc folded waveguide and other deformed folded waveguide slow wave structures are proposed and used for designing millimeter wave and terahertz traveling wave tubes.
Referring to fig. 1, the ridge-loaded folded waveguide slow-wave structure is formed by loading a metal ridge sheet on the inner wall of a straight waveguide section of the folded waveguide slow-wave structure; and punching holes from the top to the bottom on the metal wall along the symmetrical axis of the slow wave structure to form an electron beam channel. Due to the loading of the ridge, the field of the waveguide gap is enhanced to a certain extent, and when an electron beam is transmitted through the waveguide gap along the electron beam channel, stronger electromagnetic field force acts on the electron beam, so that the energy exchange between the electromagnetic field and the electron beam can be carried out more fully, and the energy of a high-frequency field can be amplified more effectively.
The utility model discloses the people discovers through the research, and the shortcoming of ridge loading folding waveguide slow wave structure lies in, because the impedance discontinuity can be introduced to loading metal ridge piece on straight waveguide section inner wall, arouses the impedance in the slow wave structure to mismatch, therefore the electromagnetic wave can form the reflection in transmission process, leads to this kind of deterioration of slow wave structure transmission characteristic. Therefore, compared with the folded waveguide traveling wave tube, the working bandwidth of the ridge-loaded folded waveguide traveling wave tube is limited, and the risk of generating self-oscillation is higher.
In order to improve the coupling impedance of the conventional Folded Waveguide and change the frequency range of the first stop band, an eccentric Circular arc Folded Waveguide Slow Wave Structure (as shown in fig. 2) is proposed (IEEE TRANSACTIONS ELECTRON DEVICES, vol.61, No.10, OCTOBER 2014). Similar to the ridge-loaded folded waveguide slow-wave structure, the slow-wave structure improves the coupling impedance by changing the longitudinal electric field distribution in the electron beam channel.
However, the utility model discloses a research discovery, this slow wave structure of folding waveguide of eccentric circular arc's shortcoming lies in, because the cross section of straight waveguide section and eccentric circular arc bending segment is different in the structure of folding waveguide slow wave of eccentric circular arc, exists impedance mismatch easily between straight waveguide section and the eccentric circular arc bending segment, can lead to the transmission reflection of this kind of slow wave structure great. Similar to the ridge-loaded folded waveguide slow wave structure, compared with the folded waveguide traveling wave tube, the working bandwidth of the eccentric arc folded waveguide traveling wave tube is limited, and the risk of generating self-excited oscillation is higher.
Therefore, the utility model is especially provided.
SUMMERY OF THE UTILITY MODEL
An object of the utility model is to provide a folding waveguide of weak reflection-type is wave structure slowly, promotes the coupling impedance of the folding waveguide of conventionality slow wave structure and reduces the reflection coefficient in the slow wave structure simultaneously.
In order to solve the above problem, an embodiment of the present invention provides a weak reflection type folded waveguide slow wave structure, including straight waveguide section and bending region the straight waveguide section with be equipped with impedance matching region between the bending region, so that be used for the straight waveguide section with impedance matching between the bending region connects.
Further, the cross section of the impedance matching region formed on the section perpendicular to the wide surface of the straight waveguide section is triangular.
Further, the bending region includes an inner arc and an outer arc, the inner arc is eccentric to a side close to the electron injection channel of the slow wave structure, and the outer arc is a non-eccentric arc of 180 degrees.
Further, the slow wave structure is constructed according to the following geometric constraints:
wherein a is the width of the wide side of the folded waveguide, b is the width of the narrow side of the folded waveguide, p is the length of the half period of the folded waveguide, and h 1 Is the length of the impedance matching region, h in The inward eccentricity distance used for the inner arc of the bending zone.
Further, the slow wave structure is also providedThe following geometric constraints are satisfied: h is 1 ＝h out Wherein h is out The eccentric distance of the circle center of the outer circular arc of the bending area.
Further, the radius R of the outer circular arc of the bending area out Satisfies the following conditions: r out ＝0.5(p+b)。
Further, the radius R of the eccentric inner arc of the bending region in Satisfies the following conditions:
because the impedance matching section is introduced into the weak reflection type folding slow wave structure in the scheme of the utility model, good impedance matching is realized, and therefore the slow wave structure has good radio frequency transmission characteristic; meanwhile, compared with the conventional folded waveguide and the eccentric arc folded waveguide slow wave structure with the same physical size, the scheme of the utility model has excellent reflection performance; and compare with the folding waveguide of the conventional of the same physical dimension, the utility model discloses the scheme compares coupling impedance with the folding waveguide of conventional and obviously promotes, based on the utility model discloses the travelling wave tube of scheme will have physical performance advantages such as bigger output, higher interaction efficiency, lower oscillation risk.
Drawings
FIG. 1 is a schematic structural diagram of a ridge-loaded folded waveguide slow-wave structure in the prior art;
FIG. 2 is a schematic structural diagram of a conventional eccentric arc folded waveguide slow wave structure;
fig. 3 is a schematic side sectional view of a weak reflection type folded waveguide slow wave structure according to an embodiment of the present invention;
fig. 4 is a schematic three-dimensional structure diagram of a weak reflection type folded waveguide slow wave structure provided by an embodiment of the present invention;
fig. 5 is a graph comparing the normalized phase velocity of a slow wave structure and a conventional folded waveguide according to an embodiment of the present invention;
fig. 6 is a graph comparing the coupling impedance of the slow wave structure and the conventional folded waveguide according to the embodiment of the present invention;
fig. 7 is a reflection parameter contrast diagram of the slow wave structure of the embodiment of the present invention and the conventional folded waveguide and the eccentric circular arc folded waveguide slow wave structure.
In the figure: 1-a straight waveguide segment; 2-a bending region; 3-an impedance matching region; 4-electron beam channel.
Detailed Description
The principles and spirit of the present invention will be described with reference to a number of exemplary embodiments shown in the drawings. It should be understood that these embodiments are described only to enable those skilled in the art to better understand the invention and to implement the invention, and are not intended to limit the scope of the invention in any way.
In describing embodiments of the present invention, the terms "include" and its derivatives should be interpreted as being inclusive, i.e., "including but not limited to. The term "based on" should be understood as "based at least in part on". The term "one embodiment" or "the embodiment" should be understood as "at least one embodiment". The terms "first," "second," and the like may refer to different or the same object. Other explicit and implicit definitions are also possible below.
As described above, in the prior art, the ridge-loading folded waveguide slow-wave structure and the eccentric arc folded waveguide slow-wave structure have respective disadvantages. However, before the present invention provides the following technical solutions to solve the above disadvantages and problems, the above problems have not been found in the related art, and the inherent causes of the above problems have not been found.
In view of this, the utility model discloses not only the technical problem that two kinds of slow wave structures exist has been found to the people, has still carried out research and analysis to above technical problem. The utility model discloses the people discovers through the research, causes the inherent reason of above-mentioned problem, utilizes ingenious technical conception to solve.
Below, will combine the utility model people to make the utility model discloses thinking process when improving, it is right the technical scheme of the utility model introduces, it should be understood that the part about thinking process is also the part of the creative work of utility model people.
The embodiment of the utility model provides a slow wave structure is the component part of travelling wave tube, and the travelling wave tube mainly comprises slow wave structure, electron gun, magnetic focusing system, high frequency input-output structure and step-down collection level. In the working process of the traveling wave tube, an electron beam emitted by an electron gun exchanges energy with an electromagnetic field in a slow wave structure; in a magnetic focusing system, a magnetic field force is utilized to counteract space charge repulsive force existing in an electron beam, and the electron beam is restrained to smoothly pass through the whole slow wave structure without being intercepted; the slow wave structure has the main functions of transmitting high-frequency electromagnetic waves and reducing the phase speed of the electromagnetic waves to be close to the injection speed of the electron beam, is a main place for realizing the injection-wave interaction, and modulates the electron beam to enable the electron beam to give out energy to the high-frequency electromagnetic field. The high-frequency input and output structure is mainly used for coupling high-frequency input signal energy into the slow wave structure and coupling the amplified high-frequency signal energy onto an output loop; the collecting stage is used for collecting electrons which have been converted with the electromagnetic field, and the electrons are converted into heat energy to be dissipated when striking the collecting stage.
As mentioned above, the slow wave structure is a core component in the traveling wave tube, and the dispersion characteristic, coupling impedance and rf transmission characteristic of the slow wave structure play a critical role in the performance of the device. The dispersion characteristic is one of the key characteristics of a slow wave structure, and can determine indexes such as synchronous working voltage, working bandwidth and the like of a traveling wave tube; the coupling impedance is another key characteristic of the slow wave structure, and generally depends on parameters such as longitudinal electric field intensity and transmission power flow in an electron beam channel, and the coupling impedance is related to a series of important indexes such as output power, interaction efficiency and output gain of a traveling wave tube; in addition, the transmission performance of the slow-wave structure in millimeter wave and terahertz wave bands is obviously deteriorated, the interaction efficiency and gain of the device are reduced due to the increase of transmission loss, the self-oscillation risk in the high-gain traveling-wave tube is increased due to the deterioration of reflection performance, and therefore the radio-frequency transmission characteristic of the slow-wave structure determines the physical performance of the device to a great extent.
The utility model discloses people find that the conventional folding waveguide slow wave structure has proper radio frequency transmission performance, but the coupling impedance is lower, so that the output power and the electronic efficiency of the conventional folding waveguide traveling wave tube are lower; the utility model discloses the people still discovers, and the ridge loading folding waveguide slow wave structure that proposes among the prior art all can realize the inside vertical electric field reinforcing of electron beam passageway with the folding waveguide slow wave structure of eccentric circular arc, nevertheless because there is the increase that impedance mismatch can arouse reflection coefficient between the bending section of slow wave structure and the straight waveguide section, leads to the travelling wave tube self-oscillation risk increase based on this type of slow wave structure.
Accordingly, embodiments of the present invention provide a weak reflection type folded waveguide slow wave structure, as shown in fig. 3 and 4. Different from the prior art, the embodiment of the utility model provides an add one section cross-section for triangular impedance matching district 3 (the cross-section is for following the vertical cross-section of cutting open, and the wide face of section and straight waveguide section 1 is mutually perpendicular promptly, and the axis of electron injection channel 4 overlaps or is parallel) between the straight waveguide section 1 of folding waveguide slow wave structure and bending region 2 for realize the impedance matching connection between straight waveguide section 1 and the bending region 2, with the transmission reflection in reducing the slow wave structure. In one embodiment, the impedance matching region 3 is a cavity structure with an outer wall made of a metal material. In addition, in one embodiment, the bottom surface of the impedance matching region 3 is a continuous plane formed by extending from one top edge of the inner wall of the straight waveguide section 1 to the other top edge, and the vertical surface of the impedance matching region 3 is a continuous plane formed by extending from the top edge of the inner wall of the straight waveguide section 1 near the outer side of the slow wave structure and upward according to the designed length. The inclined surface of the impedance matching section 3 is a continuous plane formed by extending from the top edge of the vertical surface of the impedance matching section 3 to the edge of the bottom surface of the impedance matching section 3 near the inner side of the slow wave structure, so that the cross section of the impedance matching section 3 forms a triangle.
Further, in order to improve the longitudinal electric field intensity of the slow wave structure in the electron beam channel 4, the inner arc of the bending region 2 is designed to be an inward eccentric arc (the circle center is close to the electron beam channel side), and the outer arc of the bending region 2 is designed to be a non-eccentric 180-degree arc curve to achieve smooth connection with the impedance matching area, so that the reflection is not deteriorated while the coupling impedance of the slow wave structure is improved.
In one embodiment, the weakly reflective folded waveguide slow wave structure of the present invention has dimensions such asAs shown in fig. 3 and 4, the wide side of the folded waveguide is a, the narrow side of the folded waveguide is b, the length of the straight waveguide segment is h, the half-period length of the folded waveguide is p, the diameter of the electron beam channel is d, and the length of the impedance matching region is h 1 The inner arc of the bending region adopts an inward eccentric distance (OO) 1 ) Is h in Eccentricity of the outer circular arc centre of the bending zone (OO) 2 ) Is h out Radius of the inner arc of the bending region is R in The radius of the outer circular arc of the bending area is R out . O is the center point between the top edges of the outer walls of adjacent straight waveguide segments, i.e., the dot of the inner arc of the inflection zone if it is constructed non-eccentrically according to a 180 degree arc. O is 2 Is the center of an outer circular arc of the bending region, O 1 Is the center of an inner circular arc in the bending area.
The above structural parameters need to satisfy the following geometric constraint relationship:
1. in order to meet the requirement that the electromagnetic wave keeps the main mode TE in the transmission process 10 The mode transmission and impedance matching region can realize impedance matching effect, and the length h of the impedance matching region 1 The following relationship needs to be satisfied:
2. to ensure smooth connection of the outer arc impedance matching region of the bend region, the length h of the impedance matching region 1 Simultaneously, the requirements are satisfied: h is 1 ＝h out ；
3. The radius of the outer arc of the bending area is R out The requirements are as follows: r out ＝0.5(p+b)；
4. The radius of the eccentric inner circular arc of the bending area is R in The requirements are as follows:
example 1
Taking the slow wave structure of the W-band millimeter wave traveling wave tube as an example, the length a of the wide side is 1.8mm, the length b of the narrow side of the folded waveguide is 0.3mm, the length h of the straight waveguide is 0.52mm, the length p of the half period of the folded waveguide is 0.6mm,the diameter d of the electron beam channel is 0.48mm, and the length h of the impedance matching region 1 Is 0.05mm, and the inner arc of the bending area adopts an inward eccentric distance h in 0.1mm, and the eccentric distance h of the center of the outer arc of the bending area out Is 0.05 mm.
It can be found through the simulation result (as shown in fig. 5), under the condition of the same size structure, the utility model discloses compare and have higher normalized phase velocity, flatter dispersion curve in conventional folding waveguide, this presupposes that the travelling wave tube based on the utility model discloses scheme slow wave structure will have higher synchronous voltage, wider synchronous bandwidth.
As shown in fig. 6, it can be seen that the coupling impedance of the slow-wave structure of the embodiment of the present invention in the operating frequency band is significantly higher than that of the conventional folded waveguide, and the coupling impedance at the typical frequency of 94GHz is higher than that of the conventional sine waveguide by about 37.5%, which indicates that the traveling-wave tube based on the slow-wave structure of the embodiment of the present invention will have greater output power, higher interaction efficiency and output gain.
With the structural parameters of the weak reflection type folded slow wave structure in the embodiment of the present invention given above, 23 main periods were selected, and the effective conductivity was set to 2.25 × 10 7 And (5) S/m. A transmission characteristic calculation model is established in electromagnetic simulation software, a simulation calculation result of the transmission parameter of the weak reflection type folded slow wave structure can be obtained by solving through time domain simulation in the software, and the simulation calculation result is compared with a conventional folded waveguide and an eccentric arc folded waveguide slow wave structure in the prior scheme-2, as shown in fig. 7. Within the range of 88-102GHz working frequency band, the reflection parameter of the weak reflection type folding slow wave structure is less than-23.7 dB, which is lower than the conventional folding waveguide and the weak reflection type folding slow wave structure by 10dB, which shows that the weak reflection type folding slow wave structure in the scheme of the utility model has good radio frequency transmission performance.
As can be seen from the simulation analysis results of the embodiment of the utility model, the impedance matching section is introduced into the weak reflection type folding slow wave structure in the scheme of the utility model, so that the slow wave structure has good radio frequency transmission characteristics; meanwhile, compared with the conventional folded waveguide and the eccentric arc folded waveguide slow wave structure with the same physical size, the scheme of the utility model has excellent reflection performance; and compare with the folding waveguide of the conventional of the same physical dimension, the utility model discloses the scheme compares coupling impedance with the folding waveguide of conventional and obviously promotes, based on the utility model discloses the travelling wave tube of scheme will have physical performance advantages such as bigger output, higher interaction efficiency, lower oscillation risk.
The present invention has been described in detail with reference to specific embodiments, and the description of the embodiments is only for the purpose of helping understanding the core idea of the present invention. It should be understood that any obvious modifications, equivalents and other improvements made by those skilled in the art without departing from the spirit of the present invention are intended to be included within the scope of the present invention.
Claims (6)
1. A weak reflection type folded waveguide slow wave structure is characterized by comprising a straight waveguide section and a bent region, wherein an impedance matching region is arranged between the straight waveguide section and the bent region and is used for impedance matching connection between the straight waveguide section and the bent region; the section of the impedance matching region formed on the section perpendicular to the wide surface of the straight waveguide section is triangular.
2. The slow wave structure of claim 1, wherein the bending region comprises an inner arc and an outer arc, the inner arc is eccentric to a side close to the electron injection channel of the slow wave structure, and the outer arc is a non-eccentric arc of 180 degrees.
3. The weakly reflective folded waveguide slow wave structure of claim 2, wherein the slow wave structure is constructed according to the following geometric constraints:
wherein a is the width of the wide side of the folded waveguide, b is the width of the narrow side of the folded waveguide, p is the length of the half period of the folded waveguide, and h 1 Is the length of the impedance matching region, h in The inward eccentric distance used for the inner arc of the bending zone.
4. The weakly reflective folded waveguide slow wave structure of claim 3, wherein the slow wave structure further satisfies the following geometric constraints: h is 1 ＝h out Wherein h is out The eccentric distance of the circle center of the outer circular arc of the bending area.
5. The weakly-reflective folded waveguide slow wave structure of claim 4, wherein a radius R of an outer arc of the inflection region out Satisfies the following conditions: r out ＝0.5(p+b)。
6. The weakly reflective folded waveguide slow wave structure of claim 5, wherein the radius R of the eccentric inner circular arc of the inflection zone in Satisfies the following conditions:
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