Axial mechanical tuning device for broadband continuous frequency modulation of time-of-flight oscillators

Abstract

The invention belongs to a microwave source device in the field of high-power microwaves, and particularly relates to an axial mechanical tuning device for broadband continuous frequency modulation of a transit time oscillator. Comprising a front adjusting piece, a front adjusting ring, a rear adjusting piece and a rear adjusting ring, the front adjusting piece in a modulation cavity and the rear adjusting piece in an extraction cavity are driven to axially slide through axial movement of the front adjusting ring and the rear adjusting ring, the sizes of the modulation cavity and the extraction cavity are synchronously changed, and then intrinsic mode electric field distribution of the transit time oscillator is changed. The working frequency of the device is finally changed; the method is different from a radial mechanical tuning method, and broadband continuous tuning can be performed on the transit time oscillator through axial mechanical tuning on the basis of not influencing the position of an external solenoid magnetic field; according to the invention, synchronous sliding adjustment along the whole circumference can be ensured, the angular and radial uniformity of the slow wave structure is not influenced, and the experimental feasibility is high.

Description

Technical Field

[0001] The invention belongs to the field of high-power microwave source devices, and in particular relates to an axial mechanical tuning device for broadband continuous frequency modulation of a transit time oscillator. Background Art

[0002] High-power microwaves usually refer to electromagnetic waves with a peak power greater than 100MW and a frequency between 1 and 300GHz. They are currently used in many fields such as radar, satellite communications, remote sensing and radiation measurement.

[0003] High-power microwave sources are the core of high-power microwave generation devices. They utilize the interaction of an intense electron beam with a resonant cavity to generate high-power microwaves. Transit-time oscillators (TTOs) utilize the interaction of an intense electron beam with the resonant cavity's eigenmode standing wave field to generate transit radiation for energy exchange. TTOs have attracted significant research interest due to their high efficiency, single operating mode, and stable frequency.

[0004] Frequency modulation technology has important research significance and application value in fields such as communications, remote sensing, and high-power microwave effects. Currently, there is some research on frequency modulation technology in magnetrons and magnetically insulated wire oscillators. The literature [Yuwei Fan, Xiaoyu Wang, Guolin Li, Hanwu Yang, Huhuang Zhong, Jiande Zhang. Experimental Demonstration of a Tunable Load-Limited Magnetically Insulated Transmission Line Oscillator. [J]. IEEE Transactions on Electron Devices, 2016, Vol. 63(3): 1307-1311] experimentally demonstrates that a magnetically insulated wire oscillator can achieve frequency modulation in the frequency range of 1.337 GHz to 1.760 GHz, with a maximum efficiency of 15.2%. In the literature [Fen Qin, Yong Zhang, Sha Xu, Lurong Lei, Binquan Ju, Dong Wang. A Frequency-AgileRelativistic Magnetron With Axial Tuning [J]. IEEE Electron Device Letters, 2020, Vol. 41 (5): 781-783], it was experimentally found that a frequency-adjustable magnetron can achieve frequency modulation in the frequency range of 1.23 GHz to 1.70 GHz, with an efficiency of 54.5% to 32%. However, there are few studies on transit time oscillators. In the literature [Gao Minghao. Research on a Tunable Coaxial Transit Time Oscillator Across Three Bands [D]. National University of Defense Technology, 2017], frequency modulation was achieved by radially changing the inner conductor in the three frequency bands of 6.27 to 6.70 GHz, 11.35 to 11.70 GHz, and 12.70 to 13.70 GHz in simulation, with a maximum efficiency of 38%. However, the above tuning methods are complex to implement and cannot be tuned in real time.

[0005] The existing technology (publication number: CN106531598B) overcomes the problem of conventional transit-time oscillators being frequency-independent. This solution achieves frequency modulation by adjusting the radial depth of the modulation and extraction cavities through radial movement of an adjustment rod outside an outer conductor. This solution suffers from at least two prominent issues: First, because a toroidal magnetic field is required outside the outer conductor, the space between the outer conductor and the toroidal magnetic field is very narrow, making radial movement of the adjustment rod difficult within such a narrow space and technically difficult to industrialize. Second, because the metal sheet is moved by pressing multiple adjustment pins, it is difficult to ensure uniform movement of the metal sheet, making it difficult to guarantee frequency modulation stability. Summary of the Invention

[0006] The present invention provides an axial mechanical tuning device for broadband continuous frequency modulation of a transit time oscillator, which overcomes the problems of the existing radial mechanical tuning device of the transit time oscillator having a complex structure and being difficult to implement in practical applications and being unable to achieve continuous broadband frequency modulation in a high frequency band.

[0007] To achieve the above purpose, the technical solution of the present invention is: an axial mechanical tuning device for broadband continuous frequency modulation of a transit time oscillator, comprising a front adjustment plate 1, a front adjustment ring 2, a rear adjustment plate 3, and a rear adjustment ring 4.

[0008] The front adjustment plate 1 consists of a set of axial rings and a connecting handle. The number of axial ring groups is the same as the number of transit time oscillator modulation cavities. Their inner radius is larger than the inner radius of the modulation cavity, and the outer surface of the ring abuts the bottom of the modulation cavity. The connecting handle is set on the outer surface of the axial rings and is composed of multiple sets of radial sector rings, whose outer surface ends are connected to the front adjustment ring 2. The front adjustment ring 2 is located outside the outer conductor of the transit time oscillator modulation cavity, and its inner radius is closely aligned with the outer radius of the outer conductor, allowing axial sliding outside the outer conductor. The connecting handle converts the axial sliding of the front adjustment ring 2 outside the transit time oscillator into the axial sliding of the front adjustment plate 1 inside the modulation cavity. The length of the front adjustment ring 2 is the same as the total length of the modulation cavity, thereby ensuring that all adjustment plates located in the modulation cavity slide synchronously.

[0009] The rear adjustment plate 3 is also composed of a plurality of axial rings and a connecting handle. The number of axial ring groups is the same as the number of transit time oscillator extraction cavities. The rear adjustment plate 3 is located at the left end of the transit time oscillator extraction cavity. The inner radius of the axial rings is larger than the inner radius of the modulation cavity. The outer surface of the rings abuts the bottom of the modulation cavity. The connecting handle is provided on the outer surface of the axial rings and is composed of multiple groups of radial sector rings. The outer surface of the rings is connected to the rear adjustment ring 4. The rear adjustment ring 4 is located outside the outer conductor of the transit time oscillator extraction cavity. The inner radius of the rings is close to the outer radius of the outer conductor and can slide axially outside the outer conductor. The length of the rear adjustment ring 4 is the same as the total length of the extraction cavity, thereby ensuring that all adjustment plates located in the modulation cavity slide synchronously.

[0010] The front adjusting piece 1, the front adjusting ring 2, the rear adjusting piece 3 and the rear adjusting ring 4 are all made of stainless steel.

[0011] The working principle is as follows: the motor drives the front adjustment ring 2 and the rear adjustment ring 4 to move axially, and the front adjustment ring 2 and the rear adjustment ring 4 respectively drive the front adjustment plate 1 and the rear adjustment plate 3 to move axially. The front adjustment plate 1 slides in or out of the modulation cavity, and the rear adjustment plate 3 slides in or out of the extraction cavity, thereby continuously changing the axial length of the adjustment plate within the modulation cavity and the extraction cavity, and thus continuously changing the eigenmode electric field distribution within the modulation cavity and the extraction cavity. By continuously changing the eigenmode electric field distribution within the modulation cavity and the extraction cavity, the technical effect of continuous frequency modulation is achieved. At the same time, the use of an axial mechanical frequency modulation mechanism can effectively overcome problems such as limited space and difficulty in industrialization, uneven movement of the adjustment plate, and structural deformation caused by the adjustment plate's own gravity squeezing the cavity wall.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] 1. The present invention proposes an axial mechanical tuning device for broadband continuous frequency modulation of a transit-time oscillator. Through axial adjustment, a tuning plate is continuously moved within a resonant cavity, thereby continuously changing the axial length of the tuning plate within the resonant cavity, thereby continuously changing the eigenmode electric field distribution within the resonant cavity, thereby achieving the technical effect of continuous frequency modulation.

[0014] 2. This invention proposes an axial mechanical tuning device for broadband continuous frequency modulation of a transit-time oscillator. This device adjusts the cavity frequency by axially sliding front and rear adjustment plates, respectively fixed to front and rear adjustment rings. Frequency modulation is achieved by simply moving the adjustment mechanism in the oscillator's axial direction. Compared to the prior art method of achieving frequency modulation by radially moving the adjustment mechanism, this method effectively overcomes the technical difficulty of industrialization due to the limited space between the outer conductor and the solenoid's magnetic field.

[0015] 3. The present invention's axially mechanical continuously frequency-modulated transit-time oscillator ensures synchronized movement of the regulating plate along its entire circumference by enabling the regulating plate to move axially. Compared to the method of radially pressing the regulating plate with an adjusting bolt, as discussed in the background art, this method effectively avoids uneven plate movement and structural deformation caused by the plate's own gravity squeezing the cavity wall, making it more suitable for high-frequency applications.

[0016] 4. The axial mechanical tuning system for broadband continuous frequency modulation of a transit-time oscillator proposed in the present invention is applied to the Ku-band transit-time oscillator in the example, which can achieve a frequency modulation range of 14.27 GHz to 15.283 GHz, and the power conversion efficiency in the entire range is greater than 27%, the power conversion efficiency between 14.27 GHz and 15.017 GHz is greater than 30%, and the highest efficiency is 40%. It has the advantages of a wide tuning range and high power conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1This is the principle structure diagram of the transit time oscillator;

[0018] Figure 2 A front cross-sectional view of an axial mechanical tuning device for broadband continuous frequency modulation of a transit-time oscillator according to the present invention, loaded on a transit-time oscillator;

[0019] Figure 3 A perspective view of an axial mechanical tuning device for broadband continuous frequency modulation of a transit time oscillator according to the present invention;

[0020] Figure 4 A cross-sectional view of an axial mechanical tuning device for broadband continuous frequency modulation of a transit-time oscillator according to the present invention;

[0021] Figure 5 A front cross-sectional view of a Ku-band transit time oscillator according to an application example of the present invention;

[0022] Figure 6 This is a three-dimensional schematic diagram of an axial mechanical tuning system for broadband continuous frequency modulation of a transit time oscillator according to an application example of the present invention loaded on a Ku-band transit time oscillator;

[0023] Figure 7 This is a schematic diagram showing the axial movement distance of the front adjustment plate 1 corresponding to the movement distance of the rear adjustment plate 4 when the axial mechanical tuning system for broadband continuous frequency modulation of a transit time oscillator described in an application example of the present invention is loaded on the Ku-band transit time oscillator;

[0024] Figure 8 This is a schematic diagram showing the effect of the axial movement distance of the front adjustment plate 1 on the frequency and power conversion efficiency when the axial mechanical tuning system for broadband continuous frequency modulation of a transit-time oscillator described in an application example of the present invention is loaded on the Ku-band transit-time oscillator. DETAILED DESCRIPTION

[0025] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 This is a schematic diagram of the principle structure of a transit-time oscillator. The transit-time oscillator consists of a cathode A, an inner conductor B, an outer conductor C, an external magnetic field D, a modulation cavity E, and an extraction cavity F. The entire structure is rotationally symmetrical about the central axis. The left end of cathode A is connected to the inner conductor of an external pulse power source, the right end of inner conductor B is connected to the inner conductor of the radiation system, the left end of outer conductor C is connected to the outer conductor of the pulse power source, and the right end of outer conductor C is connected to the outer conductor of the radiation system. The modulation cavity E and extraction cavity F form a coaxial resonant cavity between the inner conductor B and the outer conductor C.

[0027] Figure 2 This is a front cross-sectional view of an axial mechanical tuning device for broadband continuous frequency modulation of a transit time oscillator according to the present invention, which is loaded on a transit time oscillator. The front adjustment plate 1 is located in the transit time oscillator modulation cavity, the rear adjustment plate 3 is located in the transit time oscillator extraction cavity, and the front adjustment ring 2 and the rear adjustment ring 4 are located outside the transit time oscillator outer conductor.

[0028] Figure 3 and Figure 4 These are stereoscopic and cross-sectional views of an axial mechanical tuning device for broadband continuous frequency modulation of a transit-time oscillator according to the present invention. The device as a whole is rotationally symmetrical about the central axis. The front adjustment ring 2 and the rear adjustment ring 4 are both sleeved on the outer surface of the outer conductor C, and the entire device remains concentric.

[0029] like Figure 5 The axial mechanical tuning device for broadband continuous frequency modulation of a transit-time oscillator according to the present invention is shown as follows: it comprises a front adjustment plate 1, a front adjustment ring 2, a rear adjustment plate 3, a rear adjustment ring 4, a front adjustment rod 5, a rear adjustment rod 6, a motor 7, a fixing ring 8, and a fixing rod 9. In this example, the front adjustment plate 1 comprises three sets of axial circular rings, installed in the modulation cavity E. One end of the ring enters the modulation cavity through the right end of the circular channel, and the other end connects to the front adjustment ring 2 outside the outer conductor C through the upper end of the circular channel. The rear adjustment plate 3 is installed in the extraction cavity F. One end of the ring enters the extraction cavity through the right end of the circular channel, and the other end connects to the rear adjustment ring 4 outside the outer conductor C through the upper end of the circular channel. The front adjustment plate 1 and the rear adjustment plate 3 have the same radius.

[0030] The outer high circular ring of the front adjustment ring 2 has four holes uniformly angularly and at the same radial height for connection to the front adjustment rod 5. The front adjustment rods 5 are cylindrical metal rods, numbering four to the same number of holes, and are sized to fit through the holes in the front adjustment ring 3 and the holes of the same size at the same location on the fixed ring 8. A motor 7 is mounted near the end of each metal rod of the front adjustment ring 5 near the fixed ring 8. One end of the motor 7 is connected to the front adjustment rod 5 and the other end is screwed to the fixed ring 8. The fixed ring 8 is a radial ring located outside the end of the outer conductor in the transit time oscillator structure and is used to secure the outer conductor. Four holes are formed at the same radial position in the fan-shaped ring of the rear adjustment ring 4. The rear adjustment rods 6 are cylindrical metal rods, numbering four to the same number of holes, and are sized to fit through the holes in the rear adjustment ring 4 and the holes of the same size at the same location on the fixed ring 8. A motor 7 is installed at the end of each metal rod of the rear adjusting rod 6 near the fixed ring 8, one end of which is connected to the rear adjusting rod 6 and the other end is fixed to the fixed ring 8 by a screw. The front adjusting rod 5 and the rear adjusting rod 6 are staggered with each other and evenly distributed in the angular direction. The motor 7 can drive each metal rod of the front adjusting rod 5 and the rear adjusting rod 6 to slide axially, thereby driving the front adjusting plate 1 fixed on the front adjusting ring 2 and the rear adjusting plate 3 on the rear adjusting ring 4 to move axially. The uniform and symmetrical distribution of the motors allows the adjusting plates to keep the entire circular ring moving in unison. The front adjusting plate 1 is located in the modulation cavity E of the transit time oscillator and is close to the outer wall, and the rear adjusting plate 4 is located in the extraction cavity F of the transit time oscillator and is close to the outer wall. The fixed rod 9 is a metal rod fixed to the fixed ring 8 by a nut. The function of the fixed rod 9 is to fix the inner conductor and outer conductor of the transit time oscillator

[0031] The motor 7 drives the axial movement of the front adjustment rod 5, which in turn causes the front adjustment plate 1 to move axially within the modulation cavity channel E, changing its length within the modulation cavity, thereby altering the internal eigenmode electric field distribution and ultimately changing the modulation cavity operating frequency. For each movement of the front adjustment plate 1, the rear adjustment plate 3, driven by the motor 7 and via the rear adjustment rod 6, can also move axially, changing its length within the extraction cavity, thereby altering the internal eigenmode electric field distribution and ultimately changing the extraction cavity operating frequency.

[0032] This preferred embodiment achieves a frequency modulation range of 14.27GHz to 15.283GHz. In particle simulation, the efficiency reaches 40% at the device's center operating frequency of 14.27GHz, the power conversion efficiency in the entire range is greater than 27%, and the power conversion efficiency between 14.27GHz and 15.017GHz is greater than 30%.

[0033] Figure 6A schematic diagram of a Ku-band transit-time oscillator (TTO) with a broadband continuous frequency modulation axial mechanical tuning system, as described in an application example of the present invention. The system is mounted outside the external channel, between two sets of retaining rings. The front and rear adjustment rods 5 and 6 are each secured to retaining rings 8 with four sets of screws. The two sets of retaining rings 8 are located before the modulation cavity and after the extraction cavity, respectively. The retaining rods 9 are secured to the retaining rings 8 with nuts, enhancing mechanical strength and facilitating disassembly.

[0034] Figure 7 This diagram shows the relationship between the axial movement distance of the front adjusting plate 1 and the movement distance of the rear adjusting plate 3 when the axial mechanical tuning system for broadband continuous frequency modulation of a transit-time oscillator, described in an application example of the present invention, is loaded onto a Ku-band transit-time oscillator. The abscissa Δq1 represents the axial sliding length of the front adjusting plate 1, and the ordinate Δq2 represents the axial movement distance of the rear adjusting plate 3 corresponding to the maximum power conversion efficiency when the axial sliding length of the front adjusting plate 1 is matched.

[0035] Figure 8 This diagram shows the effect of the axial movement distance of the front adjusting plate 1 on the frequency and power conversion efficiency when the axial mechanical tuning system for broadband continuous frequency modulation of a transit-time oscillator, described in an application example of the present invention, is loaded onto a Ku-band transit-time oscillator. The abscissa Δq1 represents the axial sliding length of the front adjusting plate 1, the left ordinate represents the frequency, and the right ordinate represents the power conversion efficiency.

[0036] See also Figure 7 For different lengths of the front adjusting piece 1, the length of the rear adjusting piece 3 can be adjusted to maximize the power conversion efficiency of the output microwave. The adjustable length of the front adjusting piece 1 is Δq1 = 4.5 mm, and the corresponding adjustable length of the rear adjusting piece 3 is Δq2 = 3.5 mm. Figure 8 In a mechanically tunable Ku-band transit time oscillator, by adjusting the lengths of the front adjustment loop 2 and the rear adjustment loop 4, a frequency modulation range of 14.27 GHz to 15.283 GHz can be achieved. The power conversion efficiency in the full range is greater than 27%, and the power conversion efficiency between 14.27 GHz and 15.017 GHz is greater than 30%.

Claims

1. An axial mechanical tuning device for broadband continuous frequency modulation of a transit-time oscillator, characterized in that: It comprises a front adjusting plate (1), a front adjusting ring (2), a rear adjusting plate (3), and a rear adjusting ring (4); The front adjustment plate (1) is composed of a plurality of axial rings and a connecting handle; the number of axial ring groups is the same as the number of transit time oscillator modulation cavities, the inner radius of the axial rings is larger than the inner radius of the modulation cavity, and the upper part of the rings is in close contact with the outer wall of the modulation cavity; the connecting handle is located at the left end of the axial rings, and is a plurality of radial sector rings, the outer radius end of which is connected to the front adjustment ring (2); the front adjustment ring (2) is located outside the outer conductor of the transit time oscillator modulation cavity, the inner radius of the front adjustment ring is in close contact with the outer radius of the outer conductor, and can slide axially outside the outer conductor; the axial sliding of the front adjustment ring (2) outside the transit time oscillator is converted to the axial sliding of the front adjustment plate (1) inside the modulation cavity by the connecting handle; The rear adjustment plate (3) is composed of a plurality of axial rings and a connecting handle; the number of the axial ring groups is the same as the number of the transit time oscillator extraction cavity, and is located at the left end of the transit time oscillator extraction cavity, and its inner radius is larger than the inner radius of the adjustment extraction cavity, and the upper part of the ring is in close contact with the outer wall of the extraction cavity; the connecting handle is located at the left end of the axial ring, and is a plurality of radial sector rings, and its outer radius end is connected to the rear adjustment ring (4); the rear adjustment ring (4) is located outside the outer conductor of the transit time oscillator extraction cavity, and its inner radius is in close contact with the outer radius of the outer conductor, and can slide axially outside the outer conductor; Through the axial movement of the front adjustment ring (2) and the rear adjustment ring (4), the front adjustment plate (1) in the modulation cavity and the rear adjustment plate (3) in the extraction cavity are driven to slide axially, thereby synchronously changing the sizes of the modulation cavity and the extraction cavity, thereby changing the electric field distribution of the intrinsic mode of the transit time oscillator, and ultimately changing the operating frequency of the device.

2. The axial mechanical tuning device for broadband continuous frequency modulation of a transit time oscillator according to claim 1, characterized in that: The length of the front adjusting ring (2) is the same as the total length of the modulation cavity, thereby ensuring that all adjusting pieces located in the modulation cavity slide synchronously.

3. The axial mechanical tuning device for broadband continuous frequency modulation of a transit time oscillator according to claim 1, characterized in that: The length of the rear adjustment ring (4) is the same as the total length of the extraction chamber, thereby ensuring that all adjustment pieces located in the modulation chamber slide synchronously.

4. The axial mechanical tuning device for broadband continuous frequency modulation of a transit time oscillator according to claim 1, characterized in that: The front adjusting pieces (1) and the rear adjusting pieces (3) are each in three groups.

5. The axial mechanical tuning device for broadband continuous frequency modulation of a transit time oscillator according to any one of claims 1 to 4, characterized in that: The front adjusting piece (1), the front adjusting ring (2), the rear adjusting piece (3) and the rear adjusting ring (4) are all made of stainless steel.

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