Broadband random noise source with high excess noise ratio

Abstract

The invention discloses a broadband random noise source with a high excess noise ratio, and belongs to the technical field of microwave and millimeter wave vacuum devices. The broadband random noise source comprises a medium-loaded gyrotron traveling wave tube and a Bragg filter, a wide-spectrum noise floor signal is generated by increasing the axial length of a medium loading circuit in the medium loading gyrotron traveling wave tube, and reflection filtering is performed on the wide-spectrum noise floor signal by arranging a Bragg filter between a collecting stage and an output window, so that a high-flatness wide-spectrum random noise signal is obtained. The characteristics of high power, high frequency and wide bandwidth of the gyrotron traveling wave tube for amplifying microwaves are utilized, noise floor signals can be amplified to generate high-power noise signals, meanwhile, the Bragg filter is loaded to carry out filtering and power balancing on the noise floor signals, and therefore high-power, wide-frequency-spectrum and high-flatness random noise signal output is achieved. And the output power of the generated noise signal is effectively improved.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave and millimeter wave vacuum devices, and in particular relates to a random noise source with high super noise ratio and broadband characteristics based on a gyrotron traveling wave tube. Background Art

[0002] A noise source refers to an instrument that artificially generates noise with a flat power spectrum and randomly changing amplitude within a specific frequency range. It has a wide range of applications in system noise factor measurement, noise radar systems, target detection and imaging, electromagnetic interference, and secure communications. At present, there are three main technical solutions for noise generation: thermodynamics, electronics, and photonics. Commonly used noise sources include cold and hot load noise sources, active cold noise sources, gas discharge noise sources, saturated vacuum diode noise sources, solid-state noise sources, photon noise sources, etc. However, these noise sources are difficult to meet the requirements of radar and long-distance communications for higher power and higher efficiency.

[0003] Gyrotron traveling wave tubes based on the electron cyclotron maser mechanism can achieve high-power, wide-bandwidth, and high-frequency microwave amplification of the order of hundreds of kW, making them potential broadband high-power noise sources. However, in traditional gyrotron traveling wave tubes, the noise floor signal gain is usually low to maintain a high signal-to-noise ratio. Summary of the invention

[0004] The technical problem to be solved by the present invention is that the power of the traditional noise source is low and it is difficult to meet the noise power requirements of noise radar and long-distance communication. In view of this problem, the present invention proposes a high-power broadband random noise source. The noise source uses a dielectric-loaded gyrotron traveling wave tube to generate an extremely wide spectrum noise floor signal, and then combines it with a Bragg filter to reflect and filter it, and finally generates a high-power, high-flatness, wide-spectrum random noise signal.

[0005] The technical solution adopted by the present invention is as follows:

[0006] A broadband random noise source with high super noise ratio is characterized by comprising: a dielectric loaded gyrotron traveling wave tube and a Bragg filter.

[0007] The dielectric-loaded gyrotron traveling wave tube generates a wide-spectrum noise floor signal by increasing the axial length of the dielectric-loaded circuit.

[0008] The Bragg filter is arranged between the collecting stage and the output window of the dielectric loaded gyrotron traveling wave tube to perform reflection filtering on the wide spectrum noise floor signal to obtain a random noise signal with high flatness and wide spectrum.

[0009] Furthermore, when the dielectric-loaded gyrotron traveling wave tube operates in the Ku band, the axial length of the dielectric-loaded circuit ranges from 400 mm to 600 mm.

[0010] Furthermore, the Bragg filter includes a main waveguide and a non-periodic cylindrical grating tooth structure loaded on the main waveguide to achieve better passband transmission and lower stopband transmission.

[0011] Furthermore, the Bragg filter is connected to the collection stage through a first gradient waveguide, and is connected to the output window through a second gradient waveguide.

[0012] Furthermore, the radius R1 of the main waveguide is (1-1.3) R0, where R0 is the waveguide radius of the dielectric loading circuit; the radius of the main waveguide is set within this range in order to cut off microwave transmission in the low-frequency stop band.

[0013] Furthermore, the axial lengths of the grating tooth structures in the non-periodic cylindrical grating tooth structure are not completely the same, and the radii are not completely the same, and the radii of all grating tooth structures are in the range of (1 to 1.5)R1.

[0014] Furthermore, the first tapered waveguide and the second tapered waveguide satisfy the Chebyshev curve to achieve low-reflection transmission of microwaves.

[0015] The working principle of the present invention is as follows:

[0016] The present invention designs a novel broadband random noise source with a high super-noise ratio, with a dielectric-loaded gyrotron traveling wave tube as the main structure. In the absence of an input microwave signal, the gyrotron electron beam emitted by the magnetron injection electron gun is pre-grouped in the extended lossy dielectric loading circuit and excites a wide-spectrum noise floor signal; then in the nonlinear beam-wave interaction circuit, the electron beam that has completed the pre-grouping will perform high-power microwave amplification on the noise floor signal. At this time, the amplified wide-spectrum noise floor signal is a high-power, low super-noise ratio flatness wide-spectrum noise signal; when the noise signal enters the Bragg filter, microwaves of a specific wavelength (i.e., the noise signal within the required frequency band) will be transmitted through the output window for microwave output, and microwaves of the remaining wavelengths will be reflected back to the lossy dielectric loading circuit and absorbed by the attenuation ceramic. Therefore, the noise floor signal generated by the dielectric-loaded gyrotron traveling wave tube can be filtered and a certain degree of power balancing with the help of the Bragg filter, thereby outputting random noise with a wide spectrum, high power, and high flatness. Compared with the prior art, the present invention mainly has the following advantages:

[0017] The present invention realizes a new broadband random noise source with high super noise ratio, which can amplify the noise floor signal to generate a high-power noise signal by utilizing the high power, high frequency and wide bandwidth characteristics of the gyrotron traveling wave tube to amplify the microwave. At the same time, the Bragg filter structure is loaded to filter and power balance the noise floor signal, thereby realizing the output of high-power, wide-spectrum and high-flatness random noise signals, effectively improving the output power of the noise signal generated by the prior art.

[0018] In the present invention, the Bragg filter is integrated into the dielectric loaded gyrotron traveling wave tube, making the overall system more compact and integrated. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the structure of a broadband random noise source with high super noise ratio in an embodiment.

[0020] Figure 2 3D vacuum simulation model diagram of the Bragg filter in the embodiment.

[0021] Figure 3 FIG. 4 is a schematic longitudinal cross-sectional view of a Bragg filter in an embodiment.

[0022] Figure 4 The transmission coefficient and reflection coefficient of the Bragg filter simulated by CST high frequency simulation software are shown in the following figure.

[0023] Figure 5 This is the output signal of the noise source of the present invention obtained by simulating with the CST 3D Particle Studio simulation software.

[0024] Figure 6 It is the super-noise ratio of the noise signal generated by the noise source of the present invention simulated by the CST 3D Particle Studio simulation software in Example.

[0025] Explanation of the reference numerals: 1 is a magnetron injection electron gun, 2 is an electron beam channel, 3 is a compensation magnetic field coil, 4 is a lossy dielectric loading circuit, 5 is a superconducting magnet, 6 is a nonlinear beam-wave interaction circuit, 7 is an electron beam, 8 is a collection stage, 9 is a first gradient waveguide, 10 is a Bragg filter, 11 is a second gradient waveguide, and 12 is an output window. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below in conjunction with a design example of a high-noise-ratio broadband random noise source operating in the Ku band and the accompanying drawings.

[0027] like Figure 1 As shown, a broadband random noise source with a high super-noise ratio in this embodiment includes: a dielectric-loaded gyrotron traveling wave tube and a Bragg filter.

[0028] The medium loaded gyrotron traveling wave tube operates in the circular waveguide TE mode. 11mode, the operating frequency band is Ku band (12.4GHz-18GHz), the operating voltage is 60kV, the operating current is 10A, and the magnetic field amplitude is 0.6T. The dielectric-loaded cyclotron traveling wave tube includes a magnetron injection electron gun, an electron injection channel, a compensation magnetic field coil, a lossy dielectric loading circuit, a superconducting magnet, a nonlinear injection-wave interaction circuit, a first gradient waveguide, a second gradient waveguide, a collection stage, and an output window; that is, compared with a conventional cyclotron traveling wave tube, the dielectric-loaded cyclotron traveling wave tube in the present invention only lengthens the axial length of the lossy dielectric loading circuit, and a Bragg filter is arranged between the collection stage and the output window, so other structures are not described in detail.

[0029] In this embodiment, the dielectric in the lossy dielectric loading circuit is a attenuation ceramic BeO-TiO2 (ε r =9,tanδ=0.5), with good electrical conductivity and heat dissipation characteristics; the ceramic thickness is 1.3mm, which can be used for working TE 11 The mode achieves a loss of 6.14dB / cm to suppress its oscillation; the axial length of the lossy dielectric loading circuit is 500mm (approximately 1.5 to 3 times that of the traditional scheme), so that the cyclotron electron beam is pre-grouped in the extended lossy dielectric loading circuit and excites a wide-spectrum noise floor signal to achieve a sufficiently high noise amplification gain.

[0030] The Bragg filter is arranged between the collecting stage and the output window of the medium-loaded gyrotron traveling wave tube, and is connected to the collecting stage through a first gradient waveguide, and is connected to the output window through a second gradient waveguide; the Bragg filter is used to perform reflection filtering on a wide-spectrum noise floor signal to obtain a random noise signal with high flatness and a wide spectrum.

[0031] like Figure 2 As shown, the Bragg filter includes a main waveguide and 11 non-periodic cylindrical grating tooth structures loaded on the main waveguide to achieve better passband transmission and lower stopband transmission. Figure 3The figure shows a schematic longitudinal section of the Bragg filter structure, where the radius of the main waveguide is R1 = 7.6 mm. After optimization, the radii of the cylindrical grating tooth structures are: R2 = 10.655 mm, R3 = 11.064 mm, R4 = 10.789 mm, R5 = 10.288 mm, R6 = 10.631 mm, R7 = 10.755 mm, R8 = 10.148 mm, R9 = 9.833 mm, R10 = 10.519 mm, R11 = 10.767 mm, R12 = 10.476 mm; the thicknesses of the cylindrical grating tooth structures are: L1 = 1.997 mm, L2 = 2.214 mm, L3 = 1.927 mm, L4 = 1.916 mm, L5=2.993mm, L6=1.980mm, L7=2.141mm, L8=2.254mm, L9=2.268mm, L10=2.120mm, L11=2.108mm; the intervals between the cylindrical grating tooth structures are: D1=2.515mm, D2=2.061mm, D3=1.516mm, D4=3.089mm, D5=4.496mm, D6=4.626mm, D7=1.257mm, D8=3.947mm, D9=4.957mm, D10=3.286mm.

[0032] Figure 4 The figure shows the transmission coefficient and reflection coefficient of the Bragg filter obtained by CST high-frequency simulation software. From this figure, it can be seen that the optimized Bragg filter has a good TE performance in the range of 11.7 to 18 GHz. 11 The transmission of the mode is greater than -0.3dB, and the reflection is less than -15dB. The transmission in the stop band is less than -20dB, and even less than -30dB in the range of 18.5 to 22GHz.

[0033] Figure 5 The output signal of the noise source of the present invention obtained by simulation using CST 3D Particle Studio simulation software is shown. 11 The mode is circularly polarized. This figure shows only the TE in one polarization direction. 11 mode output signal, another TE in the perpendicular polarization direction 11 The mode output power is consistent with it. Their average power reaches 28.81kW through integration accumulation, which meets the high power requirement of this design.

[0034] Figure 6The figure shows the super-noise ratio of the noise signal generated by the noise source of the present invention obtained by simulation with CST 3D Particle Studio simulation software. The super-noise ratio can reach 80dB, and it is relatively flat in the range of 11.7 to 18GHz, with a flatness of about ±20dB. The noise source has a high super-noise ratio and good flatness, meeting the high super-noise ratio and high flatness requirements of the present design.

[0035] The above is only a specific implementation of the present invention applied to the Ku-band gyrotron traveling wave tube. The present invention is also applicable to other frequency bands with the working mode of TE 11 Mode or TE 01 Mode gyrotron traveling wave tube.

Claims

1. A broadband random noise source with high super noise ratio, characterized in that: include: Dielectric loaded gyrotron traveling wave tube, Bragg filter; The dielectric-loaded gyrotron traveling wave tube generates a wide-spectrum noise floor signal by increasing the axial length of the dielectric-loaded circuit; The Bragg filter is arranged between the collecting stage and the output window of the dielectric loaded gyrotron traveling wave tube to perform reflection filtering on the wide spectrum noise floor signal to obtain a random noise signal with high flatness and wide spectrum.

2. A broadband random noise source with a high super noise ratio as claimed in claim 1, characterized in that: When the dielectric-loaded gyro-traveling wave tube operates in the Ku band, the axial length of the dielectric-loaded circuit ranges from 400 mm to 600 mm.

3. A broadband random noise source with a high super noise ratio as claimed in claim 1 or 2, characterized in that: The Bragg filter comprises a main waveguide and a non-periodic cylindrical grating tooth structure loaded on the main waveguide.

4. A broadband random noise source with a high super noise ratio as claimed in claim 3, characterized in that: The Bragg filter is connected to the collection stage through a first gradient waveguide, and is connected to the output window through a second gradient waveguide.

5. A broadband random noise source with high super noise ratio as claimed in claim 4, characterized in that: The radius R1 of the main waveguide is (1-1.3) R0, where R0 is the waveguide radius of the dielectric loading circuit.

6. A broadband random noise source with a high super noise ratio as claimed in claim 5, characterized in that: The axial lengths of the grating tooth structures in the non-periodic cylindrical grating tooth structure are not completely the same, and the radii are not completely the same, and the radii of all grating tooth structures are in the range of (1 to 1.5)R1.

7. A broadband random noise source with a high super noise ratio as claimed in any one of claims 4 to 6, characterized in that: The first tapered waveguide and the second tapered waveguide satisfy a Chebyshev curve.

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