Terahertz over-high-speed plasma communication test system

Abstract

The invention discloses a terahertz over-high-speed plasma communication test system, and belongs to the technical field of aerospace. The test system is composed of a communication module and a plasma generation module. The communication module can be but not limited to a solid-state communication module, and is mainly divided into two parts: a transmitting front-end module and a receiving front-end module. The high temperature plasma may employ, but is not limited to, arc plasma wind tunnel formation. The invention provides a test scheme for solving the problem of communication interruption caused by a plasma sheath generated on the surface of an aircraft when the aircraft runs at a high speed in the atmosphere. Aiming at a communication technology of a terahertz frequency band in a blackout area, the blackout stealth effect of a reentry capsule, a hypersonic aircraft and the like is solved.

Description

Technical Field

[0001] The present invention relates to the field of aerospace technology, and more specifically, to terahertz communication, return capsule measurement and control, supersonic aircraft measurement and control, anti-stealth technology and other professional fields. Background Art

[0002] When a high-speed aircraft is moving, a shock wave is generated in front of its head. Due to the compression of the shock wave and the viscosity of the atmosphere, a large amount of kinetic energy is converted into heat energy, which heats the atmosphere between the shock wave and the aircraft to thousands of degrees Celsius, causing the gas to ionize and form a plasma sheath around the aircraft. The interaction between plasma and radio waves causes the measurement, control and communication radio waves to attenuate or reflect, resulting in severe signal deterioration or even complete interruption. This communication interruption phenomenon is called "blackout".

[0003] At present, the main ways to deal with blackouts at home and abroad include increasing antenna transmission power, changing the aerodynamic shape of the aircraft, spraying electrophilic substances, and selecting appropriate frequency windows. The first three methods will introduce more problems in terms of aircraft volume, weight, aerodynamic heat, and electromagnetic compatibility. Based on the theory that when the frequency of radio waves is much lower or higher than the plasma collision frequency and plasma density, electromagnetic waves can also pass through the plasma with lower attenuation, the communication frequency band that breaks through the blackout attempts to develop in the two directions of ultra-low frequency and high frequency. The ultra-low frequency method is limited in power and information volume, so increasing the carrier frequency band to high frequency has received a lot of attention. In the return mission of the spacecraft, Ka radar and optics formed a joint force to complete the tracking and measurement mission of the spacecraft in the blackout area. However, the radar is limited to tracking according to the planned path and cannot "penetrate". There is still a "stealth zone" of tens of seconds in areas with high plasma density, and the narrow laser beam width makes this method unable to ensure the establishment of a continuous, reliable and stable ground-to-air link around the clock. In recent years, there have been a series of theories to support the theoretical and experimental research on the ability of terahertz waves to penetrate black barriers. However, these achievements are currently limited by devices and research foundations, confined to the Ka or lower frequency bands, with only detection targets and no communication signal research, and are unable to generate plasma of the expected density. Summary of the invention

[0004] The problem solved by the present invention is to provide a structure for communication through black barriers. A test scheme is proposed for the communication interruption problem caused by the plasma sheath generated on the surface of an aircraft when it is running at high speed in the atmosphere. The communication technology in the black barrier area of ​​the terahertz frequency band is used to solve the black barrier stealth effect of the return capsule and hypersonic aircraft.

[0005] The present invention adopts the following technical solution:

[0006] A terahertz ultra-high-speed plasma communication test system, comprising a communication unit and a plasma generation unit;

[0007] The communication unit is composed of two groups of front-end components, one of which is used as a transmitting front end, and the other is used as a receiving front end; each front-end component includes an intermediate frequency module, a terahertz antenna and a mixing and frequency multiplication module, and the terahertz antenna is facing the plasma generation unit;

[0008] In the transmitting front-end component, the signal generating device, the intermediate frequency module a, the frequency mixing and multiplying module a and the terahertz antenna a are connected in sequence; the signal generating device transmits an intermediate frequency signal with a specific center frequency and a specific bandwidth, and the intermediate frequency signal is up-converted with another frequency in the intermediate frequency module a, and then up-converted through the frequency mixing and multiplying module a, and the signal output with the center frequency in the terahertz frequency band is completed, and finally transmitted through the terahertz antenna a;

[0009] In the receiving front-end component, the signal acquisition and processing equipment, the intermediate frequency module b, the mixing and frequency multiplication module b, the low noise amplifier and the terahertz antenna b are connected in sequence; the intermediate frequency module b includes a local oscillator link; the terahertz signal is received by the terahertz antenna b, and the low noise amplifier amplifies the signal received by the antenna; the signal is down-converted through the mixing and frequency multiplication module b, wherein the local oscillator link realizes the output of the local oscillator signal through the sextuple frequency and the power amplifier, and the local oscillator signal is mixed with the terahertz signal, and the terahertz signal is converted into an intermediate frequency signal and output to the signal acquisition and processing equipment.

[0010] Furthermore, the plasma generating unit is an arc plasma wind tunnel.

[0011] Furthermore, it also includes a heat-insulating shell and a shielding shell; the shielding shell is placed in the heat-insulating shell, and an intermediate filler is arranged between the two; the front-end component is installed in the shielding shell.

[0012] Furthermore, it also includes a power supply module, which supplies power to the frequency mixing and multiplication module and the intermediate frequency module.

[0013] Furthermore, the heat-insulating shell and the shielding shell are also provided with lens light-through holes and wire through holes.

[0014] The advantages of the present invention compared with the prior art are:

[0015] (1) Experiments have proven that the use of electromagnetic waves in the terahertz band can achieve the ability to break through blackout areas.

[0016] (2) Currently, all research on penetrating plasma is basically still in the theoretical stage. The present invention can complete communication tests and summarize the test results to obtain a high-speed aircraft anti-blackout communication implementation plan. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of a terahertz ultra-high-speed plasma communication test system according to an embodiment of the present invention.

[0018] Figure 2 It is the insulation shell of the test system.

[0019] Figure 3 It is a spectrum analysis diagram of the test results of the present invention.

[0020] Figure 4 This is a cutoff relationship diagram of the communication frequency and plasma electron density of the present invention.

[0021] Among them: 1 and 11 are power modules; 2 is a mixing and frequency multiplication module; 8 is a low noise amplifier + mixing and frequency multiplication module; 3 and 7 are terahertz antennas; 4 and 9 are intermediate frequency modules; 1, 2, 3, and 4 are transmitting ends, which are placed in a transmitting thermal insulation shielding shell; 7, 8, 9, and 11 are receiving ends, which are placed in a receiving shielding shell; 6 is plasma, which can be but is not limited to being generated by a wind tunnel; 5 is a signal generating device; 10 is a signal acquisition and processing device.

[0022] The receiving insulation shell has the same structure as the transmitting insulation shell. 17 is a shielding shell, which is made of but not limited to high-performance aluminum and other materials; 13 is an insulation shell, which is made of but not limited to steel sheet metal materials; 14 is a sandwich insulation material, which is made of but not limited to rock wool and other materials; 12 is a light hole containing a lens; 15 is a wire penetration hole, which is made of but not limited to aviation plugs for docking. DETAILED DESCRIPTION

[0023] The present invention is described in further detail below.

[0024] Reference Figure 1 and Figure 2 This embodiment provides a terahertz super-high temperature and high-density plasma test device. The test system consists of two parts: a communication module and a plasma generation module.

[0025] The communication module may be, but is not limited to, a solid-state communication module, and is mainly divided into two parts: a transmitting link and a receiving link.

[0026] The terahertz transmitting front-end module has the same appearance as the terahertz receiving front-end module, and the internal circuit implementation form is basically the same. When used as a transmitting front-end module, the intermediate frequency port is used to input the intermediate frequency signal, the local oscillator port is connected to the local oscillator source, and the RF waveguide port is connected to the horn antenna; when used as a receiving front-end module, the intermediate frequency port is used to output the intermediate frequency signal, the local oscillator port is connected to the local oscillator source, and the RF waveguide port is connected to the horn antenna.

[0027] In the transmitting front-end component, the signal generating device, the intermediate frequency module a, the frequency mixing and multiplying module a and the terahertz antenna a are connected in sequence; the signal generating device transmits an intermediate frequency signal with a specific center frequency and a specific bandwidth, and the intermediate frequency signal is up-converted with another frequency in the intermediate frequency module a, and then up-converted through the frequency mixing and multiplying module a, and the signal output with the center frequency in the terahertz frequency band is completed, and finally transmitted through the terahertz antenna a;

[0028] In the receiving front-end component, the signal acquisition and processing equipment, the intermediate frequency module b, the mixing and frequency multiplication module b, the low noise amplifier and the terahertz antenna b are connected in sequence; the intermediate frequency module b includes a local oscillator link; the terahertz signal is received by the terahertz antenna b, and the low noise amplifier amplifies the signal received by the antenna; the signal is down-converted through the mixing and frequency multiplication module b, wherein the local oscillator link realizes the output of the local oscillator signal through the sextuple frequency and the power amplifier, and the local oscillator signal is mixed with the terahertz signal, and the terahertz signal is converted into an intermediate frequency signal and output to the signal acquisition and processing equipment.

[0029] High temperature plasma can be formed by, but is not limited to, arc plasma wind tunnel.

[0030] During the simulated plasma sheath environmental test, the impact of high temperature on the communication system needs to be considered. Even if a short-term test is conducted, the high temperature accumulated on the solid-state device cannot be ignored. In the traditional design application environment, according to the provisions of GJB151, the ambient temperature range of the device is from -40℃ to 70℃, and according to the calculation of heat conduction, the temperature near the device can reach 200℃ within 1 minute at the wind tunnel test site. Therefore, the RF device needs to be protected and the transceiver is wrapped in a shell.

[0031] The thermal insulation shell is divided into but not limited to two boxes. The inner layer is a module shielding box, which is used to seal and package various RF modules, improve the DC power supply and RF connector methods, and improve a certain degree of safety. The outer layer is a heat-insulating box, which plays a heat-insulating role when the RF module is tested in a high temperature environment.

[0032] The design of the module shielding box will focus more on convenience and lightness, while the heat insulation box focuses more on functionality and practicality. 1. The shielding box is made of high-performance aluminum or stainless steel precision-machined cavity, various RF module brackets, polytetrafluoroethylene antenna cover, aluminum heat sink, adapter, and power supply aviation plug; 2. The heat insulation box is made of steel sheet metal frame, interlayer is rock wool or other insulation materials, and high-performance materials for the antenna surface.

[0033] Plasma has three main electrical characteristic parameters, namely electron density, plasma frequency and collision frequency. Plasma electron density Ne is usually expressed as the number of electrons per cubic centimeter, which is related to the atmospheric density and the temperature of the plasma. Plasma frequency ωp generally refers to the electron oscillation frequency ωpe inside the plasma, and the collision frequency ν indicates the degree of collision between electrons and neutral particles and ions inside the plasma. The plasma frequency ωp is proportional to the square root of the electron density Ne, and the relationship between the two is as follows:

[0034]

[0035] Among them, e is the electron charge, ε0 is the vacuum contact constant, and me is the electron mass.

[0036] For the convenience of analysis, we first assume that the electromagnetic wave is incident vertically on an isotropic, uniform plasma with a plasma thickness of d. The attenuation constant a and the phase constant β can be obtained using Maxwell's equations.

[0037]

[0038] Among them, σ is the conductivity, μ is the magnetic permeability, μ = μ0μr, for isotropic plasma, the relative magnetic permeability μr = 1, so μ is equal to the vacuum magnetic permeability μ0, ε is the dielectric constant, ε = ε0εr, εr and is the relative dielectric constant, ω is the angular frequency of the electromagnetic wave. According to the elementary theory of plasma, the dielectric constant ε and the conductivity σ have the following relationship:

[0039]

[0040]

[0041] The attenuation constant is obtained from equations (2) to (5):

[0042]

[0043] Where c is the speed of light.

[0044] According to formula (6), the attenuation of electromagnetic waves after transmission in uniform plasma can be calculated, and the cutoff relationship between communication frequency and plasma electron density can be obtained, such as Figure 4 As shown:

[0045] It can be seen that the highest Ka frequency band in the microwave frequency can only work when the plasma electron density is slightly greater than 10 13 / cm 3 According to the peak distribution data of the electron density at the front and rear of the spacecraft during the reentry of my country’s manned spacecraft, the electron density at the front can reach up to 6×10 13 / cm 3，Combining the effects of plasma frequency and collision frequency on electromagnetic wave attenuation in equation (6), it can be calculated that when the electromagnetic wave frequency is greater than 100 GHz, the attenuation of the electromagnetic wave by the plasma can be controlled below 3 dB.

[0046] Therefore, increasing the communication frequency band to terahertz can theoretically solve the blackout problem.

[0047] In the field test arrangement, plasma can be generated through but not limited to plasma wind tunnel. Taking the internal structure of a plasma wind tunnel of a domestic unit as an example, according to the on-site environment of the wind tunnel test, in the specific test, the transceiver is placed in the wind tunnel test box, using but not limited to the 140GHz frequency band, the transceiver spacing is about 1.5m, the distance between the transceiver and the plasma is about 600-700mm, and the plasma is a rectangular block with a thickness of about 60mm. The transmitting end is externally connected to a signal generating device, which can but is not limited to QPSK modulation, and the receiving end is externally connected to a spectrum analyzer to perform spectrum analysis and record the test results. The results are as follows Figure 3 shown.

Claims

1. A terahertz ultra-high-speed plasma communication test system, comprising a communication unit and a plasma generation unit; characterized in that: The communication unit is composed of two groups of front-end components, one of which is used as a transmitting front end, and the other is used as a receiving front end; each front-end component includes an intermediate frequency module, a terahertz antenna and a mixing and frequency multiplication module, and the terahertz antenna is facing the plasma generation unit; In the transmitting front-end component, the signal generating device, the intermediate frequency module a, the frequency mixing and multiplying module a and the terahertz antenna a are connected in sequence; the signal generating device transmits an intermediate frequency signal with a specific center frequency and a specific bandwidth, and the intermediate frequency signal is up-converted with another frequency in the intermediate frequency module a, and then up-converted through the frequency mixing and multiplying module a, and the signal output with the center frequency in the terahertz frequency band is completed, and finally transmitted through the terahertz antenna a; In the receiving front-end component, the signal acquisition and processing device, the intermediate frequency module b, the mixing and frequency multiplication module b, the low noise amplifier and the terahertz antenna b are connected in sequence; the intermediate frequency module b includes a local oscillator link; the terahertz signal is received by the terahertz antenna b, and the low noise amplifier amplifies the signal received by the antenna; After down-conversion through the frequency mixing and frequency multiplication module b, the local oscillator link realizes the output of the local oscillator signal through the sextuple frequency multiplication and power amplifier. This local oscillator signal is mixed with the terahertz signal, and the terahertz signal is converted into an intermediate frequency signal and output to the signal acquisition and processing equipment.

2. A terahertz ultra-high-speed plasma communication test system according to claim 1, characterized in that: The plasma generating unit is an arc plasma wind tunnel.

3. The terahertz ultra-high-speed plasma communication test system according to claim 1, characterized in that: It also includes a heat-insulating shell and a shielding shell; the shielding shell is placed in the heat-insulating shell, and an intermediate filler is arranged between the two; the front-end component is installed in the shielding shell.

4. The terahertz ultra-high-speed plasma communication test system according to claim 1, characterized in that: It also includes a power supply module, which supplies power to the frequency mixing and multiplication module and the intermediate frequency module.

5. The terahertz ultra-high-speed plasma communication test system according to claim 3, characterized in that: The heat-insulating shell and the shielding shell are also provided with a lens light-through hole and a wire through hole.

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