A liquid metal based radio frequency coaxial cable connector

Abstract

The application discloses a liquid metal-based radio frequency coaxial cable connector, which comprises a Type-N male head at one end, a Type-N female head at the other end and liquid metal connecting the Type-N male head and the Type-N female head; the Type-N male head is fixed on a swing arm of a thrust measuring device, the Type-N female head is fixed on a base of the thrust measuring device, the liquid metal connects the Type-N male head and the Type-N female head and realizes radio frequency / microwave power transmission, and the Type-N male head rotates coaxially relative to the Type-N female head. By adopting the liquid metal bridging and zero stiffness coaxial cable connection mode, the influence of the coaxial cable on the torsional pendulum stiffness is significantly reduced, the torsional pendulum can more accurately measure the small thrust of an electric thruster, and the thrust measurement precision is improved; the liquid metal-based connector design realizes good impedance matching, ensures efficient transmission of radio frequency / microwave power, reduces the loss in the signal transmission process and improves the working efficiency of the electric thruster.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aerospace propulsion technology, in particular to a liquid metal-based radio frequency coaxial cable connector. BACKGROUND

[0002] At present, the market demand for micro-propulsion systems is increasing with the vigorous development of micro-satellite and micro-nano-satellite technologies. Internationally, various advanced electric propulsion technologies are emerging, among which electric thrusters based on radio frequency / microwave / spiral wave discharge modes have attracted widespread attention due to their unique advantages. During the operation of such electric thrusters, coaxial cables are needed to achieve efficient transmission of radio frequency / microwave energy.

[0003] The design difficulties of coaxial cables for radio frequency and microwave discharge mode electric thrusters are:

[0004] Firstly, the commonly used coaxial cables have high stiffness, and the measured thrust is micro-newton level thrust, which makes it extremely challenging to accurately measure the thrust: the stiffness of the coaxial cable causes little change when measuring micro-newton level thrust. For example, when using a torsion pendulum device to measure the thrust of the thruster, the high stiffness of the coaxial cable will interfere with the movement of the torsion pendulum, and in severe cases, it will even cause the torsion pendulum to fail to accurately measure the thrust, greatly limiting the accuracy and reliability of electric thruster performance testing.

[0005] Secondly, the coaxial cable will heat up when passing through a large radio frequency power or microwave power, and the heated radio frequency cable will creep, causing the entire torsion pendulum measurement force to be completely wrong and drift severely. For kilowatt-level electric thrusters, due to the influence of coaxial cables, direct thrust measurement by a thrust measurement device is no longer possible. Therefore, effectively solving the adverse effects of coaxial cables on the stiffness of the torsion pendulum during electric thruster thrust testing has become an important problem that needs to be solved in the field of aerospace propulsion technology. SUMMARY

[0006] To solve the problems in the prior art, the present application proposes a method of bridging a coaxial cable based on liquid metal, the first purpose is to solve the problem that the high stiffness of the coaxial cable will interfere with the movement of the torsion pendulum, and the second purpose is to solve the problem that the coaxial cable will heat up when passing through a large radio frequency power or microwave power, and the heated radio frequency cable will creep, causing the entire torsion pendulum measurement force to drift severely.

[0007] To solve the technical problems, the present application proposes the following technical solutions:

[0008] A liquid metal based radio frequency coaxial cable connector, characterized in that: the coaxial cable connector comprises a Type-N male head (1) at one end, a Type-N female head (3) at the other end, and a liquid metal (2) connecting the Type-N male head (1) and the Type-N female head (3); the Type-N male head (1) is fixed on a torsion pendulum of a micro-newton level thrust measurement device, the Type-N female head (3) is fixed on a pivot of a base of the micro-newton level thrust measurement device, the liquid metal (2) conducts the Type-N male head (1) and the Type-N female head (3) and realizes radio frequency / microwave power transmission, and the Type-N male head (1) rotates coaxially relative to the Type-N female head (3).

[0009] Further, the Type-N male head (1) is provided with three layers of inner and outer layers: the outer layer is provided with two parts of a male head outer thread (1-1) close to the end of the male head and a male head outer conductor (1-2) below the outer thread; the middle layer is a male head insulator (1-3); and the inner layer is an inner conductor pin (1-4), and a shielding layer (1-5) is further arranged between the inner conductor pin (1-4) and the male head outer conductor (1-2) in the radial direction.

[0010] Further, the Type-N female head (3) is provided with three layers of inner and outer layers: the outer layer is provided with a female head outer thread (3-5) close to the end of the female head and a female head outer conductor (3-4) below the outer thread; the middle layer is a female head insulator (3-2); and the inner layer is a female head inner conductor pin seat (3-3); the female head outer conductor (3-4) is further provided with a liquid pool (3-1), and the liquid pool (3-1) is divided into two layers of inner and outer layers, a female head outer conductor liquid pool (3-1-1) on the female head outer conductor and a female head inner conductor liquid pool (3-1-2) on the female head inner conductor pin seat, the female head outer conductor liquid pool (3-1-1) is axially butted against the shielding layer (1-5) of the Type-N male head (1); and the female head inner conductor liquid pool (3-1-2) is axially butted against the inner conductor pin (1-4) of the Type-N male head (1).

[0011] Further, the liquid metal (2) is a gallium-indium-tin alloy, which has the characteristics of low melting point, high density, low volatility, good electric and thermal conductivity, and is non-toxic, non-polluting and has good liquid flowability, and has a density of 6.44 g / mL, a viscosity of 0.0024 PAS, a melting point of 6-10℃, an electrical conductivity of 3.46×106 S / M, and a volatility of 0.001%; the male head insulator (1-3) and the female head insulator (3-2) are made of polytetrafluoroethylene.

[0012] Further, the cable impedance of the radio frequency coaxial cable connector is 50Ω, and the characteristic impedance of the single-core coaxial cable is calculated according to the formula:

[0013]

[0014] In the formula, D T D is the outer diameter of the inner conductor of the coaxial cable, d T The inner diameter of the male outer conductor (1-2) and the female outer conductor (3-4) is D T The outer diameter of the male inner conductor pin (1-4) and the female inner conductor pin seat (3-3) is d T The inner and outer diameters of the male insulator (1-3) and the female outer conductor (3-4) must meet the above requirements.

[0015] Further, the Type-N male head (1) is fixed on the torsion pendulum of the micro-newton level thrust measurement device, and the Type-N female head (3) is fixed on the pivot of the base of the micro-newton level thrust measurement device, that is, the Type-N male head (1) is coaxially installed with the torsion pendulum, and the Type-N female head (3) is coaxially installed with the torsion pendulum pivot.

[0016] Further, the Type-N male head (1) and the Type-N female head (3) need to be immersed in the liquid metal in advance before being in contact with the liquid metal, and the material surface needs to be kept clean.

[0017] Advantages and effects of the present application

[0018] 1. Improved measurement accuracy: By using liquid metal bridging and zero stiffness coaxial cable connection method, the influence of coaxial cable on the stiffness of the torsion pendulum is significantly reduced, so that the torsion pendulum can more accurately measure the small thrust of the thruster, and the precision of the thrust measurement is improved, providing reliable data support for the performance optimization and research of the electric thruster.

[0019] 2. Efficient RF transmission: Based on the connector design of liquid metal, good impedance matching is achieved, ensuring efficient transmission of RF / microwave power, reducing signal transmission loss, and improving the working efficiency of the electric thruster.

[0020] 3. Wide application prospect: The present application is not only suitable for existing microwave / radio frequency ion class electric thruster thrust test, but also can be applied to other fields requiring low stiffness coaxial cable connection and RF energy transmission, such as satellite communication, radar system, etc., with broad market application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0021] Fig. 1 is a schematic diagram of the assembly of the coaxial connector of the present application;

[0022] Fig. 2 is a schematic diagram of the structure of the coaxial connector 1 of the present application;

[0023] Fig. 3 is a schematic diagram of the structure of the coaxial connector 3 of the present application;

[0024] In the figure, 1: Type-N male head; 1-1: male head external thread; 1-2: male head outer conductor; 1-3: male head insulator; 1-4: inner conductor pin; 1-5: shielding layer; 2: liquid metal; 3: Type-N female head; 3-1: liquid pool; 3-1-1: female head outer conductor liquid pool; 3-1-2: female head inner conductor liquid pool; 3-2: female head insulator; 3-3: inner conductor pin seat; 3-4: female head outer conductor; 3-5: female head external thread. DETAILED DESCRIPTION

[0025] Design principle of the application

[0026] 1, The innovation of the application: ①One of the innovations: liquid metal is used as the connecting medium. The Type-N coaxial cable connector based on liquid metal is designed with a male head and a female head. The two heads are not in mechanical contact. There is a pin hole in the middle. The female head is screwed onto the base, and the male head is screwed onto the swing rod. After being inserted, it cannot move horizontally but only rotate. The male head will also rotate slightly relative to the female head. The male head has a shielding head and an insulator. The female head also has a shielding shell and an insulator. The space between the male head and the female head is empty. The middle is separated by an insulator to form a liquid pool. There is a hollow column in the concentric circle. The liquid is a metal liquid. The metal liquid can be in contact with brass and conduct electricity. The outside is also a liquid pool. The outer metal liquid is separated from the inner metal liquid. The outer shell is stainless steel. The outer shell is connected to the outer metal liquid, which is conductive. After the pin is inserted, the metal liquid outside becomes higher. The pin and the metal liquid are in contact, and the two brasses are conductive. The outer shielding layer is also conductive, which is equivalent to being connected inside and outside. The insulation size of the coaxial cable connector based on liquid metal has physical requirements and must meet the physical formula. Coaxial cables generally have 25 ohms, 70 ohms, and 50 ohms. This embodiment uses a 50-ohm coaxial cable. The outer diameter of the inner core and the inner diameter of the outer core of the coaxial cable have specific requirements. These parameters must be designed to meet the 50-ohm requirement. The actual value is 50.76 ohms, which is within the allowed range of 1-2 ohms. ②The second innovation: the innovative application of liquid metal in the field of coaxial cable connectors. No one has ever thought of using liquid metal to solve the problem of the stiffness of coaxial cables affecting measurement. Many people have thought of using liquid metal to connect single cables, but no one has thought of using it on coaxial cables. The coaxial cable connector based on liquid metal in this embodiment connects with metal liquid, which only has damping when rotating and does not cause stiffness problems. The pin of the male head is inserted into the surface of the metal liquid instead of being mechanically connected.

[0027] 2. Key technical points of the present invention: First, coaxial installation: Liquid metal is mostly used in mechanical parts, pipelines, engine cylinders, welding, complex shape manufacturing, neural connections, electronic ink, etc. The present invention transfers it to the coaxial cable for micro-newton thrust measurement and torsion pendulum, and overcomes the difficulties that the existing technology does not have, that is, not only to achieve the bridging of the metal liquid, but also to ensure the coaxial installation of the male head, female head and torsion pendulum pivot, which is more difficult to achieve; Second, when purchasing coaxial cables on the market, you only need to choose the one that meets the required ohm number, but the coaxial cable based on metal liquid of the present invention must meet the predetermined ohm number requirement by matching the dimensions of each part, including the inner diameter D of the male outer conductor 1-2 and the female outer conductor 3-4. T Design; the outer diameter d of the inner conductor pins 1-4 and the female inner conductor pin seat 3-3 T In the design, the inner and outer diameters of the male insulator 1-3 and the female outer conductor 3-4 must meet the requirements of formula (1).

[0028] Based on the above invention principle, the present invention relates to a radio frequency coaxial cable connector based on liquid metal, such as Figs. 1-3 As shown, its characteristics are: the coaxial cable connector includes a Type-N male connector 1 at one end, a Type-N female connector 3 at the other end, and a liquid metal 2 connecting the Type-N male connector 1 and the Type-N female connector 3; the Type-N male connector 1 is fixed on the swing arm of the thrust measuring device, the Type-N female connector 3 is fixed on the base of the thrust measuring device, the liquid metal 2 connects the Type-N male connector 1 and the Type-N female connector 3 to achieve radio frequency / microwave power transmission, and the Type-N male connector 1 rotates coaxially relative to the Type-N female connector (3).

[0029] like Fig. 2 As shown, the Type-N male connector 1 has three layers: the outer layer has two parts: the male external thread 1-1 near the end of the male connector and the male external conductor 1-2 below the external thread; the middle layer is the male insulator 1-3; the inner layer is the inner conductor pin 1-4, and a shielding layer 1-5 is also provided radially between the inner conductor pin 1-4 and the male external conductor 1-2.

[0030] like Fig. 3As shown, the Type-N female head 3 is provided with three layers of inner and outer: the outer layer is provided with the female head outer thread 3-5 close to the end of the female head and the female head outer conductor 3-4 below the female head outer thread; the middle layer is provided with the female head insulator 3-2; the inner layer is provided with the female head inner conductor needle seat 3-3; the female head outer conductor 3-4 is further provided with a liquid pool 3-1, which is divided into two layers of inner and outer, the female head outer conductor liquid pool 3-1 on the female head outer conductor and the female head inner conductor liquid pool 3-1 on the female head inner conductor needle seat, the female head outer conductor liquid pool 3-1 is axially connected with the shielding layer 1-5 of the Type-N male head 1; the female head inner conductor liquid pool 3-1 is axially connected with the inner conductor pin 1-4 of the Type-N male head 1.

[0031] The liquid metal 2 adopts gallium-indium-tin alloy, which has the characteristics of low melting point, high density, low volatility, good electrical and thermal conductivity, and is non-toxic, non-polluting and good liquid flowability, and has a density of 6.44 g / mL, a viscosity of 0.0024 PAS, a melting point of 6-10℃, an electrical conductivity of 3.46×106 S / M, and a volatility of 0.001%; the male head insulator (1-3) and the female head insulator (3-2) are made of polytetrafluoroethylene.

[0032] The cable impedance of the radio frequency coaxial cable connector is 50Ω, and the characteristic impedance calculation formula of the single-core coaxial cable is:

[0033]

[0034] In the formula, D T is the inner diameter of the outer conductor of the coaxial cable, d T is the outer diameter of the inner conductor, the inner diameter of the male head outer conductor 1-2 and the female head outer conductor 3-4 is D T ; the outer diameter of the inner conductor pin 1-4 and the female head inner conductor needle seat 3-3 is d T , and the inner and outer diameters of the male head insulator 1-3 and the female head outer conductor 3-4 need to meet the above requirements.

[0035] The Type-N male head 1 is fixed on the torsion pendulum of the micro-newton level thrust measurement device, and the Type-N female head 3 is fixed on the pivot of the base of the micro-newton level thrust measurement device, that is, the Type-N male head 1 is coaxially installed with the torsion pendulum pivot, and the Type-N female head 3 is coaxially installed with the torsion pendulum pivot.

[0036] The Type-N male head 1 and the Type-N female head 3 need to be immersed in the liquid metal in advance before being in contact with the liquid metal, and the surface of the material needs to be clean.

[0037] It should be noted that the above specific embodiments are only an explanation of the present application, and are not a limitation of the present application, and those skilled in the art can make modifications to the above embodiments without creative contribution after reading the specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A liquid metal based radio frequency coaxial cable connector, characterized by: The coaxial cable connector comprises a Type-N male head (1) at one end, a Type-N female head (3) at the other end, and a liquid metal (2) connecting the Type-N male head (1) and the Type-N female head (3); the Type-N male head (1) is fixed on a torsion pendulum of a micro-newton level thrust measuring device, the Type-N female head (3) is fixed on a pivot of a base of the micro-newton level thrust measuring device, the liquid metal (2) conducts the Type-N male head (1) and the Type-N female head (3) and realizes radio frequency / microwave power transmission, and the Type-N male head (1) rotates coaxially relative to the Type-N female head (3).

2. A liquid metal based radio frequency coaxial cable connector according to claim 1, wherein: The Type-N male head (1) is provided with three layers of inner and outer layers, the outer layer is provided with two parts of a male head outer thread (1-1) close to the end of the male head and a male head outer conductor (1-2) below the male head outer thread, the middle layer is a male head insulator (1-3), and the inner layer is an inner conductor pin (1-4), and a shielding layer (1-5) is further arranged between the inner conductor pin (1-4) and the male head outer conductor (1-2) in the radial direction.

3. A liquid metal based radio frequency coaxial cable connector according to claim 1, wherein: The Type-N female head (3) is provided with three layers of inner and outer layers, the outer layer is provided with a female head outer thread (3-5) close to the end of the female head and a female head outer conductor (3-4) below the female head outer thread, the middle layer is a female head insulator (3-2), and the inner layer is a female head inner conductor pin seat (3-3); the female head outer conductor (3-4) is further provided with a liquid pool (3-1), the liquid pool (3-1) is divided into two layers of inner and outer layers, the female head outer conductor liquid pool (3-1-1) on the female head outer conductor and the female head inner conductor liquid pool (3-1-2) on the female head inner conductor pin seat, the female head outer conductor liquid pool (3-1-1) is in abutment with the shielding layer (1-5) of the Type-N male head (1) in the axial direction, and the female head inner conductor liquid pool (3-1-2) is in abutment with the inner conductor pin (1-4) of the Type-N male head (1) in the axial direction.

4. A liquid metal based radio frequency coaxial cable connector according to claim 1, wherein: The liquid metal (2) is gallium-indium-tin alloy, whose density is 6.44 g / mL, viscosity is 0.0024 PAS, melting point is 6-10℃, electric conductivity is 3.46×10 6 S / M, volatile rate is 0.001%; the male head insulator (1-3) and the female head insulator (3-2) are made of polytetrafluoroethylene.

5. A liquid metal based radio frequency coaxial cable connector according to claim 1, wherein: The cable impedance of the radio frequency coaxial cable connector is 50 Ω, and the characteristic impedance calculation formula of a single-core coaxial cable is as follows: In the formula, D T is the inner diameter of the outer conductor of the coaxial cable, d T is the outer diameter of the inner conductor, the inner diameter of the male outer conductor (1-2) and the female outer conductor (3-4) is D T ; the outer diameter of the male inner conductor pin (1-4) and the female inner conductor pin seat (3-3) is d T , and the inner and outer diameters of the male insulator (1-3) and the female outer conductor (3-4) need to meet the above requirements.

6. A liquid metal based radio frequency coaxial cable connector according to claim 1, wherein: The Type-N male head (1) is fixed on a torsion pendulum of a micro-newton level thrust measuring device, the Type-N female head (3) is fixed on a pivot of a base of the micro-newton level thrust measuring device, that is, the Type-N male head (1) is coaxially installed with the torsion pendulum, and the Type-N female head (3) is coaxially installed with the pivot of the torsion pendulum.

7. A liquid metal based radio frequency coaxial cable connector as claimed in claim 1, wherein: Before the Type-N male head (1) and the Type-N female head (3) are in contact with the liquid metal, they need to be immersed in the liquid metal in advance, and the material surface needs to be kept clean.

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