Radio frequency coaxial cable connector based on liquid metal

Abstract

The invention discloses a radio frequency coaxial cable connector based on liquid metal. The coaxial cable connector comprises a Type-N male head at one end, a Type-N female head at the other end and the 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 the thrust measuring device, the Type-N female head is fixed on a base of the thrust measuring device, the Type-N male head and the Type-N female head are conducted by the liquid metal to realize radio frequency / microwave power transmission, and the Type-N male head coaxially rotates relative to the Type-N female head. By adopting the liquid metal bridging and zero-rigidity coaxial cable connection mode, the influence of a coaxial cable on the torsional pendulum rigidity is obviously reduced, the torsional pendulum can more accurately measure the micro thrust of the thruster, and the thrust measurement precision is improved; based on the liquid metal connector design, good impedance matching is achieved, efficient transmission of radio frequency / microwave power is ensured, loss in the signal transmission process is reduced, and the working efficiency of the electric thruster is improved.

Description

Technical Field

[0001] The present invention relates to the field of aerospace propulsion technology, and in particular to a radio frequency coaxial cable connector based on liquid metal. Background Art

[0002] With the booming development of microsatellite and micro-nanosatellite technologies, the market demand for micro-propulsion systems is increasing day by day. Internationally, a variety of advanced electric propulsion technologies are emerging. Among them, electric thrusters based on discharge modes such as RF / microwave / spiral waves have attracted widespread attention due to their unique advantages. During the operation of such electric thrusters, coaxial cables are required to achieve efficient transmission of RF / microwave energy.

[0003] The design difficulties of coaxial cables for electric thrusters in discharge modes such as RF and microwave are:

[0004] First, the commonly used coaxial cable has a large stiffness, and the thrust measured is at the micro-newton level, which makes it extremely challenging to accurately measure its thrust: the stiffness of the coaxial cable causes almost no change when measuring the micro-newton 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 may even cause the torsion pendulum to be unable to accurately measure the thrust, greatly limiting the accuracy and reliability of the electric thruster performance test.

[0005] Second, when a coaxial cable passes a large RF power or a small power, it will heat up, and the heated RF cable will creep, causing the force of the entire torsion pendulum measurement to be completely incorrect and drifting seriously. For kilowatt-class electric thrusters, due to the influence of coaxial cables, etc., it is no longer possible to directly measure the thrust through the thrust measurement device. Therefore, effectively solving the adverse effects of coaxial cables on torsion pendulum stiffness during thrust testing of electric thrusters has become an important problem that needs to be overcome in the current field of aerospace propulsion technology. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the present invention proposes a method based on liquid metal bridging coaxial cable. 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; the second purpose is to solve the problem that the coaxial cable will generate heat when passing through a large radio frequency power or a small power, and the heated radio frequency cable will creep, resulting in serious force drift of the entire torsion pendulum measurement.

[0007] The present invention proposes the following technical solutions to solve the technical problems:

[0008] A radio frequency coaxial cable connector based on liquid metal, characterized in that: the coaxial cable connector includes a Type-N male head (1) at one end, a Type-N female head (3) at the other end, and 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 the torsion pendulum of the micro-newton level thrust measurement device, the Type-N female head (3) is fixed on the pivot of the 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) to achieve 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) has three layers inside and outside: the outer layer has two parts up and down: the male head external thread (1-1) near the end of the male head and the male head outer conductor (1-2) below the external thread; the middle layer is the male head 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 head outer conductor (1-2).

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

[0011] Further, the liquid metal (2) uses a gallium-indium-tin alloy, which has characteristics such as low melting point, high density, low volatility, good electrical and thermal conductivity, and is non-toxic, pollution-free and has good liquid fluidity. Its density is 6.44 g / mL, viscosity is 0.0024 PAS, melting point is 6-10 °C, electrical conductivity is 3.46×106 S / M, and volatility is 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 50 Ω. According to the characteristic impedance calculation formula of a single-core coaxial cable:

[0013]

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

[0015] Furthermore, the Type-N male head (1) is fixed on the torsion pendulum of the micro-newton thrust measurement device, and the Type-N female head (3) is fixed on the pivot of the base of the micro-newton 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] Furthermore, before the Type-N male head (1) and the Type-N female head (3) come into contact with the liquid metal, they need to be pre-wetted in the liquid metal, and the material surface needs to be kept clean.

[0017] Advantages and effects of the present invention

[0018] 1. Improve measurement accuracy: By adopting the liquid metal bridging and zero-stiffness coaxial cable connection method, the influence of the coaxial cable on the stiffness of the torsion pendulum is significantly reduced, enabling the torsion pendulum to more accurately measure the micro-thrust of the thruster, improving the accuracy of thrust measurement, and 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 losses during signal transmission, and improving the working efficiency of the electric thruster.

[0020] 3. Wide application prospects: The present invention is not only applicable to the thrust test of existing microwave / radio frequency ion thrusters, but also can be extended to other fields that require low-stiffness coaxial cable connection and RF energy transmission, such as satellite communication, radar systems, etc., and has broad market application prospects. Description of the drawings

[0021] Figure 1 is the schematic assembly diagram of the coaxial connector of the present invention;

[0022] Figure 2 is the schematic structural diagram of the coaxial connector 1 of the present invention;

[0023] Figure 3 is the schematic structural diagram of the coaxial connector 3 of the present invention;

[0024] In the figure, 1: Type-N male connector; 1-1: external thread of male connector; 1-2: external conductor of male connector; 1-3: insulator of male connector; 1-4: inner conductor pin; 1-5: shielding layer; 2: liquid metal; 3: Type-N female connector; 3-1: liquid pool; 3-1-1: liquid pool of external conductor of female connector; 3-1-2: liquid pool of inner conductor of female connector; 3-2: insulator of female connector; 3-3: inner conductor pin socket; 3-4: external conductor of female connector, 3-5: external thread of female connector. Detailed implementation

[0025] Design principle of the present invention

[0026] 1. Innovation points of the present invention: ① One of the innovation points: Using liquid metal as the connection medium. The design of the RF coaxial cable connector based on liquid metal has a male connector and a female connector. There is no mechanical contact between the two connectors. There is a pin hole inside. The female connector is installed on the base through a thread, and the male connector is arranged on the swing rod through a thread. After being inserted, it can only rotate and cannot translate. The male connector will also rotate slightly relative to the female connector. There is a shielding head and an insulator outside the male connector. The female connector also has a shielding shell and an insulator. The blank area between the male and female connectors is empty and separated by an insulator into a liquid pool. There is a hollow column in the concentric circles. The liquid is metal liquid. When the metal liquid comes into contact with brass, it conducts electricity. There is also a liquid pool outside. The outer metal liquid is separated from the middle inside. The outer shell is made of stainless steel. When the outer shell is connected to the outer metal liquid, it conducts electricity. After the pin is inserted, the level of the outer metal liquid rises a little. When the pin contacts the metal liquid, it conducts electricity with two brass conductors, and the outer shielding layer also conducts electricity, which is equivalent to being connected inside and outside. The insulation size of the RF coaxial cable connector based on liquid metal has physical requirements and needs to satisfy this physical formula. Coaxial cables generally have 25 ohms, 70 ohms, and 50 ohms. In this embodiment, 50-ohm coaxial cables are used. There are requirements for the outer diameter of the inner core and the inner diameter of the outer core of the coaxial cable. Only by designing these parameters can the requirement of 50 ohms be achieved. Actually, it is 50.76 ohms, and a difference of 1 - 2 ohms is within the allowable range. ② Another innovation point: The innovative application of liquid metal in the field of RF coaxial cable connectors. Currently, no one at home and abroad has thought about using a coaxial connector based on liquid metal to solve the problem of the influence of the stiffness of coaxial cables on measurement. Many people have thought about using liquid metal to achieve the connection of a single cable, but using it on coaxial cables has not been thought of by anyone. In this embodiment, the RF coaxial cable connector based on liquid metal, due to the connection of metal liquid, only has damping during rotation and will not cause stiffness problems. The pin of the male connector is inserted into the surface of the metal liquid instead of mechanical connection.

[0027] 2. Key technical points of the present invention: First, coaxial installation: Most liquid metals are applied to mechanical parts, pipelines, engine cylinders, welding, manufacturing of complex shapes, nerve connections, electronic ink, etc. The present invention transfers it to the coaxial cable of a micro-newton-level thrust measurement torsion pendulum. It is necessary to overcome difficulties that do not exist in the prior art, that is, not only to achieve the bridging of liquid metal, but also to ensure the coaxial installation of the male head, female head and torsion pendulum pivot, which is relatively difficult to achieve; Second, when purchasing a coaxial cable on the market, only an ohm number that meets the requirements needs to be selected. However, for the coaxial cable based on liquid metal of the present invention, it is necessary to achieve the requirement of a predetermined ohm number through the cooperation of the dimensions of each part, including the inner diameter D T of the outer conductor 1-2 of the male head and the outer conductor 3-4 of the female head; the outer diameter d T of the inner conductor pin 1-4 and the inner conductor pin seat 3-3 of the female head. The inner and outer diameters of the male head insulator 1-3 and the outer conductor 3-4 of the female head both need to 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, as Figures 1 - 3 shown. Its characteristics are: The coaxial cable connector includes 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 the swing arm of the thrust measurement device, the Type-N female head 3 is fixed on the base of the thrust measurement device, the liquid metal 2 conducts the Type-N male head 1 and the Type-N female head 3 to achieve radio frequency / microwave power transmission, and the Type-N male head 1 rotates coaxially relative to the Type-N female head (3).

[0029] As Figure 2 shown, the Type-N male head 1 is provided with three inner and outer layers: The outer layer is provided with two upper and lower parts: the male head external thread 1-1 near the end of the male head and the outer conductor 1-2 of the male head below the external thread; the middle layer is the male head 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 outer conductor 1-2 of the male head.

[0030] As Figure 3As shown in the figure, the Type-N female connector 3 has three layers: an outer layer provided with an external female thread 3-5 near the end of the female connector and an external female conductor 3-4 below the external female thread; a middle layer provided with a female connector insulator 3-2; and an inner layer provided with a female conductor pin base 3-3. There is also a liquid pool 3-1 on the external female conductor 3-4, which is divided into two layers, namely, the external female conductor liquid pool 3-1 on the external female conductor and the internal female conductor liquid pool 3-1 on the internal female conductor pin base. The external female conductor liquid pool 3-1 on the external female conductor is axially docked with the shielding layer 1-5 of the Type-N male connector 1; the internal female conductor liquid pool 3-1 is axially docked with the inner conductor pin 1-4 of the Type-N male connector 1.

[0031] The liquid metal 2 is a 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, pollution-free and has good liquid fluidity. Its density is 6.44 g / mL, viscosity is 0.0024 PAS, melting point is 6-10 °C, electrical conductivity is 3.46×106 S / M, and volatility is 0.001%. The male connector insulator (1-3) and the female connector insulator (3-2) are made of polytetrafluoroethylene.

[0032] The cable impedance of the RF coaxial cable connector is 50 Ω. According to the characteristic impedance calculation formula of a single-core coaxial cable:

[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 diameters of the external male conductor 1-2 and the external female conductor 3-4 are D T ; the outer diameters of the inner conductor pin 1-4 and the internal female conductor pin base 3-3 are d T . The inner and outer diameters of the male connector insulator 1-3 and the external female conductor 3-4 need to meet the requirements of the above formula.

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

[0036] Before the Type-N male connector 1 and the Type-N female connector 3 come into contact with the liquid metal, they need to be pre-wetted in the liquid metal, and the material surface needs to be kept clean.

[0037] It should be emphasized that the above specific embodiments are merely explanations of the present invention and not limitations thereof. After reading this specification, those skilled in the art may make modifications to the above embodiments that do not contribute creatively, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A radio frequency coaxial cable connector based on liquid metal, characterized in that: 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 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 torsion pendulum of the micro-newton level thrust measurement device, the Type-N female connector (3) is fixed on the pivot of the base of the micro-newton level thrust measurement device, the liquid metal (2) conducts 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).

2. The RF coaxial cable connector based on liquid metal according to claim 1, wherein: The Type-N male connector (1) has three layers inside and outside: the outer layer has two parts up and down: the male external thread (1-1) near the end of the male connector and the male outer 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 outer conductor (1-2).

3. The RF coaxial cable connector based on liquid metal according to claim 1, wherein: The Type-N female connector (3) has three layers inside and outside: the outer layer has the female external thread (3-5) near the end of the female connector and the female outer conductor (3-4) below the female external thread; the middle layer has the female insulator (3-2); the inner layer has the female inner conductor pin seat (3-3); a liquid pool (3-1) is also provided on the female outer conductor (3-4), and the liquid pool (3-1) is divided into two layers inside and outside, the female outer conductor liquid pool (3-1-1) on the female outer conductor and the female inner conductor liquid pool (3-1-2) on the female inner conductor pin seat, and the female outer conductor liquid pool (3-1-1) is axially docked with the shielding layer (1-5) of the Type-N male connector (1); the female inner conductor liquid pool (3-1-2) is axially docked with the inner conductor pin (1-4) of the Type-N male connector (1).

4. The radio frequency coaxial cable connector based on liquid metal according to claim 1, wherein: The liquid metal (2) is a 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, pollution-free and has good liquid fluidity. Its density is 6.44 g / mL, viscosity is 0.0024 PAS, melting point is 6 - 10 °C, electrical conductivity is 3.46×10 6 S / M, and the volatility is 0.001%; the male insulator (1-3) and the female insulator (3-2) are made of polytetrafluoroethylene.

5. The radio frequency coaxial cable connector based on liquid metal according to claim 1, wherein: The cable impedance of the radio frequency coaxial cable connector is 50Ω. According to the characteristic impedance calculation formula of a single-core coaxial cable: Wherein, D T is the inner diameter of the outer conductor of the coaxial cable, and 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 inner conductor pin (1-4) and the female inner conductor socket (3-3) is d T . The inner and outer diameters of the male insulator (1-3) and the female outer conductor (3-4) shall meet the requirements of the above formula.

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

7. The radio frequency coaxial cable connector based on liquid metal according to claim 1, wherein: Before the Type-N male connector (1) and the Type-N female connector (3) come into contact with the liquid metal, they need to be pre-wetted in the liquid metal, and the material surface needs to be kept clean.

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