Coaxial transmission device for a satellite communication system

Abstract

The embodiment of the specification discloses a coaxial transmission device of a satellite communication system, comprising a first transmission module, a second transmission module and a coaxial transmission cable; the first transmission module and the second transmission module both comprise a signal conversion unit for converting Ethernet signals and single-end signals based on 100BASE-TI technology, a conversion control unit for connecting the signal conversion unit and controlling the signal conversion direction thereof and a frequency selection filter unit connected with the signal conversion unit; the first transmission module further comprises a power input interface, an indoor end coaxial interface, a first coaxial transmission interface and an indoor end Ethernet interface; the second transmission module further comprises a power output interface, an outdoor end coaxial interface, a second coaxial transmission interface and an outdoor end Ethernet interface. The fusion of radio frequency signals, single-end Ethernet signals and direct current power is realized, the coaxial transmission of power supply and Ethernet in the satellite communication system is realized, the circuit is simple and reliable, and the cost is low.

Description

Technical Field

[0001] Several embodiments in this specification relate to the field of satellite communication networking technology, specifically to the optimization of transmission media for high-speed networking equipment between ODU and ACU. Background Technology

[0002] Satellite communication systems typically consist of two parts: an Outdoor Unit (ODU) and an Antenna Control Unit (ACU). The ODU is deployed in open environments (such as rooftops, ship decks, or vehicle roofs) and is responsible for the physical transmission and reception of satellite signals and high-frequency processing. The ACU is located indoors or in a sealed cabin and performs core functions such as signal demodulation, data transmission, and antenna attitude control. This system is widely used in maritime communications, emergency rescue and disaster relief, and network access in remote areas, and its reliability highly depends on the coordinated operation between the ODU and ACU.

[0003] Currently, the industry commonly uses composite cable assemblies to achieve functional connections between the ODU and ACU. These mainly consist of three types of independent cables: power lines supplying power to loads such as motors and amplifiers in the ODU; control signal lines transmitting antenna turning commands and status feedback signals sent by the ACU; and communication data lines carrying demodulated baseband network data or intermediate frequency modulated signals. Multiple independent cables result in excessively large cable bundle diameters, making conduit installation difficult, especially when installed on mobile platforms such as ships and vehicles, requiring multiple perforations and significantly increasing sealing and maintenance costs. Furthermore, composite cables are susceptible to electromagnetic interference during long-distance transmission, requiring additional shielding, which increases weight and cost.

[0004] Commonly used methods (such as FSK modulation) only support low-speed control commands or narrowband data backhaul, which cannot meet the requirements of 100 Mbps Ethernet transmission, thus restricting modern applications such as high-definition video and real-time telemetry. Satellite antenna equipment that supports RF coaxial transmission in the form of "power + Ethernet" often uses MOCA communication technology. The MOCA communication chips for this high-speed solution are mainly monopolized by foreign technology, facing chip control risks and patent barriers, which drive up system costs. Utility Model Content

[0005] This specification provides a coaxial transmission device for a satellite communication system. It uses a domestically produced chip solution based on 100BASE-T technology to achieve coaxial transmission of "power supply + Ethernet" between satellite antenna equipment and ACU controller. The circuit is simple, reliable, and low in cost.

[0006] The technical solution is as follows:

[0007] This specification provides a coaxial transmission device for a satellite communication system. The satellite communication system includes an indoor control unit and an outdoor unit. The coaxial transmission device includes a first transmission module connected to the indoor control unit, a second transmission module connected to the outdoor unit, and a coaxial transmission cable connecting the first transmission module and the second transmission module.

[0008] Both the first transmission module and the second transmission module include a signal conversion unit that converts Ethernet signals to single-ended signals based on 100BASE-T technology, a conversion control unit that connects to the signal conversion unit and controls its signal conversion direction, and a frequency selective filtering unit that connects to the signal conversion unit.

[0009] The first transmission module also includes a power input interface, an indoor coaxial interface and a first coaxial transmission interface connected to the frequency selective filtering unit corresponding to itself, and an indoor Ethernet interface connected to the signal conversion unit corresponding to itself.

[0010] The second transmission module also includes a power output interface, an outdoor coaxial interface and a second coaxial transmission interface connected to the frequency selective filtering unit corresponding to itself, and an outdoor Ethernet interface connected to the signal conversion unit corresponding to itself.

[0011] As a preferred embodiment, the signal conversion unit includes a first conversion subunit that converts Ethernet signals to parallel signals and vice versa, a second conversion subunit that converts parallel signals to differential signals and vice versa, and a third conversion subunit that converts differential signals to single-ended signals and vice versa, connected in sequence.

[0012] As a preferred embodiment, the first conversion subunit uses a 100base-TX chip, and the second conversion subunit uses a 100base-T1 chip.

[0013] As a preferred embodiment, the third conversion subunit includes a common-mode inductor L3 connected to the differential signal terminal of the second conversion subunit, capacitors C2 and C6 connected to the common-mode inductor L3, and a Balun converter whose differential terminal is connected to the capacitors C2 and C6 and whose single-ended terminal is connected to the frequency selective filtering unit.

[0014] As a preferred embodiment, the frequency selective filtering unit includes a first filtering subunit connected between the first coaxial transmission interface and the power input interface, or connected between the second coaxial transmission interface and the power output interface, for filtering radio frequency signals, and a second filtering subunit for filtering the high-frequency signals remaining after filtering by the first filtering subunit.

[0015] The frequency selective filtering unit also includes a DC blocking capacitor C1 connected to the indoor coaxial interface or the outdoor coaxial interface, and a DC blocking capacitor C3 connected to one end of the Balun converter.

[0016] As a preferred embodiment, the first filter subunit includes an inductor L1 and a capacitor C4. One end of the inductor L1 is connected to the DC blocking capacitor C1 and the first coaxial transmission interface or the second coaxial transmission interface, and the other end is connected to the DC blocking capacitor C3 and the capacitor C4. The capacitor C4 is grounded.

[0017] As a preferred embodiment, the second filter subunit includes an inductor L2 and a capacitor C8. One end of the inductor L2 is connected to the inductor L1, and the other end is connected to the capacitor C8 and the power input interface or the power output interface. The capacitor C8 is grounded.

[0018] As a preferred embodiment, the capacitance of the DC blocking capacitor C1 is 30pF.

[0019] The beneficial effects of the technical solutions provided in some embodiments of this specification include at least the following:

[0020] Transmission modules based on 100BASE-T technology are set up at both the front and back ends of the satellite communication system to integrate radio frequency signals, single-ended Ethernet signals, and DC power supply. This enables coaxial transmission of "power supply + Ethernet" between the satellite antenna equipment and the ACU controller. The circuit is simple, reliable, and inexpensive, and can replace coaxial transmission solutions based on MOCA communication technology to cope with chip control risks and patent barriers. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the architecture of a coaxial transmission device for a satellite communication system provided in the embodiments of this specification, showing the wiring method of the satellite communication system.

[0023] Figure 2 This is a schematic diagram of the structure of a coaxial transmission device for a satellite communication system provided in the embodiments of this specification.

[0024] Figure 3 This is a circuit diagram of the first conversion subunit in a coaxial transmission device of a satellite communication system provided in the embodiments of this specification.

[0025] Figure 4 This is a circuit diagram of the second and third conversion subunits in a coaxial transmission device of a satellite communication system provided in the embodiments of this specification.

[0026] Figure 5 This is a circuit diagram of a conversion control unit in a coaxial transmission device of a satellite communication system provided in the embodiments of this specification.

[0027] Figure 6 This is a circuit diagram of a frequency selective filtering unit in a coaxial transmission device of a satellite communication system provided in the embodiments of this specification (taking the first transmission module as an example).

[0028] In the diagram: 1. Indoor control unit; 2. Outdoor unit; 3. First transmission module; 31. Power input interface; 32. Indoor coaxial interface; 33. First coaxial transmission interface; 34. Indoor Ethernet interface; 4. Second transmission module; 41. Power output interface; 42. Outdoor coaxial interface; 43. Second coaxial transmission interface; 44. Outdoor Ethernet interface; 5. Coaxial transmission cable; 6. Signal conversion unit; 7. Conversion control unit; 8. Frequency selective filtering unit. Detailed Implementation

[0029] The technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings.

[0030] The terms "first," "second," "third," etc., in the description, claims, and accompanying drawings are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such processes, methods, products, or apparatus.

[0031] The following description provides examples and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made to the function and arrangement of the described elements without departing from the scope of this specification. Various processes or components may be appropriately omitted, substituted, or added to the examples. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.

[0032] At least three separate cables are required to connect the ODU and ACU: a network cable for transmitting control signals, a coaxial cable for transmitting radio frequency signals, and a power cable for supplying power to the ODU. These three separate cables result in an excessively large cable bundle diameter, making conduit installation difficult, especially when installed on mobile platforms such as ships and vehicles, requiring multiple perforations and significantly increasing sealing and maintenance costs. Furthermore, composite cables are susceptible to electromagnetic interference over long distances, necessitating additional shielding, which increases weight and cost.

[0033] To simultaneously transmit control signals, radio frequency signals, and power the ODU using a single coaxial cable, existing technologies employ transmission devices with MOCA communication chips. However, MOCA communication chips are primarily monopolized by foreign technology, posing risks of chip control and patent barriers, thus increasing system costs. Therefore, this application proposes a domestically produced chip alternative.

[0034] Reference Figure 1 , Figure 2 As shown, Figure 1 This is a schematic diagram of the architecture of a coaxial transmission device for a satellite communication system according to an embodiment of this specification. Figure 2 This is a schematic diagram of the structure of a coaxial transmission device for a satellite communication system provided in the embodiments of this specification.

[0035] A coaxial transmission device for a satellite communication system, the satellite communication system including an indoor control unit 1 and an outdoor unit 2, the coaxial transmission device including a first transmission module 3 connecting the indoor control unit 1, a second transmission module 4 connecting the outdoor unit 2, and a coaxial transmission cable 5 connecting the first transmission module 3 and the second transmission module 4.

[0036] Both the first transmission module 3 and the second transmission module 4 include a signal conversion unit 6 that converts Ethernet signals to single-ended signals based on 100BASE-T technology, a conversion control unit 7 that connects to the signal conversion unit 6 and controls its signal conversion direction, and a frequency selective filtering unit 8 that connects to the signal conversion unit 6.

[0037] The first transmission module 3 also includes a power input interface 31, an indoor coaxial interface 32 and a first coaxial transmission interface 33 connected to its corresponding frequency selective filtering unit 8, and an indoor Ethernet interface 34 connected to its corresponding signal conversion unit 6.

[0038] The second transmission module 4 also includes a power output interface 41, an outdoor coaxial interface 42 and a second coaxial transmission interface 43 connected to its corresponding frequency selective filtering unit 8, and an outdoor Ethernet interface 44 connected to its corresponding signal conversion unit 6.

[0039] To clarify, 100BASE-T technology refers to Ethernet technology that achieves 100 Mbps baseband transmission (0-66MHz) via twisted-pair cabling, representing a physical layer standard of "100 Mbps (rate) + Baseband (baseband transmission) + Twisted-pair (twisted-pair)". MoCA, on the other hand, is a high-frequency broadband modulation and demodulation technology (1-2.5GHz band), and the physical layer processing paths of the two are completely different. MoCA first down-converts the RF signal to the MoCA operating frequency band, and then uses QAM demodulation to extract the digital baseband signal; the entire process relies on a high-frequency mixer and a dedicated demodulation chip. In contrast, the frequency-selective filtering in this solution performs LC filtering on the Ethernet signal at the baseband level to avoid high-frequency interference affecting communication quality.

[0040] Explained, the indoor control unit 1 is connected to the first transmission module 3 via network cable, coaxial cable, and power cable. The outdoor unit 2 is also connected to the second transmission module 4 via network cable, coaxial cable, and power cable. The first transmission module 3 and the second transmission module 4 are connected via coaxial transmission cable 5, reducing the diameter of the transmission cable bundle and the difficulty of conduit wiring. Since standard Ethernet (such as 100BASE-TX) uses serial differential transmission, and coaxial cable is a single-conductor transmission structure (core wire + shielding layer), it cannot directly transmit differential signals. Therefore, a signal conversion unit 6 is set up. Both the first transmission module 3 and the second transmission module 4 can realize mutual conversion between Ethernet signals and single-ended signals and transmit them to each other via coaxial transmission cable 5. After the signal conversion unit 6 in the first transmission module 3 converts the Ethernet signal output by the indoor control unit 1 into a single-ended signal, it is then fused with DC power and radio frequency signals and transmitted to the second transmission module 4 connected to the outdoor unit 2 via coaxial transmission cable 5. The fused signal is separated according to frequency characteristics by the frequency selective filtering unit 8. The separated single-ended signal is converted into an Ethernet signal by the signal conversion unit 6 in the second transmission module 4 and then output to the outdoor unit 2. Conversely, this also applies. This enables coaxial transmission via "power supply + Ethernet" between the satellite antenna equipment and the ACU controller. The circuitry is simple, reliable, and inexpensive, and can replace coaxial transmission solutions based on MOCA communication technology to address chip control risks and patent barriers.

[0041] In one embodiment of this specification, the signal conversion unit 6 includes a first conversion subunit that converts Ethernet signals to parallel signals, a second conversion subunit that converts parallel signals to differential signals, and a third conversion subunit that converts differential signals to single-ended signals, all connected in sequence.

[0042] Explaining the process of converting Ethernet signals from parallel (RMII) to differential (MDI) and then to single-ended signals, it is essentially a phased signal adaptation strategy designed to balance transmission performance, power consumption, and cost. First, parallel conversion is used to solve clock synchronization issues and avoid timing skew in long-distance transmission. Then, differential signaling is used to combat common-mode noise, such as reflection interference from ship metal bulkheads. Finally, single-ended adaptation is used to match the characteristics of coaxial cable (75Ω impedance matching).

[0043] Specifically, the first conversion subunit uses a 100base-TX chip, and the second conversion subunit uses a 100base-T1 chip.

[0044] Illustratively, Ethernet MDI interface to RMII parallel interface conversion: (See attached diagram) Figure 3 The first circuit module, consisting of J1, U1, X1, C5, and R1, converts the Ethernet MDI interface into an RMII parallel interface. J1 is an RJ45 Ethernet interface with a built-in network transformer, enabling the antenna motherboard or ACU network signal to connect to the EOC motherboard; U1 is a 100base-TX chip that converts the Ethernet MDI interface to the RMII parallel interface; X1 is a 50MHz active crystal oscillator providing a precise clock frequency for the U1 chip; capacitor C5 is used for power supply filtering of the U1 chip; and bias resistor R1 is used to set the DC bias voltage of the U1 chip to ensure reliable operation.

[0045] Illustratively, RMII parallel interface to differential Ethernet MDI interface conversion: (See attached diagram) Figure 4 The second circuit module, consisting of U2, X2, C7, C9, R2, and X2, converts the RMII parallel interface to a differential signal. U2 is a 100base-T1 PHY chip that performs signal conversion between the MDI and RMII parallel interfaces of a single differential Ethernet network; X2 is a 25MHz passive crystal oscillator used to provide the precise clock frequency for the U2 chip; capacitors C7 and C9 are used for power supply filtering of the U2 chip; and the bias resistor R2 is used to set the DC bias voltage of the U2 chip to ensure reliable operation.

[0046] Explanatory configuration of U1 and U2: (Refer to the appendix) Figure 5 The third circuit module, consisting of J2, C10, R3, C11, X3, U3, and R4, implements the minimum system function of the microcontroller. J2 is a 4-pin single-row pin header used for programming the microcontroller U3; U3 is used to configure the parameters of the U1 and U2 chips; capacitor C10 is used for power supply filtering of the U3 chip; resistor R3 and capacitor C11 are used for power-on reset of the U3; X3 is an 8MHz passive crystal oscillator used to provide the precise clock frequency for the U3 chip; and resistor R4 is used to select the U3 boot mode.

[0047] In one embodiment of this specification, reference is made to the appendix. Figure 4 The third conversion subunit includes a common-mode inductor L3 connected to the differential signal terminal of the second conversion subunit, capacitors C2 and C6 connected to the common-mode inductor L3, and a Balun converter with capacitors C2 and C6 connected to the differential terminal and a single-ended connection to the frequency selection filter unit 8.

[0048] Explained, the Balun (balanced-unbalanced) converter T1 enables the conversion between balanced signals (such as differential signals) and unbalanced signals (such as single-ended signals). The common-mode inductor L3 exhibits high inductance for common-mode signals but has minimal impact on differential-mode signals. External interference is typically common-mode (e.g., lightning strikes affecting the entire line), while the differential receiver only detects the differential-mode portion, naturally suppressing common-mode noise. This meets the anti-interference requirements of long-distance satellite antenna transmission and enables filtering of differential Ethernet MDI signals.

[0049] Explanatory, in conjunction with appendix Figure 4 The fourth circuit module, consisting of L3, C2, C6, and T1, converts the differential Ethernet MDI interface to a single-ended signal. The common-mode inductor L3, capacitors C2 and C6 form an LC resonant circuit to filter the differential Ethernet MDI signal.

[0050] In one embodiment of this specification, the frequency selective filtering unit 8 includes a first filtering subunit connected between the first coaxial transmission interface 33 and the power input interface 31, or connected between the second coaxial transmission interface 43 and the power output interface 41, for filtering radio frequency signals and a second filtering subunit for filtering the high-frequency signals remaining after filtering by the first filtering subunit.

[0051] The frequency selective filtering unit 8 also includes a DC blocking capacitor C1 connected to the indoor coaxial interface 32 or the outdoor coaxial interface 42, and a DC blocking capacitor C3 connected to one end of the Balun converter.

[0052] Illustratively, DC blocking capacitors C1 and C3 isolate the DC current in the coaxial transmission cable 5, preventing DC power supply interference with the signal.

[0053] For details, please refer to the appendix. Figure 6 The first filter subunit includes an inductor L1 and a capacitor C4. One end of the inductor L1 is connected to the DC blocking capacitor C1 and the first coaxial transmission interface 33 or the second coaxial transmission interface 43, and the other end is connected to the DC blocking capacitor C3 and the capacitor C4. The capacitor C4 is grounded.

[0054] The second filter subunit includes an inductor L2 and a capacitor C8. One end of the inductor L2 is connected to the inductor L1, and the other end is connected to the capacitor C8 and the power input interface 31 or the power output interface 41. The capacitor C8 is grounded.

[0055] Illustratively, the fusion of radio frequency signals, Ethernet single-ended signals, and DC power supply: see appendix. Figure 6 The fifth circuit module, consisting of RF1 (coaxial interface), C1, C3, L1, C4, L2, C8, and RF2 (coaxial transmission interface), integrates radio frequency (RF) signals, Ethernet single-ended signals, and DC power. For example, RF1 is an SMA RF connector for satellite antenna TX / RX RF signal input; capacitors C1 and C3 are DC blocking capacitors; inductors L1 and L2 and capacitors C4 and C8 form an LC network for filtering and feeding DC power to connector RF2; RF2 is an N-type RF connector for connection to the RF coaxial line, simultaneously transmitting RF signals, Ethernet single-ended signals, and DC power.

[0056] It is important to note that Figure 6 This is a schematic diagram of the frequency selection filter unit 8 in the first transmission module 3. The inductor L2 is connected to a 48V DC voltage input. The DC power supply is only available in the indoor control unit 1, which converts 220V AC to 48V DC and supplies power to the outdoor unit 2 through the coaxial transmission cable 5.

[0057] To illustrate, taking outdoor unit 2 as an example, after the fused signal enters through the coaxial transmission interface (RF2): one branch blocks the DC signal in it through C1, retaining the high-frequency signal to the coaxial interface (RF1); the other branch filters out the antenna TX / RX signal (960~5900MHz) in the high-frequency signal through L1 and C4, and then blocks the DC signal in it through C3 in the same way as C1, retaining the remaining high-frequency signal (tens of MHz Ethernet single-ended signal) to T1. At the same time, the other branch filters out the remaining high-frequency signal (tens of MHz Ethernet single-ended signal) through L2 and C8 and outputs it to power outdoor unit 2.

[0058] For illustrative purposes, the mainboards of indoor control unit 1 and outdoor unit 2 have built-in frequency selection functions, automatically selecting the antenna TX / RX signals from the high-frequency signals.

[0059] In one embodiment of this specification, the DC blocking capacitor C1 has a capacitance of 30pF.

[0060] Explanatoryly, choosing a smaller capacitance value for C1, while having a larger capacitive reactance for the control signal, can also achieve a certain filtering effect.

[0061] Working principle:

[0062] Balun: Translates the single differential MDI signal output by the 100BASE-T1 chip with a single-ended signal that can travel on a coaxial cable.

[0063] 100BASE-T1: Efficiently and reliably transmits and receives high-speed Ethernet signals on coaxial cable according to the 100BASE-T1 standard. Outputs a single differential MDI (Media Dependent Interface) signal.

[0064] 100BASE-TX PHY: A standard 100Mbps Ethernet chip found in home routers or computer network cards (usually corresponding to the RJ45 port on a network cable). It converts the Ethernet signal from a standard network cable into an RMII (Simplified Media Independent Interface) signal.

[0065] MCU: Microcontroller chip (similar to a single-chip microcomputer). It uses the SMI interface (a special interface for managing Ethernet chips) to configure and control two Ethernet PHY chips.

[0066] N-type connector: A plug / socket for connecting RF coaxial cables.

[0067] RJ45 connector: Standard network cable interface, used to connect other network-required components on indoor and antenna equipment (such as connecting the ACU to the router, and the antenna end to the modem circuit).

[0068] Power transmission path: The DC power supply in the ACU is fed to the RF coaxial line through the inductor of the first transmission module 3 and transmitted to the second transmission module 4 connected to the ODU. The ODU draws power through the inductor on the second transmission module 4.

[0069] Ethernet transmission implementation path: Ordinary Ethernet signals are connected to the RJ45 connector (indoor Ethernet interface 34) on the first transmission module 3 via a network cable. The signal is converted to an RMII signal via standard 100BASE-TX and communicates with 100BASE-T1. The single differential MDI signal output from 100BASE-T1 is converted to a single-ended signal via a Balun and connected to an N-pin connector via a DC blocking capacitor. The MCU configures 100BASE-TX and 100BASE-T1 using the SMI interface.

[0070] The above embodiments are merely preferred embodiments described in this specification and are not intended to limit the scope of this specification. Any modifications and improvements made by those skilled in the art to the technical solutions of this specification without departing from the spirit of this specification should fall within the protection scope defined by the claims of this specification.

Claims

1. A coaxial transmission device for a satellite communication system, the satellite communication system comprising an indoor control unit (1) and an outdoor unit (2), characterized in that, The coaxial transmission device includes a first transmission module (3) connected to the indoor control unit (1), a second transmission module (4) connected to the outdoor unit (2), and a coaxial transmission cable (5) connecting the first transmission module (3) and the second transmission module (4). The first transmission module (3) and the second transmission module (4) both include a signal conversion unit (6) that converts Ethernet signals to single-ended signals based on 100BASE-T technology, a conversion control unit (7) that connects to the signal conversion unit (6) and controls its signal conversion direction, and a frequency selective filtering unit (8) that connects to the signal conversion unit (6). The first transmission module (3) also includes a power input interface (31), an indoor coaxial interface (32) and a first coaxial transmission interface (33) connected to the frequency selective filtering unit (8) corresponding to itself, and an indoor Ethernet interface (34) connected to the signal conversion unit (6) corresponding to itself. The second transmission module (4) also includes a power output interface (41), an outdoor coaxial interface (42), and a second coaxial transmission interface (43) connected to the frequency selective filtering unit (8) corresponding to itself, and an outdoor Ethernet interface (44) connected to the signal conversion unit (6) corresponding to itself.

2. The coaxial transmission device for a satellite communication system according to claim 1, characterized in that, The signal conversion unit (6) includes a first conversion subunit that converts Ethernet signals to parallel signals, a second conversion subunit that converts parallel signals to differential signals, and a third conversion subunit that converts differential signals to single-ended signals, all connected in sequence.

3. The coaxial transmission device for a satellite communication system according to claim 2, characterized in that, The first conversion subunit uses a 100base-TX chip, and the second conversion subunit uses a 100base-T1 chip.

4. A coaxial transmission device for a satellite communication system according to any one of claims 2-3, characterized in that, The third conversion subunit includes a common-mode inductor L3 connected to the differential signal terminal of the second conversion subunit, capacitors C2 and C6 connected to the common-mode inductor L3, and a Balun converter whose differential terminal is connected to the capacitors C2 and C6 and whose single-end is connected to the frequency selective filter unit (8).

5. A coaxial transmission device for a satellite communication system according to claim 4, characterized in that, The frequency selective filtering unit (8) includes a first filtering subunit that filters radio frequency signals and a second filtering subunit that filters the remaining high-frequency signals after the first filtering subunit is connected between the first coaxial transmission interface (33) and the power input interface (31) or between the second coaxial transmission interface (43) and the power output interface (41). The frequency selective filtering unit (8) also includes a DC blocking capacitor C1 connected to the indoor coaxial interface (32) or the outdoor coaxial interface (42) and a DC blocking capacitor C3 connected to one end of the Balun converter.

6. The coaxial transmission device for a satellite communication system according to claim 5, characterized in that, The first filter subunit includes an inductor L1 and a capacitor C4. One end of the inductor L1 is connected to the DC blocking capacitor C1 and the first coaxial transmission interface (33) or the second coaxial transmission interface (43), and the other end is connected to the DC blocking capacitor C3 and the capacitor C4. The capacitor C4 is grounded.

7. A coaxial transmission device for a satellite communication system according to claim 6, characterized in that, The second filter subunit includes an inductor L2 and a capacitor C8. One end of the inductor L2 is connected to the inductor L1, and the other end is connected to the capacitor C8 and the power input interface (31) or the power output interface (41). The capacitor C8 is grounded.

8. A coaxial transmission device for a satellite communication system according to any one of claims 5-7, characterized in that, The DC blocking capacitor C1 has a capacitance of 30pF.

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