Space-borne short message terminal air and ground docking test system and method based on indoor signal link construction

Abstract

The invention discloses a space-borne short message terminal air and ground docking test system and method constructed based on an indoor signal link. The outdoor receiving antenna is installed outdoors and used for receiving outdoor Beidou satellite signals. The indoor L-band low-power amplifier is installed indoors and used for amplifying outdoor Beidou satellite signals transmitted by the outdoor receiving antenna; the indoor transmitting antenna is installed indoors and is used for forwarding the amplified Beidou satellite signal to an indoor to-be-tested satellite Beidou terminal; the indoor receiving antenna is installed indoors and used for receiving signals transmitted by the satellite Beidou terminal to be tested. The outdoor L-band high-power amplifier is installed outdoors and used for amplifying signals transmitted by the indoor receiving antenna and emitted by the indoor satellite Beidou terminal to be tested. The outdoor transmitting antenna is installed outdoors and is used for forwarding the amplified signal transmitted by the to-be-tested satellite Beidou terminal to an outdoor Beidou satellite; the accuracy and the reliability of the test are improved, and many limitations of external field test are overcome at the same time.

Description

Technical Field

[0001] This invention relates to the field of satellite communication technology, and in particular to a space-to-ground docking test system and method for a satellite-borne short message terminal based on an indoor signal link. The system aims to simulate a real outdoor satellite communication environment and achieve comprehensive testing of the various performance characteristics of the satellite-borne short message terminal indoors. Background Technology

[0002] Currently, most satellite-borne short message terminal testing systems on the market rely on BeiDou signal simulators. These simulators conduct joint debugging tests by directly connecting to the BeiDou short message terminal. However, the state of the BeiDou signal simulator differs significantly from that of the BeiDou satellites in orbit, causing the test results to fail to accurately reflect the terminal's performance in the actual operating environment. Specific shortcomings include:

[0003] Key performance indicators cannot be tested: The BeiDou signal simulator cannot simulate factors such as the orbital deviation of BeiDou satellites, signal propagation delay, message data routing and forwarding delay, BeiDou network busy / idle status, signal attenuation, Doppler frequency shift, and performance aging. Therefore, it cannot accurately test the performance of the onboard short message terminal in terms of its adaptability to message data delay, message data error and packet loss handling mechanism, and Doppler frequency shift compensation function.

[0004] Unable to test real data protocols: The simulator cannot fully simulate the encryption / decryption protocols of message data.

[0005] It is impossible to achieve connectivity with the actual user control terminal, and end-to-end loopback testing cannot be completed.

[0006] Field testing is limited by the satellite's stringent requirements for cleanliness, temperature and humidity, its large size and weight, and the limitations of site conditions, making it difficult to place the antenna of the satellite under test outdoors and point it accurately at the sky, thus making it difficult to carry out field testing effectively. Summary of the Invention

[0007] This invention aims to solve the problems of existing testing systems' inability to realistically simulate the communication environment between a spaceborne short message terminal and the BeiDou satellite, as well as the difficulties in field testing. It proposes a space-to-ground docking testing system and method for spaceborne short message terminals based on an indoor signal link. By building an indoor testing system, the system enables communication between the satellite under test and the BeiDou satellite under indoor conditions, allowing for comprehensive testing of communication, positioning, and other functions, improving the accuracy and reliability of the test, and overcoming many limitations of field testing. Specific advantages include:

[0008] 1. Realistic Simulation of Satellite Communication Environment: By combining indoor and outdoor antennas, high-frequency cables, and power amplifiers, a realistic communication link with BeiDou satellites is constructed in an indoor environment. This solves the problem that existing BeiDou signal simulator technology cannot simulate a real satellite communication environment, improving the accuracy and reliability of the test.

[0009] 2. Precise signal processing: Power amplifiers with different gains are precisely configured to amplify the transmitted and received signals according to the signal transmission characteristics and terminal requirements, ensuring the stability and effectiveness of the signal during transmission.

[0010] 3. Testing key performance indicators: It can accurately test key indicators such as satellite-to-ground time delay, signal error rate and packet loss rate, and Doppler frequency compensation performance.

[0011] 4. Suitable for cleanroom testing: It avoids the environmental limitations of field testing, meets the high cleanliness requirements of satellite testing, and reduces testing costs while improving testing efficiency.

[0012] The technical solution of the present invention is: a spaceborne short message terminal ground-to-ground docking test system based on an indoor signal link, characterized in that: it includes an outdoor receiving antenna, an indoor L-band low-power amplifier, an indoor transmitting antenna, an indoor receiving antenna, an outdoor L-band high-power amplifier, and an outdoor transmitting antenna;

[0013] The outdoor receiving antenna is installed outdoors and is used to receive BeiDou satellite signals outdoors; the frequency band of the outdoor receiving antenna includes the BeiDou B2I frequency point of 1207.14±10.23MHz for short message reception.

[0014] The indoor L-band low-power amplifier is installed indoors, and its receiving end is connected to the output end of the outdoor receiving antenna to receive and amplify the BeiDou satellite signal transmitted from the outdoor receiving antenna. The output end of the indoor L-band low-power amplifier is connected to the receiving end of the indoor transmitting antenna to transmit the amplified BeiDou satellite signal to the indoor transmitting antenna.

[0015] The indoor transmitting antenna is installed indoors, and its output end is connected to the receiving end of the BeiDou terminal under test indoors, for forwarding the amplified BeiDou satellite signal to the BeiDou terminal under test indoors.

[0016] The indoor receiving antenna is installed indoors, and the receiving end of the indoor receiving antenna is connected to the output end of the Beidou terminal of the satellite under test, for receiving the signal transmitted by the Beidou terminal of the satellite under test;

[0017] The outdoor L-band high-power amplifier is installed outdoors. The receiving end of the outdoor L-band high-power amplifier is connected to the output end of the indoor receiving antenna to receive and amplify the signal transmitted by the indoor Beidou terminal of the satellite under test transmitted by the indoor receiving antenna. The output end of the outdoor L-band high-power amplifier is connected to the receiving end of the outdoor transmitting antenna to transmit the amplified signal transmitted by the Beidou terminal of the satellite under test to the outdoor transmitting antenna.

[0018] The outdoor transmitting antenna is installed outdoors and is used to forward the amplified signal transmitted by the BeiDou terminal of the satellite under test to the BeiDou satellite outdoors; the frequency band of the outdoor transmitting antenna includes the BeiDou short message uplink frequency of 1624.524MHz±1.6376MHz, which is used for inbound short message transmission.

[0019] Furthermore, the outdoor receiving antenna also includes the GPS L1 C / A frequency of 1575.42±1.023MHz and the Beidou B1I frequency of 1561.098±2.046MHz in the frequency band, which are used for the satellite under test to receive navigation signals for positioning and velocity measurement, thereby performing transmission Doppler compensation.

[0020] Furthermore, the outdoor L-band high-power amplifier has a gain range of 30dB to 50dB, a frequency range covering the L-band 1.55-1.65GHz, and a maximum input level of 0dBm; the indoor L-band low-power amplifier also has a gain range of 30dB to 50dB, a frequency range covering the L-band 1.20-1.65GHz, and is used for signal amplification.

[0021] Furthermore, the outdoor receiving antenna and the outdoor transmitting antenna operate in a time-division multiplexing manner using the same antenna.

[0022] Furthermore, the outdoor receiving antenna and the outdoor transmitting antenna are two independent antennas. A receiving low-pass filter is placed behind the outdoor receiving antenna, and a transmitting bandpass filter is placed behind the outdoor transmitting antenna.

[0023] Furthermore, the outdoor receiving antenna is an active receiving antenna with a gain of 20dBi and a frequency range of 1.19-1.58GHz;

[0024] The outdoor transmitting antenna is a passive omnidirectional antenna with a gain of 3dBi and a frequency range of 1.62-1.63GHz.

[0025] Furthermore, the indoor transmitting antenna is an omnidirectional transmitting antenna with a gain of 3dBi and a frequency range of 1.19-1.58GHz.

[0026] Furthermore, the indoor receiving antenna is a directional receiving antenna with a gain of 15dBi and a frequency range of 1.62-1.63GHz.

[0027] This invention also provides a test method for space-to-ground docking of a satellite-borne short message terminal based on an indoor signal link, the specific steps of which are as follows:

[0028] Step 1: The outdoor receiving antenna receives BeiDou satellite signals and transmits them to an indoor L-band low-power amplifier via a high-frequency cable for amplification; the amplified signal is then relayed to the indoor BeiDou terminal under test via the indoor transmitting antenna to simulate real outdoor satellite signals.

[0029] Step 2: After receiving the signal, the indoor Beidou terminal of the satellite under test processes it and transmits the signal back.

[0030] Step 3: The indoor receiving antenna receives the signal transmitted by the Beidou terminal of the satellite under test indoors, and transmits it to the outdoor L-band high-power amplifier for amplification through a high-frequency cable;

[0031] Step 4: The amplified return signal is transmitted to the BeiDou satellite via an outdoor transmitting antenna.

[0032] Furthermore, the link between the outdoor receiving antenna, the indoor transmitting antenna, and the BeiDou terminal receiver for the satellite under test can also be used for the satellite under test to receive navigation signals for positioning and velocity measurement, thereby performing transmission Doppler compensation and simulating the function of compensating for transmission Doppler when a real satellite uses BeiDou short messages in orbit.

[0033] The beneficial effects of this invention are: it provides a space-to-ground docking test system and method for spaceborne short message terminals based on indoor signal links;

[0034] Structural advantages: The system has a simple structure, clear connections between components, and is easy to assemble and maintain. By rationally arranging the antennas and power amplifiers, and using high-frequency cables for signal transmission, the problem of indoor-outdoor signal connectivity is effectively solved.

[0035] Precise signal processing: Power amplifiers with different gains are precisely configured to amplify the transmitted and received signals according to the signal transmission characteristics and terminal requirements, ensuring the stability and effectiveness of the signal during transmission.

[0036] Indoor testing environment construction: It can simulate the communication between the spaceborne short message terminal and the Beidou satellite in an indoor environment, which solves the problem that the existing testing system cannot accurately simulate the status of the satellite in orbit.

[0037] A realistic satellite communication environment is simulated: A true communication link with BeiDou satellites is constructed indoors using a combination of indoor and outdoor antennas, high-frequency cables, and power amplifiers. This solves the problem that existing BeiDou signal simulators cannot simulate a real satellite communication environment, improving the accuracy and reliability of the test.

[0038] Precise performance testing: This system can realistically simulate the communication environment between a spaceborne short message terminal and the BeiDou satellite, enabling precise testing of key performance indicators such as satellite-to-ground latency and signal error rate. Taking satellite-to-ground latency testing as an example, through the real communication link established by this system, timestamp technology is used to accurately record the time at both ends of the signal transmission and reception, according to the formula... (in, For satellite-to-ground time delay, For receiving time, The system can accurately calculate the satellite-to-ground time delay based on the launch time. Compared to traditional BeiDou signal simulator tests, this system provides test data that more closely resembles the actual space environment, effectively improving the accuracy and reliability of test results. This system can also be used for positioning and velocity measurement of the satellite receiving navigation signals, thereby performing launch Doppler compensation and simulating the function of compensating for launch Doppler when a real satellite uses BeiDou short message service in orbit.

[0039] Breaking through testing environment limitations: It fundamentally overcomes many limitations of field testing. Testing can be completed in an indoor environment that meets the satellite's cleanliness, temperature, and humidity requirements, expanding the implementation conditions and application scenarios for satellite testing, avoiding the limitations of field testing, reducing testing costs, and improving testing efficiency.

[0040] Power amplification and signal matching optimization: Indoor L-band low-power amplifiers and outdoor L-band high-power amplifiers are precisely configured to amplify the signal accurately according to the different requirements of signal transmission and reception. In the transmission link, the signal transmitted by the short message terminal of the satellite under test is amplified to a level close to the transmission power to ensure successful reception by the satellite. In the reception link, the satellite signal is amplified to near the medium-high level of the receiver of the satellite under test to ensure effective reception and resolution. This optimized design of power amplification and signal matching effectively improves the stability and reliability of the test system.

[0041] Testing with real data protocols: It is possible to test using real encryption / decryption / scrambling protocols.

[0042] It can achieve connectivity with real user control terminals and complete end-to-end loopback testing. Attached Figure Description

[0043] Figure 1 This is a block diagram of the indoor testing system for a spaceborne short message terminal.

[0044] Figure 2 This is a block diagram of the indoor testing system for a spaceborne short message terminal. Detailed Implementation

[0045] The present invention will now be further described with reference to the accompanying drawings.

[0046] like Figure 1 As shown, the indoor testing system for the spaceborne short message terminal of the present invention mainly consists of the following parts:

[0047] L-band power amplifiers: These include an indoor L-band low-power amplifier and an outdoor L-band high-power amplifier. The indoor L-band low-power amplifier amplifies the received outdoor BeiDou satellite signals, while the outdoor L-band high-power amplifier amplifies the signals transmitted by the indoor BeiDou terminal under test, ensuring signal strength during transmission. The outdoor L-band high-power amplifier has a gain range of 30dB to 50dB, covering the L-band (1.55-1.65GHz), with a maximum input level of 0dBm. The indoor L-band low-power amplifier also has a gain range of 30dB to 50dB, covering the L-band (1.20-1.65GHz), and is used for signal amplification.

[0048] Outdoor receiving antenna: An active receiving antenna with a gain of 20dBi, operating in the frequency range of 1.19-1.58GHz, used to receive BeiDou satellite signals outdoors. Its frequency band includes the BeiDou B2I frequency point of 1207.14±10.23MHz for short message reception, and the GPS L1 C / A frequency point of 1575.42±1.023MHz and the BeiDou B1I frequency point of 1561.098±2.046MHz for receiving navigation signals from the satellite under test for positioning and velocity measurement, thereby performing transmit Doppler compensation.

[0049] Indoor transmitting antenna: An omnidirectional transmitting antenna with a gain of 3dBi and a frequency range of 1.19-1.58GHz, used to forward amplified BeiDou satellite signals to the indoor BeiDou terminal under test.

[0050] Indoor receiving antenna: A directional receiving antenna with a gain of 15dBi and a frequency range of 1.62-1.63GHz, used to receive signals transmitted by the short message terminal of the satellite under test.

[0051] Outdoor transmitting antenna: A passive omnidirectional antenna with a gain of 3dBi and a frequency range of 1.62-1.63GHz, used to forward the amplified signal transmitted by the BeiDou terminal of the satellite under test to the outdoor BeiDou satellite. Its frequency band includes the BeiDou short message uplink frequency of 1624.524MHz±1.6376MHz, used for incoming short message transmission.

[0052] Receiver low-pass filter: Placed behind the outdoor receiving antenna to avoid interference between transmit and receive signals. The received signal is a bandpass signal, but because the transmit and receive frequencies are close, a bandpass filter is not effective at suppressing the transmitted signal; therefore, a low-pass filter is used. Passband response: Upper frequency limit 1.58 GHz, with a suppression level better than 50 dBc at 1.61 GHz.

[0053] Transmit bandpass filter: Placed behind the outdoor transmitting antenna to avoid interference between transmit and receive signals. The signal passband is 1.62-1.63 GHz, with a suppression level better than 50 dBc at 1.58 GHz.

[0054] High-frequency cables: Low-loss coaxial cables are used, with lengths ranging from 50 meters to 200 meters, to connect antennas and power amplifiers, as well as to connect power amplifiers and indoor terminals under test.

[0055] Connection relationships:

[0056] 1. The outdoor receiving antenna receives signals from BeiDou and GPS satellites and transmits them via high-frequency cable to an indoor L-band low-power amplifier for signal amplification. The cable length is between 50-200 meters depending on the actual site layout. The amplified signal is then transmitted via high-frequency cable to the indoor transmitting antenna, which relays the signal indoors.

[0057] 2. The indoor receiving antenna receives the signal transmitted by the short message terminal of the satellite under test, transmits it through a high-frequency cable to the outdoor L-band high-power amplifier for signal amplification, and then connects it to the outdoor transmitting antenna to forward the signal to the Beidou satellite.

[0058] 3. The BeiDou satellite and the ground operation and control system are connected via a microwave link. The BeiDou satellite forwards the incoming short messages from the BeiDou terminal of the satellite under test to the ground operation and control system, and forwards the outgoing short messages sent by the ground operation and control system to the BeiDou terminal of the satellite under test.

[0059] 4. Through this series of connections, the system realizes two-way communication between the indoor short message terminal of the satellite under test and the Beidou satellite, thus simulating the real satellite communication environment in an indoor environment.

[0060] like Figure 2 As shown, the working principle is as follows:

[0061] 1. The outdoor receiving antenna receives BeiDou satellite signals and transmits them via high-frequency cable to an indoor L-band low-power amplifier for amplification. The amplified signal is then relayed through the indoor transmitting antenna to the indoor BeiDou terminal under test, simulating real outdoor satellite signals.

[0062] 2. After receiving the signal, the Beidou terminal of the satellite under test indoors processes it and transmits the signal back.

[0063] 3. The indoor receiving antenna receives the signal transmitted by the Beidou terminal of the satellite under test indoors, and transmits it to the outdoor L-band high-power amplifier for amplification through a high-frequency cable.

[0064] 4. The amplified return signal is transmitted to the BeiDou satellite via an outdoor transmitting antenna (if necessary, a different antenna than the receiving antenna can be used, or the same antenna can be used but operating in a time-sharing manner).

[0065] 5. If the outdoor receiving antenna and the outdoor transmitting antenna are two independent antennas, a cavity filter needs to be added to the rear end of the antennas to prevent spurious transmitted signals from entering the outdoor receiving antenna and saturating the front-end amplifier of the receiving channel. The received signal from the receiving antenna is a bandpass signal, but because the transmitting and receiving frequencies are close, a bandpass filter is not effective at suppressing the transmitted signal; therefore, a low-pass filter is used. Passband response: upper frequency limit 1.58GHz, with a suppression level better than 50dBc at 1.61GHz. A bandpass filter is selected for the transmitting antenna, and the outdoor transmitting antenna is placed after it to avoid transmitting and receiving interference. The signal passband is 1.62 - 1.63GHz, with a suppression level better than 50dBc at 1.58GHz.

[0066] 6. The outdoor receiving antenna-indoor transmitting antenna-BeiDou terminal receiver link of the satellite under test can also be used for the satellite under test to receive navigation signals for positioning and velocity measurement, thereby performing transmission Doppler compensation and simulating the function of compensating for transmission Doppler when a real satellite uses BeiDou short messages in orbit.

[0067] Example 1

[0068] Taking a certain type of short message terminal for a satellite under test as an example, the rated output power of this terminal is... Its operating frequency band is the L band, 1624.524MHz±1.6376MHz.

[0069] When setting up the transmission link for the indoor test system, a high-frequency cable with a characteristic impedance of 50Ω was selected. The path between the indoor receiving antenna and the outdoor L-band high-power amplifier consisted of a 100m cable length and a 1m spatial path. The indoor receiving antenna had a gain of 15dBi, and the outdoor transmitting antenna had a gain of 3dBi. A transmit bandpass filter was installed before the outdoor transmitting antenna. The selected L-band low-loss cable had a insertion loss of 0.23dB / m and an attenuation of 23dB over 100 meters. According to the signal transmission loss formula... (Where L is the signal loss and c is the speed of light, approximately 3 x 10^8 m / s), the signal loss during transmission over a 1m space can be calculated. 36.6dB. To compensate for signal loss, a gain of is selected. An outdoor L-band high-power amplifier amplifies the signal to 10 + 15 - 20 * log10(1.6 * 2) - 23 + 44.5 + 3 = 13 dBW, or approximately 10W. The amplified signal is then transmitted through a passive antenna and successfully received and analyzed by the BeiDou satellite.

[0070] In terms of the receiving link, an active receiving antenna placed on the factory roof captures satellite signals. After passing through a receiving filter, a long high-frequency cable, and an indoor L-band low-power amplifier, the signal reaches the indoor directional transmitting antenna. After spatial transmission, the signal is received by the receiving antenna of the short message system of the satellite under test. The outdoor active receiving antenna has a gain of 20dBi and receives signals at the BeiDou B2I frequency of 1207.14±10.23MHz for short message reception, and GPS L1 C / A at 1575.42±1.023MHz and BeiDou B1I at 1561.098±2.046MHz for receiving navigation signals from the satellite under test for positioning and velocity measurement, thereby performing transmit Doppler compensation. The signal strength of the navigation and short message outgoing signals received by this antenna is approximately -125+20=-105dBm.

[0071] The antenna is connected to the indoor L-band low-power amplifier via a 100m high-frequency cable. Calculations show that the signal loss during transmission through this cable is approximately 23dB. After being amplified by the low-power external amplifier, the signal is transmitted via the passive antenna and successfully received and analyzed by the satellite under test.

[0072] Gain of indoor L-band low-power amplifier The settings can be adjusted according to the sensitivity of the satellite receiver under test, with an adjustment range of 0-40dB. Assuming the receiver's medium-high level input requirement is -130dBm, the gain of the indoor L-band low-power amplifier is set to... If the gain of the indoor omnidirectional receiving antenna is 3dBi, then the signal power received by the receiving antenna is -105 - 23 + 25 + 3 = -100dBm.

[0073] This indoor testing system enabled stable and reliable communication between the indoor satellite short message terminal under test and the BeiDou satellite. It comprehensively tested the terminal's communication and positioning functions, measured key indicators such as satellite-to-ground delay and signal error rate, and verified the short message terminal's transmit Doppler compensation function. The system's effectiveness and accuracy in practical applications were validated.

[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A space-to-ground docking test system for a satellite-borne short message terminal based on an indoor signal link, characterized in that: This includes an outdoor receiving antenna, an indoor L-band low-power amplifier, an indoor transmitting antenna, an indoor receiving antenna, an outdoor L-band high-power amplifier, and an outdoor transmitting antenna; The outdoor receiving antenna is installed outdoors and is used to receive BeiDou satellite signals outdoors; The outdoor receiving antenna has a frequency band including the BeiDou B2I frequency point of 1207.14±10.23MHz, which is used for short message reception. The indoor L-band low-power amplifier is installed indoors, and its receiving end is connected to the output end of the outdoor receiving antenna to receive and amplify the BeiDou satellite signal transmitted from the outdoor receiving antenna. The output end of the indoor L-band low-power amplifier is connected to the receiving end of the indoor transmitting antenna to transmit the amplified BeiDou satellite signal to the indoor transmitting antenna. The indoor transmitting antenna is installed indoors, and its output end is connected to the receiving end of the BeiDou terminal under test indoors, for forwarding the amplified BeiDou satellite signal to the BeiDou terminal under test indoors. The indoor receiving antenna is installed indoors, and the receiving end of the indoor receiving antenna is connected to the output end of the Beidou terminal of the satellite under test, for receiving the signal transmitted by the Beidou terminal of the satellite under test; The outdoor L-band high-power amplifier is installed outdoors, and the receiving end of the outdoor L-band high-power amplifier is connected to the output end of the indoor receiving antenna to receive and amplify the signal transmitted by the indoor Beidou terminal of the satellite under test transmitted by the indoor receiving antenna. The output of the outdoor L-band high-power amplifier is connected to the receiving end of the outdoor transmitting antenna, and is used to transmit the amplified signal transmitted by the Beidou terminal of the satellite under test to the outdoor transmitting antenna. The outdoor transmitting antenna is installed outdoors and is used to forward the amplified signal transmitted by the Beidou terminal of the satellite under test to the outdoor Beidou satellite; The outdoor transmitting antenna has a frequency band that includes the BeiDou short message uplink frequency of 1624.524MHz±1.6376MHz, which is used for inbound short message transmission.

2. The space-to-ground docking test system for a satellite-borne short message terminal based on an indoor signal link as described in claim 1, characterized in that: The outdoor receiving antenna also includes the GPS L1 C / A frequency of 1575.42±1.023MHz and the Beidou B1I frequency of 1561.098±2.046MHz in the frequency band, which are used for the satellite under test to receive navigation signals for positioning and velocity measurement, thereby performing transmission Doppler compensation.

3. The space-to-ground docking test system for a satellite-borne short message terminal based on an indoor signal link as described in claim 1, characterized in that: The outdoor L-band high-power amplifier has a gain range of 30dB to 50dB, a frequency range covering the L-band 1.55-1.65GHz, and a maximum input level of 0dBm; the indoor L-band low-power amplifier also has a gain range of 30dB to 50dB, a frequency range covering the L-band 1.20-1.65GHz, and is used for signal amplification.

4. The space-to-ground docking test system for a satellite-borne short message terminal based on an indoor signal link as described in claim 1, characterized in that: The outdoor receiving antenna and the outdoor transmitting antenna operate in a time-division multiplexing manner using the same antenna.

5. The space-to-ground docking test system for a satellite-borne short message terminal based on an indoor signal link as described in claim 1, characterized in that: The outdoor receiving antenna and the outdoor transmitting antenna are two independent antennas. A receiving low-pass filter is placed behind the outdoor receiving antenna, and a transmitting band-pass filter is placed behind the outdoor transmitting antenna.

6. The space-to-ground docking test system for a satellite-borne short message terminal based on an indoor signal link as described in claim 5, characterized in that: The outdoor receiving antenna is an active receiving antenna with a gain of 20dBi and a frequency range of 1.19-1.58GHz. The outdoor transmitting antenna is a passive omnidirectional antenna with a gain of 3dBi and a frequency range of 1.62-1.63GHz.

7. The space-to-ground docking test system for a satellite-borne short message terminal based on an indoor signal link as described in claim 1, characterized in that: The indoor transmitting antenna is an omnidirectional transmitting antenna with a gain of 3dBi and a frequency range of 1.19-1.58GHz.

8. The space-to-ground docking test system for a satellite-borne short message terminal based on an indoor signal link as described in claim 1, characterized in that: The indoor receiving antenna is a directional receiving antenna with a gain of 15dBi and a frequency range of 1.62-1.63GHz.

9. A test method for spaceborne short message terminal-to-ground docking based on an indoor signal link, implemented according to any one of claims 1-8, is characterized in that... The specific steps are as follows: Step 1: The outdoor receiving antenna receives BeiDou satellite signals and transmits them to an indoor L-band low-power amplifier via a high-frequency cable for amplification; the amplified signal is then relayed to the indoor BeiDou terminal under test via the indoor transmitting antenna to simulate real outdoor satellite signals. Step 2: After receiving the signal, the indoor Beidou terminal of the satellite under test processes it and transmits the signal back. Step 3: The indoor receiving antenna receives the signal transmitted by the Beidou terminal of the satellite under test indoors, and transmits it to the outdoor L-band high-power amplifier for amplification through a high-frequency cable; Step 4: The amplified return signal is transmitted to the BeiDou satellite via an outdoor transmitting antenna.

10. The method for testing space-to-ground docking of a spaceborne short message terminal based on an indoor signal link as described in claim 9, characterized in that: The outdoor receiving antenna-indoor transmitting antenna-BeiDou terminal receiver link for the satellite under test can also be used for the satellite under test to receive navigation signals for positioning and velocity measurement, thereby performing transmission Doppler compensation and simulating the function of compensating for transmission Doppler when a real satellite uses BeiDou short messages in orbit.

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