Testing method and system for small-step frequency modulation function of satellite time and frequency reference

Abstract

A test method and system for satellite time and frequency reference small-step frequency modulation (SMMT) function are provided. The test method includes: setting initial clock information for the satellite under test, including initial time and initial frequency; obtaining a clock frequency adjustment strategy for the satellite under test based on the clock deviation information between the reference clock at the test terminal and the initial clock information; continuously adjusting the clock frequency of the satellite under test according to the clock frequency adjustment strategy; wherein the frequency adjustment amplitude of each adjustment is less than or equal to a first threshold; and completing the test of the satellite under test based on the ranging information between the test terminal and the satellite under test during the continuous adjustment process. This disclosure can verify the impact of satellite small-step frequency modulation on various communication and navigation payloads, and is applicable to the functional and performance testing and verification of communication and navigation fusion systems.

Description

Technical Field

[0001] This disclosure relates to the field of time and frequency measurement technology for low-orbit satellites, and specifically to a test method, on-board test system, ground test system, and test system for a satellite time and frequency reference small step frequency adjustment function. Background Technology

[0002] For on-orbit satellites requiring high precision and stability in time and frequency systems, the main types are navigation satellites in medium and high orbits. Extensive research has been conducted on high-precision time and frequency systems for navigation satellites. For high-throughput communication satellites in medium and high orbits, the core requirement for their time and frequency systems is ensuring accurate time synchronization between the satellite and the ground.

[0003] In recent years, with the rapid development of large-scale low-Earth orbit (LEO) constellation technology, time and frequency generation technology for LEO satellites and corresponding testing methods have become a research hotspot. However, due to limitations in satellite manufacturing costs, overall mass, and size, large-scale LEO constellations are no longer suitable for using onboard atomic clocks commonly used on navigation satellites as frequency sources. LEO satellite time and frequency systems are rapidly developing towards high performance, miniaturization, and low cost, which correspondingly requires improvements and innovations in testing methods for LEO satellite time and frequency systems. However, traditional testing methods can only achieve simple frequency or phase modulation functions for satellites and cannot effectively verify the satellite's ability to autonomously adjust the frequency reference in small steps. Summary of the Invention

[0004] Providing a mechanism to alleviate, reduce or eliminate at least one of the above problems would be beneficial.

[0005] In a first aspect, a test method for the small-step frequency adjustment function of a satellite time and frequency reference is provided. The test method includes: setting initial clock information for the satellite under test, the initial clock information including initial time and initial frequency; obtaining a clock frequency adjustment strategy for the satellite under test based on clock deviation information between a reference clock at a test terminal and the initial clock information; continuously adjusting the clock frequency of the satellite under test according to the clock frequency adjustment strategy; wherein the frequency adjustment amplitude of each adjustment is less than or equal to a first threshold; and completing the test of the satellite under test based on the ranging information between the test terminal and the satellite under test during the continuous adjustment process.

[0006] In a second aspect, an on-board test system with a small-step frequency adjustment function for a satellite time and frequency reference is provided for the satellite under test to implement the above-described test method. The on-board test system includes: an onboard rubidium clock for setting the initial clock information of the satellite under test, the initial clock information including initial time and initial frequency; an onboard timing receiver for receiving uplink messages transmitted from the test end, the uplink messages including clock deviation information between the reference clock of the test end and the initial clock information; a navigation enhancement processor for generating a clock frequency adjustment strategy based on the clock deviation information and satellite equipment delay difference parameters, and continuously adjusting the clock frequency of the satellite under test according to the clock frequency adjustment strategy; and a communication payload for generating ranging information between the test end and the satellite under test during the continuous adjustment process.

[0007] In a third aspect, a ground testing system for satellite time and frequency reference small-step frequency adjustment function is provided for the testing end to implement the above testing method, including: a ground testing hydrogen clock for generating a reference clock for the testing end; a navigation data processing system for calculating the clock deviation information between the reference clock and the initial clock information of the satellite under test in real time, and generating a clock frequency adjustment strategy and adjustment command for the satellite under test based on the clock deviation information and the small-step frequency adjustment strategy; a communication network simulator for uploading the clock frequency adjustment strategy and the adjustment command to the satellite under test; a time interval frequency counter for measuring the time difference between the time of the satellite under test and the reference clock; a phase comparator for measuring the frequency difference between the frequency of the satellite under test and the reference clock; a navigation enhancement ground terminal and a ground communication terminal for generating ranging information between the testing end and the satellite under test during the continuous adjustment process.

[0008] In the fourth aspect, a test system for the small-step frequency adjustment function of a satellite time and frequency reference is provided. This test system includes the on-board test system described above, as well as the ground test system described above.

[0009] It should be understood that the summary section is not intended to identify key or essential features of the embodiments of this disclosure, nor is it intended to limit the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0010] The above and other objects, features, and advantages of this disclosure will become more apparent from the more detailed description of some embodiments thereof in the accompanying drawings, in which:

[0011] Figure 1 A flowchart illustrating a test method for the small-step frequency modulation function of a satellite time and frequency reference according to an embodiment of this disclosure is shown;

[0012] Figure 2A flowchart of a satellite time and frequency reference small step frequency modulation service function in one embodiment of this disclosure is shown;

[0013] Figure 3 A schematic diagram of a test system for small-step frequency modulation of a satellite time and frequency reference in an autonomous satellite control mode, as shown in one embodiment of this disclosure, is illustrated; and

[0014] Figure 4 A schematic diagram of a test system for small-step frequency modulation of a satellite time and frequency reference in ground control mode is shown in one embodiment of this disclosure.

[0015] Explanation of reference numerals in the accompanying drawings for specific embodiments:

[0016] 310. Navigation data processing system;

[0017] 320. Ground-based test of the hydrogen clock;

[0018] 330. Communication network simulator;

[0019] 340. Phase comparator;

[0020] 350. Navigation-enhanced ground terminal;

[0021] 360. Ground communication terminal;

[0022] 370. Spaceborne rubidium clock;

[0023] 380. Navigation enhancement processor;

[0024] 390. Communication payload;

[0025] 3110. Spaceborne timing receiver. Detailed Implementation

[0026] The principles of this disclosure will now be described with reference to some embodiments. It should be understood that these embodiments are described for illustrative purposes only and to assist those skilled in the art in understanding and implementing this disclosure, and do not impose any limitation on the scope of this disclosure. The disclosure described herein may be implemented in ways other than those described below.

[0027] In the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0028] References to "an embodiment," "embodiment," "exemplary embodiment," etc., in this disclosure indicate that the described embodiments may include specific features, structures, or characteristics, but not every embodiment needs to include specific features, structures, or characteristics. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, when a specific feature, structure, or characteristic is described in connection with an exemplary embodiment, whether explicitly described or not, those skilled in the art will recognize that such a feature, structure, or characteristic affects its connection to other embodiments.

[0029] It should be understood that while the terms “first” and “second”, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of the exemplary embodiments, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. The term “and / or” as used herein includes any and all combinations of one or more of the listed terms.

[0030] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments. The singular forms “a,” “an,” and “the” used herein also include the plural forms unless the context clearly indicates otherwise. The terms “a group of elements” or “a collection of elements” as used herein are intended to include one or more elements. It should also be understood that the terms “comprising,” “including,” “having,” “possessing,” “including,” and / or “comprising,” when used herein, specify the presence of the stated features, elements, and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0031] As used in this disclosure, the term "circuit" may refer to one or more of the following:

[0032] (a) Hardware circuit implementation only (e.g., implementation only in analog and / or digital circuits)

[0033] (b) A combination of hardware circuitry and software, such as (if applicable):

[0034] (i) A combination of analog and / or digital hardware circuitry with software / firmware; and

[0035] (ii) Any part of a hardware processor (including a digital signal processor), software, and memory that work together to enable a device such as a mobile phone or server to perform various functions, and

[0036] (c) Hardware circuitry and / or processors, such as microprocessors or a portion thereof, which require software (e.g., firmware) to operate, but may be absent when software is not required to operate.

[0037] The definition of "circuit" applies to all uses of the term in this disclosure, including in any claim. As another example, as used in this disclosure, the term "circuit" also includes implementations of hardware circuitry or processors (or processors in general) or a portion thereof and their accompanying software and / or firmware. The term "circuit" also includes, for example, baseband integrated circuits or processor integrated circuits for mobile devices, or similar integrated circuits in servers, cellular network devices, or other computing network devices, if applicable to a particular claim element.

[0038] As used herein, the term "communication network" refers to a network that conforms to any suitable communication standard, such as Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed ​​Packet Access (HSPA), Narrowband Internet of Things (NB-IoT), New Radio (NR), Non-Terrestrial Network (NTN), etc. Furthermore, communication between terminal devices and network devices in a communication network can be performed according to any suitable generation of communication protocol, including but not limited to first-generation (1G), second-generation (2G), 2.5G, 2.75G, third-generation (3G), fourth-generation (4G), 4.5G, fifth-generation (5G), and future sixth-generation (6G) communication protocols, and / or any other protocols currently known or to be developed in the future. Embodiments of this disclosure can be applied to satellite communication systems. Given the rapid development in communications, future types of communication technologies and systems will naturally exist, and this disclosure can be implemented using these technologies and systems. The scope of this disclosure should not be considered limited to the aforementioned systems.

[0039] As used herein, the terms "satellite equipment" and "network equipment" refer to a node located on a satellite or ground segment in a satellite communication network. Terminal devices access the network and receive services through this node. Depending on the terminology and technology used, satellite equipment and network equipment can refer to a base station (BS) or access point (AP) that serves as a satellite payload, such as a Node B (NodeB or NB), an evolved Node B (eNodeB or eNB), an NR NB (also called a gNB), a Remote Radio Unit (RRU), a Radio Header (RH), a Remote Radio Header (RRH), or a relay node. An example of a relay node can be an Integrated Access and Backhaul (IAB) node. The Distributed Unit (DU) portion of an IAB node can perform the functions of "satellite equipment" and "network equipment" and therefore can operate as satellite equipment and network equipment. In the following description, the terms "satellite equipment," "network equipment," "BS," and "node" are used interchangeably.

[0040] The term "terminal" or "terminal device" refers to any terminal device capable of wireless communication. As an example and not a limitation, a terminal device may also be referred to as a communication device, user equipment (UE), subscriber station (SS), portable subscriber station, mobile station (MS), or access terminal (AT). This terminal device may include, but is not limited to, mobile phones, cellular phones, smartphones, Voice over IP (VoIP) phones, wireless local loop phones, tablets, wearable terminal devices, personal digital assistants (PDAs), portable computers, desktop computers, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEEs), laptop installed devices (LMEs), USB dongles, smart devices, wireless subscriber equipment (CPEs), Internet of Things (IoT) devices, watches or other wearable devices, head-mounted displays (HMDs), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in the context of industrial and / or automated processing chains), consumer electronics devices, relay nodes, devices operating on commercial and / or industrial wireless networks, etc. The mobile terminal (MT) portion of an IAB node can perform the functions of a "terminal device" and therefore can operate as a terminal device. In the following description, the terms "terminal device," "communication device," "terminal," "user equipment," and "UE" are used interchangeably.

[0041] While the functions described herein may be implemented in fixed and / or wireless network nodes in various exemplary embodiments, in other exemplary embodiments, they may be implemented in user equipment devices (such as cellular phones, tablet computers, laptop computers, desktop computers, mobile IoT devices, or fixed IoT devices). For example, the user equipment device may suitably have the corresponding capabilities described in relation to fixed and / or wireless network nodes. The user equipment device may be user equipment and / or control devices, such as chipsets or processors, configured to control the user equipment when it is installed therein. Examples of these functions include boot server functions and / or home subscriber servers, which may be implemented in the user equipment device by providing the user equipment device with software configured to cause the user equipment device to perform from the perspective of these functions / nodes.

[0042] The following section introduces the knowledge related to the technical solution disclosed herein, as well as the technical concept of this disclosure.

[0043] A communication satellite is an artificial Earth satellite in space used as a radio communication relay station. It is the space segment of a satellite communication system, used to relay or process radio communication signals, enabling communication between earth stations (including handheld terminals) or between spacecraft and earth stations. A navigation satellite is an artificial satellite used to provide radio navigation signals and navigation information, offering users navigation, positioning, and timing services. Navigation satellite systems offer high positioning accuracy, wide service range, and provide continuous navigation and positioning services around the clock and in all weather conditions.

[0044] In recent years, with users demanding wider coverage, higher efficiency, and higher precision, the integrated development of communication and navigation has become an important direction. This integrated communication and navigation system requires the integration of time and frequency across the entire satellite, but communication and navigation have different time and frequency requirements. High-precision satellite-to-ground broadband communication requires the deviation between the satellite's 1PPS (Pulse Per Second) and ground time to be within ±50ns (nanoseconds), with no requirement for the stability of the 1PPS. However, navigation enhancement requires the 1PPS to be as stable as possible, and a deviation from ground time within ±1ms (milliseconds) is acceptable. This means that traditional communication time synchronization mechanisms based on GNSS (Global Navigation Satellite System) or navigation time synchronization mechanisms based on atomic clocks that do not adjust for long periods are unable to meet the requirements of time and frequency unification for communication and navigation signals under the integrated communication and navigation system.

[0045] In practical applications, the frequency of low-Earth orbit satellites can be generated by small rubidium clocks or high-stability crystal oscillators. Based on the measurement results of the initial frequency accuracy, the initial frequency of the satellite is calibrated to adjust the frequency accuracy to 10. -13 Scale. The ground-based telemetry, tracking, and command (TT&C) system can use the measurement results of the satellite-to-ground clock difference as a basis to send control commands and phase adjustment parameters to test the satellite's time, frequency, and phase functions.

[0046] The functionality of a satellite time and frequency reference can be verified by sending control commands and phase adjustment parameters from the ground system, thus facilitating frequency modulation and phase modulation. The autonomous micro-step frequency modulation function of a satellite time and frequency reference can be understood as the ability of the satellite's clock system to autonomously make minute frequency adjustments based on deviations from its own time and frequency reference, maintaining time synchronization and frequency stability. Traditional testing methods can only perform simple frequency or phase modulation functions and lack the capability to perform closed-loop verification of the satellite time and frequency reference's autonomous micro-step frequency modulation function.

[0047] Figure 2 A flowchart 200 of a satellite time and frequency reference small-step frequency modulation service function according to an embodiment of this disclosure is shown. Exemplarily, refer to... Figure 2As shown, during the small-step frequency modulation process of the satellite time and frequency reference, the following steps are performed: step S210: parsing of small-step frequency modulation control data; step S220: parsing of small-step frequency modulation service data; step S221: outputting the satellite-to-ground clock difference; step S222: outputting the frequency adjustment amount; step S230: configuring parameters; step S240: converting existing information into frequency and phase adjustment parameters; step S250: performing digital phase adjustment; step S260: performing digital frequency adjustment; and step S270: controlling and outputting via an oven-controlled crystal oscillator (OCXO).

[0048] This disclosure addresses the need for effective verification of the satellite's autonomous small-step frequency adjustment capability for time and frequency references, and therefore proposes a testing method for this function. This method generates a small-step frequency adjustment strategy based on the clock deviation information between the reference clock of the test terminal (such as a ground test system) and the initial clock information of the satellite under test. It continuously adjusts the clock frequency of the satellite under test, with each frequency adjustment increment less than or equal to a first threshold, effectively avoiding the impact of large frequency adjustments on the stability of the satellite system. By combining the ranging information between the test terminal and the satellite under test, the impact of the continuous adjustment process on ranging accuracy can be determined. This disclosure provides reliable testing support for small-step frequency adjustment functionality in applications such as satellite navigation and communication.

[0049] This disclosure is equivalent to a test method for autonomous small-step frequency modulation of a communication and navigation fusion satellite. It enables closed-loop verification of the satellite's autonomous small-step frequency modulation function and can be used to test the satellite's time and frequency reference signal. For example, by injecting a message containing satellite-to-ground clock difference information into the satellite through a ground test system, refined testing of the small-step frequency modulation can be achieved, verifying the satellite's autonomous small-step frequency modulation step size with an accuracy of up to 10⁻⁶. -12 The test method disclosed herein can verify the impact of satellite small step frequency modulation on various communication and navigation payloads, and is applicable to the functional and performance testing and verification of other communication and navigation fusion systems.

[0050] This paper first introduces the test system for implementing the small-step frequency modulation function of a satellite time and frequency reference, designed in accordance with the present disclosure, to facilitate understanding of the test method described later. This test system is equivalent to the system test environment.

[0051] The test system disclosed herein includes an on-board test system and a ground test system. The on-board test system is installed on the satellite under test and is used to provide the data and information required for the test method. The ground test system is installed at the test terminal, which is equivalent to a ground system, and is used to provide the data and information required for the test method. The satellite under test disclosed herein can operate in either satellite autonomous control mode or ground control mode, and the components of the test system differ for these two control modes.

[0052] Figure 3 A schematic diagram 300 of a test system for small-step frequency modulation of a satellite time and frequency reference in an autonomous satellite control mode according to an embodiment of this disclosure is shown. (Reference) Figure 3 As shown, this test system includes components for both an on-board test system and a ground test system. The on-board test system includes: a navigation enhancement processor 380, a communication payload 390, and an on-board rubidium clock 370. The ground test system includes: a navigation data processing system 310, a time interval frequency counter (such as SR620), a ground test hydrogen clock 320, a communication network simulator 330, a phase comparator 340 (such as a PICOTIME phase comparator), a navigation enhancement ground terminal 350, and a ground communication terminal 360.

[0053] Figure 4 A schematic diagram 400 of a test system for small-step frequency modulation of a satellite time and frequency reference in ground control mode according to an embodiment of this disclosure is shown. (Refer to...) Figure 4 As shown, this test system includes components for both an on-board test system and a ground test system. The on-board test system includes: a navigation enhancement processor 380, a communication payload 390, an on-board rubidium clock 370, and an on-board timing receiver 3110. The ground test system includes: a navigation data processing system 310, a communication network simulator 330, a navigation enhancement ground terminal 350, and a ground communication terminal 360.

[0054] Exemplary, in practical applications, the components of the test system can be freely configured as needed. In some embodiments, the on-board test system installed on the satellite under test includes one or any combination of the following: a navigation enhancement processor 380, a communication payload 390, an on-board rubidium clock 370, and an on-board timing receiver 3110; the ground test system at the test end includes one or any combination of the following: a navigation data processing system 310, a time interval frequency counter (such as SR620), a ground test hydrogen clock 320, a communication network simulator 330, a phase comparator 340 (such as a PICOTIME phase comparator), a navigation enhancement ground terminal 350, and a ground communication terminal 360.

[0055] For example, the navigation enhancement processor 380 can be used as the device under test. The capabilities of the navigation data processing system 310 include: the ability to measure and read time differences and generate messages, and the ability to fit the relative frequency difference between the satellite and the ground based on the measurement results.

[0056] In some embodiments, the functions of each component in the on-board testing system are as follows:

[0057] The onboard rubidium clock 370 is used to set the initial clock information of the satellite under test, which includes the initial time and initial frequency.

[0058] The spaceborne timing receiver 3110 is used to receive the uplink message transmitted by the test end. The uplink message includes clock deviation information between the reference clock and the initial clock information of the test end.

[0059] The navigation enhancement processor 380 is used to generate a clock frequency adjustment strategy based on clock deviation information and satellite equipment delay difference parameters, and continuously adjust the clock frequency of the satellite under test according to the clock frequency adjustment strategy.

[0060] The communication payload 390 is used to generate ranging information between the test terminal and the satellite under test during continuous adjustment.

[0061] In some embodiments of the ground testing system, the functions of each component are as follows:

[0062] The ground-based hydrogen clock 320 is used to generate a reference clock for the test.

[0063] The navigation data processing system 310 is used to calculate the clock deviation information between the reference clock and the initial clock information of the satellite under test in real time, and to generate the clock frequency adjustment strategy and adjustment command of the satellite under test based on the clock deviation information and the small step frequency adjustment strategy.

[0064] The communication network simulator 330 is used to transmit clock frequency adjustment strategies and adjustment commands to the satellite under test.

[0065] A time interval frequency counter is used to measure the time difference between the time of the satellite under test and a reference clock.

[0066] The phase comparator 340 is used to measure the frequency difference between the frequency of the satellite under test and the reference clock.

[0067] The navigation enhancement ground terminal 350 and the ground communication terminal 360 are used to generate ranging information between the test terminal and the satellite under test during continuous adjustment.

[0068] For example, when the satellite-to-ground clock difference and its drift value exceed a threshold, the satellite frequency can be adjusted. The adjustment amount and frequency of the satellite frequency can be implemented in two modes: ground control mode and on-board autonomous control mode. For example: (1) When the frequency adjustment method is in ground control mode, the ground can transmit frequency modulation parameters to the satellite, and the satellite adjusts its own frequency according to the frequency modulation parameters transmitted from the ground. (2) When the frequency adjustment method is in satellite autonomous control mode, the ground can transmit the calculated satellite-to-ground clock difference to the satellite, and the satellite executes the satellite-to-ground time synchronization method for communication and navigation fusion according to the satellite-to-ground clock difference measurement results transmitted from the ground.

[0069] Considering that the satellite can operate in either satellite autonomous control mode or ground control mode, the test methods disclosed herein can be divided into two types: type a and type b. Type a test method can be considered to correspond to the test of satellite autonomous small step frequency modulation (i.e., satellite autonomous control mode), and type b test method can correspond to the test of ground control small step frequency modulation (i.e., ground control mode).

[0070] The following will refer to Figure 1 The principles and implementation of this disclosure are described in detail.

[0071] Figure 1 A flowchart 100 illustrates a test method for a satellite time and frequency reference small-step frequency modulation function according to an embodiment of this disclosure, with reference to... Figure 1 As shown, the test method for the satellite time and frequency reference small-step frequency adjustment function in this embodiment includes the following steps:

[0072] Step S1: Set the initial clock information of the satellite under test. The initial clock information includes the initial time and the initial frequency.

[0073] Step S2: Based on the clock deviation information between the reference clock and the initial clock information at the test end, obtain the clock frequency adjustment strategy of the satellite under test;

[0074] Step S3: Continuously adjust the clock frequency of the satellite under test according to the clock frequency adjustment strategy; wherein the frequency adjustment range of each clock adjustment is less than or equal to the first threshold.

[0075] Step S4: During the continuous adjustment process, the test of the satellite is completed based on the ranging information between the test terminal and the satellite under test.

[0076] For example, the main difference between the satellite autonomous control mode and the ground control mode lies in step S2. Steps S1 to S4 will be described in detail below:

[0077] In step S1, the initial clock information of the satellite under test is set, including the initial time and initial frequency. For example, the initial clock information can be set after the satellite under test (i.e., the satellite payload) is started. For instance, the ground test terminal sends a command to the telemetry and control link to start the satellite under test and monitors its operational status based on telemetry signals; wherein the telemetry signals include one or any combination of voltage, temperature, and lockout indication.

[0078] refer to Figure 3 and Figure 4 As shown, in some embodiments, the clock of the satellite under test includes an onboard rubidium clock 370.

[0079] In step S2, the clock frequency adjustment strategy for the satellite under test is obtained based on the clock deviation information between the reference clock and the initial clock information at the test end. (Reference) Figure 3 As shown, in some embodiments, the reference clock includes a ground-based hydrogen clock (i.e., a ground-based test hydrogen clock 320).

[0080] In some embodiments, the time deviation between the initial time and the reference clock is less than or equal to a second threshold. The second threshold includes 20 ns, where ns represents nanoseconds. Exemplarily, the satellite-to-ground clock difference can be obtained by calculating the time difference between the ground test terminal and the satellite under test, and this difference can be adjusted to be less than or equal to the second threshold (e.g., ±20 ns). The second threshold can be -20 ns, -10 ns, 0 ns, +10 ns, +20 ns, etc. This disclosure improves the time synchronization accuracy of the satellite time and frequency reference and reduces the impact of time deviation on ranging and navigation performance by ensuring that the time deviation between the initial time and the reference clock is less than or equal to the second threshold.

[0081] In some embodiments, the frequency deviation between the initial frequency and the reference clock is less than or equal to a third threshold. The third threshold includes: 10 -13 For example, the relative frequency difference of the atomic clock can be obtained by calculating the frequency deviation between the ground test terminal and the satellite under test, and the relative frequency difference of the atomic clock can be adjusted to be less than or equal to a third threshold (such as 10). -13 This disclosure improves the frequency stability and synchronization accuracy of the satellite time and frequency reference by ensuring that the frequency deviation between the initial frequency and the reference clock is less than or equal to a third threshold, thereby reducing the impact of frequency deviation on satellite navigation.

[0082] In some embodiments, under satellite autonomous control mode, a clock frequency adjustment strategy for the satellite under test is obtained based on the clock deviation information between the reference clock and the initial clock information at the test end, including:

[0083] The satellite under test receives the uplink message transmitted by the test terminal, which includes clock deviation information;

[0084] The satellite under test generates a clock frequency adjustment strategy based on clock deviation information and satellite equipment delay difference parameters.

[0085] For example, the satellite under test parses the message to obtain clock offset information. The satellite equipment delay difference parameter refers to the delay of the navigation enhancement transmission signal channel. Since the clock offset results of low-Earth orbit satellites are mainly obtained through GNSS monitoring receivers, and this satellite-to-ground clock offset does not include the delay of each transmission channel, in order to achieve high-precision navigation enhancement, it is necessary to add the satellite-to-ground clock offset to the delay of the transmission channel to obtain the clock offset of the downlink transmission signal.

[0086] For example, a ground test terminal can inject a message containing satellite-to-ground clock difference information into the satellite under test. After parsing this clock difference information, the satellite under test will autonomously generate a small-step frequency modulation strategy and execute the small-step frequency modulation operation, thereby smoothly adjusting its time and frequency reference. This process can control the deviation between satellite time and ground time within ±50ns, while ensuring that the normal operation of communication services is not affected. This disclosure can verify the satellite's autonomous clock difference prediction and satellite's autonomous control of small-step frequency modulation capabilities, achieving a full closed-loop verification of the satellite's small-step frequency modulation function, thereby improving the efficiency of system testing.

[0087] In some embodiments, in ground control mode, a clock frequency adjustment strategy for the satellite under test is obtained based on the clock deviation information between the reference clock and the initial clock information at the test terminal, including:

[0088] The test terminal calculates clock deviation information in real time and generates clock frequency adjustment strategies and adjustment instructions based on clock deviation information and small-step frequency adjustment strategies.

[0089] The test terminal uploads the clock frequency adjustment strategy and adjustment commands to the satellite under test.

[0090] For example, the ground test terminal can generate frequency adjustment commands based on the relative frequency difference of the atomic clock and the small-step frequency modulation strategy; wherein, the frequency adjustment command includes the frequency adjustment amount and the frequency of frequency adjustment. The ground test terminal uploads the frequency adjustment commands to the satellite under test. Subsequently, the satellite under test executes the frequency adjustment commands to synchronize satellite-ground time, and telemetry is used to determine the execution status of the frequency adjustment commands. This disclosure can ensure high-precision time synchronization, and the execution effect is verified through telemetry, enhancing the reliability of the small-step frequency modulation function, and providing a stable and accurate time reference for satellite navigation, communication and other applications.

[0091] In step S3, the clock frequency of the satellite under test is continuously adjusted according to the clock frequency adjustment strategy; wherein the frequency adjustment magnitude of each adjustment is less than or equal to a first threshold. For example, when the satellite under test continuously adjusts its clock frequency, the first threshold for the frequency adjustment magnitude of each adjustment can be 10. -11 Hz or 10-5 Hz.

[0092] In step S4, during the continuous adjustment process, the test of the satellite under test is completed based on the ranging information between the test terminal and the satellite under test. In some embodiments, before completing the test of the satellite under test, the following steps are also included:

[0093] Calculate the first mean and / or first standard deviation of the ranging information prior to continuous adjustment;

[0094] Calculate the second mean and / or second standard deviation of the ranging information during the continuous adjustment process;

[0095] The difference between the first mean and the second mean is greater than a first preset difference, and / or the difference between the first standard deviation and the second standard deviation is greater than a second preset difference;

[0096] It has been determined that the continuous adjustment process affects the ranging accuracy.

[0097] For example, to determine the impact of small step frequency modulation (FPM) on the ranging accuracy of the communication payload terminal, monitoring is required. By observing changes in the ranging information of the navigation augmentation ground terminal, it is possible to assess whether FPM affects the operation of the navigation augmentation processor, and thus determine whether FPM meets the time-frequency requirements of the communication navigation payload. If the mean and standard deviation of the ranging information do not change before and after FPM, it can be considered that FPM has no impact on ranging accuracy. Conversely, if the mean changes and the standard deviation increases by more than 0.1 ns, it can be considered that there is an impact.

[0098] This disclosure, through quantitative analysis of the changes in ranging data before and after frequency modulation, can accurately identify whether small-step frequency modulation operations introduce ranging errors, thus providing an intuitive and accurate basis for evaluating and optimizing the performance of satellite time and frequency systems, and helping to further improve the ranging accuracy and reliability of satellites in navigation, communication and other services.

[0099] The following is a specific embodiment, with reference to Figure 3 The article will also introduce the Type A test method mentioned earlier, which is based on the on-board test system and the ground test system. The Type A test method corresponds to the test of satellite autonomous small step frequency modulation (i.e., satellite autonomous control mode).

[0100] (a1) Send instructions to the telemetry and control link through the communication network simulator to turn on the satellite under test, and judge the basic health status of the powered-on payload based on telemetry signals such as voltage, temperature, and lockout indication;

[0101] (a2) Measure the time difference between the ground time and the navigation augmentation processor, i.e. the phase difference of the 1PPS signal, using the SR620 (time interval frequency counter);

[0102] (a3) The communication network simulator sends a time synchronization command or a phase adjustment command to adjust the satellite-to-ground time deviation (i.e., satellite-to-ground clock difference) a0 to within ±20ns;

[0103] (a4) Measure the frequency difference between the satellite clock and the ground-based test hydrogen clock using a PICOTIME phase comparator;

[0104] (a5) Based on the frequency difference measured by the PICOTIME phase comparator, the communication network simulator sends a frequency modulation command through the ground control channel to adjust the relative frequency difference a1 between the satellite and the ground atomic clocks to 10. -13 the following;

[0105] (a6) The navigation data processing system automatically reads the measurement results of SR620 and updates the star-ground clock difference a0 in the above-mentioned message every 10 seconds based on the measurement results;

[0106] (a7) The communication network simulator sends the message containing the star-to-ground clock difference a0 generated by the navigation data processing system to the navigation enhancement processor through the ground operation control channel;

[0107] (a8) The navigation enhancement processor formulates a frequency modulation strategy based on the low-orbit satellite clock bias results transmitted from the ground and the satellite equipment delay difference parameters, and autonomously implements small-step frequency modulation of the satellite, with each frequency adjustment not exceeding 10. -11 Hz (Hertz) or 10 - 5 Hz;

[0108] (a9) The relative deviation of 1PPS between the satellite and the ground test hydrogen clock was monitored by SR620, and the relative frequency difference between the satellite and the ground clock was monitored by PICOTIME phase comparator;

[0109] (a10) Does the ranging value of the observation navigation enhancement ground terminal and the ground communication terminal affect the ranging accuracy during the small step frequency modulation process?

[0110] For example, the Class A test method of this disclosure uses a ground-based hydrogen atomic clock to ensure the high stability of the ground time and frequency system, ensuring that the satellite-to-ground frequency deviation will not change rapidly due to the instability of the ground time and frequency system. Before initiating small-step frequency modulation, a phase modulation command needs to be sent to adjust the satellite-to-ground clock difference to within ±20ns, and a frequency modulation command needs to be sent to adjust the satellite-to-ground frequency difference to 10ns. -13The SR620 was used to verify the changes in satellite-to-ground clock bias during the small-step frequency modulation (MBFM) process in a closed loop. Ground control updated the satellite-to-ground clock bias measurement results in a message every 10 seconds. Based on the clock bias measurement results in the ground-uploaded message, the satellite autonomously generated and executed a small-step frequency modulation strategy. The PICROTIME closed-loop method was used to verify the satellite-to-ground frequency changes during the MBFM process. During MBFM, the ranging values ​​of the navigation augmentation ground terminal and the ground communication terminal were observed in real time to determine whether the MBFM process affected ranging accuracy.

[0111] The following is a specific embodiment, with reference to Figure 4 The article will also introduce the Class B test method mentioned earlier, which is based on the on-board test system and the ground test system. The Class B test method corresponds to the test of ground control small step frequency modulation (i.e., ground control mode).

[0112] (b1) Send instructions through the communication network simulator to turn on the satellite under test, and judge the basic health status of the powered-on payload based on telemetry signals such as voltage, temperature, and lockout indication;

[0113] (b2) The navigation data processing system uses the measurement results from the onboard timing receiver and the ranging results from the rapid and precise positioning to determine the satellite-to-ground clock difference and frequency deviation;

[0114] (b3) Based on the measurement results of the star-to-ground clock difference, the communication network simulator sends a phase adjustment command to adjust the star-to-ground clock difference to within ±20ns;

[0115] (b4) Based on the measured frequency deviation, the communication network simulator sends a frequency modulation command to adjust the frequency difference between the satellite and the ground atomic clock to 10. -13 the following;

[0116] (b5) The navigation data processing system calculates the clock error and frequency deviation measurement results in real time, and then formulates the frequency adjustment amount and adjustment frequency based on the frequency deviation results and the small step frequency adjustment strategy;

[0117] (b6) The communication network simulator sends the frequency adjustment command generated by the navigation data processing system to the navigation enhancement processor;

[0118] (b7) The satellite's navigation enhancement processor executes the frequency adjustment commands transmitted from the ground and determines the execution status of the commands based on the received command count and the frequency adjustment value telemetry.

[0119] (b8) Does the ranging accuracy of the ground terminal and ground communication terminal for observation and navigation enhancement affect the ranging accuracy during the small step frequency modulation process?

[0120] For example, this disclosure can use a ground-based hydrogen atomic clock to ensure the high stability of the ground time and frequency system, ensuring that the satellite-to-ground frequency deviation will not change rapidly due to the instability of the ground time and frequency system. Before initiating small-step frequency modulation, a phase modulation command needs to be sent to adjust the satellite-to-ground clock difference to within ±20ns, and a frequency modulation command needs to be sent to adjust the satellite-to-ground frequency difference to within 10ns. -13 Inside, the navigation data processing system uses satellite-to-ground ranging values ​​to calculate satellite-to-ground clock errors and frequency deviations. The navigation augmentation processor executes frequency adjustment commands transmitted from the ground, and determines the command execution status based on received command counts and telemetry of frequency adjustment values. It observes the ranging values ​​of the navigation augmentation ground terminal and the ground communication terminal to determine whether the small-step frequency adjustment process affects ranging accuracy.

[0121] The criteria for judging the small step frequency modulation test results disclosed herein are summarized here.

[0122] For example, the satellite can adjust the phase of its 1PPS signal based on the satellite-to-ground clock difference injected from the ground, thus achieving a small-step frequency modulation function. The criteria for determining the small-step frequency modulation function are:

[0123] (1) The star-to-ground clock difference can be controlled within ±50ns;

[0124] (2) The frequency adjustment amount can be 10 each time. -5 Below Hz;

[0125] (3) The accuracy of the ranging value of the communication payload terminal is not affected by the small step frequency modulation (FPM), but it is necessary to determine the impact on it. By monitoring the changes in the ranging value of the navigation augmentation ground terminal, it can be determined whether the small step frequency modulation has any impact on the operation of the navigation augmentation processor, thereby determining whether the small step frequency modulation can meet the time and frequency requirements of the communication and navigation payload.

[0126] Generally, the various embodiments of this disclosure can be implemented in hardware or dedicated circuitry, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while others may be implemented in firmware or software, which may be executed by a controller, microprocessor, or other computing device. Although various aspects of the embodiments of this disclosure are shown and described as block diagrams, flowcharts, or other graphical representations, it should be understood that, as non-limiting examples, the blocks, devices, systems, techniques, or methods described herein may be implemented in hardware, software, firmware, dedicated circuitry or logic, general-purpose hardware or controllers or other computing devices, or some combination thereof.

[0127] This disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer-executable instructions, such as instructions included in a program module, which execute in a device on a target real or virtual processor to perform the aforementioned references. Figure 1The aforementioned testing method. Typically, a program module includes routines, programs, libraries, objects, classes, components, data structures, etc., that perform specific tasks or implement specific abstract data types. In various embodiments, the functionality of a program module can be combined or separated as needed. The machine-executable instructions used in the program module can execute locally or on a distributed device. In a distributed device, the program module can reside on both local and remote storage media.

[0128] Program code used to perform the methods of this disclosure may be written in any combination of one or more programming languages. This program code may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, such that when executed by the processor or controller, the functions / operations specified in the flowcharts and / or block diagrams are implemented. The program code may be executed entirely on a machine, partially on a machine, partially on a remote machine, partially on a remote machine, or entirely on a remote machine or server as a standalone software package.

[0129] In the context of this disclosure, computer program code or related data may be carried by any suitable carrier to enable a device, apparatus, or processor to perform the various processes and operations described above. Examples of carriers include signals, computer-readable media, etc.

[0130] Computer-readable media can be computer-readable signal media or computer-readable storage media. Computer-readable media can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or apparatuses, or any suitable combination thereof. More specific examples of computer-readable storage media include electrical connections having one or more wires, portable computer floppy disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable optical disc read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0131] Furthermore, although the operations are described in a specific order, this should not be construed as requiring that these operations be performed in the specific order or sequence shown, or that all of the operations shown be performed to obtain the desired result. In some cases, multitasking and parallel processing may be advantageous. Similarly, while several specific implementation details are included in the foregoing discussion, these details should not be construed as limiting the scope of this disclosure, but rather as descriptions of features specific to particular embodiments. Certain features described in the context of individual embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented individually or in any suitable sub-combination in multiple embodiments.

[0132] Although this disclosure has been described in language specific to structural features and / or methodological behavior, it should be understood that this disclosure as defined in the appended claims is not necessarily limited to the specific features or behaviors described above. Rather, the specific features and actions described above are disclosed as exemplary forms for implementing the claims.

Claims

1. A test method for the small-step frequency modulation function of a satellite time and frequency reference, characterized in that, include: The initial clock information of the satellite under test is set, including the initial time and initial frequency. The satellite under test is equipped with a navigation enhancement processor. Based on the clock deviation information between the reference clock of the test terminal and the initial clock information, the clock frequency adjustment strategy of the satellite under test is obtained, and the test terminal includes a navigation enhancement ground terminal. The clock frequency of the satellite under test is continuously adjusted according to the clock frequency adjustment strategy; wherein the frequency adjustment magnitude of each adjustment is less than or equal to a first threshold. During the continuous adjustment process, the test of the satellite is completed based on the ranging information between the test terminal and the satellite under test, including: By monitoring the changes in the ranging information of the navigation enhancement ground terminal, the impact of small step frequency modulation on the operation of the navigation enhancement processor can be determined. Before completing the testing of the satellite under test, the following steps are also included: Calculate the first mean and first standard deviation of the ranging information prior to the continuous adjustment; Calculate the second mean and second standard deviation of the ranging information during the continuous adjustment process; The difference between the first mean and the second mean is greater than a first preset difference, and the difference between the first standard deviation and the second standard deviation is greater than a second preset difference; It was determined that the continuous adjustment process affected the ranging accuracy.

2. The test method as described in claim 1, characterized in that, Based on the clock deviation information between the reference clock at the test end and the initial clock information, the clock frequency adjustment strategy of the satellite under test is obtained, including: The satellite under test receives the uplink message transmitted by the test terminal, and the uplink message includes the clock deviation information; The satellite under test generates the clock frequency adjustment strategy based on the clock deviation information and the satellite equipment delay difference parameter.

3. The test method as described in claim 1, characterized in that, Based on the clock deviation information between the reference clock at the test end and the initial clock information, the clock frequency adjustment strategy of the satellite under test is obtained, including: The test terminal calculates the clock deviation information in real time, and generates the clock frequency adjustment strategy and adjustment command based on the clock deviation information and the small-step frequency adjustment strategy. The test terminal uploads the clock frequency adjustment strategy and the adjustment command to the satellite under test.

4. The test method as described in claim 1, characterized in that, The time deviation between the initial time and the reference clock is less than or equal to a second threshold; the frequency deviation between the initial frequency and the reference clock is less than or equal to a third threshold.

5. The test method according to any one of claims 1-4, characterized in that, The clock of the satellite under test includes an onboard rubidium clock.

6. The test method according to any one of claims 1-4, characterized in that, The reference clock includes a ground-based hydrogen clock.

7. The test method as described in claim 4, characterized in that, The second threshold includes 20 ns, where ns represents nanoseconds.

8. The test method as described in claim 4, characterized in that, The third threshold includes: 10 -13 .

9. The test method according to any one of claims 1-4, characterized in that, The satellite under test is also equipped with one or any combination of the following: a communication payload, an onboard rubidium clock, and an onboard timing receiver; The test terminal also includes one or any combination of the following: a navigation data processing system, a time interval frequency counter, a ground test hydrogen clock, a communication network simulator, a phase comparator, and a ground communication terminal.

10. An on-board test system for satellite time and frequency reference small-step frequency adjustment function, characterized in that, For use on the satellite under test, to implement the test method as described in any one of claims 1-8, comprising: A spaceborne rubidium clock is used to set the initial clock information of the satellite under test, the initial clock information including initial time and initial frequency; A spaceborne timing receiver is used to receive the uplink message transmitted by the test end, wherein the uplink message includes clock deviation information between the reference clock of the test end and the initial clock information; A navigation enhancement processor is used to generate a clock frequency adjustment strategy based on the clock deviation information and satellite equipment delay difference parameters, and to continuously adjust the clock frequency of the satellite under test according to the clock frequency adjustment strategy. A communication payload is used to generate ranging information between the test terminal and the satellite under test during the continuous adjustment process.

11. A ground test system for satellite time and frequency reference small-step frequency adjustment function, characterized in that, For use in the testing end, to implement the testing method as described in any one of claims 1-8, comprising: A ground-based hydrogen clock is used to generate a reference clock for the test terminal; The navigation data processing system is used to calculate the clock deviation information between the reference clock and the initial clock information of the satellite under test in real time, and to generate the clock frequency adjustment strategy and adjustment command of the satellite under test based on the clock deviation information and the small step frequency adjustment strategy. A communication network simulator is used to upload the clock frequency adjustment strategy and the adjustment command to the satellite under test. A time interval frequency counter is used to measure the time difference between the time of the satellite under test and the reference clock; A phase comparator is used to measure the frequency difference between the frequency of the satellite under test and the reference clock. A navigation enhancement ground terminal and a ground communication terminal are used to generate ranging information between the test terminal and the satellite under test during the continuous adjustment process.

12. A test system for satellite time and frequency reference small-step frequency adjustment function, characterized in that, It includes the on-board testing system as described in claim 10, and the ground testing system as described in claim 11.

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