Methods, systems, apparatuses, devices, storage media, and products for out-of-band frequency synchronization

Abstract

The application relates to a remote frequency synchronization method, system, device, equipment, storage medium and product. The method comprises the following steps: performing phase compensation processing on uplink signals between a ground station to be synchronized and a UAV, and sending a first uplink signal to the UAV after the phase compensation processing, wherein the frequency standard of the first uplink signal is a first frequency standard; receiving a first downlink signal and a second downlink signal sent by the UAV; the second downlink signal is a second uplink signal forwarded by the UAV, and the second uplink signal is an uplink signal sent by a remote ground station to the UAV after the phase compensation processing; and adjusting the frequency standard of the ground station to be synchronized from the first frequency standard to a second frequency standard according to the first downlink signal and the second downlink signal. The method can realize high-precision remote time-frequency synchronization without the support of a relay station or a relay satellite.

Description

Technical Field

[0001] This application relates to the field of unmanned aerial vehicle (UAV) communication technology, and in particular to a method, system, device, computer equipment, computer-readable storage medium, and computer program product for remote frequency synchronization. Background Technology

[0002] The measurement of time forms the basis of the International System of Units (SI) and plays a vital role in production, daily life, and scientific research. The study of time is mainly divided into two parts: timekeeping and time dissemination. Time dissemination aims to establish a traceable, distributed time and frequency standard within the scope of human activity, and is primarily divided into time transfer and frequency transfer.

[0003] Depending on the transmission medium, time-frequency transmission systems include wired links, free-space links, and network links. Among them, free-space links are widely used due to their flexibility and wide coverage; however, most free-space links rely heavily on broadcast stations, relay stations, or relay satellites for signal return and forwarding, and are not feasible in the absence of relay stations or when satellites deny access. Summary of the Invention

[0004] Therefore, it is necessary to provide a method, system, device, computer equipment, computer-readable storage medium, and computer program product for remote frequency synchronization that does not rely on relay stations or satellites, in order to address the above-mentioned technical problems.

[0005] Firstly, this application provides a method for off-site frequency synchronization, applicable to ground stations to be synchronized, including:

[0006] Phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, and after phase compensation processing, a first uplink signal is sent to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard.

[0007] The system receives a first downlink signal and a second downlink signal sent by the UAV. The first downlink signal is a first uplink signal forwarded by the UAV. The second downlink signal is a second uplink signal forwarded by the UAV. The second uplink signal is an uplink signal sent to the UAV by a remote ground station after performing phase compensation processing on the uplink signal. The frequency standard corresponding to the second uplink signal is the second frequency standard.

[0008] Based on the first downlink signal and the second downlink signal, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0009] In one embodiment, phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, including:

[0010] Based on the link data obtained by the ground station to be synchronized, determine the first phase before the uplink signal is sent by the ground station to be synchronized, and the second phase after the UAV transmits the downlink signal fed back by the uplink signal to the ground station to be synchronized.

[0011] Calculate the uplink phase compensation amount based on the first phase and the second phase;

[0012] The phase of the uplink signal is adjusted based on the uplink phase compensation amount.

[0013] In one embodiment, after performing phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, the method further includes:

[0014] Calculate the downlink phase compensation amount based on the first phase and the second phase;

[0015] The phase of the downlink signal is adjusted based on the downlink phase compensation amount.

[0016] In one embodiment, the uplink phase compensation amount is calculated based on the first phase and the second phase, including:

[0017] Calculate the total phase compensation based on the first phase and the second phase;

[0018] Calculate the uplink carrier angular frequency ratio based on the uplink carrier angular frequency and downlink carrier angular frequency extracted from the link data;

[0019] The uplink phase compensation is calculated based on the total phase compensation and the uplink carrier angular frequency ratio.

[0020] In one embodiment, receiving a first downlink signal and a second downlink signal transmitted by the drone includes:

[0021] At the same time, the first and second downlink signals transmitted by the UAV are received along the same downlink.

[0022] In one embodiment, adjusting the frequency standard of the ground station to be synchronized from the first frequency standard to the second frequency standard based on the first downlink signal and the second downlink signal includes:

[0023] The phase difference between the first uplink signal and the second uplink signal is determined based on the first downlink signal and the second downlink signal;

[0024] Based on the phase difference, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0025] Secondly, this application also provides a remote frequency synchronization system, which includes a ground station to be synchronized, a remote ground station, and a UAV, wherein:

[0026] The ground station to be synchronized is used to perform phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, and after the phase compensation processing, it sends a first uplink signal to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard.

[0027] The remote ground station is used to perform phase compensation processing on the uplink signal between the remote ground station and the UAV, and after phase compensation processing, it sends a second uplink signal to the UAV. The frequency standard of the second uplink signal is the second frequency standard. After the second uplink signal is transmitted to the UAV, the corresponding frequency standard is the second frequency standard.

[0028] The drone is used to send first and second downlink signals to the ground station to be synchronized.

[0029] The ground station to be synchronized is also used to adjust the frequency standard from the first frequency standard to the second frequency standard based on the first downlink signal and the second downlink signal.

[0030] Thirdly, this application also provides a remote frequency synchronization device, including a phase compensation module, a receiving module, and a frequency modulation module, wherein:

[0031] The phase compensation module is used to perform phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, and after the phase compensation processing, it sends a first uplink signal to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard.

[0032] The receiving module is used to receive a first downlink signal and a second downlink signal sent by the UAV. The first downlink signal is a first uplink signal forwarded by the UAV. The second downlink signal is a second uplink signal forwarded by the UAV. The second uplink signal is an uplink signal sent to the UAV by a remote ground station after performing phase compensation processing on the uplink signal. The frequency standard corresponding to the second uplink signal is the second frequency standard.

[0033] The frequency modulation module is used to adjust the frequency standard of the ground station to be synchronized from the first frequency standard to the second frequency standard based on the first downlink signal and the second downlink signal.

[0034] Fourthly, this application also provides a computer device, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to perform the following steps:

[0035] Phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, and after phase compensation processing, a first uplink signal is sent to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard.

[0036] The system receives a first downlink signal and a second downlink signal sent by the UAV. The first downlink signal is a first uplink signal forwarded by the UAV. The second downlink signal is a second uplink signal forwarded by the UAV. The second uplink signal is an uplink signal sent to the UAV by a remote ground station after performing phase compensation processing on the uplink signal. The frequency standard corresponding to the second uplink signal is the second frequency standard.

[0037] Based on the first downlink signal and the second downlink signal, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0038] Fifthly, this application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the following steps:

[0039] Phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, and after phase compensation processing, a first uplink signal is sent to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard.

[0040] The system receives a first downlink signal and a second downlink signal sent by the UAV. The first downlink signal is a first uplink signal forwarded by the UAV. The second downlink signal is a second uplink signal forwarded by the UAV. The second uplink signal is an uplink signal sent to the UAV by a remote ground station after performing phase compensation processing on the uplink signal. The frequency standard corresponding to the second uplink signal is the second frequency standard.

[0041] Based on the first downlink signal and the second downlink signal, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0042] Sixthly, this application also provides a computer program product, including a computer program that, when executed by a processor, performs the following steps:

[0043] Phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, and after phase compensation processing, a first uplink signal is sent to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard.

[0044] The system receives a first downlink signal and a second downlink signal sent by the UAV. The first downlink signal is a first uplink signal forwarded by the UAV. The second downlink signal is a second uplink signal forwarded by the UAV. The second uplink signal is an uplink signal sent to the UAV by a remote ground station after performing phase compensation processing on the uplink signal. The frequency standard corresponding to the second uplink signal is the second frequency standard.

[0045] Based on the first downlink signal and the second downlink signal, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0046] The aforementioned remote frequency synchronization method, system, device, computer equipment, computer-readable storage medium, and computer program product, by performing phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, can establish a reproduced signal of the ground station to be synchronized on the UAV. After the UAV receives the phase-compensated first and second uplink signals, the ground station to be synchronized receives the first and second downlink signals from the UAV. Based on the first and second downlink signals, the frequency standard of the ground station to be synchronized is shifted to achieve remote frequency synchronization. By reproducing the ground station's frequency standard on the UAV to achieve remote frequency synchronization, the UAV solves the dependence on relay stations or relay satellites in traditional free-space time-frequency synchronization. It can effectively ensure the frequency synchronization accuracy of time-frequency transmission without the need for relay stations or relay satellites. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the drawings used in the description of the embodiments of this application or related technologies will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a flowchart illustrating a remote frequency synchronization method in one embodiment;

[0049] Figure 2 This is a flowchart illustrating the compensation of uplink signals in one embodiment;

[0050] Figure 3 This is a flowchart illustrating the calculation of the upper-level compensation amount in one embodiment;

[0051] Figure 4 This is an example diagram of a remote frequency synchronization method in one embodiment;

[0052] Figure 5 This is a structural block diagram of a remote frequency synchronization device in one embodiment;

[0053] Figure 6 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0055] It should be noted that the terms "first," "second," etc., used in this application can be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from the second element. The terms "comprising" and "having," and any variations thereof, used in this application, are intended to cover non-exclusive inclusion. The term "multiple" used in this application refers to two or more. The term "and / or" used in this application refers to one of the embodiments, or any combination of multiple embodiments.

[0056] To enable those skilled in the art to better understand the embodiments of this application, the terms involved in the embodiments of this application are explained below.

[0057] SI (International System of Units) is a globally unified system of modern measurement standards based on fundamental physical constants. It is based on seven base units: meter, kilogram, second, ampere, kelvin, mole, and candela. Through its derived units and prefixes, it provides precise, consistent, and reproducible measurement benchmarks for science, engineering, trade, and daily life, and is the fundamental basis for ensuring the comparability and accuracy of global measurement results.

[0058] UAV (unmanned aerial vehicle): An aircraft that flies without an operator and relies on remote control or autonomous program control. Its core feature is that it does not require an onboard pilot and is usually controlled by a ground control station, an autopilot system, or a combination of both. It is widely used in various civilian and military fields such as reconnaissance, surveying, transportation, agriculture, and photography.

[0059] Depending on the transmission medium, time and frequency transmission systems include wired links, free-space links, and network links. Wired links typically use optical fibers or coaxial cables as the medium, while free-space links transmit and forward signals through broadcast stations, relay stations, or relay satellites. Internet-based time and frequency transmission is a more general method suitable for scenarios with lower precision requirements.

[0060] Free-space time-frequency synchronization is affected by the curvature of the Earth and the limitations of the horizon. It usually requires the use of broadcasting stations, relay stations or relay satellites for signal transmission and forwarding. It cannot be achieved in the absence of relay stations and when satellites refuse to transmit signals.

[0061] In one exemplary embodiment, such as Figure 1 As shown, a method for off-site frequency synchronization is provided, applicable to ground stations awaiting synchronization that lack underground fiber optic link connections and are not continuously visible to relay stations such as satellites. In this embodiment, the method includes steps 102 to 106. Wherein:

[0062] Step 102: Perform phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, and after phase compensation processing, send a first uplink signal to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard.

[0063] In this embodiment, the ground station to be synchronized is the ground station whose frequency standard needs to be adjusted. The frequency standard of the ground station to be synchronized needs to be adjusted with reference to the frequency standard of a remote ground station. The ground station to be synchronized acts as the control entity and establishes a continuously visible two-way microwave link with the UAV. This two-way microwave link includes an uplink and a downlink. The ground station to be synchronized sends an uplink signal carrying the time-frequency information of the ground station to the UAV via the uplink, using carrier phase as the information transmission medium. Due to the influence of relative position changes and the Doppler effect, the uplink signal introduces a phase change in the uplink, resulting in a phase difference between the uplink signal transmitted by the ground station to be synchronized and the uplink signal received by the UAV.

[0064] Since both the uplink and downlink between the ground station to be synchronized and the UAV introduce phase changes, the phase difference between the uplink and downlink signals at the ground station to be synchronized can be calculated by obtaining the phase of the uplink signal received by the UAV and the phase of the downlink signal fed back by the UAV based on the uplink signal. This phase difference is the total phase change of the bidirectional microwave link between the ground station to be synchronized and the UAV, and it is also the phase compensation amount that the ground station to be synchronized needs to compensate for in the bidirectional microwave link.

[0065] The total phase change includes both uplink and downlink phase changes, requiring separate compensation for each. This can be achieved by determining the carrier angular frequency ratio and allocating the phase compensation proportionally to determine the uplink and downlink phase compensation amounts. The uplink signal is compensated according to the uplink phase compensation amount, and the downlink signal is compensated according to the downlink phase compensation amount. In step 102, based on the uplink signal compensation amount calculated at the ground station to be synchronized, phase compensation processing is performed on the uplink signal of the ground station to be synchronized to eliminate the phase change introduced by the uplink between the ground station to be synchronized and the UAV.

[0066] In step 102, after the ground station to be synchronized performs phase compensation processing on the uplink signal, the ground station to be synchronized sends a first uplink signal to the UAV. The frequency standard of the first uplink signal is the first frequency standard. The phase of the compensated uplink signal on the UAV is equivalent to the phase of the uncompensated uplink signal on the ground station to be synchronized. Correspondingly, the phase of the compensated downlink signal on the ground station to be synchronized is equivalent to the phase of the uncompensated downlink signal on the UAV. Here, the first uplink signal is the uplink signal sent by the ground station to be synchronized to the UAV, and the first frequency standard is the time-frequency standard of the ground station to be synchronized.

[0067] By performing phase compensation processing on the first uplink signal at the ground station to be synchronized, the phase of the first uplink signal received by the UAV is made the same as the phase of the first uplink signal transmitted by the ground station to be synchronized. After the UAV receives the first uplink signal, the frequency standard of the first uplink signal at the UAV is also the first frequency standard, that is, a replica signal of the ground station to be synchronized is established on the UAV. In the above compensation process, the purpose of establishing a replica signal of the ground station to be synchronized is achieved by compensating the uplink signal.

[0068] Through the aforementioned phase compensation, the phase change introduced by the carrier phase in the bidirectional microwave link can be effectively removed, enabling the ground station to be synchronized to construct the reproduction signal of the ground station to be synchronized on the UAV.

[0069] Step 104: Receive the first downlink signal and the second downlink signal sent by the UAV. The first downlink signal is the first uplink signal forwarded by the UAV. The second downlink signal is the second uplink signal forwarded by the UAV. The second uplink signal is the uplink signal sent to the UAV by the remote ground station after performing phase compensation processing on the uplink signal. The frequency standard corresponding to the second uplink signal is the second frequency standard.

[0070] In this embodiment, the ground station to be synchronized performs phase compensation on the uplink signal, sends a first uplink signal to the UAV, and then receives a first downlink signal and a second downlink signal from the UAV. The first downlink signal is the downlink signal fed back by the UAV based on the first uplink signal, and the second downlink signal is the downlink signal fed back by the UAV based on the second uplink signal. The second uplink signal is obtained by the remote ground station performing phase compensation processing on the uplink signal and then sending it to the UAV. A bidirectional microwave link is established between the remote ground station and the UAV, using carrier phase as the information transmission medium to send time and frequency information to the UAV. The second frequency standard of the remote ground station can be used as a reference frequency standard, and the first frequency standard of the ground station to be synchronized can be used as the frequency standard to be synchronized. The first frequency standard is subsequently adjusted according to the second frequency standard. Here, the first downlink signal is the downlink signal fed back by the UAV based on the uplink signal sent by the ground station to be synchronized.

[0071] The remote ground station also needs to establish a replica signal with the same UAV. The specific process is similar to that of the ground station to be synchronized establishing a replica signal on the UAV. The remote ground station detects the phase change of the bidirectional microwave link between the remote ground station and the UAV. Based on the phase change of the bidirectional microwave link between the remote ground station and the UAV, the uplink signal of the remote ground station is phase compensated. After phase compensation, the remote ground station sends a second uplink signal to the UAV. The frequency standard of the second uplink signal at the remote ground station is the second frequency standard. This ensures that the phase of the second uplink signal received by the UAV is the same as that of the UAV to be synchronized. The second uplink signal sent by the ground station is in phase. After the UAV receives the second uplink signal, the frequency standard of the second uplink signal at the UAV is also the second frequency standard, that is, a replica signal of the ground station to be synchronized is established on the UAV. At this time, the frequency standard of the first downlink signal received by the ground station to be synchronized is the frequency standard of the ground station to be synchronized, and the frequency standard of the second downlink signal received by the ground station to be synchronized is the frequency standard of the remote ground station. The second uplink signal here is the uplink signal sent by the remote ground station to the UAV, and the second downlink signal is the downlink signal fed back by the UAV based on the uplink signal sent by the remote ground station. The second frequency standard is the time and frequency standard of the remote ground station.

[0072] Step 106: Based on the first downlink signal and the second downlink signal, adjust the frequency standard of the ground station to be synchronized from the first frequency standard to the second frequency standard.

[0073] In this embodiment, the ground station to be synchronized determines the phase difference between the first downlink signal and the second downlink signal by phase comparison based on the received first downlink signal and second downlink signal. Based on the phase difference, the frequency standard of the ground station to be synchronized is adjusted by frequency shifting, that is, the first time-frequency standard of the ground station to be synchronized is adjusted to the second time-frequency standard of the remote ground station; thus realizing the remote frequency synchronization between the ground station to be synchronized and the remote ground station.

[0074] The aforementioned off-site frequency synchronization method performs phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, thereby establishing a replica signal of the ground station to be synchronized on the UAV. After the UAV receives the phase-compensated first and second uplink signals, the ground station to be synchronized receives the first and second downlink signals from the UAV. Based on the first and second downlink signals, the frequency standard of the ground station to be synchronized is shifted to achieve off-site frequency synchronization. By replicating the ground station's frequency standard on the UAV to achieve off-site frequency synchronization, the UAV solves the dependence on relay stations or relay satellites in traditional free-space time and frequency synchronization. It can effectively ensure the frequency synchronization accuracy of time and frequency transmission without the need for relay stations or relay satellites.

[0075] In one embodiment, such as Figure 2 As shown, in step 102, phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, which may include the following steps 202 to 206, wherein:

[0076] Step 202: Based on the link data obtained by the ground station to be synchronized, determine the first phase before the uplink signal is sent by the ground station to be synchronized, and the second phase after the UAV transmits the downlink signal fed back by the uplink signal to the ground station to be synchronized.

[0077] In this embodiment, the ground station to be synchronized acquires the link data of the bidirectional microwave link between the ground station and the UAV, and extracts the first phase of the uplink signal before the ground station to be synchronized transmits the signal, and the second phase of the downlink signal after the UAV transmits the signal to the ground station to be synchronized based on the feedback of the uplink signal. By directly acquiring the first phase of the transmitted uplink signal and the second phase of the received downlink signal, the phase change of the entire bidirectional microwave link can be determined, as shown in formula (1). The link data includes the uplink carrier angular frequency, downlink carrier angular frequency, the first phase before the uplink signal is transmitted, and the second phase of the received downlink signal of each ground station.

[0078] In this embodiment, to achieve high-precision remote frequency comparison and synchronization based on a UAV platform, the frequency standards of each ground station must first be reproduced on the UAV to achieve frequency synchronization between the ground station and the UAV. Taking a single ground station as an example, the phase of the uplink signal transmitted by the ground station is denoted as... The phase of the downlink signal, which is relayed by the UAV and then received by the ground station, is denoted as... The total compensation introduced by the ground closed-loop control and feedback system is denoted as After the control system locks into a stable state, the phase relationship at the ground station receiver can be expressed as:

[0079]

[0080] Next, the uplink and downlink processes of the signal are analyzed, considering factors such as the constantly changing relative positions between the UAV and the ground station, and the Doppler effect. The carrier phase transmitted from the ground station and received by the UAV after the uplink is... This can be expressed by the following equation:

[0081]

[0082] in, This is the uplink carrier angular frequency. It is the distance from the phase center of the ground station antenna to the phase center of the UAV antenna. It is at the speed of light. Similarly, the phase of the signal transmitted from the ground station, relayed by the drone, and returned to the ground station is... This can be described using the following relationship:

[0083]

[0084] in, Phase drift introduced by the crystal oscillator on the drone This refers to the downlink carrier angular frequency.

[0085] The total compensation amount is denoted as The compensation amount of the uplink signal before the ground station transmits the signal is denoted as... The compensation amount for the received downlink signal is denoted as Due to the phase drift introduced by the crystal oscillator on the drone It is a random quantity and is usually not considered separately during compensation, that is:

[0086]

[0087] The relationship between the compensation amounts satisfies:

[0088]

[0089] Combining equations (1) and (4), the expression for the total compensation at the ground station receiver can be obtained as follows:

[0090]

[0091] Furthermore, to achieve real-time synchronization between the frequency standard phase recovered on the UAV and the ground station frequency standard, the phase received by the UAV should meet the following requirements:

[0092]

[0093] Therefore, we can conclude that:

[0094]

[0095] Combining equations (5), (6), and (8), we obtain:

[0096]

[0097] At this point, the carrier phases compensated by the first phase before the uplink signal is transmitted from the ground station and the second phase after the downlink signal is received by the ground station satisfy the following relationship:

[0098]

[0099] Step 204: Calculate the uplink phase compensation amount based on the first phase and the second phase.

[0100] In this embodiment of the application, the phase difference between the first phase and the second phase is determined by phase comparison based on the first phase and the second phase. The total phase change generated by the ground station to be synchronized during the process of sending an uplink signal to the UAV and receiving the downlink signal fed back by the UAV can be determined as the total phase compensation amount. The uplink phase compensation amount is determined based on the total phase compensation amount, as shown in the above formula (10). The ratio of the uplink phase compensation amount to the downlink phase compensation amount is equal to the ratio of the uplink carrier angular frequency to the downlink carrier angular frequency.

[0101] Therefore, when performing separate compensation for uplink and downlink, the total compensation amount is allocated according to the proportion of carrier angular frequency shown in equation (10). This avoids dealing with time-varying and unobtainable unknowns. The measurement, namely:

[0102]

[0103]

[0104] All terms in equations (11) and (12) are known constants or quantities that can be measured by the ground station. At this time, the phase received by the UAV satisfies equation (7), realizing real-time synchronization between the phase of the clock signal reproduced on the UAV and the phase of the uplink signal transmitted by the ground station.

[0105] Both the ground station to be synchronized and the remote ground station use the above principle to proportionally compensate for uplink and downlink signals, and synchronize the ground signals of the two stations to the UAV in real time, thus achieving:

[0106]

[0107]

[0108] in, The carrier phase received by the UAV from the remote ground station. The carrier phase received by the UAV from the ground station to be synchronized. This refers to the phase of the uplink signal transmitted from a remote ground station. This refers to the phase of the uplink signal transmitted by the ground station to be synchronized. Specifically, the frequency standard of the first downlink signal transmitted by the UAV is the frequency standard of the ground station to be synchronized, and the frequency standard of the second downlink signal transmitted by the UAV is the frequency standard of the remote ground station. After receiving the first and second downlink signals, the ground station to be synchronized can obtain the phase difference and frequency standard difference between the ground station to be synchronized and the remote ground station.

[0109] Step 206: Adjust the phase of the uplink signal according to the uplink phase compensation amount.

[0110] In this embodiment of the application, before the ground station to be synchronized transmits the uplink signal, it adjusts the phase of the uplink signal according to the uplink phase compensation amount to offset the phase change introduced by the uplink.

[0111] In an exemplary embodiment, after performing phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, the method further includes:

[0112] Calculate the downlink phase compensation amount based on the first phase and the second phase;

[0113] The phase of the downlink signal is adjusted based on the downlink phase compensation amount.

[0114] In this embodiment, the ground station to be synchronized determines the total phase change generated during the process of sending an uplink signal to the UAV and receiving a downlink signal from the UAV in a single operation, based on the first phase and the second phase, and uses this as the total phase compensation amount; the downlink phase compensation amount is determined based on the total phase compensation amount; after receiving the downlink signal, the ground station to be synchronized adjusts the phase of the downlink signal according to the downlink phase compensation amount to offset the phase change introduced by the downlink.

[0115] In this embodiment, during a single off-site frequency synchronization, only the uplink signal needs to be adjusted before transmitting the uplink signal to reproduce the frequency standard of the ground station to be synchronized on the UAV; during off-site frequency synchronization closed-loop locking, the ground station to be synchronized needs to perform phase compensation on the downlink signal after receiving the downlink signal to ensure that the frequency standard of the ground station to be synchronized is consistent with the frequency standard of the UAV.

[0116] For example, in an experimental system, when establishing a ground station reproduction signal on a UAV, the ground station may not actually compensate for the downlink signal, but it needs to determine the calculation results of the bidirectional link virtual execution in order to maintain the continuous closed-loop locking of the system so that the phase of the UAV in motion can still maintain the ratio.

[0117] Furthermore, since the data processing of each synchronization cycle depends on the execution result of the previous synchronization cycle in the closed-loop locked state, if only the uplink signal is processed, the uplink compensation result of the previous cycle, plus the bidirectional link change caused by the movement of the UAV in the current cycle, will cause the phase of the uplink and the phase of the downlink in the bidirectional link to no longer maintain a fixed ratio, which will lead to the inability to calculate the compensation amount of the current cycle, and the system will not be able to continue to close the loop, eventually leading to loss of lock.

[0118] Therefore, in each synchronization cycle, the uplink signal needs to be compensated according to the aforementioned uplink phase compensation amount, and the downlink signal needs to be compensated according to the downlink signal compensation amount, so that the carrier angular frequency of the compensated uplink signal and the carrier angular frequency of the downlink signal are still proportional in the next synchronization cycle. Thus, the total amount to be compensated can continue to be allocated according to the carrier angular frequency ratio in the next synchronization cycle, ensuring that the synchronization system can operate in a closed loop according to the same algorithm.

[0119] In one embodiment, such as Figure 3 As shown, in step 204, the uplink phase compensation amount is calculated based on the first phase and the second phase, which may include the following steps 302 to 306:

[0120] Step 302: Calculate the total phase compensation based on the first phase before the uplink signal is sent and the second phase after the downlink signal is transmitted to the ground station to be synchronized.

[0121] In this embodiment of the application, the ground station to be synchronized determines the total phase change generated during the process of sending an uplink signal to the UAV and receiving the downlink signal fed back by the UAV based on the first phase before the uplink signal is sent by the ground station to be synchronized and the second phase after the UAV sends the downlink signal fed back by the uplink signal to the ground station to be synchronized. This total phase change is used as the total phase compensation amount, as shown in the above formula (6).

[0122] Step 304: Calculate the uplink carrier angular frequency ratio based on the uplink carrier angular frequency and the downlink carrier angular frequency.

[0123] In this embodiment, the uplink carrier angular frequency and downlink carrier angular frequency are obtained from the link data. The uplink carrier angular frequency ratio is obtained based on the proportion of the uplink carrier angular frequency in the sum of the uplink carrier angular frequency and the downlink carrier angular frequency, as shown in formula (10).

[0124] Step 306: Calculate the uplink phase compensation amount based on the total phase compensation amount and the uplink carrier angular frequency ratio.

[0125] In this embodiment of the application, the uplink phase compensation amount is allocated from the total phase compensation amount according to the uplink carrier angular frequency ratio, and the uplink signal is phase compensated according to the uplink phase compensation amount. The remaining phase compensation amount is the downlink phase compensation amount, as shown in formula (11).

[0126] In a specific embodiment, the calculation of the uplink phase compensation amount based on the first phase and the second phase in step 204 can be implemented according to the following process:

[0127] A1. Data Acquisition and Phase Determination:

[0128] The phase detection unit of the ground station to be synchronized generates an uplink signal with a defined first phase, driven by its internal frequency source, i.e., the first frequency standard. This uplink signal is transmitted to the UAV. Subsequently, the ground station receives the downlink signal from the UAV. The receiver is phase-locked with the same frequency source to accurately measure the second phase of the downlink signal when it arrives at the ground station.

[0129] A2. Calculate the total phase compensation:

[0130] The signal processing unit of the ground station to be synchronized determines the total phase change of a single round trip link, i.e., the total phase compensation, by calculating the phase difference between the first phase and the second phase. The total phase change includes the phase offset introduced by the uplink, the phase offset introduced by the downlink, and the phase drift generated by the UAV crystal oscillator. The most important factor is the phase delay caused by the change in distance between the antenna center of the ground station to be synchronized and the antenna center of the UAV.

[0131] A3. Obtain the frequency scaling factor:

[0132] The ground station to be synchronized acquires the parameters in the two-way microwave link between the UAV and the UAV, including the uplink carrier angular frequency and the downlink carrier angular frequency, and then calculates the uplink carrier angular frequency scaling factor and the downlink carrier angular frequency scaling factor.

[0133] A4. Allocate uplink phase compensation amount:

[0134] The uplink phase compensation is allocated from the total phase compensation based on the uplink carrier angular frequency scaling factor. This calculation process cleverly avoids direct, high-precision measurement of time-varying distance. It calculates the required uplink compensation value using only the measurable end-to-end phase difference and known frequency parameters.

[0135] A5. Phase Compensation:

[0136] In the next signal transmission cycle, when the transmitter at the ground station generates the uplink signal, it pre-adds an uplink phase compensation amount to its phase. The uplink signal, after this compensation, is then transmitted, which can offset the phase disturbance that will be introduced into the uplink.

[0137] Through steps A1-A5 described above, the ground station can achieve predictive compensation, ensuring that the phase of the signal transmitted from the ground station, after experiencing uplink disturbances, arrives at the UAV precisely at the same phase as the original phase the ground station intended to transmit. This allows for accurate reproduction of the ground station's frequency standard on the UAV. By using bidirectional measurements and frequency ratios, uplink channel disturbances, which are difficult to observe directly, are transformed into quantities that can be calculated using downlink feedback signals.

[0138] After simultaneously replicating the high-precision frequency standards of both the ground station to be synchronized and the remote ground station on the UAV, the ground station to be synchronized simultaneously receives the downlink signals from both stations after they have been relayed on the UAV. Since the microwave links traversed by the downlink signals are almost identical, the phase noise introduced during the downlink process can be largely canceled out by common-mode noise. Therefore, by directly comparing the two signals on the ground station to be synchronized before compensating for downlink phase changes, the following can be obtained:

[0139]

[0140] in, Let be the phase difference. Combining equations (13), (14), and (15), we obtain the phase difference between the uplink signals transmitted by the ground station to be synchronized and the remote ground station:

[0141]

[0142] Based on phase difference By adjusting the frequency standard of the ground station to be synchronized, frequency synchronization between the ground station to be synchronized and the ground station in another location can be achieved.

[0143] In one exemplary embodiment, receiving a first downlink signal and a second downlink signal transmitted by a drone includes:

[0144] At the same time, the first and second downlink signals transmitted by the UAV are received along the same downlink.

[0145] In this embodiment of the invention, the distance between the UAV and the ground station to be synchronized may change over time. The ground station to be synchronized needs to receive the first downlink signal and the second downlink signal sent by the UAV simultaneously along the same downlink to ensure that the downlinks through which the two downlink signals pass are the same, thereby enabling the phase change introduced by the two downlink signals in the downlink to be canceled out by common mode.

[0146] In an exemplary embodiment, adjusting the frequency standard of the ground station to be synchronized from the first frequency standard to the second frequency standard based on the first downlink signal and the second downlink signal may include:

[0147] The phase difference between the first uplink signal and the second uplink signal is determined based on the first downlink signal and the second downlink signal;

[0148] Based on the phase difference, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0149] In this embodiment, when a UAV uses the same antenna or beam to transmit two signals, and the downlink carrier frequency and polarization of the two signals are the same, and their propagation paths almost overlap, it can be considered that the downlink channels they experience are highly consistent. This condition is easily met when the UAV is a point source and the ground station to be synchronized is far away from the UAV. The ground station to be synchronized receives the first downlink signal and the second downlink signal from the UAV. Since the microwave links traversed by the downlink signals are almost completely identical, the phase noise introduced by the first downlink signal and the second downlink signal during the downlink process cancels out in common mode. Therefore, the phase difference between the first downlink signal and the second downlink signal can be directly compared. Based on the phase difference, the first frequency standard of the ground station to be synchronized is adjusted by frequency shifting, and the first frequency standard of the ground station to be synchronized is adjusted to the second frequency standard.

[0150] To enable those skilled in the art to better understand the embodiments of this application, the embodiments of this application are described below through specific examples.

[0151] The off-site frequency synchronization method proposed in the embodiments of this application, such as Figure 4 As shown, ground station A and ground station B establish a continuously visible bidirectional microwave link with the UAV. Ground station A acts as a remote ground station, and ground station B acts as a ground station to be synchronized. The carrier phase is used as the information transmission medium. The ground stations detect the phase change introduced by the bidirectional microwave link in real time, and compensate for the phase changes of each uplink and downlink signal based on the real-time detection results. This ensures that the phase of the uplink signal sent to the UAV by each ground station is the same as the phase of the uplink signal of each ground station before transmission, thus achieving the goal of reproducing the high-precision frequency standard of the ground on the UAV.

[0152] The remote ground station serves as a reference station, performing the exact same local closed-loop compensation process as the aforementioned ground station awaiting synchronization. Its purpose is to independently and accurately reproduce its own second frequency standard on the UAV. In this scheme, the UAV primarily acts as a transparent, low-additional-phase-noise relay platform. Its functions include:

[0153] Reception: Simultaneously receive uplink signals from ground station A and ground station B, which have undergone their respective uplink phase compensation.

[0154] Processing and forwarding: The received signal undergoes pre-programmed processing such as low-noise amplification and frequency conversion. The key point is that the UAV does not need to perform complex phase calculations or compensation; its task is to broadcast or separately transmit the received signal, which already carries ground station phase information, back to the ground with minimal additional phase distortion.

[0155] Signal generation: The UAV transmits the reproduced signals from stations A and B to the ground station B to be synchronized via the same downlink carrier link. This ensures the subsequent common-mode cancellation condition.

[0156] After simultaneously replicating the high-precision frequency standards of ground station A and ground station B on the UAV, ground station B simultaneously receives the second downlink signal relayed by the UAV from ground station A and the first downlink signal relayed by ground station B on the UAV. Since the microwave links through which the two downlink signals pass are almost identical, the phase noise introduced during the downlink process cancels out. Therefore, by directly comparing the two downlink signals, which have not yet been compensated for the phase changes of the downlink signals, at ground station B, the phase difference between the high-precision frequency standards of ground station A and ground station B can be obtained. By adjusting the frequency standard of ground station B according to the phase difference, frequency synchronization between ground station A and ground station B can be achieved.

[0157] In one specific embodiment, a complete synchronization cycle can be described as follows:

[0158] B1. Initialization and Link Establishment:

[0159] The drone flies to the common communication airspace of ground station A and ground station B. The two ground stations establish stable two-way microwave links with the drone and negotiate or determine the communication frequency.

[0160] B2, Independent Local Closed Loop:

[0161] Ground station A and ground station B each run the closed-loop process of steps A1-A5 independently and in parallel, and reproduce the frequency standards of ground station A and ground station B on the UAV terminal.

[0162] B3. Downlink forwarding comparison:

[0163] 1. The drone will transmit the reproduced signals from stations A and B downlink to ground station B.

[0164] 2. Ground station B performs common-mode comparison to obtain the phase difference.

[0165] 3. Ground station B adjusts its own frequency standard based on this phase difference.

[0166] B4. Closed-loop locking and maintenance:

[0167] Steps B2 and B3 form a larger new closed loop. The frequency modulation action of ground station B in step B3 slightly alters its transmitted uplink signal, thus affecting the local closed-loop measurement in step B2. After several iterations, the entire system will enter a stable locked state, at which point the frequency standard of ground station B is synchronized with that of ground station A, and the two reproduced signals on the UAV are also synchronized.

[0168] The calculation process involved in the above synchronization period is as follows:

[0169] Ground station B sends the first uplink signal to the UAV, the carrier angular frequency of which is... Phase is (The carrier angular frequency can be set by ground station B, and the phase can be acquired, calculated, and recorded by ground station B in real time.) The first uplink signal is sent from ground station B to the UAV, passing through a free-space link with a link length of [length missing]. , It changes in real time and cannot be directly measured. The phase change of the first uplink signal is introduced. The phase of the first uplink signal received by the UAV is shown in formula (2).

[0170] After receiving the first uplink signal, the UAV performs on-board mixing and forwarding, which introduces phase drift of the on-board crystal oscillator during the forwarding process. The first downlink signal is obtained, and the phase of the signal after mixing and forwarding becomes... Meanwhile, the carrier angular frequency of the first downlink signal after mixing becomes The first downlink signal passes through the same link. The signal is sent back to ground station B. The phase of the first downlink signal received by the ground station is shown in formula (3).

[0171] The phase drift of the crystal oscillator on the UAV in equation (3) It is a random quantity that is difficult to measure and separate, and is usually not considered separately. That is, the phase of the first downlink signal received by ground station B is shown in formula (4).

[0172] Ground station B transmits the first uplink signal phase Phase of the first downlink signal received By collecting and calculating data, the total amount to be compensated introduced by the uplink and downlink can be obtained. As shown in formula (1);

[0173] Formulas (5) and (6) can be obtained from formulas (1) and (4).

[0174] Based on link modeling analysis, to ensure that the first uplink signal phase received by the UAV is... Phase of the first uplink signal transmitted from the ground Synchronization, the compensation amount for the first uplink signal is given by formula (8).

[0175] If ground station B compensates before the first uplink signal is transmitted The phase of the first uplink signal received by the UAV is shown in formula (7).

[0176] It can achieve synchronization between the frequency signal reproduced on the UAV and the frequency standard of the ground station.

[0177] Meanwhile, in order to ensure that the UAV can maintain synchronization between the UAV signal and the ground station signal for a long time under dynamic conditions, the system needs to continuously perform closed-loop compensation, that is, real-time compensation for both the uplink and downlink. According to formulas (5), (6), and (8), when the system performs closed-loop compensation and runs continuously, the amount to be compensated for the first downlink signal is shown in formula (9).

[0178] At this time, the amount to be compensated for in the first uplink signal The amount to be compensated for in the first downlink signal The proportional relationship related to the signal frequency is shown in formula (10).

[0179] Therefore, data can be collected directly from ground station B. , get Then, using the known proportional relationships right Distribute the data so that it can be measured. The uplink and downlink compensation amounts are obtained as shown in formulas (11) and (12).

[0180] At this time, based on the uplink compensation amount Compensating for the first uplink signal allows for the reproduction of the ground station's frequency signal on the UAV; then, based on the downlink compensation amount... Compensating for the first downlink signal enables long-term closed-loop effective operation of the system, ensuring that the phase changes introduced by the UAV's motion in the next cycle and the uplink and downlink compensation quantities maintain a definite proportional relationship. Ultimately, this achieves real-time synchronization between the UAV's first frequency standard and the ground frequency standard.

[0181] During synchronization, ground station B needs to perform the following operations: acquire the phase of the first uplink signal transmitted. Phase of the first downlink signal received Calculate the total compensation amount The uplink and downlink compensation amounts are calculated based on the ratio between the total compensation amount and the carrier angular frequency. and Execute on the first uplink signal The compensation operation must be performed correctly for the first uplink signal and for the first downlink signal. The compensation operation for the first downlink signal may not be actually performed, but a virtual compensation calculation result is required to keep the system in a closed loop.

[0182] At the same time, the same UAV frequency reproduction process is performed on ground station A in a different location to reproduce the second uplink signal, the second frequency standard, and the second downlink signal. The first downlink signal and the second downlink signal are then sent to ground station B, and the phase difference between the two downlink signals received by ground station B is recorded.

[0183] Since the reproduced signals from the two ground stations on the UAV have passed through the same forwarding stage and the same downlink, the phase noise of the forwarding stage and the downlink can be considered to be approximately common-mode canceling. Therefore, the phase difference between the two downlink signals received by ground station B is equal to the phase difference between the first frequency standard and the second frequency standard.

[0184] Meanwhile, since the ground frequency standard is reproduced on the UAV, the phase difference is also equal to the phase difference of the ground frequency standards transmitted by the two stations.

[0185] As can be seen from the above derivation process, the phase difference between the first downlink signal and the second downlink signal received by the ground station is the phase difference between the frequency standards of the two stations. By shifting the frequency standard of the ground station B to be synchronized according to the phase difference, frequency synchronization between different locations can be achieved.

[0186] The specific execution steps are as follows:

[0187] 1. Ground station A and ground station B respectively detect the phase change on their respective bidirectional microwave links; each ground station sends uplink signals to the UAV, receives downlink signals fed back by the UAV based on the uplink signals, calculates the phase change of the uplink and downlink signals, corresponding to formula (1), the total phase compensation in formula (1) is the total phase change to be confirmed, that is, the phase change of the downlink signal received by the ground station compared to the phase change of the uplink signal transmitted by the ground station;

[0188] The ground station determines the phase change introduced by its bidirectional microwave link based on the phase of the transmitted uplink signal and the phase of the received downlink signal. The total phase change is the difference between the phase of the downlink signal received by the ground station and the phase of the uplink signal before transmission.

[0189] 2. Ground station A and ground station B compensate for the uplink signal based on the phase change; based on the phase change introduced by the bidirectional microwave link, determine the uplink phase compensation amount of the uplink signal, and compensate for each uplink signal based on the uplink phase compensation amount.

[0190] 2.1 Determine the ratio of uplink carrier angular frequency to downlink carrier angular frequency in each ground station link. Based on the ratio of uplink carrier angular frequency to downlink carrier angular frequency, determine the uplink compensation amount for each ground station link according to the phase change. Allocate the total compensation amount according to the carrier angular frequency ratio and compensate for the uplink and downlink separately.

[0191] 2.2 The uplink signal is compensated based on the uplink phase compensation amount, and the downlink signal is compensated based on the downlink phase compensation amount, so as to realize the reproduction of the frequency standards of each ground station on the UAV. The calculation and compensation are completed by each ground station, and the UAV is only involved in signal transmission and reception.

[0192] 3. Ground station B receives downlink signals from the UAV that reproduce the signals from ground station A and ground station B respectively. It directly compares the two downlink signals to determine the phase difference. Based on the phase difference, the time and frequency standard of ground station B is adjusted. Since ground station B receives two signals from the same downlink, the phase noise between the two signals can cancel each other out. The two signals are directly compared without compensating for the phase change of the downlink. The resulting phase difference is the phase difference between the frequency standard of ground station B and the frequency standard of ground station A. The time and frequency standard of ground station B is shifted according to the phase difference. After the shift, the time and frequency standards of the two ground stations are consistent and the frequencies are consistent.

[0193] The uplink and downlink signals can be continuous waveguide signals or communication signals modulated with data, as long as their carrier phase can be detected and tracked with high precision.

[0194] The calculation and updating of the uplink phase compensation can be periodic, with a period much smaller than the correlation time of channel changes (such as UAV movement and atmospheric disturbances) to achieve real-time tracking.

[0195] Frequency synchronization is not limited to two ground stations. A UAV can simultaneously act as a common relay for multiple (more than two) ground stations. Any ground station wishing to synchronize with a reference station only needs to receive and compare its own downlink repeating signals from the reference station.

[0196] In practical systems, if the common-mode conditions of the downlink are not ideal, an initial calibration phase can be introduced. For example, when ground station B knows its own phase, calibration can be performed by measuring the downlink phase deviation of a single signal, or digital signal processing techniques can be used to estimate and subtract residual non-common-mode errors in subsequent comparisons.

[0197] Compared to fiber optic time and frequency synchronization, the off-site frequency synchronization method based on a UAV platform offers controllable costs and is suitable for scenarios requiring mobility or frequent changes. Furthermore, this method can still be implemented even without a relay station and in situations where satellite rejection is possible, making its application scenarios more flexible and adaptable compared to conventional free-space time and frequency synchronization based on relay stations or satellites. In addition, this scheme achieves high off-site frequency comparison accuracy, potentially reaching picosecond levels, thus enabling high off-site frequency synchronization accuracy, exceeding that of network clock synchronization.

[0198] The off-site frequency synchronization proposed in this application provides an efficient solution for high-precision off-site frequency comparison and synchronization, realizing frequency synchronization between UAVs and multiple ground stations. This can promote the development of high-precision integrated air-space-ground time and frequency synchronization networks and is expected to be further applied to future time and frequency transmission systems based on UAV platforms. This method can be used for mutual comparison of time and frequency references among multiple ground stations, as well as for the distribution of time and frequency references. For example, when two ground stations have good frequency references to compare, a UAV can be used as a relay station for frequency reproduction, with each station receiving signals from the other station transmitted by the UAV for real-time comparison. If each ground station has only a small number of high-performance time and frequency references, the time and frequency reference reproduced by the UAV can be distributed, and other ground stations receive the signals, reproduce them, and use them for internal reference, thus achieving time and frequency reference sharing.

[0199] It should be understood that although the steps in the flowcharts of the embodiments described above are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some steps in the flowcharts of the embodiments described above may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these steps or stages is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the steps or stages of other steps.

[0200] Based on the same inventive concept, this application also provides a remote frequency synchronization system for implementing the aforementioned remote frequency synchronization method. The solution provided by this system is similar to the implementation scheme described in the above method; therefore, the specific limitations in one or more remote frequency synchronization system embodiments provided below can be found in the limitations of the remote frequency synchronization method described above, and will not be repeated here.

[0201] In one exemplary embodiment, a remote frequency synchronization system is provided, comprising a ground station to be synchronized, a remote ground station, and a drone, wherein:

[0202] The ground station to be synchronized is used to perform phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, and after the phase compensation processing, it sends a first uplink signal to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard.

[0203] The remote ground station is used to perform phase compensation processing on the uplink signal between the remote ground station and the UAV, and after phase compensation processing, it sends a second uplink signal to the UAV. The frequency standard of the second uplink signal is the second frequency standard. After the second uplink signal is transmitted to the UAV, the corresponding frequency standard is the second frequency standard.

[0204] The drone is used to send first and second downlink signals to the ground station to be synchronized.

[0205] The ground station to be synchronized is also used to adjust the frequency standard from the first frequency standard to the second frequency standard based on the first downlink signal and the second downlink signal.

[0206] In one embodiment, phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, including:

[0207] Based on the link data obtained by the ground station to be synchronized, determine the first phase before the uplink signal is sent by the ground station to be synchronized, and the second phase after the UAV transmits the downlink signal fed back by the uplink signal to the ground station to be synchronized.

[0208] Calculate the uplink phase compensation amount based on the first phase and the second phase;

[0209] The phase of the uplink signal is adjusted based on the uplink phase compensation amount.

[0210] In one embodiment, after performing phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, the method further includes:

[0211] Calculate the downlink phase compensation amount based on the first phase and the second phase;

[0212] The phase of the downlink signal is adjusted based on the downlink phase compensation amount.

[0213] In one embodiment, the uplink phase compensation amount is calculated based on the first phase and the second phase, including:

[0214] Calculate the total phase compensation based on the first phase and the second phase;

[0215] Calculate the uplink carrier angular frequency ratio based on the uplink carrier angular frequency and downlink carrier angular frequency extracted from the link data;

[0216] The uplink phase compensation is calculated based on the total phase compensation and the uplink carrier angular frequency ratio.

[0217] In one embodiment, adjusting the frequency standard of the ground station to be synchronized from the first frequency standard to the second frequency standard based on the first downlink signal and the second downlink signal includes:

[0218] The phase difference between the first uplink signal and the second uplink signal is determined based on the first downlink signal and the second downlink signal;

[0219] Based on the phase difference, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0220] Based on the same inventive concept, this application also provides a remote frequency synchronization device for implementing the aforementioned remote frequency synchronization method. The solution provided by this device is similar to the implementation described in the above method; therefore, the specific limitations in one or more remote frequency synchronization device embodiments provided below can be found in the limitations of the remote frequency synchronization method described above, and will not be repeated here.

[0221] In one exemplary embodiment, such as Figure 5 As shown, a remote frequency synchronization device 500 is provided, including a phase compensation module 502, a receiving module 504, and a frequency modulation module 506, wherein:

[0222] The phase compensation module 502 is used to perform phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, and after the phase compensation processing, it sends a first uplink signal to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard.

[0223] The receiving module 504 is used to receive a first downlink signal and a second downlink signal sent by the UAV. The first downlink signal is a first uplink signal forwarded by the UAV. The second downlink signal is a second uplink signal forwarded by the UAV. The second uplink signal is an uplink signal sent to the UAV by a remote ground station after performing phase compensation processing on the uplink signal. The frequency standard corresponding to the second uplink signal is the second frequency standard.

[0224] The frequency modulation module 506 is used to adjust the frequency standard of the ground station to be synchronized from the first frequency standard to the second frequency standard based on the first downlink signal and the second downlink signal.

[0225] In one embodiment, phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, including:

[0226] Based on the link data obtained by the ground station to be synchronized, determine the first phase before the uplink signal is sent by the ground station to be synchronized, and the second phase after the UAV transmits the downlink signal fed back by the uplink signal to the ground station to be synchronized.

[0227] Calculate the uplink phase compensation amount based on the first phase and the second phase;

[0228] The phase of the uplink signal is adjusted based on the uplink phase compensation amount.

[0229] In one embodiment, after performing phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, the method further includes:

[0230] Calculate the downlink phase compensation amount based on the first phase and the second phase;

[0231] The phase of the downlink signal is adjusted based on the downlink phase compensation amount.

[0232] In one embodiment, the uplink phase compensation amount is calculated based on the first phase and the second phase, including:

[0233] Calculate the total phase compensation based on the first phase and the second phase;

[0234] Calculate the uplink carrier angular frequency ratio based on the uplink carrier angular frequency and downlink carrier angular frequency extracted from the link data;

[0235] The uplink phase compensation is calculated based on the total phase compensation and the uplink carrier angular frequency ratio.

[0236] In one embodiment, adjusting the frequency standard of the ground station to be synchronized from the first frequency standard to the second frequency standard based on the first downlink signal and the second downlink signal includes:

[0237] The phase difference between the first uplink signal and the second uplink signal is determined based on the first downlink signal and the second downlink signal;

[0238] Based on the phase difference, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0239] Each module in the aforementioned remote frequency synchronization device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in the processor of a computer device in hardware form or independent of it, or stored in the memory of a computer device in software form, so that the processor can call and execute the corresponding operations of each module.

[0240] In one exemplary embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as follows: Figure 6As shown, this computer device includes a processor, memory, input / output (I / O) interfaces, and a communication interface. The processor, memory, and I / O interfaces are connected via a system bus, and the communication interface is also connected to the system bus via the I / O interfaces. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system, computer programs, and a database. The internal memory provides the environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The database stores link data and frequency standard data. The I / O interfaces are used for exchanging information between the processor and external devices. The communication interface is used for communication with external terminals via a network connection. When executed by the processor, the computer program implements a remote frequency synchronization method.

[0241] Those skilled in the art will understand that Figure 6 The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0242] In one exemplary embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor executes the computer program to perform the following steps:

[0243] Phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, and after phase compensation processing, a first uplink signal is sent to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard.

[0244] The system receives a first downlink signal and a second downlink signal sent by the UAV. The first downlink signal is a first uplink signal forwarded by the UAV. The second downlink signal is a second uplink signal forwarded by the UAV. The second uplink signal is an uplink signal sent to the UAV by a remote ground station after performing phase compensation processing on the uplink signal. The frequency standard corresponding to the second uplink signal is the second frequency standard.

[0245] Based on the first downlink signal and the second downlink signal, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0246] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0247] Based on the link data obtained by the ground station to be synchronized, determine the first phase before the uplink signal is sent by the ground station to be synchronized, and the second phase after the UAV transmits the downlink signal fed back by the uplink signal to the ground station to be synchronized.

[0248] Calculate the uplink phase compensation amount based on the first phase and the second phase;

[0249] The phase of the uplink signal is adjusted based on the uplink phase compensation amount.

[0250] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0251] Calculate the downlink phase compensation amount based on the first phase and the second phase;

[0252] The phase of the downlink signal is adjusted based on the downlink phase compensation amount.

[0253] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0254] Calculate the total phase compensation based on the first phase and the second phase;

[0255] Calculate the uplink carrier angular frequency ratio based on the uplink carrier angular frequency and downlink carrier angular frequency extracted from the link data;

[0256] The uplink phase compensation is calculated based on the total phase compensation and the uplink carrier angular frequency ratio.

[0257] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0258] At the same time, the first downlink signal and the second downlink signal transmitted by the UAV are received along the same downlink.

[0259] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0260] The phase difference between the first uplink signal and the second uplink signal is determined based on the first downlink signal and the second downlink signal;

[0261] Based on the phase difference, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0262] In one embodiment, a computer-readable storage medium is provided having a computer program stored thereon, the computer program performing the following steps when executed by a processor:

[0263] Phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, and after phase compensation processing, a first uplink signal is sent to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard.

[0264] The system receives a first downlink signal and a second downlink signal sent by the UAV. The first downlink signal is a first uplink signal forwarded by the UAV. The second downlink signal is a second uplink signal forwarded by the UAV. The second uplink signal is an uplink signal sent to the UAV by a remote ground station after performing phase compensation processing on the uplink signal. The frequency standard corresponding to the second uplink signal is the second frequency standard.

[0265] Based on the first downlink signal and the second downlink signal, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0266] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0267] Based on the link data obtained by the ground station to be synchronized, determine the first phase before the uplink signal is sent by the ground station to be synchronized, and the second phase after the UAV transmits the downlink signal fed back by the uplink signal to the ground station to be synchronized.

[0268] Calculate the uplink phase compensation amount based on the first phase and the second phase;

[0269] The phase of the uplink signal is adjusted based on the uplink phase compensation amount.

[0270] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0271] Calculate the downlink phase compensation amount based on the first phase and the second phase;

[0272] The phase of the downlink signal is adjusted based on the downlink phase compensation amount.

[0273] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0274] Calculate the total phase compensation based on the first phase and the second phase;

[0275] Calculate the uplink carrier angular frequency ratio based on the uplink carrier angular frequency and downlink carrier angular frequency extracted from the link data;

[0276] The uplink phase compensation is calculated based on the total phase compensation and the uplink carrier angular frequency ratio.

[0277] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0278] At the same time, the first downlink signal and the second downlink signal transmitted by the UAV are received along the same downlink.

[0279] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0280] The phase difference between the first uplink signal and the second uplink signal is determined based on the first downlink signal and the second downlink signal;

[0281] Based on the phase difference, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0282] In one embodiment, a computer program product is provided, including a computer program that, when executed by a processor, performs the following steps:

[0283] Phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, and after phase compensation processing, a first uplink signal is sent to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard.

[0284] The system receives a first downlink signal and a second downlink signal sent by the UAV. The first downlink signal is a first uplink signal forwarded by the UAV. The second downlink signal is a second uplink signal forwarded by the UAV. The second uplink signal is an uplink signal sent to the UAV by a remote ground station after performing phase compensation processing on the uplink signal. The frequency standard corresponding to the second uplink signal is the second frequency standard.

[0285] Based on the first downlink signal and the second downlink signal, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0286] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0287] Based on the link data obtained by the ground station to be synchronized, determine the first phase before the uplink signal is sent by the ground station to be synchronized, and the second phase after the UAV transmits the downlink signal fed back by the uplink signal to the ground station to be synchronized.

[0288] Calculate the uplink phase compensation amount based on the first phase and the second phase;

[0289] The phase of the uplink signal is adjusted based on the uplink phase compensation amount.

[0290] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0291] Calculate the downlink phase compensation amount based on the first phase and the second phase;

[0292] The phase of the downlink signal is adjusted based on the downlink phase compensation amount.

[0293] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0294] Calculate the total phase compensation based on the first phase and the second phase;

[0295] Calculate the uplink carrier angular frequency ratio based on the uplink carrier angular frequency and downlink carrier angular frequency extracted from the link data;

[0296] The uplink phase compensation is calculated based on the total phase compensation and the uplink carrier angular frequency ratio.

[0297] In one embodiment, the processor, when executing a computer program, also performs the following steps:

[0298] At the same time, the first downlink signal and the second downlink signal transmitted by the UAV are received along the same downlink.

[0299] In one embodiment, when the computer program is executed by a processor, it also performs the following steps:

[0300] The phase difference between the first uplink signal and the second uplink signal is determined based on the first downlink signal and the second downlink signal;

[0301] Based on the phase difference, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

[0302] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0303] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. Any references to memory, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile memory and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM). The databases involved in the embodiments provided in this application may include at least one type of relational database and non-relational database. Non-relational databases may include, but are not limited to, blockchain-based distributed databases. The processors involved in the embodiments provided in this application may be general-purpose processors, central processing units, graphics processing units, digital signal processors, programmable logic devices, quantum computing-based data processing logic devices, artificial intelligence (AI) processors, etc., and are not limited to these.

[0304] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this application.

[0305] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method of frequency synchronization over a distance, the method comprising: Applicable to ground stations awaiting synchronization, including: Phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, and after the phase compensation processing, a first uplink signal is sent to the UAV. The frequency standard of the first uplink signal is the first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard. The system receives a first downlink signal and a second downlink signal sent by the UAV. The first downlink signal is the first uplink signal forwarded by the UAV. The second downlink signal is the second uplink signal forwarded by the UAV. The second uplink signal is the uplink signal sent to the UAV by a remote ground station after performing the phase compensation processing on the uplink signal. The frequency standard corresponding to the second uplink signal is the second frequency standard. Based on the first downlink signal and the second downlink signal, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

2. The method of claim 1, wherein, Phase compensation processing is performed on the uplink signal between the ground station to be synchronized and the UAV, including: Based on the link data obtained by the ground station to be synchronized, determine the first phase before the uplink signal is sent by the ground station to be synchronized, and the second phase after the UAV transmits the downlink signal fed back by the uplink signal to the ground station to be synchronized. Calculate the uplink phase compensation amount based on the first phase and the second phase; The phase of the uplink signal is adjusted according to the uplink phase compensation amount.

3. The method of claim 2, wherein, After performing phase compensation processing on the uplink signal between the ground station and the UAV, the process also includes: Calculate the downlink phase compensation amount based on the first phase and the second phase; The phase of the downlink signal is adjusted according to the downlink phase compensation amount.

4. The method of claim 2, wherein, Based on the first phase and the second phase, the uplink phase compensation amount is calculated, including: Calculate the total phase compensation based on the first phase and the second phase; Calculate the uplink carrier angular frequency ratio based on the uplink carrier angular frequency and downlink carrier angular frequency extracted from the link data; The uplink phase compensation amount is calculated based on the total phase compensation amount and the uplink carrier angular frequency ratio.

5. The method of claim 1, wherein, Receiving the first downlink signal and the second downlink signal transmitted by the UAV includes: At the same time, the first downlink signal and the second downlink signal transmitted by the UAV are received along the same downlink.

6. The method of claim 1, wherein, Based on the first downlink signal and the second downlink signal, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard, including: Based on the first downlink signal and the second downlink signal, determine the phase difference between the first uplink signal and the second uplink signal; Based on the phase difference, the frequency standard of the ground station to be synchronized is adjusted from the first frequency standard to the second frequency standard.

7. A remote frequency synchronization system, characterized by, The system includes a ground station to be synchronized, a remote ground station, and a drone, wherein: The ground station to be synchronized is used to perform phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, and after the phase compensation processing, send a first uplink signal to the UAV. The frequency standard of the first uplink signal is a first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard. The remote ground station is used to perform phase compensation processing on the uplink signal between the remote ground station and the UAV, and after the phase compensation processing, send a second uplink signal to the UAV. The frequency standard of the second uplink signal is the second frequency standard. After the second uplink signal is transmitted to the UAV, the corresponding frequency standard is the second frequency standard. The drone is used to send a first downlink signal and a second downlink signal to the ground station to be synchronized. The ground station to be synchronized is also used to adjust the frequency standard from the first frequency standard to the second frequency standard based on the first downlink signal and the second downlink signal.

8. A device for frequency synchronization at a remote site, characterized by It includes a phase compensation module, a receiving module, and a frequency modulation module, wherein: The phase compensation module is used to perform phase compensation processing on the uplink signal between the ground station to be synchronized and the UAV, and after the phase compensation processing, send a first uplink signal to the UAV. The frequency standard of the first uplink signal is a first frequency standard. After the first uplink signal is transmitted to the UAV, the corresponding frequency standard is the first frequency standard. The receiving module is used to receive a first downlink signal and a second downlink signal sent by the UAV. The first downlink signal is the first uplink signal forwarded by the UAV. The second downlink signal is the second uplink signal forwarded by the UAV. The second uplink signal is the uplink signal sent to the UAV by a remote ground station after performing the phase compensation processing on the uplink signal. The frequency standard corresponding to the second uplink signal is the second frequency standard. The frequency modulation module is used to adjust the frequency standard of the ground station to be synchronized from the first frequency standard to the second frequency standard based on the first downlink signal and the second downlink signal.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 6.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

11. A computer program product comprising a computer program, characterized in that, When the computer program is executed by a processor, it implements the steps of the method according to any one of claims 1 to 6.

Images