Same-time and same-frequency time synchronization system and interference cancellation method

Abstract

The invention discloses an interference elimination method for a same-time and same-frequency time synchronization system, which is suitable for a microwave time synchronization networking system and is characterized in that radio frequency domain self-interference cancellation is carried out before a signal received by a receiving end of a time synchronization networking node from an antenna enters a low noise amplifier; the introduced offset signal is obtained by coupling a part of a transmitting signal before the transmitting end enters an antenna from the transmitting end of the node, and correcting amplitude, time delay and phase through radio frequency reconstruction. The invention further discloses a same-time and same-frequency time synchronization system, the time synchronization networking node comprises a transmitting end, and a receiving end is connected to a receiving and transmitting antenna through a circulator; and a radio frequency self-interference suppression module is arranged between a first port of the circulator connected with the output of the transmitting end and a third port of the circulator connected with the input of the receiving end to sample a radio frequency signal output by the transmitting end and then realize radio frequency reconstruction, so as to generate an offset signal to be coupled to the input of the receiving end.

Description

Technical Field

[0001] The present application relates to the technical field of time synchronization, and in particular to a simultaneous and co-frequency time synchronization system and an interference cancellation method. Background Art

[0002] High-precision time and frequency transmission is of great significance in the fields of aerospace, navigation and positioning, transportation, etc. At present, high-precision time comparison systems often need to work in dynamic collaborative networking systems, such as unmanned aerial vehicle dynamic networking systems. Existing multi-node time synchronization networking systems usually use time division duplexing, frequency division duplexing and other time synchronization methods to transmit time comparison signals. However, these transmission methods have low spectrum utilization, long network construction time when large-scale nodes are synchronized, and slow node access speed.

[0003] The simultaneous frequency synchronization networking mode can support the sending and receiving of time comparison signals at the same frequency band and at the same time, which can greatly improve the spectrum utilization efficiency. However, the transmitter of the full-duplex time synchronization mode will generate strong self-interference to the receiver, resulting in the receiver being unable to demodulate the time comparison signal normally. Therefore, in the simultaneous frequency full-duplex time synchronization networking system, it is necessary to cancel the interference of the self-interference time comparison signal. Summary of the invention

[0004] The present application proposes a simultaneous and same-frequency time synchronization system and an interference cancellation method, which belongs to a simultaneous and same-frequency full-duplex microwave two-way time-frequency transmission networking system, solves the self-interference problem, realizes the self-interference suppression of the local received signal in the synchronous networking system, and is used to improve the transmission speed of the time comparison signal transmission in the microwave two-way time-frequency transmission networking system, as well as the spectrum utilization rate of the system.

[0005] An embodiment of the present application provides a simultaneous and same-frequency time synchronization system, wherein a time synchronization networking node includes a transmitting end and a receiving end connected to a transceiver antenna via a circulator.

[0006] A radio frequency self-interference suppression module is arranged between the first port of the circulator connected to the output of the transmitting end and the second port of the circulator connected to the input of the receiving end. The second port of the circulator receives the transmitting antenna.

[0007] The RF self-interference suppression module is used to sample the RF signal output by the transmitter to achieve RF reconstruction, and generate a cancellation signal to couple to the input of the receiver; the RF reconstruction includes delay, phase shift and amplitude attenuation.

[0008] In one embodiment, the RF self-interference suppression module includes multiple RF reconstruction functions, and each RF reconstruction function can adjust at least one of the following performance quantities: delay, phase shift, and amplitude attenuation.

[0009] In one embodiment, the RF reconstruction function of any one channel is implemented by a delay device, a phase shifter and an attenuator connected in series.

[0010] In one embodiment, the radio frequency self-interference suppression module includes a two-channel radio frequency reconstruction module.

[0011] In one embodiment, the RF reconstruction function of any one channel is realized by a delay device, a phase shifter and an attenuator connected in series, and the performance parameters of the delay device, the phase shifter and the attenuator are adjustable.

[0012] The embodiment of the present application also proposes a method for eliminating interference in a simultaneous and co-frequency time synchronization system, which is applicable to a microwave time synchronization networking system. The method includes: At the receiving end of the time synchronization networking node, the signal received from the antenna is offset by RF self-interference before entering the low noise amplifier, introducing the offset signal It is obtained by coupling out a part of the transmission signal from the transmitting end of the node before it enters the antenna, and correcting the amplitude, delay and phase through RF reconstruction.

[0013] In one embodiment, two channels are used to perform self-interference signal reconstruction.

[0014] In one embodiment, multiple radio frequency reconstruction functions are included, and each radio frequency reconstruction function can adjust at least one of the following performance quantities: delay, phase shift, and amplitude attenuation.

[0015] In one embodiment, the RF reconstruction function of any one channel is implemented by a delay device, a phase shifter and an attenuator connected in series, and the performance parameters of the delay device, the phase shifter and the attenuator are adjusted so that the remaining self-interference signal is less than a set threshold.

[0016] In one embodiment, the remaining self-interference signal is processed using a baseband self-interference time ratio signal suppression method.

[0017] At least one of the above technical solutions adopted in the embodiments of the present application can achieve the following beneficial effects: The present invention applies direct radio frequency self-interference time comparison signal suppression technology to a time synchronization system. The method can improve spectrum utilization and improve the interference suppression capability of the radio frequency end in a simultaneous and co-frequency time synchronization system.

[0018] The present invention proposes a method for canceling the self-interference of time comparison signals based on the radio frequency domain for a simultaneous and same-frequency time-synchronized microwave networking system. The present invention reconstructs the self-interference time comparison signal generated by the transmitter in the radio frequency domain of the time synchronization module, and reconstructs the self-interference signal by controlling the phase shifter, attenuator and delay device, thereby canceling out the cancellation signal generated by the transmitter relative to the receiver. Compared with the existing methods, it has innovation in principle. At present, the time synchronization networking system mainly adopts the frequency division duplex time synchronization method and the time division duplex time synchronization method. This method has low spectrum resource utilization, slow node access to the network, etc. The present invention can greatly improve the spectrum utilization efficiency, improve the efficiency of network construction and data transmission efficiency, and is of great significance for improving the networking efficiency of time-synchronized networking systems such as drones. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 This is a diagram of a multi-node simultaneous frequency and time synchronization networking system; Figure 2 This is an embodiment of the simultaneous and same-frequency time synchronization system of the present application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0021] The present application scheme is applicable to time-synchronized microwave networking to achieve precise time and frequency transmission.

[0022] The technical solutions provided by various embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

[0023] Figure 1 This is a diagram of a multi-node simultaneous and same-frequency time synchronization networking system. Each time synchronization module slave node compares time with the time synchronization module master node. The system can suppress self-interference signals. Therefore, simultaneous and same-frequency time comparison can be achieved between different time synchronization module nodes. Figure 2 for Figure 1 Block diagram of the RF self-interference suppression principle used in the RF front end of each time synchronization module.

[0024] The simultaneous and same-frequency time synchronization system of the present application is a microwave time synchronization networking system of the BPSK system. The time synchronization networking system performs bidirectional transmission of time comparison signals at the same time and the same frequency band. This method can save twice the frequency resources, but during the transmission process of this method, self-interference will be generated between the transmitting channel and the receiving channel. In order to eliminate the RF self-interference signal between the transmitting channel and the receiving channel signals, we will use direct RF self-interference suppression technology to suppress the RF self-interference signal of the time comparison signal.

[0025] The time synchronization signal uses a spread spectrum BPSK signal, which can be expressed as: (1) Among them, the subscript n Indicates the station sending the signal n , represents the signal amplitude, Represents the pseudo code waveform of the transmitted signal, Indicates TOA (Time of Arrival), Indicates the carrier frequency, represents the carrier phase, represents additive noise. After sampling, the output discrete sampling signal for: (2) in, represents the sampling period, express i Time Node n The PRN (Pseudo Random Noise) code is delayed The code phase, Represents the sampled noise. The PRN code has good correlation. The result of correlation between the kth PRN code and the lth PRN code is: (3) if k =l, is the autocorrelation function, if k ≠l, then is the cross-correlation function.

[0026] like Figure 2 As shown, the simultaneous and same-frequency time synchronization system embodiment of the present application includes a block diagram of a direct radio frequency self-interference suppression technology.

[0027] In a time synchronization networking system, when the time comparison is performed in a simultaneous and co-frequency manner, the local transmission signal will generate strong interference to the local reception signal. Therefore, it is necessary to suppress the self-interference signal transmitted locally at the receiving end in the RF domain. For a simultaneous and co-frequency time synchronization networking system, each time synchronization networking node includes a transmitter and a receiver. The transmitter includes a spread spectrum modulation module, an up-conversion module, a power amplifier module, a transmitting antenna module, etc., which processes the transmitted intermediate frequency time comparison signal. The receiving end includes a receiving antenna module, an isolator module, a low noise amplifier module, a down-conversion module, a despreading and demodulation module, etc., which generates a received intermediate frequency time comparison signal. The RF self-interference suppression module is used to generate a cancellation signal. I(t) , through which the RF self-interference signal in the time comparison signal is canceled.

[0028] In one embodiment, the time synchronization networking node includes a transmitting end and a receiving end connected to a transceiver antenna via a circulator. A radio frequency self-interference suppression module is provided between the first port of the circulator connected to the output of the transmitting end and the third port of the circulator connected to the input of the receiving end. The radio frequency self-interference suppression module is used to sample the radio frequency signal output by the transmitting end and then implement radio frequency reconstruction to generate a cancellation signal coupled to the input of the receiving end; the radio frequency reconstruction includes delay, phase shift and amplitude attenuation.

[0029] In one embodiment, the RF self-interference suppression module includes a time delay, an attenuator and a phase shifter. The attenuator attenuates the amplitude of the transmission signal input to the antenna, and the time delay and the phase shifter control the phase of the transmission signal. The generated cancellation signal is added to the time comparison signal received by the antenna, and the error signal obtained is used for feedback to further control the attenuator, the time delay and the phase shifter to further adjust the amplitude and phase. The method is continuously adjusted until a signal with the same amplitude and opposite phase as the time comparison interference signal is obtained.

[0030] Alternatively, the generated cancellation signal is subtracted from the time comparison signal received by the antenna, and the obtained error signal is used for feedback to further control the attenuator, delay device and phase shifter to further adjust the amplitude and phase. This method is used to continuously adjust until a signal with the same amplitude and phase as the time comparison interference signal is obtained.

[0031] It can be understood that obtaining two signals with the same absolute values ​​of amplitude and phase is an ideal state. In practice, when RF reconstruction is achieved through a series delay, phase shifter and attenuator, the performance parameters of the delay, phase shifter and attenuator are adjusted so that the remaining self-interference signal is less than the set threshold. In the multi-channel RF reconstruction function, each RF reconstruction function can adjust at least one of the following performance quantities: delay, phase shift and amplitude attenuation.

[0032] For example, suppose the attenuation of the attenuator is , the delay time of the delay device is , the phase adjustment amount is , through multi-channel RF reconstruction, the final cancellation signal can be expressed as: (4) in, i Indicates the number of channels, i.e. i The output cancellation signal is the sum of the channels. In a preferred embodiment of the present application, the processing is performed by a two-channel radio frequency reconstruction module.

[0033] Subtract the received signal , or in other words, add The inverted signal can effectively reduce the influence of the self-interference signal and suppress the self-interference signal, which can be expressed as follows: = S(t)+x(t)-I(t)+w(t) = S(t)+x(t)- +w(t) (5) in, It indicates the signal entering the baseband circuit after the RF self-interference is suppressed. It represents the signal transmitted by other time synchronization nodes and expected to be received by the local node antenna. represents the self-interference signal at the antenna receiving end, represents additive noise. In the above formula, Represents the remaining self-interference time comparison signal after RF suppression.

[0034] The remaining self-interference signal can be processed by the baseband self-interference time comparison signal suppression method to further cancel the interference. The baseband self-interference time comparison signal suppression method generally adopts the self-interference signal adaptive filtering algorithm to suppress it.

[0035] Based on the above embodiments, the present invention adopts a direct RF self-interference time comparison signal suppression technology, which adjusts the delay, amplitude and phase of a time comparison signal transmitted at the RF end to generate a signal with the same amplitude and opposite phase as the interference signal, and synthesizes it with the received self-interference time comparison signal. According to parameters such as signal power fed back by the loop, the delay, amplitude and phase are adjusted to minimize the synthesized signal power, thereby realizing the RF end self-interference time comparison signal suppression.

[0036] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of further restrictions, the elements defined by the sentence "comprises..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0037] It will be understood by those skilled in the art that, unless expressly stated, the singular forms "one", "said", and "the" used may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof. It should be understood that when an element is "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. In addition, the "connection" or "coupling" used herein may include wireless connection or wireless coupling. The term "and / or" used herein includes all or any unit and all combinations of one or more associated listed items.

[0038] Those skilled in the art will understand that unless otherwise defined, all terms (including technical, technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art to which this invention belongs.

[0039] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

Claims

1. A simultaneous and frequency time synchronization system, characterized in that: The time synchronization networking nodes include a transmitting end and a receiving end connected to a transmitting and receiving antenna via a circulator; A radio frequency self-interference suppression module is provided between the first port of the circulator connected to the output of the transmitting end and the third port of the circulator connected to the input of the receiving end; The RF self-interference suppression module is used to sample the RF signal output by the transmitter to achieve RF reconstruction, and generate a cancellation signal to couple to the input of the receiver; the RF reconstruction includes delay, phase shift and amplitude attenuation.

2. The simultaneous and same-frequency time synchronization system according to claim 1, characterized in that: The radio frequency self-interference suppression module includes multiple radio frequency reconstruction functions, and each radio frequency reconstruction function can adjust at least one of the following performance quantities: delay, phase shift and amplitude attenuation.

3. The simultaneous and same-frequency time synchronization system as claimed in claim 1, characterized in that: The radio frequency reconstruction function of any one channel is realized by a delay device, a phase shifter and an attenuator connected in series.

4. The simultaneous and same-frequency time synchronization system as claimed in claim 1, characterized in that: The radio frequency self-interference suppression module includes a two-channel radio frequency reconstruction module.

5. The simultaneous and same-frequency time synchronization system as claimed in claim 1, characterized in that: The radio frequency reconstruction function of any one channel is realized by a delay device, a phase shifter and an attenuator connected in series, and the performance parameters of the delay device, the phase shifter and the attenuator are adjustable.

6. A method for eliminating interference in a simultaneous and frequency time synchronization system, applicable to a microwave time synchronization networking system, characterized in that: The method comprises: At the receiving end of the time synchronization networking node, the signal received from the antenna is offset by RF self-interference before entering the low noise amplifier, introducing the offset signal It is obtained by coupling out a part of the transmission signal from the transmitting end of the node before it enters the antenna, and correcting the amplitude, delay and phase through RF reconstruction.

7. A method for eliminating interference in a simultaneous frequency and time synchronization system as claimed in claim 6, characterized in that: Two channels are used for self-interference signal reconstruction.

8. A method for eliminating interference in a simultaneous, co-frequency and time synchronization system as claimed in claim 6, characterized in that: Contains multi-channel RF reconstruction function, each of which can adjust at least one of the following performance quantities: delay, phase shift and amplitude attenuation.

9. A method for eliminating interference in a simultaneous, co-frequency and time synchronization system as claimed in claim 6, characterized in that: The RF reconstruction function of any one channel is realized by connecting a delay device, a phase shifter and an attenuator in series, and adjusting the performance parameters of the delay device, the phase shifter and the attenuator so that the remaining self-interference signal is less than a set threshold.

10. A method for eliminating interference in a simultaneous, frequency and time synchronization system as claimed in claim 6, characterized in that: The remaining self-interference signals are processed using the baseband self-interference time ratio signal suppression method.

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