Interference cancellation method of unmanned aerial vehicle and transceiving system

Abstract

The invention discloses an interference cancellation method of an unmanned aerial vehicle and a transceiving system, and relates to the technical field of communication. The method comprises the following steps: determining the type of a received interference signal, and determining a control strategy based on the type of the interference signal; using the control strategy to control a hardware cancellation circuit and / or a digital cancellation module to cancel the interference signal according to a preset initial cancellation parameter; receiving the cancelled interference signal, extracting each target feature of the interference signal, and adjusting a cancellation parameter based on each target feature; and repeating the step until the residual power of the received offset interference signal is lower than a preset threshold. Therefore, efficient suppression of emission leakage interference, multipath reflection and nonlinear interference is realized in an interference cancellation mode combining hardware and software.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to a method for interference cancellation of unmanned aerial vehicles (UAVs) and a transceiver system. Background Technology

[0002] In broadband data link systems for small unmanned aerial vehicles (UAVs), the transmitting and receiving equipment are deployed at the same location. Due to platform size limitations, the isolation between the transmitting and receiving antennas is limited. Transmitter leakage signals, out-of-band spurious signals, and PA nonlinear intermodulation can easily couple into the receiving link. These interferences can easily lead to receiver front-end saturation, significantly reducing the dynamic range of the receiving baseband, significantly decreasing link sensitivity and communication distance, and severely restricting the UAV mission effectiveness.

[0003] Existing UAV interference suppression solutions typically employ methods such as increasing antenna spacing, adding cavity filters, and improving duplexer isolation. However, these methods are difficult to implement due to limitations in UAV space, weight, and bandwidth requirements. While purely digital cancellation solutions offer flexibility, their cancellation capacity is often insufficient in situations involving strong leakage, large dynamic range, and PA nonlinearity, making it difficult to cover the self-interference suppression requirements of 80–110 dB. Summary of the Invention

[0004] The main objective of this application is to provide an interference cancellation method and transceiver system for unmanned aerial vehicles (UAVs), which combines hardware and software interference cancellation methods to achieve efficient suppression of transmission leakage interference, multipath reflection, and nonlinear interference.

[0005] To achieve the above objectives, this application provides an interference cancellation method for unmanned aerial vehicles (UAVs), applied to a transceiver system. The transceiver system includes a hardware cancellation circuit, a receiving link, and a transmitting link. The receiving link includes a microprocessor, which integrates a digital cancellation module and a coordination control module. The hardware cancellation circuit is connected between the coupler of the transmitting link and the synthesizer of the receiving link. The method is executed by the coordination control module and includes: Determine the type of the received interference signal and determine a control strategy based on the type of the interference signal; The control strategy is used to control the hardware cancellation circuit and / or the digital cancellation module to cancel the interference signal with preset initial cancellation parameters; Receive the canceled interference signal and extract each target feature of the interference signal, and adjust the cancellation parameters based on each target feature; repeat this step until the residual power of the received canceled interference signal is lower than a preset threshold.

[0006] Optionally, the hardware cancellation circuit includes a signal extraction module, a power divider, multiple cancellation branches, and a multipath synthesis module. The input of the signal extraction module is connected to the transmit link, and the output is connected to the power divider. The signal extraction module is used to extract the transmit signal from the transmit link. The output of the power divider is connected to each of the cancellation branches. The power divider is used to divide the transmit signal into multiple reference signals and transmit them to each of the cancellation branches. For any cancellation branch, the cancellation branch is used to adjust the amplitude, phase, and time delay of the reference signal of the corresponding leakage path to obtain a corresponding sub-cancellation signal. The input of the multipath synthesis module is connected to the output of each of the cancellation branches, and the output is connected to the receive link. The multipath synthesis module is used to synthesize the sub-cancellation signals output by each of the cancellation branches to obtain a hardware cancellation signal. The hardware cancellation signal is used to cancel the interference signal.

[0007] Optionally, the cancellation branch includes a controllable attenuator, a controllable phase shifter, and a controllable delay unit connected in sequence; the input terminal of the controllable attenuator is connected to the power divider, and the output terminal of the controllable delay unit is connected to the multipath synthesis module.

[0008] Optionally, the digital cancellation module includes a multi-tap cancellation filter and a nonlinear cancellation unit; the multi-tap cancellation filter is used to cancel the interference signal when the interference signal is a linear self-interference signal formed by the main leakage path, and each tap in the multi-tap cancellation filter corresponds to a preset delay component; the nonlinear cancellation unit is used to cancel the interference signal using a built-in nonlinear model when the interference signal is a signal generated by nonlinear distortion leakage.

[0009] Optionally, the type of interference signal includes transmit leakage interference and nonlinear interference; determining the control strategy based on the type of interference signal includes: when the type of interference signal is transmit leakage interference, the control strategy includes first controlling the hardware cancellation circuit to cancel the interference signal until the cancellation parameters of the hardware cancellation circuit are optimal, and then controlling the digital cancellation module to cancel the canceled interference signal when the residual power of the canceled interference signal is greater than or equal to the preset threshold; when the type of interference signal is nonlinear interference, the control strategy includes first controlling the digital cancellation module to cancel the interference signal until the cancellation parameters of the digital cancellation circuit are optimal, and then controlling the hardware cancellation circuit to cancel the canceled interference signal when the residual power of the canceled interference signal is greater than or equal to the preset threshold.

[0010] Optionally, the cancellation parameters include the attenuation value of the controllable attenuator, the phase shift value of the controllable phase shifter, and the delay value of the controllable delay unit; the cancellation parameters also include the tap coefficients of the multi-tap cancellation filter, the weight stability range, the number of taps of the nonlinear model, and the model parameters; the cancellation parameters also include the adjustment step size.

[0011] Optionally, the target characteristics include the relative time delay, amplitude characteristics, phase characteristics, signal stability characteristics, short-time residual power, and average residual power of the interference signal.

[0012] Optionally, adjusting the cancellation parameters based on each of the target features includes: outputting control commands to the hardware cancellation circuit based on the short-time residual power, the average residual power, the relative time delay of the interference signal, the amplitude feature, the phase feature, and the signal stability feature. The control commands are used to control the hardware cancellation unit to adjust the attenuation value of the controllable attenuator, the phase shift value of the controllable phase shifter, and the time delay value of the controllable time delay unit, and to adjust the adjustment step size and the weight stability range, and to adjust the tap coefficients of the multi-tap cancellation filter and the number of taps and model parameters of the nonlinear model using the LMS algorithm.

[0013] Optionally, the relative time delay, amplitude characteristics, phase characteristics, and signal stability characteristics of the interference signal are extracted using the sliding window technique.

[0014] To achieve the above objectives, this application also provides a UAV transceiver system, including a hardware cancellation circuit, a receiving link, and a transmitting link. The receiving link includes a microprocessor, which integrates a digital cancellation module and a coordination control module. The hardware cancellation circuit is connected between the coupler of the transmitting link and the synthesizer of the receiving link. The coordination control module is used to execute the UAV interference cancellation method described above.

[0015] The interference cancellation method for UAVs disclosed in this application utilizes a hardware cancellation circuit designed in the transceiver system. This hardware cancellation circuit is connected to the synthesizer of the receiving link and the coupler of the transmitting link. It can extract the transmitted signal output from the transmitting link as a reference and process the transmitted signal to obtain a cancellation signal to counteract multipath reflection interference. By integrating a digital cancellation module and a coordination control module into the microprocessor in the receiving link, the digital cancellation module can cancel transmission leakage interference and nonlinear interference. The coordination control module can use a control strategy to coordinate the working nodes of the hardware cancellation circuit and the digital cancellation module, determine the interference signal cancellation effect based on the received canceled interference signal, and adjust the cancellation parameters of the hardware cancellation circuit and the digital cancellation module based on the cancellation effect. This effectively achieves efficient suppression of transmission leakage interference, multipath reflection, and nonlinear interference. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the transceiver system according to an embodiment of this application; Figure 2 This is a circuit diagram of the hardware cancellation circuit in an embodiment of this application; Figure 3 This is a schematic diagram of the structure of the digital cancellation module according to an embodiment of this application; Figure 4 This is a flowchart of the interference cancellation method according to an embodiment of this application; In the diagram, 100 is the hardware cancellation circuit; 200 is the transmit link; 300 is the receive link; 310 is the digital cancellation module; and 320 is the coordination control module.

[0017] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] In small unmanned aerial vehicle (UAV) systems, to perform tasks such as real-time communication, mapping, and reconnaissance, it is usually necessary to simultaneously mount and operate data link transmitting and receiving equipment on the same platform. Due to the strict size, weight, and power consumption constraints of the UAV platform, the physical distance between the transmitting and receiving antennas is often extremely limited, resulting in insufficient isolation between the antennas.

[0020] In this situation, the signal generated by the transmitter will leak into the receiving link through various pathways such as spatial coupling, near-field radiation, and co-located conduction, forming strong self-interference. This interference includes not only local oscillator leakage of the transmitter carrier and out-of-band spurious signals from the power amplifier, but is further aggravated by intermodulation products generated by the power amplifier operating in the nonlinear region. After such strong interference signals couple into the receiving front end, they will cause a series of serious consequences: First, it may cause the low-noise amplifier in the first stage of the receiving link to enter a compressed or saturated state, causing the weak useful signal to be submerged; second, the dynamic range required for the receiver baseband signal processing is occupied by a large number of useless interference signals, and the effective dynamic range is significantly reduced; third, the overall receiving sensitivity of the data link decreases as a result, directly leading to a shortened communication distance and seriously affecting mission efficiency. Particularly complicated is that in the specific application scenario of UAVs, their metal fuselage structure, high-speed rotating propellers, and externally mounted load equipment constitute a dynamically changing and complex electromagnetic scattering environment. After being reflected by these objects, the transmitted signal creates leakage interference with multipath effects. This interference exhibits significant frequency selectivity and time delay spread characteristics, and can typically be decomposed into multiple interference signal branches with different time delays, amplitudes, and phases. This characteristic makes the interference signal complex in both the frequency and time domains, posing a serious challenge to traditional interference cancellation techniques.

[0021] To address the aforementioned self-interference problem, the industry traditionally employs the following solutions: First, increasing the physical distance between the transmitting and receiving antennas to improve spatial isolation. However, this is generally not feasible for small UAV platforms with extremely limited space. Second, introducing high-quality cavity filters at the RF front end to filter out out-of-band interference. However, such filters are often large, heavy, and expensive, contradicting the lightweight and highly integrated requirements of UAVs. Third, using high-isolation duplexers. However, traditional duplexers typically have narrow operating bandwidths, making it difficult to meet the communication requirements of modern broadband, software-reconfigurable data links, and their effectiveness in suppressing nonlinear interference components within the broadband range is limited. Therefore, these traditional solutions struggle to achieve an ideal balance between size, weight, power consumption, cost, and performance, failing to meet the comprehensive requirements of small UAVs for lightweight design, high integration, and broadband communication capabilities.

[0022] With the development of digital signal processing technology, pure digital domain cancellation schemes have attracted attention due to their flexibility. These schemes estimate and reconstruct interference signals in the baseband or intermediate frequency range using adaptive algorithms, and then subtract them from the received signal. However, in the context of UAV scenarios, with their extremely strong initial leakage, wide dynamic range, and power amplifier nonlinear distortion, pure digital schemes have inherent performance bottlenecks. Because their processing occurs after analog-to-digital conversion, when strong interference causes the front-end low-noise amplifier to saturate or the quantization bits of the analog-to-digital converter to be occupied by a large number of interference signals, the digital domain can no longer accurately recover and characterize the clipped or submerged useful signal. This severely limits the cancellation capability, typically making it difficult to independently cover the 80 to 110 dB level of deep self-interference suppression required by small UAV data links.

[0023] In summary, existing technologies, whether traditional RF solutions based on hardware isolation and filtering or purely digital adaptive cancellation schemes, all have their limitations and cannot efficiently, economically, and compactly solve the strong self-interference problem exacerbated by multipath effects and nonlinear characteristics in the broadband data links of small UAVs. Therefore, there is an urgent need for a new, efficient interference cancellation method that integrates the advantages of hardware, software, and cross-domain processing to adapt to the stringent constraints of UAV platforms and achieve deep, broadband interference suppression, thereby ensuring the reliability and communication performance of the data link.

[0024] Therefore, this application provides an interference cancellation method and transceiver system for unmanned aerial vehicles (UAVs). By combining simulated hardware cancellation, digital baseband cancellation, and cross-domain adaptive control, it achieves efficient suppression of transmission leakage interference, multipath reflection, and nonlinear interference, thereby improving the sensitivity of the receiving link, extending the communication distance, avoiding overload of the receiving front end, reducing the platform's dependence on filters and antenna isolation, and realizing system miniaturization and low power consumption.

[0025] For ease of understanding, the drone transceiver system of this application embodiment will be described in detail below.

[0026] Figure 1 This is a schematic diagram of the transceiver system according to an embodiment of this application. Figure 1 As shown, the transceiver system of this application embodiment may include a hardware cancellation circuit 100, a receiving link 300, and a transmitting link 200.

[0027] The receiving link 300 includes a microprocessor, which integrates a digital cancellation module 310 and a coordination control module 320; the hardware cancellation circuit 100 is connected between the coupler of the transmitting link 200 and the synthesizer of the receiving link 300; the coordination control module 320 can execute the interference cancellation method proposed in the embodiments of this application.

[0028] In this embodiment, the transmit link 200 is used to amplify, filter, and frequency convert the transmit signal output by the digital-to-analog converter (DAC), and output the processed radio frequency transmit signal through the transmit antenna. The transmit link 200 may include a baseband signal source, a digital-to-analog converter, an up-converter, a power amplifier (PA), a low-pass filter, and a transmit antenna.

[0029] The system consists of a baseband signal source that generates the baseband transmission signal, containing communication data, control commands, or payload sensor information required for the UAV to perform its mission. A digital-to-analog converter (DAC) converts the digital signal output from the baseband signal source into an analog intermediate frequency (IF) signal, which is then up-converted to the radio frequency (RF) band by an up-converter. A power amplifier amplifies the RF signal to achieve the required transmission power level. A low-pass filter removes out-of-band spurious and high-order harmonic components from the power amplifier output signal to meet electromagnetic compatibility requirements. Finally, the transmitting antenna transmits the RF signal into the target airspace.

[0030] In this embodiment, the receiving link 300 is used to receive radio frequency signals in space, including target useful signals and various interference signals. The receiving link 300 may include a receiving antenna, a low-noise amplifier (LNA), a downconverter, an analog-to-digital converter (ADC), and a microprocessor. Specifically, the radio frequency signal captured by the receiving antenna is first amplified by the LNA; then downconverted to an intermediate frequency signal by the downconverter, and then converted into a digital signal by the analog-to-digital converter and sent to the microprocessor for processing.

[0031] The hardware cancellation circuit 100 is deployed between the receiving antenna and the input of the low-noise amplifier. The hardware cancellation circuit 100 is mainly used to coarsely compensate for strong direct leakage and short-delay multipath interference signals, achieve broadband suppression of 25 to 45 dB at the front end, and then cancel multipath reflection interference and interference signals with interference energy concentrated in the strong components at the front end.

[0032] Furthermore, the digital cancellation module 310 and the coordination control module 320 are deployed in the microprocessor of the receiving link 300. The digital cancellation module 310 is mainly used to perform fine compensation for residual interference, transmission leakage interference, and nonlinear interference after cancellation by the hardware cancellation circuit 100. It accurately estimates and reconstructs the interference signal in the digital domain through built-in filters or models, achieving an additional 30-60 dB of deep suppression. The coordination control module 320 is mainly used to monitor the residual power and interference characteristics of the interference signal to identify the main components of the current interference signal, so as to adjust the cancellation parameters of the hardware cancellation circuit 100 and the digital cancellation module 310, and to make the analog domain cancellation and digital domain cancellation complementary and non-conflicting, thereby maintaining the best self-interference suppression performance of the entire link under the conditions of UAV attitude changes and dynamic multipath environment.

[0033] The internal structures of the hardware cancellation circuit 100 and the digital cancellation module 310 are described in detail below.

[0034] Figure 2 This is a circuit diagram of the hardware cancellation circuit according to an embodiment of this application. For example... Figure 2 As shown, in some embodiments, the hardware cancellation circuit 100 may include a signal extraction module, a power divider, multiple cancellation branches, and a multipath synthesis module.

[0035] The signal extraction module has its input connected to the transmit link 200 and its output connected to the power divider. The signal extraction module extracts the transmitted signal from the transmit link 200. The power divider's output is connected to each cancellation branch. The power divider divides the transmitted signal into multiple reference signals and transmits them to each cancellation branch. For any cancellation branch, the cancellation branch adjusts the amplitude, phase, and time delay of the reference signal for the corresponding leakage path to obtain the corresponding sub-cancellation signal. The multipath synthesis module has its input connected to the output of each cancellation branch and its output connected to the receive link 300. The multipath synthesis module synthesizes the sub-cancellation signals output from each cancellation branch to obtain a hardware cancellation signal. The hardware cancellation signal is used to cancel interference signals.

[0036] The hardware cancellation circuit 100 in this embodiment is used to perform broadband, low-latency pre-suppression of the transmitted leakage signal at the radio frequency front end, so as to reduce the dynamic range pressure of the receiving link 300. The hardware cancellation circuit 100 mainly consists of a signal extraction module, a power divider, multiple cancellation branches, and a multipath synthesis module, forming a "multipath equivalent compensation structure".

[0037] Specifically, the signal extraction module may include an RF directional coupler. The signal extraction module can use the RF directional coupler to extract a portion of the transmitted signal from the power amplifier output of the transmit link 200 as a reference signal for subsequent analog cancellation. This ensures that the reference signal and the leakage interference signal are structurally homogeneous and have a stable relative phase relationship, thereby providing a reliable reference source for the hardware cancellation circuit 100. The coupling degree of this directional coupler can be selected according to the output power of the transmit link 200 and the dynamic range requirements of the hardware cancellation circuit 100. For example, selecting a device with a 15dB coupling degree ensures that the amplitude of the extracted signal is sufficient for subsequent processing without causing excessive loss to the main signal power of the transmit link 200.

[0038] It is understandable that on a UAV platform, signals emitted due to antenna coupling, body scattering, and structural reflection will all be received by the receiving link 300, becoming interference signals on the receiving link 300. Therefore, these interference signals typically exhibit multipath leakage characteristics. In this embodiment, to accommodate multipath leakage interference signals formed by antenna coupling, body scattering, and structural reflection on the UAV platform, the transmitted signal is divided into N parallel reference signals (N≥2) by a power divider.

[0039] The power divider can be an unequal power divider with a microstrip line structure, and the number of its output ports matches the preset number of interference multipath branches. For example, when the interference signal in the target scene is mainly decomposed into 3 significant multipath branches, the power divider can be designed as a 1-to-3 structure, distributing the extracted reference signal with equal power (or according to a preset ratio) to 3 independent cancellation branches.

[0040] In this embodiment, each cancellation branch corresponds to an analog compensation channel for interference multipath. Its core function is to adjust the amplitude, phase and time delay of the reference signal to generate a corresponding sub-cancellation signal, so that the sub-cancellation signal cancels out the corresponding type of interference signal at the front end. Each branch corresponds to a type of equivalent leakage path compensation, thereby achieving accurate matching of broadband and multipath interference.

[0041] Continue to refer to Figure 2 In some implementations, the cancellation branch includes a controllable attenuator, a controllable phase shifter, and a controllable time delay unit connected in sequence. The input of the controllable attenuator is connected to the power divider, and the output of the controllable time delay unit is connected to the multipath combining module.

[0042] Specifically, each cancellation branch includes an independent controllable attenuator, a controllable phase shifter, and a controllable time delay unit. The controllable attenuator is used to precisely compensate for the amplitude of the corresponding leakage interference component, and the controllable phase shifter is used to precisely compensate for the phase of the corresponding leakage interference component. Both the controllable attenuator and the controllable phase shifter are controlled by a microprocessor. The microprocessor adjusts the attenuation of the controllable attenuator and the phase offset of the controllable phase shifter to ensure that the sub-cancellation signal generated by the cancellation branch has the same amplitude and opposite phase as the corresponding leakage interference component in vector terms, thereby achieving path-level front-end cancellation.

[0043] The controllable delay unit can compensate for the delay of the sub-cancellation signals in the cancellation branches for interference signals in each leakage path. It is understood that leakage paths in the UAV data link may have delays ranging from several nanoseconds to tens of nanoseconds. This means that the radio frequency signal emitted by the transmit link 200 will experience a certain delay when it is received by the receive link 300 after reflection or scattering. Therefore, delay compensation is needed for the reference signal directly extracted from the transmit link 200 to ensure that the generated sub-cancellation signals are time-aligned with the actual multipath interference signals, thereby achieving cancellation. Based on this, this embodiment introduces a controllable delay unit in the cancellation branches. Each cancellation branch can independently calibrate the delay difference between paths based on the microprocessor's estimation results, ensuring that the generated sub-cancellation signals are time-aligned with the corresponding leakage interference components.

[0044] In this embodiment, the multipath synthesis module may include a synthesizer. The multipath synthesis module is mainly used to uniformly vector-superimpose the sub-cancellation signals of each cancellation branch after amplitude, phase, and time delay compensation. Specifically, the synthesizer can be a broadband power synthesizer or a vector synthesizer, with the number of its input ports matching the number of cancellation branches. Each input port receives a sub-cancellation signal output from one cancellation branch. Internally, the synthesizer vector-synthesizes the multiple sub-cancellation signals to generate the final hardware cancellation signal. The amplitude, phase, and time delay characteristics of this hardware cancellation signal are the vector sum of the sub-cancellation signals from each branch, capable of covering the superposition characteristics of multiple leakage paths. This achieves preliminary cancellation with the composite interference signal generated by multipath effects in the receiving link 300 at the RF front end, realizing overall broadband suppression.

[0045] Figure 3 This is a schematic diagram of the structure of the digital cancellation module according to an embodiment of this application. Figure 3 As shown, the digital cancellation module 310 includes a multi-tap cancellation filter and a nonlinear cancellation unit.

[0046] Among them, the multi-tap cancellation filter is used to cancel the interference signal when the interference signal is a linear self-interference signal formed by the main leakage path. Each tap in the multi-tap cancellation filter corresponds to a preset delay component. The nonlinear cancellation unit is used to cancel the interference signal by using the built-in nonlinear model when the interference signal is a signal generated by nonlinear distortion leakage.

[0047] In this embodiment, the digital cancellation module 310 is used to further suppress the residual leakage signal after hardware cancellation, achieving an additional strong cancellation amount of 30-60 dB. Application scenario example: After the microprocessor controls the hardware cancellation circuit 100 to cancel the interference signal from the receiving link 300, the microprocessor detects the residual power of the cancelled interference signal. If the residual power is still greater than or equal to a preset threshold, and the components of the hardware cancellation circuit 100 have been optimally adjusted, and the residual power of the interference signal cannot be reduced further by adjusting the cancellation parameters of the hardware cancellation circuit 100, then the microprocessor's coordination control module 320 can control the digital cancellation module 310 to continue cancelling the interference signal until the residual power is lower than the preset threshold.

[0048] In this embodiment, the digital cancellation module 310 may include a multi-tap cancellation filter (FIR) and a nonlinear cancellation unit.

[0049] The multi-tap cancellation filter is primarily used to model and cancel linear self-interference generated by the main leakage path of the UAV platform. It should be noted that the main leakage path includes the most energetic leakage path among all leakage paths. In practical applications, one or more main leakage paths can be identified by the peak value of the interference signal. Each tap in the multi-tap cancellation filter corresponds to a possible leakage delay component, generating a linear cancellation signal with the same amplitude but opposite phase as the interference signal, thus canceling the strong interference signal. Furthermore, the weight of each tap can be updated in real time using adaptive algorithms such as Least Mean Square Error (LMS) or Recursive Least Squares (RLS) to track the dynamic changes of the leakage path.

[0050] As an example, if the delay spread of the main leakage path is 100ns and the sampling clock is 100MHz (i.e., the sampling interval is 10ns), then the multi-tap cancellation filter can be set with 10 taps, each tap corresponding to a delay step of 10ns. The weight coefficients of each tap are dynamically adjusted through an adaptive algorithm (such as the minimum mean square error algorithm) so that the reconstructed linear interference signal and the actual residual linear interference are accurately matched in the digital domain.

[0051] The nonlinear cancellation unit compensates for interference signals introduced by the nonlinear distortion of the power amplifier (PA). Since the power amplifier in the UAV transmission link 200 is prone to entering the nonlinear region when operating with large signals, exhibiting problems such as AM-AM, AM-PM, and memory effects, these leakage components leak along with the transmitted signal to the receiving link 300 and cannot be completely suppressed by the linear cancellation mechanism. Therefore, this embodiment incorporates a nonlinear cancellation unit in the digital cancellation module 310.

[0052] The nonlinear cancellation unit in this embodiment incorporates a nonlinear model based on a memory polynomial. The order and memory depth of the model can be adjusted according to the actual scenario. For example, when the power amplifier of the transmit link 200 operates in the saturation region, the nonlinear distortion intensifies. The model order can be increased from the 3rd to the 5th order, and the memory depth can be extended from 2 symbol periods to 4 symbol periods to more accurately fit the characteristics of the nonlinear interference. In addition, the coordination control module 320 can dynamically adjust the nonlinear model coefficients based on the residual interference in the received canceled interference signal, so that the canceled signal output by the nonlinear cancellation unit has the same amplitude and opposite phase to the actual nonlinear distortion component.

[0053] The above is a detailed description of the transceiver system according to the embodiments of this application. The interference cancellation method according to the embodiments of this application will be described in detail below with reference to the specific structure of the transceiver system described above.

[0054] Figure 4 This is a flowchart of an interference cancellation method according to an embodiment of this application. This interference cancellation method can be executed by the coordination control module 320 in the microprocessor described above. Figure 4 As shown, the interference cancellation method may include the following steps: Step 410: Determine the type of the received interference signal and determine the control strategy based on the type of interference signal.

[0055] Step 420: Use the control strategy to control the hardware cancellation circuit 100 and / or the digital cancellation module 310 to cancel the interference signal with preset initial cancellation parameters.

[0056] Step 430: Receive the canceled interference signal and extract each target feature of the interference signal, and adjust the cancellation parameters based on each target feature; repeat this step until the residual power of the received canceled interference signal is lower than the preset threshold.

[0057] It should be noted that the preset threshold can be set by staff according to actual needs, and no specific restrictions are imposed on the preset threshold here.

[0058] Specifically, after the receiving link 300 receives an interference signal, the coordination control module 320 can first determine the type of the interference signal. This can be done by analyzing the main components of the interference signal. In some implementations, the type of interference signal may include (but is not limited to) transmit leakage interference and nonlinear interference.

[0059] As an example, when the coordination control module 320 analyzes that the main components of the interference signal are strong direct leakage signals and short-delay multipath interference, and the interference energy is concentrated in the strong components at the front end, it is determined to be a transmission leakage interference type. Since strong direct leakage signals and short-delay multipath interference are mainly canceled using the hardware cancellation circuit 100, the corresponding control strategy prioritizes activating the hardware cancellation circuit 100. If the analysis reveals that the interference signal contains obvious nonlinear distortion components (such as harmonic interference caused by power amplifier saturation), and the interference is frequency-selective or affected by PA nonlinearity, it is determined to be a nonlinear interference type. Therefore, the corresponding control strategy can prioritize activating the digital cancellation module 310.

[0060] Thus, through this cross-domain collaborative approach, the hardware cancellation circuit 100 and the digital cancellation module 310 can each perform their respective functions without conflict, avoiding redundant compensation or antagonistic effects, thereby ensuring stable and deep self-interference suppression in the complex and dynamic channel environment of the UAV platform.

[0061] In some implementations, determining the control strategy based on the type of interference signal in step 410 may include: if the type of interference signal is transmit leakage interference, the control strategy includes first controlling the hardware cancellation circuit 100 to cancel the interference signal until the cancellation parameters of the hardware cancellation circuit 100 are optimal, and then controlling the digital cancellation module 310 to cancel the cancelled interference signal if the residual power of the cancelled interference signal is greater than or equal to a preset threshold; if the type of interference signal is nonlinear interference, the control strategy includes first controlling the digital cancellation module 310 to cancel the interference signal until the cancellation parameters of the digital cancellation circuit are optimal, and then controlling the hardware cancellation circuit 100 to cancel the cancelled interference signal if the residual power of the cancelled interference signal is greater than or equal to a preset threshold.

[0062] Specifically, when the interference signal type is transmit leakage interference, the coordination control module 320 first triggers the start-up process of the hardware cancellation circuit 100: the signal extraction module extracts the transmit signal from the power amplifier output of the transmit link 200 as a reference, and the power divider divides the reference signal into multiple reference signals according to the pre-stored multipath quantity configuration, which are then sent to each cancellation branch. The cancellation branch first calls the preset initial amplitude, phase, and time delay parameters to generate the corresponding sub-cancellation signal. The multipath synthesis module synthesizes the sub-cancellation signals to obtain the hardware cancellation signal and then injects it into the receive link 300 to complete the first round of hardware cancellation.

[0063] Subsequently, the coordination control module 320 receives the interference signal after the first round of cancellation through the receiving link 300 and detects the residual power of the newly received interference signal. If the residual power is still higher than the preset threshold, the cancellation parameters of each cancellation branch can be adjusted to generate a new hardware cancellation signal to cancel the current interference signal. This process is repeated until the residual power no longer decreases (the hardware parameters are optimal). If the residual power is still not lower than the preset threshold at this time, the coordination control module 320 switches to the digital cancellation module 310, which configures the number of filter taps based on the time delay characteristics of the interference signal after hardware cancellation. If there are nonlinear components in the interference signal, the nonlinear cancellation unit is used to further suppress nonlinear distortion interference until the residual power of the received interference signal is lower than the threshold.

[0064] When the interference signal is nonlinear, the coordination control module 320 prioritizes the activation of the digital cancellation module 310, which uses a multi-tap cancellation filter and a nonlinear cancellation unit to generate nonlinear and linear cancellation signals that are injected into the receiving link 300. If the residual of the received interference signal after cancellation still does not meet the standard, the coordination control module 320 activates the hardware cancellation circuit 100 for supplementary cancellation, ultimately achieving coordinated optimization of hardware and digital cancellation.

[0065] In some implementations, the cancellation parameters include the attenuation value of the controllable attenuator, the phase shift value of the controllable phase shifter, and the delay value of the controllable delay unit; the cancellation parameters also include the tap coefficients of the multi-tap cancellation filter, the weight stability range, and the number of taps and model parameters of the nonlinear model; the cancellation parameters also include the adjustment step size.

[0066] After determining the control strategy, the coordination control module 320 can first control the hardware cancellation circuit 100 and / or the digital cancellation module 310 according to the control strategy. In the first round of cancellation, the hardware cancellation circuit 100 and the digital cancellation module 310 can cancel with the initial cancellation parameters.

[0067] Specifically, during the first round of cancellation in the hardware cancellation circuit 100, the microprocessor can first send a preset initial attenuation value, phase shift value, and time delay to the hardware cancellation circuit 100, so that the controllable attenuator, controllable phase shifter, and controllable time delay unit of each cancellation branch of the hardware cancellation circuit 100 can generate sub-cancellation signals according to the initial cancellation parameters.

[0068] As an example, for a hardware cancellation circuit 100 with three cancellation branches, the initial attenuation value can be set to -10dB, the initial phase shift value can be allocated according to empirical values ​​of multipath phase difference (e.g., 0°, 120°, 240°), and the initial delay can be set based on the typical multipath delay range of the UAV platform (e.g., 5ns, 10ns, 15ns). These initial parameters can be determined through pre-experiments or simulation data to ensure that preliminary interference suppression can be achieved in the first round of cancellation, avoiding excessive deviation of initial parameters that could lead to a reverse deterioration of the cancellation effect.

[0069] In the first round of cancellation in the digital cancellation module 310, the initial tap coefficients of the multi-tap cancellation filter can be randomly initialized with zero mean or pre-trained based on historical cancellation data. The weight stability range is preset to ±0.5 to limit the fluctuation range of the tap coefficients. The initial model parameters of the nonlinear cancellation unit are generated by fitting the static nonlinear characteristics of the power amplifier (such as AM-AM / AM-PM curves). The number of taps is configured according to the nonlinear order requirements (such as 5 taps for 3rd order nonlinearity).

[0070] Furthermore, the coordination control module 320 adjusts the relevant cancellation parameters of the hardware cancellation circuit 100 and the digital cancellation module 310 according to the set adjustment step size. As an example, the initial adjustment step size of the hardware cancellation circuit 100 can be set to a larger value (such as a 1dB attenuation step, a 10° phase shift step, and a 1ns delay step) to quickly approximate the optimal parameter range; while the initial adjustment step size of the digital cancellation module 310 is relatively smaller (such as an LMS algorithm step size μ=0.01) to avoid oscillations in the tap coefficients or nonlinear model parameters.

[0071] In step 430, the coordination control module 320 continuously receives the canceled interference signal and extracts the target features of the interference signal. Based on the extracted target features, the coordination control module 320 uses an adaptive optimization algorithm to iteratively update the hardware or digital cancellation parameters.

[0072] In some implementations, the target characteristics include the relative time delay, amplitude characteristics, phase characteristics, signal stability characteristics, short-time residual power, and average residual power of the interference signal.

[0073] It should be noted that relative delay refers to the time delay difference between the interference signal received by the receiving link 300 and the extracted reference signal; signal stability characteristics characterize the fluctuation of the interference signal; short-time residual power can be the residual power within a short-time sampling window, while average residual power can be the average residual power of a consecutive preset number of sampling windows. The combination of the two can avoid the impact of single sampling fluctuations on parameter adjustment.

[0074] The determination of whether the residual power is lower than the preset threshold in the foregoing embodiments can be specifically: whether the short-time residual power is lower than its corresponding preset threshold; specifically: whether the average residual power is lower than its corresponding preset threshold; specifically: whether the short-time residual power is lower than its corresponding preset threshold and whether the average residual power is lower than its corresponding preset threshold.

[0075] In some implementations, the relative time delay, amplitude characteristics, phase characteristics, and signal stability characteristics of the interference signal are extracted using a sliding window technique.

[0076] During flight, unmanned aerial vehicle (UAV) platforms experience frequent and dynamic changes in flight attitude due to various factors such as airflow disturbances, maneuvering, and altitude variations. This unstable motion further complicates the near-field electromagnetic environment of their onboard antennas, resulting in numerous and widely distributed multipath propagation paths with significant time-varying characteristics, and path parameters fluctuating rapidly over time. To address this complex scenario, this embodiment employs a sliding window-based real-time signal processing technique, which can dynamically track and estimate leakage channels over continuous time periods, thereby obtaining continuous relative time delay, amplitude characteristics, phase characteristics, and signal stability characteristics.

[0077] In some implementations, adjusting the cancellation parameters based on each target characteristic may include: outputting control commands to the hardware cancellation circuit 100 based on short-time residual power, average residual power, relative delay of the interference signal, amplitude characteristics, phase characteristics, and signal stability characteristics. The control commands are used to control the hardware cancellation unit to adjust the attenuation value of the controllable attenuator, the phase shift value of the controllable phase shifter, and the delay value of the controllable delay unit, and to adjust the adjustment step size and weight stability range. The LMS algorithm is also used to adjust the tap coefficients of the multi-tap cancellation filter and the number of taps and model parameters of the nonlinear model.

[0078] Specifically, after the first round of cancellation is completed, the coordination control module 320 extracts target features of the interference signal, such as relative time delay, amplitude characteristics, phase characteristics, signal stability characteristics, short-time residual power, and average residual power, through the signal detection unit of the receiving link 300. These target features can characterize the cancellation effect and determine whether the current cancellation effect is at its optimal state.

[0079] Specifically, the coordination control module 320 can utilize the LMS algorithm and, based on relative time delay, amplitude characteristics, phase characteristics, and signal stability characteristics, update the tap coefficients of the multi-tap cancellation filter and the number of taps and model parameters of the nonlinear model in real time, ensuring that the cancellation signal generated in the next round of cancellation process maintains optimal cancellation matching with the actual leakage signal. The LMS algorithm can acquire the residual signal between the received signal and the cancellation signal, and adaptively iteratively update the tap coefficients of the multi-tap cancellation filter and the nonlinear model parameters based on the residual signal, feeding the updated parameters back to the cancellation signal generation path, thereby achieving continuous tracking and real-time cancellation of the leakage signal. The LMS algorithm is an existing algorithm and will not be described in detail here.

[0080] Secondly, the coordination control module 320 can also adjust the adjustment step size of the parameters of the hardware cancellation circuit 100 and the digital cancellation module 310, as well as the weight stability range of the multi-tap cancellation filter, based on whether the short-time residual power and average residual power of the currently received interference signal are lower than their preset thresholds. For example, when a slower rate of decrease in residual power or a rebound is detected, it indicates that the parameters are close to optimal. At this point, the adjustment step size is reduced, and the amplitude, phase, and time delay of each cancellation branch are further fine-tuned. The filter order or weight stability range in the digital cancellation module 310 is also updated to ensure stable convergence of the adaptive algorithm and avoid over-adjustment or divergence.

[0081] The above parameter adjustment and cancellation process is repeated until the residual power of the newly received interference signal is lower than the preset threshold. At this point, the coordination control module 320 stops parameter adjustment, locks the current cancellation parameters, and achieves stable self-interference suppression of the UAV transceiver system. The coordination control module 320 establishes a dynamic coordination mechanism between the hardware cancellation circuit 100 and the digital cancellation module 310 to achieve globally optimal control of the entire cancellation link, forming a unified closed loop.

[0082] In some implementations, the presence of motors, servo motors, and other devices on the UAV platform can generate irregular pulse interference. If these pulses enter the adaptive iteration, it can lead to weight divergence or incorrect updates. Therefore, the coordination control module 320 in this embodiment can also freeze updates such as the LMS algorithm during the pulse period when high-amplitude, narrow-pulse-width interference is detected, preventing incorrect weights from causing a decrease in cancellation performance.

[0083] Therefore, by deeply coupling the cancellation process of the hardware cancellation circuit 100 and the digital cancellation module 310 through the coordination control module 320, a closed-loop control logic of "dynamic detection - strategy matching - parameter iteration - effect verification" is constructed. This logic can quickly match the optimal cancellation path for different types of interference signals such as transmission leakage and nonlinearity, and can also track time-varying multipath interference during UAV maneuvering in real time through sliding window technology. Combined with the algorithm freezing mechanism during pulse interference, the robustness of the cancellation system is further improved. This achieves efficient suppression of transmission leakage, multipath reflection, and nonlinear intermodulation, thereby significantly improving the receiving sensitivity of the receiving link 300, extending its communication distance, avoiding overload of the receiving front end, reducing the platform's dependence on filters and antenna isolation, and realizing system miniaturization and low power consumption.

[0084] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for canceling interference from unmanned aerial vehicles (UAVs), characterized in that, The transceiver system includes a hardware cancellation circuit, a receiving link, and a transmitting link. The receiving link includes a microprocessor that integrates a digital cancellation module and a coordination control module. The hardware cancellation circuit is connected between the coupler of the transmitting link and the combiner of the receiving link. The method is executed by the coordination control module, and the method includes: Determine the type of the received interference signal and determine a control strategy based on the type of the interference signal; The control strategy is used to control the hardware cancellation circuit and / or the digital cancellation module to cancel the interference signal with preset initial cancellation parameters; Receive the canceled interference signal and extract each target feature of the interference signal, and adjust the cancellation parameters based on each target feature; repeat this step until the residual power of the received canceled interference signal is lower than a preset threshold.

2. The interference cancellation method for unmanned aerial vehicles according to claim 1, characterized in that, The hardware cancellation circuit includes a signal extraction module, a power divider, multiple cancellation branches, and a multipath synthesis module. The input terminal of the signal extraction module is connected to the transmission link, and the output terminal is connected to the power divider. The signal extraction module is used to extract the transmission signal from the transmission link. The output terminal of the power divider is connected to each of the cancellation branches. The power divider is used to divide the transmitted signal into multiple reference signals and transmit them to each of the cancellation branches. For any cancellation branch, the cancellation branch is used to adjust the amplitude, phase and time delay of the reference signal of the corresponding leakage path to obtain the corresponding sub-cancellation signal; The input terminal of the multipath synthesis module is connected to the output terminal of each of the cancellation branches, and the output terminal is connected to the receiving link. The multipath synthesis module is used to synthesize the sub-cancellation signals output by each of the cancellation branches to obtain a hardware cancellation signal; the hardware cancellation signal is used to cancel the interference signal.

3. The interference cancellation method for unmanned aerial vehicles according to claim 2, characterized in that, The cancellation branch includes a controllable attenuator, a controllable phase shifter, and a controllable time delay unit connected in sequence; The input terminal of the controllable attenuator is connected to the power divider, and the output terminal of the controllable delay unit is connected to the multipath synthesis module.

4. The interference cancellation method for unmanned aerial vehicles according to claim 3, characterized in that, The digital cancellation module includes a multi-tap cancellation filter and a nonlinear cancellation unit; The multi-tap cancellation filter is used to cancel the interference signal when the interference signal is a linear self-interference signal formed by the main leakage path. Each tap in the multi-tap cancellation filter corresponds to a preset delay component. The nonlinear cancellation unit is used to cancel the interference signal using a built-in nonlinear model when the interference signal is a signal generated by nonlinear distortion leakage.

5. The interference cancellation method for unmanned aerial vehicles according to claim 4, characterized in that, The types of interference signals include transmission leakage interference and nonlinear interference; The control strategy determination based on the type of the interference signal includes: When the type of interference signal is transmission leakage interference, the control strategy includes first controlling the hardware cancellation circuit to cancel the interference signal until the cancellation parameters of the hardware cancellation circuit are optimal, and then controlling the digital cancellation module to cancel the interference signal after cancellation when the residual power of the cancelled interference signal is greater than or equal to the preset threshold. When the type of interference signal is nonlinear interference, the control strategy includes first controlling the digital cancellation module to cancel the interference signal until the cancellation parameters of the digital cancellation circuit are optimal, and then controlling the hardware cancellation circuit to cancel the interference signal after cancellation when the residual power of the cancelled interference signal is greater than or equal to the preset threshold.

6. The interference cancellation method for unmanned aerial vehicles according to claim 4 or 5, characterized in that, The cancellation parameters include the attenuation value of the controllable attenuator, the phase shift value of the controllable phase shifter, and the delay value of the controllable delay unit; The cancellation parameters also include the tap coefficients and weight stability range of the multi-tap cancellation filter, as well as the number of taps and model parameters of the nonlinear model; The cancellation parameters also include adjusting the step size.

7. The interference cancellation method for unmanned aerial vehicles according to claim 6, characterized in that, The target characteristics include the relative time delay, amplitude characteristics, phase characteristics, signal stability characteristics, short-time residual power, and average residual power of the interference signal.

8. The interference cancellation method for unmanned aerial vehicles according to claim 7, characterized in that, The adjustment of the cancellation parameters based on each of the target features includes: Based on the short-time residual power, the average residual power, the relative time delay of the interference signal, the amplitude characteristics, the phase characteristics, and the signal stability characteristics, control commands are output to the hardware cancellation circuit. The control commands are used to control the hardware cancellation unit to adjust the attenuation value of the controllable attenuator, the phase shift value of the controllable phase shifter, and the time delay value of the controllable time delay unit, and to adjust the adjustment step size and the weight stability range. The LMS algorithm is also used to adjust the tap coefficients of the multi-tap cancellation filter and the number of taps and model parameters of the nonlinear model.

9. The interference cancellation method for unmanned aerial vehicles according to claim 7, characterized in that, The relative time delay, amplitude characteristics, phase characteristics, and signal stability characteristics of the interference signal are extracted using the sliding window technique.

10. A transceiver system for unmanned aerial vehicles (UAVs), characterized in that, It includes a hardware cancellation circuit, a receiving link, and a transmitting link. The receiving link includes a microprocessor, which integrates a digital cancellation module and a coordination control module. The hardware cancellation circuit is connected between the coupler of the transmit link and the combiner of the receive link; The coordination control module is used to execute the interference cancellation method for the UAV as described in any one of claims 1 to 9.

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