A GNSS air interface test spurious signal active cancellation method and system

Abstract

The present application belongs to the technical field of satellite navigation receiver test, and discloses a GNSS air interface test leakage signal active cancellation method and system. Real leakage signals are tracked by star-by-star despreading in the vicinity of the antenna to be tested, complex weights are determined according to the spatial sampling vector and the transmission relationship from the cancellation unit to the sampling point, and the opposite copies are reconstructed and radiated; in the closed loop stage, the self-transmission coupling component in the despreading tracking branch is reconstructed and deducted according to the known cancellation copy, the current complex weight and the transmission relationship, and the complex weight is adjusted after the residual error measurement branch deducts the simulated constellation component. The present application can suppress the real leakage signal, retain the simulated constellation, reduce the risk of integrity decision abnormality, and is suitable for non-shielded multi-opening GNSS air interface test environment.

Description

Technical Field

[0001] This invention belongs to the field of satellite navigation receiver testing technology, specifically relating to an active cancellation method and system for GNSS air interface testing leakage signals. Background Technology

[0002] In the research, development, production, and verification of global navigation system receivers, it is typically necessary to generate controllable and repeatable test signals indoors using a GNSS simulator, and then transmit these signals wirelessly to the receiver under test (DUT) to evaluate its acquisition, tracking, positioning, and integrity performance. This wireless radiation testing is called over-the-air (OTA) radiation testing. Compared to cable-conducted injection, OTA radiation testing can cover the DUT's antenna pattern, RF front-end, and overall integrated characteristics, more closely resembling real-world usage conditions. One of the fundamental requirements for OTA radiation testing is the absence of co-frequency satellite navigation signals other than the GNSS simulator signal within the test area.

[0003] However, in actual production lines, factories, machine racks, or temporary testing sites, the testing space often lacks complete RF shielding and frequently contains multiple openings such as windows, roller shutters, and skylights. Real satellite navigation signals may leak in through these openings and, after reflection from walls, floors, or equipment surfaces, reach the vicinity of the antenna under test from multiple directions, spatially mixing and superimposing with the simulated constellation signals generated by the GNSS simulator. In this situation, the receiver under test may simultaneously capture both the simulated constellation and the leaked real constellation. Because the satellite position, time parameters, and pseudorange measurements corresponding to the two constellations are independent and inconsistent, the receiver's autonomous integrity monitoring or similar integrity judgment mechanism may determine that the measurements are inconsistent, thus refusing to output positioning results, preventing the air interface radiation test from proceeding normally.

[0004] To address the issue of real satellite navigation signal leakage, existing technologies typically employ methods such as physical shielding, increasing simulator output power, staggering simulated constellations from real constellations, or enhancing the integrity algorithm of the receiver under test. Physical shielding relies on continuously closed shielding boundaries, which is costly and inflexible in open environments such as large racks and assembly plants. Increasing simulator output power only affects acquisition priority and does not eliminate the leakage of real signals themselves, meaning that two mutually exclusive measurements may still occur during subsequent tracking and integrity determination. Staggering time or constellations reduces the consistency between the test scenario and the preset scenario and cannot prevent the leakage of real constellations from being acquired. Improving the integrity algorithm requires modifying the receiver under test, making it unsuitable for testing purchased or third-party finished receivers.

[0005] Besides the aforementioned processing methods, existing technologies also employ air interface cancellation using a coherent and out-of-phase copy of the target satellite navigation signal. However, such methods are typically geared towards single-direction or local single-point scenarios, relying on the premise that the cancellation wavefront and the leakage wavefront are approximately matched. In unshielded multi-aperture environments, the same real satellite navigation signal may simultaneously arrive at the neighborhood of the tested antenna from different directions through multiple openings and multiple reflections, forming a multi-directional diffuse leakage field. In this case, a single cancellation wavefront is difficult to match the multi-directional wavefront simultaneously. If a reference receiver and cancellation antenna are deployed at each opening, the hardware scale increases with the number of openings, and it is difficult to cover non-opening paths such as wall reflections, making it impractical for engineering applications. Therefore, to overcome the dependence on specific leakage directions and specific opening locations, air interface cancellation schemes need to implement local sensing and closed-loop cancellation based on the actual leakage composite field formed within the neighborhood of the tested antenna.

[0006] However, when both the leaky signal sensing unit and the cancellation copy radiating unit are located in the neighborhood of the antenna under test, and closed-loop cancellation is performed based on the signal observation results of this neighborhood, the problem of coupling of the cancellation copy to the sensing and receiving link arises. Specifically, during the radiation of the cancellation copy by the cancellation unit, when the sensing unit receives synchronously, the cancellation copy enters the sensing and receiving link through the spatial coupling path between the cancellation unit and the sensing unit. This causes the complex baseband sampling sequence received by the sensing unit to simultaneously contain the simulated constellation component, the leaked real satellite navigation signal component, and the self-emission coupling component of the cancellation copy. If despreading tracking is performed directly based on this complex baseband sampling sequence, the self-emission coupling component will again participate in the reconstruction of the cancellation copy and the update of the complex weights, forming a recursive feedback consisting of measurement, reconstruction, radiation, and remeasurement. Especially when the canceled copy and the leaked real satellite navigation signal use the same pseudo-random code and have the code phase aligned, the despreading correlation peaks of the two merge into the same complex observation, which contaminates the complex amplitude, carrier phase and Doppler measurement results of the real satellite navigation signal, and may cause despreading tracking lock-out, complex weight oscillation or closed loop non-convergence. Summary of the Invention

[0007] The technical problem to be solved by this invention is: how to effectively suppress real satellite navigation signals leaking into the vicinity of the antenna under test from multiple directions without modifying the test site as a whole, without altering the receiver under test, and without separately deploying cancellation hardware at each opening, and to avoid contaminating the despreading tracking and closed-loop update of the real satellite navigation signals after the cancellation copy is sampled back by the sensing unit, thereby ensuring the stable operation of the active cancellation system and enabling the receiver under test to complete the air interface radiation test based on the simulated constellation generated by the GNSS simulator.

[0008] To address the aforementioned technical issues, this invention proposes an active cancellation method and system for GNSS air interface testing of leaked signals. By setting up an attached active cancellation node close to the antenna under test, the leaked real satellite navigation signal is despread and tracked satellite by satellite, the cancellation copy is reconstructed, the weighted radiation is restored, the self-emission coupling component is compensated, and the residual closed-loop adjustment is performed.

[0009] On the one hand, the active cancellation method for GNSS air interface test leakage signals includes the following steps: The GNSS simulator radiates a simulated constellation to the receiver under test via the main transmitting antenna; Before canceling the duplicate radiation, at the antenna under test of the receiver under test, each real satellite navigation signal that leaks in through multiple openings and arrives at the antenna under test from multiple directions via direct or reflected propagation paths is despread and tracked to obtain the complex amplitude, code phase, carrier phase and Doppler of each real satellite navigation signal at multiple sampling points. The spatial sampling vector is constructed based on the complex amplitude. For each real satellite navigation signal, based on the transmission relationship from one or more cancellation units arranged around the antenna under test to multiple sampling points and the spatial sampling vector, the corresponding complex weights are determined; according to the code phase, carrier phase and Doppler, a cancellation copy with the same code, aligned code phase, opposite carrier phase and consistent Doppler of the real satellite navigation signal is reconstructed; the code phase of the cancellation copy is different from the code phase of the simulated constellation; The cancellation copy is distributed to one or more cancellation units with complex weights to form a local suppression region around the antenna under test. During the closed-loop operation phase, the complex baseband sampling sequences at multiple sampling points are input into the despreading tracking branch and the residual measurement branch, respectively. In the despreading tracking branch, the self-emission coupling component is reconstructed based on the current radiated cancellation copy, the corresponding complex weights, and the transmission relationship. After deducting the self-emission coupling component from the complex baseband sampling sequence, despreading tracking continues. In the residual measurement branch, the known simulated constellation components are subtracted from the complex baseband sampling sequence to obtain the superposition component of the real satellite navigation signal and the canceled copy as the residual. When the carrier-to-noise ratio corresponding to the residual is not lower than the acquisition threshold of the receiver under test, the complex weighting value is adjusted according to the residual.

[0010] On the other hand, the GNSS air interface test leakage signal active cancellation system includes: GNSS simulator, accompanying active cancellation node and control unit; The GNSS simulator includes a normal test channel group and a cancellation channel group. The normal test channel group is used to generate a simulated constellation and radiate the simulated constellation to the receiver under test via the main transmitting antenna. The cancellation channel group is used to reconstruct a cancellation copy of the real satellite navigation signal based on the code phase, carrier phase, and Doppler of the real satellite navigation signal. The code phase of the cancellation copy is different from the code phase of the simulated constellation. An attached active cancellation node is positioned close to the antenna under test and includes one or more cancellation units and one or more sensing units arranged around the antenna under test. The cancellation units are used to radiate cancellation copies according to complex weights to form a local suppression region around the antenna under test. The sensing units are used to acquire complex baseband sampling sequences at multiple sampling points in the neighborhood of the antenna under test. During the radiating of cancellation copies by the cancellation units, the complex baseband sampling sequences include: simulated constellation components, leaked real satellite navigation signals, and self-emission coupling components of the cancellation copies that reach the corresponding sensing units after being radiated by the cancellation units. The control unit is connected to the GNSS simulator and the accompanying active cancellation node, respectively, to input the complex baseband sampling sequence into the despreading tracking branch and the residual measurement branch. In the despreading tracking branch, the self-emission coupling component is reconstructed and subtracted based on the current radiated cancellation copy, the corresponding complex weights, and the transmission relationship from the cancellation unit to multiple sampling points. Based on the subtracted complex baseband sampling sequence, the navigation signal of each real satellite is despread and tracked, and a spatial sampling vector is constructed. The complex weights are determined based on the spatial sampling vector and the transmission relationship. In the residual measurement branch, the known simulated constellation components are subtracted from the complex baseband sampling sequence to obtain the superposition component of the real satellite navigation signal and the cancellation copy as the residual. The complex weights are then adjusted based on the residual.

[0011] Compared with the prior art, the present invention has the following advantages and beneficial effects: Based on the GNSS simulator radiating a simulated constellation to the receiver under test, the sensing, cancellation, and residual feedback of real satellite navigation leakage signals are all arranged and executed in close proximity to the antenna under test; for each real satellite navigation signal that leaks into the neighborhood of the antenna under test from multiple directions through multiple openings and reflections, the complex amplitude, code phase, carrier phase, and Doppler at multiple sampling points are first obtained by despreading and tracking, and the complex amplitude at multiple sampling points constitutes a spatial sampling vector. Then, the corresponding complex weights are determined by combining the transmission relationship from the cancellation unit to multiple sampling points, so that the cancellation control object is transformed from a single incident direction into a leakage synthesis field in the neighborhood of the antenna under test, thereby adapting to the multi-directional diffuse leakage field formed by multiple openings and multiple reflections, avoiding the need to deploy cancellation hardware separately for each opening. Meanwhile, this invention uses the code phase and carrier phase of the leaked real satellite navigation signal to create a canceled copy with the same code but opposite phase as the Doppler reconstruction, and distinguishes the code phase of this canceled copy from the code phase of the analog constellation. This ensures the canceled copy primarily acts on the leaked real satellite navigation signal, while retaining the analog constellation radiated by the GNSS simulator. The canceled copy, after being weighted, is radiated by one or more canceling units arranged around the antenna under test, forming a local suppression region around the antenna suitable for multi-directional leaks, thereby reducing the carrier-to-noise ratio (CNR) of the real satellite navigation signal at the antenna under test. By measuring the residual within the local suppression region in the neighborhood of the antenna under test, and adjusting the weighting value with the goal of ensuring the CNR of the real satellite navigation signal at the antenna under test is lower than the acquisition threshold of the receiver under test, a closed-loop control is formed from leak signal sensing, weighting value determination, canceled copy reconstruction, air interface radiation to residual feedback correction. This makes it difficult for the receiver under test to stably acquire the leaked real satellite navigation signal, reducing measurement conflicts caused by the coexistence of the real and analog constellations, thus ensuring that the receiver under test can complete air interface radiation tests based on the analog constellation.

[0012] Furthermore, this invention divides the complex baseband sampling sequence output by the sensing unit into a despreading tracking branch and a residual measurement branch. In the despreading tracking branch, based on the cancellation replica waveform, the current complex weights, and the transmission relationship from the cancellation unit to the sampling point, the self-emission coupling component of the cancellation replica is reconstructed and deducted, avoiding the recursive feedback formed by the self-emission coupling component participating again in the cancellation replica reconstruction and complex weight update after being sampled back by the sensing unit. In the residual measurement branch, the actual superposition result of the real satellite navigation signal and the cancellation replica is retained, so that the despreading tracking process and the residual closed-loop process are decoupled from each other, thereby reducing the risk of despreading tracking lock-up, complex weight oscillation, and closed-loop non-convergence. Attached Figure Description

[0013] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings: Figure 1This is a schematic diagram of the active cancellation method for GNSS air interface test leakage signals provided in Embodiment 1 of the present invention; Figure 2 This is a geometric schematic diagram of the local suppression region formed around the antenna under test by the attached active cancellation node provided in Embodiment 1 of the present invention under multi-directional leakage. Figure 3 This is a schematic diagram of the overall structure and signal flow of the GNSS air interface test leakage signal active cancellation system provided in Embodiment 2 of the present invention.

[0014] The attached diagram shows the following labels and corresponding component names: 20-GNSS simulator; 21-Normal test channel group; 22-Cancellation channel group; 31-Main transmitting antenna; 50-Receiver under test; 51-Antenna under test; 60-Control unit; 100-Attached active cancellation node; 110-Cancellation unit; 120-Sensing unit; W-Multiple openings. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The illustrative embodiments and descriptions of this invention are for illustrative purposes only and are not intended to limit the invention. The embodiments described below are some, but not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0016] Example 1: Addressing the technical problem of real satellite navigation signals leaking into the vicinity of the tested antenna in an unshielded indoor testing environment with multiple openings, propagating directly or through reflection from multiple directions, forming a multi-directional diffuse composite field, and the potential for recursive feedback after the cancellation copy is sampled back by the sensing unit, this example provides an active cancellation method for leaked signals in GNSS air interface testing. The overall technical approach is as follows: Each leaked real satellite navigation signal is despread and tracked immediately adjacent to the tested antenna; the complex weights are determined based on the spatial sampling vector and the transmission relationship from the cancellation unit to multiple sampling points; and the signal is reconstructed satellite-by-satellite. The code phase and carrier phase of the real satellite navigation signal are continuously acquired based on the code phase, carrier phase, and Doppler of the real satellite navigation signal. In the residual measurement branch, the code phase and carrier phase of the real satellite navigation signal are acquired based on the code phase and carrier phase of the real satellite navigation signal. In the residual measurement branch, the superposition relationship between the real satellite navigation signal and the cancellation copy is retained, and an error signal is formed after deducting the known simulated constellation components. The complex weights are adjusted in the closed loop according to the error signal.

[0017] Based on the above overall technical approach, the active cancellation method for GNSS air interface test leakage signals described in this embodiment includes: Figure 1 The following steps are shown: Step 1: The GNSS simulator radiates a simulated constellation to the receiver under test via the main transmitting antenna.

[0018] The purpose of this step is to provide the receiver under test with a controllable and repeatable simulated satellite navigation signal under a preset test scenario, which constitutes the basic input for air interface radiation testing.

[0019] The simulated constellation is a collection of signals from multiple simulated satellites generated according to a preset test scenario. Each simulated satellite signal uses a pseudo-random code, code phase, carrier phase, Doppler effect, and amplitude known from the GNSS simulator. The known pseudo-random code, code phase, carrier phase, Doppler effect, and amplitude will serve as the basis for subtracting the simulated constellation components in step 6. The position, polarization, and radiation direction of the main transmitting antenna are arranged according to conventional air interface radiation test specifications.

[0020] In this step, by radiating a simulated constellation to the receiver under test, the simulated constellation radiation and the cancelling copy radiation are spatially superimposed on the neighborhood of the antenna under test.

[0021] Step 2: At the location adjacent to the antenna under test of the receiver under test, despread and track each real satellite navigation signal that leaks in through multiple openings and arrives at the neighborhood of the antenna under test from multiple directions via direct or reflected propagation paths. Obtain the complex amplitude, code phase, carrier phase, and Doppler at multiple sampling points, and construct a spatial sampling vector.

[0022] The purpose of this step is to address the problem that the leaked real satellite navigation signals cannot be directly observed and the spatial distribution of the leaked synthetic field is unknown.

[0023] The leaked real satellite navigation signal is buried about 20dB to 30dB below thermal noise when it reaches the vicinity of the antenna under test, and the instantaneous waveform cannot be directly observed. The satellite navigation signal is modulated by spread spectrum code. Correlation despreading of the spread spectrum signal can obtain correlation processing gain. Taking the GPS L1 C / A signal (center frequency of 1575.42MHz, corresponding to a carrier wavelength of about 19cm and half carrier wavelength of about 9.5cm) as an example, the correlation processing gain is about 43dB, which can extract the leaked real satellite navigation signal from the noise and obtain complex observation measurement.

[0024] In this step, the following steps are performed in parallel for each leaked real satellite navigation signal: Step 2.1: Perform initial despreading tracing.

[0025] When one or more cancellation units have not yet radiated cancellation copies, the pseudo-random code of the corresponding satellite is used as the local reference code. Correlation despreading and carrier tracking are performed on the complex baseband sampling sequence at multiple sampling points in the neighborhood of the antenna under test to obtain the complex amplitude of the corresponding satellite at each sampling point, as well as the code phase, carrier phase, Doppler and rate of change of the corresponding satellite.

[0026] Multiple sampling points are spatially distributed in the vicinity of the antenna under test, forming a spatial sampling of the closed boundary where the aperture of the antenna under test is located.

[0027] Step 2.2: Perform reconstruction and subtraction of self-emission coupling components in the closed-loop phase.

[0028] After one or more cancellation units begin radiating cancellation copies, the first n The complex baseband sampling sequence at each sampling point includes: analog constellation components, leaked real satellite navigation signals, self-emission coupling components formed by each in-use cancellation copy after being radiated by one or more cancellation units, and noise components.

[0029] Record the number of canceled copies currently in operation as follows: Q The number of elimination units will be recorded as M ;No. q The complex baseband waveform of each canceled copy is denoted as c q ( t ), No. m The current weighting value applied by each cancellation unit to the q-th cancellation copy is denoted as... w m,q , No. m The first cancellation unit to the first n The complex transfer coefficient and propagation delay of each sampling point are denoted as follows: g n,m and τ n,m Then the first n The estimated values ​​of the self-emission coupling components at each sampling point are: For different navigation frequencies, the complex transfer coefficients, propagation delays, and transfer matrices corresponding to those frequencies are used respectively.

[0030] Complex baseband sampling sequence from the nth sampling point y n ( t Subtracting the estimated value of the self-emission coupling component from the sampled data, the tracking sampling sequence is obtained: The tracking sampling sequence is used to perform correlation despreading and carrier tracking of the real satellite navigation signal. After deducting the self-emission coupling component, the tracking sampling sequence still includes the simulated constellation component and the leaked real satellite navigation signal; the two are distinguished by the code phase difference between them, or the leaked real satellite navigation signal is despread and tracked after deducting the simulated constellation component based on the known parameters of the GNSS simulator.

[0031] Step 2.3: Construct the spatial sampling vector.

[0032] The complex amplitudes obtained from multiple sampling points after self-emission coupling compensation are arranged geometrically to form a spatial sampling vector corresponding to the real satellite navigation signal. The spatial sampling vector is used to characterize the spatial distribution of the leakage composite field of the corresponding real satellite navigation signal on the boundary of the neighborhood of the antenna under test. It can cover multipath components that leak in from multiple directions through multiple openings and wall reflections without distinguishing a single direction of arrival.

[0033] Step 2.4: Update the real satellite set.

[0034] When the actual satellite set changes, the pseudo-random code space is continuously scanned to detect newly emerging leaked satellites and corresponding despreading tracking is initiated. For leaked satellites that have disappeared, the corresponding processing resources are released.

[0035] The spatial sampling vector output in this step provides input data for solving the complex weights in step 3; the code phase, carrier phase, and Doppler output in this step provide input data for reconstructing the cancellation copy in step 4.

[0036] Step 3: For each real satellite navigation signal, determine the corresponding complex weighting value based on the transmission relationship from one or more cancellation units arranged around the antenna under test to multiple sampling points and the spatial sampling vector.

[0037] The purpose of this step is to transform the cancellation problem of multi-directional diffuse leakage field into a linear solution problem at sampling points in the neighborhood of the antenna under test, thus avoiding direct estimation of each leakage direction.

[0038] The transfer relationship from the cancellation unit to multiple sampling points characterizes the amplitude-phase response and propagation delay generated at each sampling point when each cancellation unit radiates a unit signal. This transfer relationship is obtained through pre-calibration, which includes: the control unit causing each cancellation unit to radiate a known calibration signal one by one according to a distinguishable time slot, code pattern, or frequency identifier; each sensing unit synchronously receiving the corresponding calibration signal to determine the amplitude response, phase response, and propagation delay from each cancellation unit to each sampling point, thereby forming a transfer matrix or a set of transfer responses. This transfer relationship is used, on the one hand, to solve for the complex weights of each cancellation unit based on the spatial sampling vector; on the other hand, it is used to reconstruct the self-emission coupling components at each sampling point based on each in-use cancellation copy and its current complex weights. Calibration is re-executed when the attached active cancellation node is reinstalled, the operating frequency is switched, the relative position between the cancellation unit and the sensing unit changes, or the remaining compensation error after deducting the self-emission coupling components exceeds a preset threshold.

[0039] Let the transfer matrix be denoted as G, which is an N-row, M-column complex matrix, where N is the number of sampling points and M is the number of cancellation units. The element in the n-th row and m-th column of the complex matrix G represents the complex response generated at the n-th sampling point when the m-th cancellation unit radiates a unit signal, where n is a positive integer not greater than N and m is a positive integer not greater than M.

[0040] Let s be the spatial sampling vector corresponding to the real satellite navigation signal, where s is an N-dimensional complex vector; the complex vector s represents the leakage composite field of the real satellite navigation signal at multiple sampling points.

[0041] Since the cancellation copy generated in step 4 is out of phase with the corresponding real satellite navigation signal on the reference waveform, the inverse cancellation field generated by one or more cancellation units at multiple sampling points is represented as −G·w, and the residual vector is represented as e=s−G·w. Therefore, a least squares objective function is constructed according to J(w)=‖G·w−s‖2², and the vector that minimizes J(w) is determined as the complex weight vector w.

[0042] When the transfer matrix G has full column rank, the complex weight vector can be represented as w = (GᴴG)⁻¹Gᴴs; when the transfer matrix G has less than full rank, w = G + When the transfer matrix G is ill-conditioned, the regularized form w = (GᴴG + λI)⁻¹Gᴴs can be used, where Gᴴ represents the conjugate transpose of G, and G... + Let G denote the Moore-Penrose pseudoinverse of G, I denote the identity matrix, and λ be a regularization coefficient greater than 0.

[0043] The complex weight vector w is solved independently for each real satellite navigation signal that is missed, and the solution process for each real satellite navigation signal does not affect each other. Since the transfer matrix G depends on the cancellation unit, sampling point and operating frequency, each satellite at the same navigation frequency shares the transfer matrix G corresponding to that navigation frequency, and only the spatial sampling vector s is distinguished by satellite. Different navigation frequencies are calibrated and the corresponding transfer matrix is ​​used.

[0044] Step 4: Reconstruct a canceled copy of the real satellite navigation signal with the same code and opposite phase, based on the code phase, carrier phase, and Doppler of the real satellite navigation signal.

[0045] The purpose of this step is to solve the problem of distinguishing between real satellite navigation signals that leak in while retaining analog constellation test signals within the same test frequency band.

[0046] Satellite navigation signals use pseudo-random code spread spectrum. When coherently synthesized with the same code, they cancel each other out; when the codes are different, they do not cancel each other out. Therefore, using a cancellation copy with the same pseudo-random code as the leaked real satellite navigation signal, and with the code phase aligned and the carrier phase out of phase with the leaked real satellite navigation signal in the vicinity of the antenna under test, only cancels the leaked real satellite navigation signal with the code phase aligned. Since the code phase of the analog constellation is different from the code phase of the leaked real satellite navigation signal, the cancellation copy does not cancel the analog constellation.

[0047] When reconstructing the canceled copy, the code phase, carrier phase, and Doppler obtained in step 2 are used as inputs to obtain a canceled copy that has the same code, aligned code phase, out-of-phase carrier phase, and consistent Doppler with the leaked real satellite navigation signal. The carrier phase of the canceled copy is determined by feedforward prediction: the carrier phase of the real satellite navigation signal varies with Doppler, with Doppler values ​​reaching several kilohertz. Taking the GPS L1 C / A signal as an example, the carrier phase changes once every approximately 1 ms. However, the loop consisting of measurement, feedback, generation, and radiation has a time delay τ. If the time delay τ is not compensated, the carrier phase of the canceled copy at the radiation time will have a systematic deviation relative to the leaked real satellite navigation signal, and the out-of-phase cancellation relationship will not hold. To compensate for the carrier phase deviation caused by the time delay τ, based on the Doppler of each real satellite navigation signal and the rate of change of the Doppler, according to... Predict the predicted carrier phase of the real satellite navigation signal after the loop delay; whereby... φ ( t )for t The carrier phase of the real satellite navigation signal at any given time, in radians, is measured by the despreading tracking in step 2; f The Doppler of the real satellite navigation signal, measured in Hertz, is obtained by despreading and tracking in step 2. df / dtThe rate of change of Doppler, in Hertz per second, is calculated from the difference of the Doppler sequence output by the despreading tracking; τ The time delay of the loop consisting of measurement, feedback, generation, and radiation is measured in seconds and is determined by measuring or calibrating the time delay of each component of the loop. φp ( t + τ (After time delay) τ The predicted carrier phase is given in radians. f is the signed Doppler frequency satisfying dφ(t) / dt=2πf.

[0048] Based on the predicted carrier phase, the carrier phase of the cancellation replica is determined according to φc(t+τ)=φp(t+τ)+π (mod 2π), ensuring that the carrier phase of the cancellation replica at the radiation time differs from the carrier phase of the leaked real satellite navigation signal in the neighborhood of the antenna under test by 180 degrees. The slowly varying residual error of the predicted carrier phase includes errors caused by amplitude drift, fixed phase offset, and multipath variation, which will be corrected through closed-loop adjustment in step 6.

[0049] During operation, when a simulated satellite in the simulated constellation and a real satellite in the leaked real constellation use the same pseudo-random code, the clock of the GNSS simulator is configured to have a code phase deviation from the real GNSS time of not less than a preset number of code chips, so as to distinguish the simulated signal from the leaked signal by the code phase during the despreading and tracking described in step 2.

[0050] This step involves independently reconstructing a cancellation copy for each leaked real satellite navigation signal. The cancellation copies are superimposed and radiate in space without affecting each other.

[0051] Step 5: Distribute the cancellation replicas to one or more cancellation elements with a complex weight to form a local suppression region around the antenna under test that is suitable for multi-directional leakage fields.

[0052] The purpose of this step is to convert the weighted value obtained in step 3 and the canceled copy obtained in step 4 into air interface radiation, thereby forming a local suppression region for multi-directional leakage fields around the antenna under test.

[0053] Specifically, the complex weighted vector w obtained in step 3 is assigned to one or more cancellation units. That is, the m-th cancellation unit is used to radiate the cancellation copy obtained in step 4 by weighting it according to the amplitude and phase of the m-th element in w, where m is a positive integer not greater than M. The cancellation copies corresponding to each leaked real satellite navigation signal are independent of each other, superimposed in space, and simultaneously act on the corresponding leaked component.

[0054] Furthermore, the local suppression region refers to the spatial region where the leakage power of the synthesized field is suppressed within the aperture of the antenna under test. To meet the spatial sampling requirements of continuous sources at the boundary and suppress grating lobes, when there are multiple cancellation units, these units are arranged around the antenna under test, with the spacing between adjacent cancellation units less than half the carrier wavelength, forming a closed or quasi-closed boundary surrounding the aperture of the antenna under test. Taking the GPS L1 C / A signal as an example, the spacing between adjacent cancellation units is less than approximately 9.5 cm. It should be noted that the size of the local suppression region needs to cover the aperture of the antenna under test, but does not need to cover the entire test area, thereby avoiding an increase in the number of radiation sources required for coherent cancellation due to the expansion of the suppression region size.

[0055] The number of cancellation units is determined through simulation verification based on the aperture of the antenna under test, carrier wavelength, target suppression depth, and residual convergence results. For example, using a GPS L1 signal as the object, the carrier wavelength is approximately 19 cm. The leakage composite field of a single leaking real satellite navigation signal is taken as the sum of six random incoming plane waves. The phase, azimuth, and elevation angles of each plane wave are randomly generated to represent the diffuse incidence formed by multiple aperture superimposed multipath reflections. The leakage composite field is sampled and normalized on the aperture of the antenna under test. The cancellation units are taken from M point sources around the antenna under test, with the distance between adjacent point sources less than half the carrier wavelength. The complex weight vector is obtained according to the least squares criterion described in step 3, representing the upper bound of closed-loop convergence. Monte Carlo simulation is performed on multiple random incoming signals, and the median is taken.

[0056] like Figure 2 As shown, multiple cancellation units and multiple sensing units are arranged around the antenna under test 51. Real satellite navigation signals leaking in from multiple directions arrive at the neighborhood of the antenna under test 51 from different directions. The cancellation copies radiated by each cancellation unit form a local suppression region around the aperture of the antenna under test 51. Based on Figure 2The arrangement shown was simulated under random incoming flow conditions. The relationship between the average suppression depth of the antenna aperture and the number of cancellation elements M and the aperture D of the antenna under test is as follows: When the aperture is 3 cm, M=1 corresponds to approximately 13.8 dB, and M=3 corresponds to approximately 31.2 dB; when the aperture is 5 cm, M=1 corresponds to approximately 9.6 dB, M=3 corresponds to approximately 22.6 dB, and M=4 corresponds to approximately 27.4 dB; when the aperture is 10 cm, M=3 corresponds to approximately 11.9 dB, and M=4 corresponds to approximately 16.0 dB; when the aperture is 15 cm, M=6 corresponds to approximately 12.8 dB. The simulation results show that when the aperture of the antenna 51 under test is no greater than 5 cm, that is, no greater than about 0.26 times the carrier wavelength, a single cancellation unit can achieve an average aperture suppression of about 10 dB, and three cancellation units can achieve an average aperture suppression of about 22 dB. When the aperture is 10 cm, three to four cancellation units are required. When the aperture is 15 cm, six cancellation units 110 are required to achieve an average aperture suppression of about 13 dB.

[0057] Step 6: Measure the residuals in the local suppression region in the residual measurement branch, and adjust the weighted values ​​according to the residuals.

[0058] The target carrier-to-noise ratio (CNR) upper limit is determined by subtracting a preset margin from the acquisition threshold of the receiver under test. When the CNR corresponding to the residual is not lower than the target CNR upper limit, the weighting value is adjusted according to the residual. When the CNR is lower than the target CNR upper limit, the adjustment is stopped and the current weighting value is maintained.

[0059] The purpose of this step is to form a complete closed loop from physical layer radiation to test results, so that the convergence target of the complex weights directly corresponds to the integrity judgment of the receiver under test, and at the same time has the ability to adaptively correct amplitude drift, fixed phase offset and multipath variation.

[0060] This step employs a residual measurement branch independent of the despreading tracking branch in step 2. The residual measurement branch receives the complex baseband sampling sequence output by the sensing unit, before deducting the self-emission coupling components of the cancellation replicas. The complex baseband sampling sequence includes analog constellation components, leaked real satellite navigation signals, components of each cancellation replica that reach the corresponding sampling point after being radiated by each cancellation unit, and noise components.

[0061] Based on the pseudo-random code, code phase, carrier phase, Doppler and amplitude of each satellite in the simulated constellation known by the GNSS simulator, as well as the transmission relationship from the main transmitting antenna to the corresponding sampling point, the simulated constellation components of each simulated satellite at the corresponding sampling point are reconstructed one by one, and the simulated constellation components are subtracted from the complex baseband sampling sequence.

[0062] In step 2, the despreading tracking branch continuously tracks the leaked real satellite navigation signal by subtracting the self-emission coupling component of the cancellation copy; in step 6, the residual measurement branch retains the actual superposition result between the leaked real satellite navigation signal and the cancellation copy, which is used to evaluate the degree of suppression corresponding to the current complex weight value. The two branches use different signal subtraction rules to decouple the despreading tracking and residual measurement.

[0063] Next, the acquisition threshold of the receiver under test is subtracted by a preset margin to obtain the target carrier-to-noise ratio (CNR) upper limit. The CNR of the residual leakage component at the antenna under test is determined based on the residual. When the CNR is not lower than the target CNR upper limit, the complex weights are iteratively corrected using a variable step size least mean square algorithm or a recursive least squares algorithm. When the CNR is lower than the target CNR upper limit, the iterative correction is stopped and the current complex weights are maintained. The acquisition threshold is the minimum carrier-to-noise ratio (CNR) required for the receiver under test (DUT) to stably acquire a satellite signal. It can be obtained from the DUT's model manual or determined through actual measurement and calibration, and is measured in dB-Hz. The preset margin is a margin used for convergence determination, which is used to balance the dispersion of the DUT's acquisition threshold with the fluctuation range of the CNR of the leaked real satellite navigation signal. The preset margin is typically set to 3dB to 6dB, and the actual value can be determined according to the DUT model and test site conditions. The step size or forgetting factor of the variable step size least mean square algorithm and the recursive least squares algorithm are configured according to the trade-off between convergence speed and steady-state error.

[0064] It should be further explained that during closed-loop operation, when changes in the opening conditions of the test site cause a step change in the leakage composite field, the error signal increases instantaneously. Increasing the adaptive step size accelerates the convergence of the complex weights. Since the self-emission components of the cancellation replicas have been deducted as described in step 2 before despreading, despreading can maintain continuous locking on the leakage real satellite navigation signal during the cancellation convergence process. As a fallback protection measure, when the despreading of a real satellite navigation signal loses lock, the radiation of the corresponding satellite's cancellation replica is suspended. Radiation resumes after despreading relocks, thus preventing the radiation of cancellation replicas out of phase with the leakage signal from actually enhancing the leakage component at the tested antenna. When a cancellation unit or sampling point malfunctions, the contribution of the faulty unit or sampling point is set to zero in the transfer matrix G, and the complex weight vector of the remaining cancellation units is recalculated.

[0065] When the system is running for the first time, the attached active cancellation node is reinstalled, the operating frequency is switched, the relative position of the antenna under test and the attached active cancellation node changes, or the remaining compensation error after self-emission coupling component subtraction exceeds a preset threshold, the closed-loop update of the weighted values ​​is paused and the transmission relationship from each cancellation unit to each sensor unit is recalibrated. After calibration, closed-loop operation resumes. When a sensor unit detects receiver front-end gain compression, automatic gain control abnormality, or analog-to-digital conversion clipping, the instantaneous radiated power of the cancellation unit is reduced, transmit / receive isolation is increased, or analog domain self-interference suppression is enabled until the sensor unit returns to linear reception state, and then digital domain self-emission coupling component subtraction is performed.

[0066] By performing this step, once the weighted values ​​converge, the carrier-to-noise ratio of each real satellite navigation signal that leaks into the neighborhood of the antenna under test is lower than the acquisition threshold of the receiver under test. The receiver under test cannot stably acquire real satellites and no longer generates measurements that conflict with the preset test scenario. The receiver under test only stably acquires the simulated constellation, passes the integrity judgment, and outputs the positioning result normally, thus meeting the signal environment requirements for conducting air interface radiation tests based on the simulated constellation.

[0067] Example 2: Corresponding to Example 1, this example provides an active cancellation system for GNSS air interface test leakage signals. For example... Figure 3 As shown, this system includes: a GNSS simulator 20, an attached active cancellation node 100, and a control unit 60.

[0068] 1. GNSS Simulator 20 The GNSS simulator 20 is a multi-channel vector signal source used to simultaneously radiate the simulated constellation and reconstruct the cancellation replicas. The GNSS simulator 20 includes a normal test channel group 21 and a cancellation channel group 22. The normal test channel group 21 generates the simulated constellation according to a preset test scenario and radiates it to the receiver under test 50 via the main transmitting antenna 31. The cancellation channel group 22 reconstructs a cancellation replica with the same code and opposite phase as the real satellite navigation signal for each real satellite navigation signal, based on the code phase, carrier phase, and Doppler of the real satellite navigation signal. The real satellite navigation signal leaks into the neighborhood of the antenna 51 of the receiver under test 50 from multiple directions through multiple openings W and reflections. The code phase of the cancellation replica is different from the code phase of the simulated constellation, thus allowing the cancellation replica to act on the leaked real satellite navigation signal while preserving the simulated constellation.

[0069] Normal test channel group 21 and cancellation channel group 22 share the same clock reference and the same frequency reference, thereby ensuring that the cancellation replicas and the simulated constellation are consistent in the time and frequency domains, and providing a basis for control unit 60 to perform residual subtraction based on known simulated constellation parameters and self-emission coupled component reconstruction based on known cancellation replicas. The number of channels in cancellation channel group 22 is configured according to the number of visible leaky satellites and frequency points in the neighborhood of the antenna under test 51. It can be implemented by reusing the existing multi-channel resources of GNSS simulator 20, or it can be implemented as an independent extended hardware implementation that shares the clock reference and frequency reference with normal test channel group 21. The inputs of cancellation channel group 22 include: code phase, carrier phase and Doppler of cancellation replicas, as well as predicted carrier phase and complex weights after feedforward extrapolation; the output of cancellation channel group 22 is a cancellation replica weighted by complex weights, and the complex baseband waveforms of each in-use cancellation replica are synchronously provided to control unit 60.

[0070] 2. Attached active cancellation node 100 The attached active cancellation node 100 is positioned close to the antenna under test 51 to perform on-site sensing of leaked real satellite navigation signals, on-site radiation of the cancellation copy, and on-site measurement of the cancellation residual. The attached active cancellation node 100 includes one or more cancellation units 110 arranged around the antenna under test 51 and one or more co-located sensing units 120.

[0071] The cancellation unit 110 is used to radiate the cancellation copy with complex weights, forming a local suppression region around the antenna under test 51 suitable for multi-directional leakage fields. When there are multiple cancellation units 110, they are arranged around the antenna under test 51, with the spacing between adjacent cancellation units 110 being less than half the carrier wavelength, forming a closed or quasi-closed boundary surrounding the aperture of the antenna under test 51. The spatial distribution of the cancellation units 110 includes: ring-shaped, arc-shaped, multi-point distribution, or three-dimensional distribution. The number of cancellation units 110 is determined based on the aperture of the antenna under test 51, the carrier wavelength, the target suppression depth, and the residual convergence result, as described in step 5 of Embodiment 1.

[0072] Sensing unit 120 is used to acquire complex baseband sampling sequences at multiple sampling points in the vicinity of the antenna under test 51, and outputs the complex baseband sampling sequences to control unit 60. During the radiation cancellation replica by cancellation unit 110, the complex baseband sampling sequence includes at least: simulated constellation components, leaked real satellite navigation signals, self-emitted coupling components formed by the coupling path between cancellation unit 110 and sensing unit 120 of the cancellation replica, and noise components. Control unit 60 inputs the complex baseband sampling sequence into the despreading tracking branch and the residual measurement branch respectively, and processes it according to the different subtraction rules described in steps 2 and 6 of Embodiment 1. The location of sensing unit 120 constitutes multiple sampling points as described in step 2 of Embodiment 1, so that the spatial sampling of the leaked signal and the radiation of the cancellation replica are processed on the same spatial boundary.

[0073] The receiving link of sensing unit 120 has a linear dynamic range that covers the power difference between the self-emitted coupling component and the leaked real satellite navigation signal. When the coupling between cancellation unit 110 and sensing unit 120 may cause gain compression or analog-to-digital conversion saturation at the receiving front end, the self-emitted coupling component entering the receiving front end of sensing unit 120 is kept within the linear dynamic range of the receiving link by adding spatial isolation, polarization isolation, transmit / receive isolation circuits, limiting instantaneous radiated power, or setting analog domain self-interference suppression circuits, and then performing digital domain self-emitted coupling component reconstruction and subtraction.

[0074] The cancellation unit 110 and the sensing unit 120 are implemented using miniaturized antenna elements, including microstrip patch antennas, printed dipoles, or miniaturized helical antennas. The overall shape of the attached active cancellation node 100 is a compact ring or multi-point distributed structure surrounding the antenna under test 51, which is mechanically implemented using clamps, brackets, or printed circuit boards, and is fixed in relative position to the antenna under test 51.

[0075] In a preferred embodiment, the cancellation unit 110 and the sensing unit 120 are the same group of antenna elements using time-division multiplexing or frequency-division multiplexing. In time-division multiplexing, the receiving time slot of the sensing unit 120 and the radiating time slot of the cancellation unit 110 do not overlap. In frequency-division multiplexing or in a mode where the receiving and radiating processes overlap, when the in-band component of the cancellation copy enters the receiving channel of the sensing unit 120, the control unit 60 performs the reconstruction and subtraction of the self-emitted coupled component.

[0076] In a preferred embodiment, the cancellation unit 110 and the sensing unit 120 employ a right-hand circular polarization structure or a dual-polarization structure. The right-hand circular polarization structure is consistent with the native polarization of the satellite navigation signal and is used to process the main polarization component with the fewest channels; the dual-polarization structure is used to process the two orthogonal polarization components of the leaked real satellite navigation signal separately, in order to cover the leaked components whose polarization state changes after reflection.

[0077] In a preferred embodiment, the system further includes multiple sets of cancellation units, sensing units, and cancellation channel groups corresponding to multiple navigation frequencies. The multiple navigation frequencies include two or more of L1, L5, B1, and B2a. The multiple sets of cancellation units, sensing units, and cancellation channel groups are used to perform despreading tracking, cancellation copy reconstruction, and radiation on the real satellite navigation signals of the multiple navigation frequencies, respectively. The processing of each navigation frequency is independent of each other and does not interfere with each other.

[0078] In a preferred embodiment, when the receiver under test 50 includes multiple antennas under test 51, there are multiple attached active cancellation nodes 100. Each attached active cancellation node 100 is configured in a one-to-one correspondence with one of the multiple antennas under test 51, and each attached active cancellation node 100 is located adjacent to its corresponding antenna 51. Since each attached active cancellation node 100 performs local suppression based on spatial sampling of the neighborhood of its corresponding antenna 51, there is no need for spatial coupling between the attached active cancellation nodes 100. Only the channel resources occupied by each attached active cancellation node 100 need to be coordinated on the GNSS simulator 20 side. The above preferred embodiment is applicable to multi-antenna test objects such as multiple navigation antennas of an entire aircraft.

[0079] 3. Control Unit 60 The control unit 60 is connected to both the GNSS simulator 20 and the accompanying active cancellation node 100. It can be integrated into the GNSS simulator 20 or the accompanying active cancellation node 100, or it can be interconnected with the GNSS simulator 20 and the accompanying active cancellation node 100 via a communication link as an independent processing platform. The control unit 60 is used to input the complex baseband sampling sequence output by the sensing unit 120 into the despreading tracking branch and the residual measurement branch, respectively. In the despreading tracking branch, after reconstructing and subtracting the self-emission coupling component, it performs satellite-by-satellite despreading tracking, spatial sampling vector construction, and complex weight solution. In the residual measurement branch, after subtracting the known simulated constellation components, it forms the residual and adjusts the complex weights based on the residual.

[0080] The control unit 60 internally includes: a self-emission coupling component reconstruction and subtraction module, a satellite-by-satellite despreading and tracking module, a carrier phase feedforward prediction module, a complex weighting solution module, and a residual closed-loop adjustment module. The self-emission coupling component reconstruction and subtraction module is connected to the sensing unit 120, the cancellation channel group 22, and the complex weighting solution module, respectively. It receives the complex baseband sampling sequence output by the sensing unit 120, the complex baseband waveforms of each in-use cancellation replica output by the cancellation channel group 22, the current complex weighting value output by the complex weighting solution module, and the pre-calibrated transmission relationship from the cancellation unit 110 to each sampling point. It reconstructs the self-emission coupling components formed by each in-use cancellation replica at each sampling point and subtracts the self-emission coupling components from the complex baseband sampling sequence input to the satellite-by-satellite despreading and tracking module. Based on the subtracted tracking sampling sequence, the satellite-by-satellite despreading and tracking module performs correlation despreading and carrier tracking on each missed real satellite navigation signal and outputs complex amplitude, code phase, carrier phase, Doppler, and Doppler rate of change.

[0081] The carrier phase feedforward prediction module is connected to the satellite-by-satellite despreading tracking module and the cancellation channel group 22. It is used to receive the Doppler and Doppler change rate output by the satellite-by-satellite despreading tracking module, output the predicted carrier phase according to the feedforward prediction relationship in step 4 of embodiment 1, and output the predicted carrier phase to the cancellation channel group 22 as the carrier phase input for the cancellation copy.

[0082] The complex weighting solution module is connected to the satellite-by-satellite despreading tracking module and the cancellation channel group 22. It is used to arrange the complex amplitudes of the corresponding satellites at multiple sampling points output by the satellite-by-satellite despreading tracking module according to their geometric positions to form a spatial sampling vector. The complex weighting vector is solved according to the least squares criterion described in step 3 of embodiment 1 and the pre-calibrated transfer matrix. The complex weighting vector is then output to the cancellation channel group 22 as the basis for the cancellation channel group 22 to weight the corresponding channels. The M elements of the complex weighting vector simultaneously determine the complex weights of each channel of the cancellation channel group 22 and the radiation amplitude and phase of each cancellation unit 110.

[0083] The residual closed-loop adjustment module is connected to the sensing unit 120, the normal test channel group 21, and the complex weight value solving module. It receives the complex baseband sampling sequence output by the sensing unit 120, before deducting the self-emission coupling component. It subtracts the known simulated constellation component corresponding to the normal test channel group 21 from the complex baseband sampling sequence to obtain the superimposed component formed by the leaked real satellite navigation signal and the canceled replica. This superimposed component is used as the error signal. When the carrier-to-noise ratio (CNR) corresponding to the error signal is not lower than the target CNR upper limit, the residual closed-loop adjustment module outputs a complex weight value correction to the complex weight value solving module. When the CNR is lower than the target CNR upper limit, it outputs a convergence status flag and maintains the current complex weight value.

[0084] Based on the above explanations of the GNSS simulator 20, the accompanying active cancellation node 100, and the control unit 60, please refer to... Figure 3 The signal flow of this system includes: first, the simulated constellation radiation flow, generated by the normal test channel group 21 of the GNSS simulator 20, radiated through the main transmitting antenna 31, and reaching the antenna under test 51; second, the leakage signal transmission flow, where real satellite navigation signals leak in through multiple openings W and propagate from multiple directions via direct or reflected paths to the antenna under test 51 and the sensing unit 120; third, the cancellation replica radiation flow, generated by the cancellation channel group 22 of the GNSS simulator 20, weighted by complex weights, and radiated by the cancellation unit 110 to the neighborhood of the antenna under test 51; and fourth, the sampling observation flow, where the sensing unit 120 transmits signals containing simulated constellation components and leakage real satellite navigation signals. The signal and the complex baseband sampling sequence of the self-emission coupling component of the cancellation copy are output to the control unit 60; the fifth is the self-emission coupling compensation flow, where the cancellation channel group 22 and the complex weight value solving module provide the cancellation copy waveform and the current complex weight value to the self-emission coupling component reconstruction and subtraction module, respectively. The reconstruction and subtraction module, in combination with the pre-calibrated transmission relationship, reconstructs and subtracts the self-emission coupling component in the despreading tracking branch; the sixth is the residual closed-loop flow, where the residual measurement branch subtracts the known simulated constellation component from the complex baseband sampling sequence of the unsubtracted self-emission coupling component to obtain the superposition component of the real satellite navigation signal and the cancellation copy. The control unit 60 updates the complex weight value according to the superposition component.

[0085] Under normal operating conditions where the leakage conditions at the test site are relatively stable, the multipath is gradually changing, and the relative positions of the antenna under test 51 and the accompanying active cancellation node 100 are fixed, the system operates stably in the closed loop described above. The carrier-to-noise ratio of each leaked real satellite navigation signal at the antenna under test 51 is reduced to below the acquisition threshold of the receiver under test 50 minus the preset margin. The receiver under test 50 only stably acquires the simulated constellation, passes the integrity judgment, and outputs the positioning result normally.

[0086] When the system is running for the first time, the attached active cancellation node 100 is reinstalled, the operating frequency is switched, the relative position of the antenna under test 51 and the attached active cancellation node 100 changes, or the remaining compensation error after deducting the self-emission coupling component exceeds a preset threshold, the control unit 60 suspends the closed-loop update of the weighted values ​​and recalibrates the transmission relationship between each cancellation unit 110 and each sensing unit 120. After calibration, closed-loop operation resumes. When the sensing unit 120 detects gain compression at the receiving front end, abnormal automatic gain control, or clipping of the analog-to-digital conversion, the control unit 60 reduces the instantaneous radiated power of the cancellation unit 110, increases transmit / receive isolation, or enables analog domain self-interference suppression until the sensing unit 120 returns to a linear receiving state.

[0087] When the set of real satellites visible in the sky changes, the control unit 60 continuously scans the pseudo-random code space to detect newly appearing leaky satellites and assigns corresponding cancellation channels to the newly appearing leaky satellites, while releasing the corresponding cancellation channels for leaky satellites that have disappeared; when the leaky composite field undergoes a step change, the control unit 60 accelerates the reconvergence of the complex weights by increasing the adaptive step size; as a fallback protection measure, when the despreading tracking of a real satellite signal loses lock at the sensing unit 120, the control unit 60 suspends the cancellation copy radiation of the corresponding satellite, and resumes radiation after the despreading tracking is relocked; when the simulated satellite... When the real constellation and the leaked real constellation use the same pseudo-random code, the clock of the GNSS simulator 20 is configured to have a code phase deviation from the real GNSS time of not less than a preset number of code chips in the test scenario configuration, so as to distinguish the analog signal and the leaked signal by code phase during despreading and tracking; when a cancellation unit 110 or a sensing unit 120 fails, the control unit 60 sets the contribution of the failed unit to zero in the transfer matrix during the weight solution, and re-solves the complex weight vector of the remaining cancellation units 110. If the number of remaining cancellation units 110 still meets the acquisition threshold requirement, the test continues; otherwise, an alarm is output.

[0088] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for active cancellation of GNSS air interface test leakage signals, characterized in that, Includes the following steps: The GNSS simulator radiates a simulated constellation to the receiver under test via the main transmitting antenna; Before canceling the duplicate radiation, at the antenna under test of the receiver under test, each real satellite navigation signal that leaks in through multiple openings and arrives at the antenna under test from multiple directions via direct or reflected propagation paths is despread and tracked to obtain the complex amplitude, code phase, carrier phase and Doppler of each real satellite navigation signal at multiple sampling points. The spatial sampling vector is constructed based on the complex amplitude. For each real satellite navigation signal, the corresponding complex weights are determined based on the transmission relationship from one or more cancellation units arranged around the antenna under test to multiple sampling points and the spatial sampling vector. Based on code phase, carrier phase, and Doppler, reconstruct a canceled copy that is identical to the real satellite navigation signal in terms of code, code phase alignment, carrier phase reversal, and Doppler consistency; the code phase of the canceled copy is different from the code phase of the simulated constellation. The cancellation copies are distributed to one or more cancellation elements with complex weights to form a local suppression region around the antenna under test; During the closed-loop operation phase, the complex baseband sampling sequences at multiple sampling points are input into the despreading tracking branch and the residual measurement branch, respectively. In the despreading tracking branch, the self-emission coupling component is reconstructed based on the current radiation cancellation copy, the corresponding complex weights, and the transmission relationship. After deducting the self-emission coupling component from the complex baseband sampling sequence, despreading tracking continues. In the residual measurement branch, the known simulated constellation components are subtracted from the complex baseband sampling sequence to obtain the superposition component of the real satellite navigation signal and the canceled copy as the residual. When the carrier-to-noise ratio corresponding to the residual is not lower than the acquisition threshold of the receiver under test, the complex weighting value is adjusted according to the residual.

2. The active cancellation method for GNSS air interface test leakage signals according to claim 1, characterized in that, When there are multiple cancellation units, the multiple cancellation units are arranged around the antenna under test, and the distance between two adjacent cancellation units is less than half the carrier wavelength of the real satellite navigation signal, forming a closed or quasi-closed boundary surrounding the aperture of the antenna under test.

3. The active cancellation method for GNSS air interface test leakage signals according to claim 1, characterized in that, The methods for determining the adjusted weights include: The transfer relationship from one or more cancellation units to multiple sampling points is represented by the transfer matrix G, and the spatial sampling vector is represented by s. The least squares objective function is constructed according to J(w)=‖G·w−s‖2², and the vector that makes the least squares objective function J(w) take the minimum value is determined as the complex weight vector w.

4. The active cancellation method for GNSS air interface test leakage signals according to claim 1, characterized in that, The methods for determining the carrier phase of the canceled replica include: Based on the Doppler and Doppler rate of change of each real satellite navigation signal, according to The predicted carrier phase of the real satellite navigation signal after a loop delay is calculated; where φ(t) is the carrier phase of the real satellite navigation signal at time t, f is the Doppler of the real satellite navigation signal, df / dt is the rate of change of the Doppler, τ is the time delay of the loop consisting of measurement, feedback, generation and radiation, and φp(t+τ) is the predicted carrier phase after a time delay τ; f is the signed Doppler frequency that satisfies dφ(t) / dt=2πf. Based on the predicted carrier phase, the carrier phase of the cancellation copy is determined according to φc(t+τ)=φp(t+τ)+π (mod 2π), and a cancellation copy that is out of phase with the real satellite navigation signal is generated.

5. The active cancellation method for GNSS air interface test leakage signals according to claim 1, characterized in that, The processing of complex baseband sampling sequences at multiple sampling points during the closed-loop operation phase includes: Obtain the complex baseband waveform of each in-use cancellation replica, the current complex weight value corresponding to each in-use cancellation replica, and the amplitude-phase transfer relationship and propagation delay from each cancellation unit to each sampling point; Based on the complex baseband waveform, the current complex weights, the amplitude-phase transfer relationship, and the propagation delay, the signal components formed at each sampling point after each in-use cancellation copy is radiated by each cancellation unit are reconstructed, and the reconstructed signal components are superimposed to obtain the self-emission coupling components at each sampling point. The self-emission coupling component at the corresponding sampling point is subtracted from the complex baseband sampling sequence of the input despreading tracking branch to obtain the tracking sampling sequence, and the real satellite navigation signal is despread and tracked based on the tracking sampling sequence; The simulated constellation components generated by the GNSS simulator and known are subtracted from the complex baseband sampling sequence of the input residual measurement branch to obtain the superposition component formed by the real satellite navigation signal and the canceled copy at the corresponding sampling point, and the superposition component is used as the error signal when adjusting the complex weights.

6. The active cancellation method for GNSS air interface test leakage signals according to claim 1, characterized in that, The adjusted weighted values ​​based on the residuals include: The target carrier-to-noise ratio (CNR) upper limit is determined by subtracting a preset margin from the acquisition threshold of the receiver under test. The CNR of the residual leakage component at the antenna under test is determined based on the residual. When the CNR is not lower than the target CNR upper limit, the complex weights are iteratively corrected using a variable step size least mean square algorithm or a recursive least squares algorithm. When the CNR is lower than the target CNR upper limit, the iterative correction is stopped and the current complex weights are maintained.

7. The active cancellation method for GNSS air interface test leakage signals according to claim 1, characterized in that, The number of one or more cancellation units is determined based on the aperture of the antenna under test, the carrier wavelength, the target suppression depth, and the residual convergence result; When the aperture of the antenna under test is no greater than 0.26 times the carrier wavelength, and a single cancellation unit ensures that the carrier-to-noise ratio of the real satellite navigation signal at the antenna under test meets the acquisition threshold requirement, the number of cancellation units is one. When a single cancellation unit cannot make the carrier-to-noise ratio meet the capture threshold requirement, the number of cancellation units should be increased.

8. A GNSS air interface test leakage signal active cancellation system, characterized in that, include: GNSS simulator (20), attached active cancellation node (100) and control unit (60); The GNSS simulator (20) includes a normal test channel group (21) and a cancellation channel group (22). The normal test channel group (21) is used to generate a simulated constellation and radiate the simulated constellation to the receiver under test (50) via the main transmitting antenna (31). The cancellation channel group (22) is used to reconstruct a cancellation copy of the real satellite navigation signal with the same code, aligned code phase, opposite carrier phase, and consistent Doppler according to the code phase, carrier phase, and Doppler of the real satellite navigation signal. The code phase of the cancellation copy is different from the code phase of the simulated constellation. An attached active cancellation node (100) is positioned close to the antenna under test (51) and includes one or more cancellation units (110) and one or more sensing units (120) arranged around the antenna under test (51); the cancellation unit (110) is used to radiate cancellation copies according to complex weights to form a local suppression region around the antenna under test (51); the sensing unit (120) is used to acquire complex baseband sampling sequences at multiple sampling points in the neighborhood of the antenna under test (51); during the radiating of cancellation copies by the cancellation unit (110), the complex baseband sampling sequence includes: simulated constellation components, leaked real satellite navigation signals, and self-emission coupling components of the cancellation copies that reach the corresponding sensing unit (120) after being radiated by the cancellation unit (110); The control unit (60) is connected to the GNSS simulator (20) and the attached active cancellation node (100) respectively, and is used to input the complex baseband sampling sequence into the despreading tracking branch and the residual measurement branch respectively. In the despreading tracking branch, the self-emission coupling component is reconstructed and deducted according to the cancellation copy of the current radiation, the corresponding complex weight value and the transmission relationship from the cancellation unit (110) to multiple sampling points. Based on the deducted complex baseband sampling sequence, the navigation signal of each real satellite is despread and tracked and a spatial sampling vector is constructed. The complex weight value is determined according to the spatial sampling vector and the transmission relationship. In the residual measurement branch, the known simulated constellation component is deducted from the complex baseband sampling sequence to obtain the superposition component of the real satellite navigation signal and the cancellation copy as the residual, and the complex weight value is adjusted according to the residual.

9. The GNSS air interface test leakage signal active cancellation system according to claim 8, characterized in that, When one or more cancellation units (110) are multiple cancellation units (110), the multiple cancellation units (110) are arranged around the antenna under test (51), and the spacing between adjacent cancellation units (110) is less than half the carrier wavelength of the real satellite navigation signal, forming a closed or quasi-closed boundary surrounding the aperture of the antenna under test (51).

10. The GNSS air interface test leakage signal active cancellation system according to claim 8, characterized in that, One or more cancellation units (110) and one or more sensing units (120) are the same group of antenna units that are time-division multiplexed or frequency-division multiplexed. In the time-division multiplexing mode, the receiving time slot of the sensing unit (120) and the radiation time slot of the cancellation unit (110) do not overlap. When the receiving process of the sensing unit (120) and the radiation process of the cancellation unit (110) overlap in time, or when the in-band component of the cancellation copy enters the receiving channel of the sensing unit (120), the control unit (60) performs reconstruction and subtraction of the self-emission coupling component.

11. The GNSS air interface test leakage signal active cancellation system according to claim 8, characterized in that, One or more cancellation units (110) and one or more sensing units (120) adopt a right-hand circular polarization structure or a dual polarization structure. The dual polarization structure is used to process the two orthogonal polarization components of the real satellite navigation signal respectively.

12. The GNSS air interface test leakage signal active cancellation system according to claim 8, characterized in that, The system also includes multiple sets of cancellation units (110), sensing units (120) and cancellation channel groups (22) corresponding to multiple navigation frequency points. The multiple sets of cancellation units (110), sensing units (120) and cancellation channel groups (22) are used to perform despreading tracking, cancellation copy reconstruction and radiation on the real satellite navigation signals of multiple navigation frequency points respectively.

13. The GNSS air interface test leakage signal active cancellation system according to claim 8, characterized in that, When the receiver under test (50) includes multiple antennas under test (51), there are multiple attached active cancellation nodes (100). The multiple attached active cancellation nodes (100) are set one-to-one with the multiple antennas under test (51), and each attached active cancellation node (100) is set in close proximity to the corresponding antenna under test (51).

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