A Doppler radio direction finding system

Abstract

The application introduces a kind of Doppler radio direction finding system, and relates to radio navigation technical field, including antenna array unit, radio frequency switch matrix, logic controller, single channel receiver and signal processing unit.The logic controller drives radio frequency switch matrix to alternately execute clockwise and counterclockwise direction antenna scanning action in single measurement cycle, signal processing unit extracts corresponding phase slope of positive and negative direction scanning respectively, generates environment error component according to the sum of two and identifies specific antenna oscillator at standing wave node, and logic controller responds to feedback instruction to physically skip on-off operation of the specific antenna oscillator in subsequent timing.The application uses physical symmetry of positive and negative scanning and environment feedback mechanism to actively avoid environment standing wave interference without increasing radio frequency channel, and realizes qualitative change promotion of multipath direction finding precision under single channel system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of radio navigation technology, in particular to a Doppler radio direction finding system. BACKGROUND

[0002] The current Doppler radio direction finding technology is based on the principle of phase modulation, and each array element of the antenna array is controlled to be turned on in turn according to a preset timing sequence. The received signal introduces a periodic phase change related to the direction of arrival of the incident wave, and a single-channel receiver is used to extract the phase change characteristics to solve the azimuth of the radiation source. This technology system has low hardware complexity, single-receiver-channel architecture and high sensitivity, and is widely used in the fields of radio spectrum monitoring, interference source positioning and air traffic control. The theoretical basis of this system relies on the assumption of uniform plane wave propagation in free space. In the actual application environment of urban dense building areas, mountainous areas or indoor environments, the multi-path propagation effect of electromagnetic waves leads to the interference and superposition of direct waves and reflected waves. In space, a complex non-uniform standing wave field is formed. When the antenna array is in such a wave field, the phase of the signal received by each array element depends not only on the geometric position relative to the radiation source, but also on the local standing wave phase distortion at the spatial position. When the direction finding system performs traditional one-way uniform circular scanning, the spatial position difference of the antenna array elements introduces a linear superposition of static geometric phase errors and dynamic Doppler frequency shifts in the time domain baseband signal introduced by scanning motion.

[0003] Both one-way scanning modes show periodic fluctuations with scanning period, and the spectrum characteristics are highly coincident. It is difficult for the receiver to distinguish whether the phase change component is derived from the real physical position of the target or the distortion of the environmental static standing wave at the mathematical processing level. The physical layer spectrum aliasing limits the accuracy of the one-way Doppler direction finding system in complex multipath environment. Although increasing the number of radio frequency channels or expanding the antenna aperture can suppress the influence of multipath, it increases the system volume, power consumption and hardware cost, which restricts the application of portable devices or distributed grid monitoring nodes. In addition to the constraints of hardware architecture, the existing technology also has principle limitations at the software level of scanning control strategy. For example, the Doppler radio direction finding method disclosed in the Chinese invention with the authorization announcement number CN101038333B realizes basic position measurement by calculating the amplitude and phase of the sine quantity, but the core logic still follows the traditional one-way uniform circular scanning mechanism. In the non-uniform standing wave field of multipath effect, the static geometric phase error introduced by the spatial position difference of the antenna element will be linearly superimposed with the dynamic Doppler frequency shift generated by the scanning motion in the time domain baseband signal. Since the scheme only performs single direction rotation scanning, it cannot construct a time sequence conjugate sampling sequence, resulting in a phase ambiguity dilemma at the spectrum analysis level: the receiver cannot distinguish and separate the two components with highly coincident spectrum characteristics from a mathematical mechanism, and cannot identify whether the phase change component is derived from the real physical position of the target or the distortion caused by the environmental standing wave. This physical layer spectrum aliasing directly leads to the serious limitation of the direction finding accuracy of such one-way direction finding system in complex multipath environment, and easily produces direction finding jitter or even false position. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art and provide a Doppler radio direction finding system that maintains a single-channel receiving architecture and low hardware cost, and realizes physical domain decoupling of real position information and environmental standing wave error through bottom-level reconstruction of the scanning control logic, to establish an active sensing and adaptation mechanism for the microscopic characteristics of the signal environment.

[0005] The technical scheme adopted by the present application is:

[0006] A Doppler radio direction finding system, comprising an antenna array unit, a radio frequency switch matrix, a logic controller, a single-channel receiver and a signal processing unit;

[0007] The antenna array unit comprises a plurality of circumferentially distributed antenna elements, and the antenna array unit senses the spatial electromagnetic wave signal and is connected to the radio frequency switch matrix at the output end.

[0008] The logic controller sends time sequence control instructions to the radio frequency switch matrix to drive the radio frequency switch matrix to alternately perform a first scanning action of conducting the antenna elements in a first rotating direction and a second scanning action of conducting the antenna elements in a second rotating direction in a single measurement period, wherein the first rotating direction is opposite to the second rotating direction.

[0009] The single-channel receiver transmits the baseband signal obtained by down-converting the radio frequency signal received by the antenna array selected by the radio frequency switch matrix to the signal processing unit.

[0010] The signal processing unit extracts a first phase slope corresponding to the first scanning action and a second phase slope corresponding to the second scanning action, respectively, and performs a summation operation on the first phase slope and the second phase slope to generate an environment error component representing the degree of multipath scattering of the current electromagnetic environment; the signal processing unit is also configured to inversely map the environment error component to each physical position of the antenna array unit, identify a specific antenna element at a standing wave node position, and feed a shielding instruction containing the address of the specific antenna element to the logic controller.

[0011] The logic controller dynamically reconstructs the time sequence control instructions of the subsequent measurement period in response to the shielding instruction, and physically skips the conducting operation of the specific antenna element in the conducting sequence of the first scanning action and the second scanning action.

[0012] The signal processing unit uses the differential phase data obtained based on the reconstructed time sequence control instructions to solve the incident signal azimuth angle.

[0013] Specifically, the logic controller divides the first scanning action and the second scanning action into multiple time slices, and drives the radio frequency switch matrix in the order of time slice interleaving to construct a time sequence conjugate sampling sequence in a single measurement period; the signal processing unit is configured to perform orthogonalization processing on the sampling sequence, and separate a dynamic Doppler component containing real physical azimuth information from a static phase error component containing an environment error component by using the physical asymmetry that the Doppler shift vector is sensitive to the rotating direction and the environment standing wave geometric phase error is not sensitive to the rotating direction.

[0014] Specifically, the signal processing unit includes an environment fingerprint register for storing and updating the environment error component in real time; the logic controller is configured to monitor the duration of the received signal, and when the duration is less than a complete period threshold required to complete the first scanning action and the second scanning action, control the antenna array unit to only perform the first scanning action to obtain a transient phase feature; the signal processing unit is configured to call the historical environment error component stored in the environment fingerprint register, perform a subtraction correction operation on the transient phase feature, and output the azimuth angle data based on the corrected operation result.

[0015] Specifically, the signal processing unit is configured to identify the specific antenna element according to a preset standing wave trap judgment logic, the standing wave trap judgment logic comprising calculating an instantaneous amplitude response eigenvalue of the specific antenna element and a forward-backward scanning phase consistency eigenvalue and checking whether the following condition is met: wherein is a normalized amplitude response of the specific antenna element in a current scanning period, is a preset amplitude fading coefficient, is an average amplitude of all effective antenna elements of the antenna array unit, is a phase residual modulus value of the specific antenna element between a first scanning action and a second scanning action, is a preset phase dispersion threshold.

[0016] Specifically, the logic controller is configured to generate a timing control instruction according to a preset pseudo-random code sequence, and control the antenna elements in the antenna array unit to be turned on in a non-continuous hopping sequence to apply spread spectrum Doppler modulation to the received signal; the signal processing unit is configured to generate a local reference phase function corresponding to the pseudo-random code sequence, and perform a sliding correlation operation on the demodulated baseband signal and the local reference phase function, and extract differential phase data based on peak phase information output by the correlation operation.

[0017] Specifically, the logic controller is configured to drive the antenna array unit to perform a first scanning action and a second scanning action at a first scanning angular velocity and a second scanning angular velocity in adjacent measurement frames respectively, wherein a ratio of the second scanning angular velocity to the first scanning angular velocity is a preset scaling constant; the signal processing unit is configured to calculate a first difference value at the first scanning angular velocity and a second difference value at the second scanning angular velocity respectively, and check whether a ratio of the second difference value to the first difference value meets the scaling constant; the signal processing unit determines that the difference value contains real physical azimuth information and outputs the azimuth angle only when the ratio meets the scaling constant.

[0018] Specifically, the signal processing unit is configured to generate an interference alarm signal and discard the current measurement data when the ratio deviates from the scaling constant and the deviation exceeds a preset linearity tolerance; the logic controller is configured to adjust a scanning angular velocity combination of a next measurement period in response to the interference alarm signal until the obtained measurement data meets a linear constraint relationship of the scaling constant.

[0019] Specifically, the logic controller is configured to, after receiving a shielding instruction, re-allocate a turn-on time slot originally allocated to a specific antenna element to a healthy antenna element that is physically adjacent to the specific antenna element and has not been identified as the specific antenna element, so as to increase a resampling frequency of the healthy antenna element while keeping a total scanning period unchanged.

[0020] Specifically, the signal processing unit is further configured to construct an environmental channel quality map representing the intensity of the multipath reflection of electromagnetic waves in the current detection area based on the amplitude distribution characteristics of the environmental error component; and the logic controller is configured to dynamically adjust the switching frequency of the first scanning action and the second scanning action according to the gradient change of the environmental channel quality map.

[0021] Specifically, the antenna array unit is composed of an even number of monopole antenna elements forming a single-layer uniform circular array; and the radio frequency switch matrix includes a plurality of PIN diode switches for switching the radio frequency channels between the antenna elements in response to the timing control instructions of the logic controller within a microsecond level.

[0022] Due to the technical solutions described above, the present application has the following advantages:

[0023] 1. In Doppler radio direction finding, the antenna array is driven to perform time-interleaved forward and backward bidirectional scanning, a time-conjugate sampling mechanism of the received signal wave field is constructed, and the physical asymmetry that the Doppler shift vector is sensitive to the rotation direction while the environmental standing wave geometric phase error is not sensitive to the rotation direction is utilized. In the demodulation process, the real azimuth dynamic Doppler component and the multipath interference static environmental error component are orthogonally separated through differential operation. This decoupling based on the physical characteristics of the wave field eliminates the theoretical error in direction finding caused by the linear aliasing of the standing wave field phase distortion and the Doppler shift in the unidirectional scanning system, so that the system can obtain high-fidelity azimuth information in a complex electromagnetic environment without increasing additional calibration channels or complex spatial spectrum estimation algorithms relying on a single-channel receiving architecture.

[0024] 2. The common-mode component is extracted using the forward and backward scanning eigenvalues and value operation, a mapping relationship representing the current spatial electromagnetic field standing wave distribution is established, the signal processing unit identifies the antenna elements in deep fading or strong interference nodes according to the mapping relationship, feeds back sector shielding instructions to the logic controller, and directly eliminates invalid element conduction actions in the subsequent measurement period bottom time sequence generation stage. This hardware closed-loop control logic based on environmental real-time feedback cuts off the input of low signal-to-noise ratio or phase singular data from the sampling source, avoids the convergence shock or direction degree jump caused by processing noise data in the backend algorithm, and ensures the sampling sequence statistical effectiveness and calculation stability of the direction finding system in dense building groups and tunnel multipath scenes.

[0025] 3. A variable rate scanning active physical verification mechanism is introduced, which drives the antenna array to perform scanning at multiple angular velocities in a multiplicative relationship, constructs multi-dimensional signal feature verification coordinates in the frequency domain, and uses the linear physical law that the true spatial Doppler shift is proportional to the scanning angular velocity to determine the linearity consistency of the azimuth component solution, identify and filter out non-linear law compliant signals, intermodulation products or false signals with specific modulation characteristics. This active change of system physical parameter verification signal authenticity detection method improves the system's ability to distinguish between physical targets and signal interference in unknown complex spectral environments, and solves the false alarm or blind speed ambiguity technical problems caused by the influence of signal source modulation characteristics on conventional Doppler direction finders. BRIEF DESCRIPTION OF DRAWINGS

[0026] Fig. 1 The signal processing and feedback control flowchart of the present application for forward and reverse scanning.

[0027] Fig. 2 The one-way and two-way differential scanning mode direction finding accuracy comparison and analysis diagram of the present application.

[0028] Fig. 3 The overall hardware topology architecture and function module composition block diagram of the system of the present application. DETAILED DESCRIPTION

[0029] The present application will be further explained and described below in conjunction with the drawings and examples, which cannot limit the protection scope of the present application. The purpose of disclosing the present application is to protect all technical improvements within the scope of the present application.

[0030] In conjunction with the drawings Figs. 1-3 The Doppler radio direction finding system, based on a single-channel receiving architecture and time sequence inversion control logic, solves the direction finding accuracy degradation problem caused by spatial standing wave field in complex multipath environment, including an antenna array unit, a radio frequency switch matrix, a logic controller, a single-channel receiver and a signal processing unit.

[0031] The antenna array unit senses the spatial electromagnetic wave signal, and the output end is connected to the radio frequency switch matrix. The logic controller serves as the timing scheduling center, and drives the radio frequency switch matrix to execute the antenna conduction sequence through the sending of digital control instructions. The signal processing unit receives the baseband signal after the radio frequency switch matrix gating and the single-channel receiver down-conversion, performs phase feature extraction, differential operation, environment error mapping and azimuth angle solution, and each module is connected through a physical bus to form a closed-loop signal acquisition and processing link. Under the drive of the logic controller, the incident signal azimuth angle solution is completed cooperatively.

[0032] In the radio navigation scene of urban building dense area or indoor, the electromagnetic wave multipath propagation forms a non-uniform standing wave field in the antenna array space, and the phase of the signal received by the antenna element contains inherent geometric phase error depending on the physical position. In order to separate the static error from the dynamic Doppler shift introduced by the antenna scanning motion, the system adopts a forward and reverse bidirectional scanning combined with a differential phase decoupling procedure. The logic controller generates a logic by presetting the timing, drives the RF switch matrix to alternately execute the first scanning action of turning on the antenna element in the first rotation direction and the second scanning action of turning on the antenna element in the second rotation direction in a single measurement period, and uses the time slot interleaving strategy to divide the first scanning action and the second scanning action into microsecond time slices and alternately execute them, so as to ensure that the forward and reverse sampling data correspond to the quasi-steady state of the signal environment. The signal processing unit extracts the phase of the demodulated baseband complex signal and obtains the first phase slope corresponding to the first scanning action and the second phase slope corresponding to the second scanning action, respectively. Based on the physical symmetry of the Doppler effect, the Doppler shift term caused by the true azimuth reverses in sign when the rotation direction is reversed, and the geometric phase error term caused by the environment standing wave remains unchanged. The signal processing unit performs a differential operation , which cancels the static phase error component irrelevant to the rotation direction and extracts the net Doppler component containing only the true physical azimuth information for solving the azimuth angle.

[0033] In view of the deep fading phenomenon caused by the multipath effect, that is, the amplitude collapse and phase noise problem introduced by the fact that part of the antenna elements are at the standing wave node position, the system uses the common mode component of the forward and reverse scanning to establish a physical layer adaptive avoidance mechanism. The signal processing unit performs a summation operation on the first phase slope and the second phase slope to generate an environment error component, which is used as a data confidence evaluation index and is mapped back to the physical address of the antenna array. The signal processing unit monitors the instantaneous amplitude response of the antenna element and the phase consistency during the forward and reverse scanning in real time. When it is detected that a certain antenna element is lower than the preset proportion of the average amplitude of the array , and the phase residual modulus exceeds the preset dispersion threshold , the signal processing unit determines that the element is in the standing wave trap, sends a shielding instruction containing the element address to the logic controller, and the logic controller responds to the instruction to dynamically reconstruct the control timing of the subsequent measurement period, physically skips the certain antenna element in the scanning sequence, or allocates its original time slice to the adjacent healthy antenna element, so as to cut off the low-quality data input at the signal acquisition source. In the embodiment, the preset proportion is , that is To prevent false Doppler orientation caused by frequency modulation of non-cooperative signal sources or external co-channel interference, the system introduces a variable-rate scanning physical truth verification mechanism. The logic controller drives the antenna array to perform measurements at a reference angular velocity in adjacent measurement frames. and angular velocity magnification Perform forward and reverse interleaving scans, and the signal processing unit calculates respectively. First difference result and The second difference result The system utilizes the physical law that the Doppler frequency shift in real space is linearly proportional to the scanning angular velocity to verify the ratio. Ratio to preset rate If the deviation is within the preset linearity tolerance range, the signal processing unit confirms that the current differential result contains the real physical location information and outputs the azimuth angle; otherwise, it determines that there is frequency aliasing interference, triggers an alarm or discards data.

[0034] For burst signals or frequency-hopping signals with extremely short durations, the system is configured with a transient compensation mode based on environmental memory. The signal processing unit maintains an environmental fingerprint register, continuously accumulating and updating the environmental error components calculated from the forward and reverse scan sums during long signal reception or standby periods, forming the current spatial multipath distribution map. When the logic controller detects that the duration of the received signal is less than the time threshold required to complete one full forward and reverse alternating scan, it controls the antenna array to perform only a unidirectional scan to capture transient phase characteristics. The signal processing unit calls the latest environmental error component stored in the environmental fingerprint register. Perform subtraction correction operation , the operation utilizes historical environmental knowledge to feed forward calibration on current transient measurement data, realizing multipath error compensation under one-way scanning restriction; to improve anti-interference ability under the same frequency interference environment, the logic controller supports pseudo-random sequence spread spectrum scanning mode, the logic controller generates discontinuous hopping conduction time sequence according to the preset pseudo-random code, controls the conduction sequence of the antenna element, the nonlinear space sampling introduces spread spectrum Doppler modulation in the received signal, the signal processing unit synchronously generates the local reference phase function corresponding to the pseudo-random code, and performs sliding correlation operation on the demodulated baseband signal and the local reference function, the interference signal or the signal itself modulation characteristics do not have correlation with the system pseudo-random scanning sequence, the energy is smoothed to the noise floor after correlation operation, and the true azimuth signal synchronized with the scanning sequence forms a correlation peak, the signal processing unit extracts the correlation peak phase information, and combines the differential logic to solve the azimuth angle; in the system engineering implementation, the antenna array unit adopts a single-layer uniform circular array layout, is composed of even omnidirectional monopole antennas, the radio frequency switch matrix is composed of high-speed PIN diode switches, has microsecond-level switching response speed, the signal processing unit is realized based on a digital signal processor or a field programmable gate array, performs complex operation, logic decision and control instruction generation, the threshold value parameters, scanning rate and pseudo-random sequence are stored in the system configuration register, and field calibration and updating are supported through an external interface.

[0035] In the wireless radio monitoring scene in the city high-rise building dense area, the Doppler radio direction finding system faces severe multipath interference challenges, the complex electromagnetic wave reflection surface formed by the steel reinforced concrete structures in the area makes the incident signal not present an ideal plane wave at the antenna array, but superimposes a large number of reflection components with random phase delay, forming a non-uniform spatial standing wave field, when the system only performs one-way rotation scanning, the static geometric phase error inherent in the antenna element due to the physical position difference appears as a periodic fluctuation with the same frequency as the rotation frequency in the time domain, directly superimposed on the real Doppler frequency shift signal, in the baseband signal spectrum output by the receiver, the environmental error component and the real azimuth information are linearly mixed, causing the azimuth angle calculated by the conventional direction finding algorithm to deviate greatly, and even pointing to the wrong reflection source direction; for this working condition, the Doppler radio direction finding system in this embodiment starts the bidirectional time sequence inversion scanning mode, the logic controller drives the radio frequency switch matrix to alternately perform the first scanning action in the clockwise direction and the second scanning action in the counterclockwise direction in a single measurement period in a microsecond-level time slot interlaced manner, the signal processing unit extracts the first phase slope corresponding to the first scanning action and the second phase slope corresponding to the second scanning action, since the Doppler frequency shift vector is sensitive to the rotation direction, i.e. the sign of the frequency shift is reversed when the rotation direction is reversed, and the geometric phase error caused by the environmental standing wave mainly depends on the spatial position of the antenna element, which is not sensitive to the rotation direction, the system performs differential operation , which utilizes the difference in physical symmetry.

[0036] The static standing wave error component is canceled at the mathematical processing level, and the net Doppler component containing only the true incident direction is separated. In the dense multipath environment, part of the antenna elements inevitably are at the node position of the standing wave field, the received signal amplitude is attenuated to the noise floor level, and the phase presents random jumps. The signal processing unit calculates the sum of the eigenvalues of the forward and reverse scanning characteristics The environmental error component is extracted and inversely mapped to the physical address of the antenna array. The system monitors the instantaneous amplitude response of each element in real time The phase consistency Once the amplitude of a specific antenna element is identified to be lower than the preset ratio of the array average amplitude, such as times, and the phase residual exceeds the threshold value, the system determines that the element falls into the standing wave trap. The logic controller dynamically reconstructs the scanning timing of the next period and physically skips the on operation of the failed element. This active avoidance mechanism based on environmental feedback cuts off the pollution of low signal-to-noise ratio data to the differential operation from the source of signal acquisition, ensuring the stability of the final azimuth angle solution. This embodiment shows that, through the differential and common mode operation of the forward and reverse bidirectional scanning, the system solves the fundamental contradiction that the single-channel system cannot separate environmental errors in a strong multipath environment without increasing the number of radio frequency channels. The system strips the static error through differential operation, identifies and avoids the standing wave trap using the common mode component, and realizes high-precision direction finding in complex electromagnetic environments.

[0037] Embodiment 2: This embodiment aims to construct a high-simulation multipath transmission test platform to quantitatively verify the anti-interference performance of the Doppler radio direction finding system in complex electromagnetic environments and empirically analyze the suppression effect of the forward and reverse bidirectional scanning and differential phase decoupling mechanism on the static standing wave error.

[0038] The test platform consists of a multipath channel simulator, a vector signal source, an N-element uniform circular array antenna model, and a prototype verification receiver. The vector signal source is used to generate a single-carrier test signal with a center frequency of The signal is fed into each port of the antenna array through the multipath channel simulator. The multipath channel simulator is configured as a Rayleigh fading channel model to simulate the typical non-line-of-sight (NLOS) propagation environment in urban dense building areas. In this model, there is a line-of-sight propagation path, and three reflection paths with different time delays , amplitudes assumed to obey Rayleigh distribution, and phases assumed to obey uniform distribution The channel multipath time delay spread is set to To simulate the real industrial electromagnetic environment, a Gaussian white noise with a signal-to-noise ratio (SNR) of is actively superimposed in the signal. The receiver sampling rate is set to The corresponding time resolution is sufficient to resolve the microsecond level scanning time slot.

[0039] The core of the test is to verify the effectiveness of the technical solution by comparing the direction finding errors under different scanning strategies, and two control groups are set up:

[0040] The control group (one-way scanning): the logic controller is configured to drive the antenna array to only perform the traditional clockwise one-way scanning, and the scanning period is .

[0041] The sample group of the application (two-way differential scanning): the logic controller is configured to drive the same antenna array to perform two-way scanning with clockwise and counterclockwise alternation, and the total scanning period is maintained at , and the forward and reverse scanning time slots each account for and are interleaved.

[0042] Both groups of tests are carried out under the same multipath channel parameters and signal-to-noise ratio conditions times of Monte Carlo simulation, and the azimuth error is counted.

[0043] The test data are recorded in Table 1, in which the root mean square value (RMSE) of the direction finding error is used to quantify the direction finding accuracy, and the error convergence probability refers to the proportion of samples whose direction finding error is less than .

[0044] Table 1: Direction finding performance comparison test data table

[0045]

[0046] Referring to Table 1, under the harsh working conditions of a signal-to-noise ratio of and the existence of 3 strong reflection paths, the direction finding error RMSE of the control group is as high as , and only of the measurement results converge around the true value, which shows that under the one-way scanning mode, the static phase error and Doppler shift introduced by the multipath effect occur serious nonlinear aliasing, resulting in algorithm failure. In comparison, the RMSE of the sample group of the application under the same conditions is reduced to , and the error convergence probability is improved to , which shows that even in an environment where strong noise and multipath interference coexist, the two-way scanning differential mechanism can still effectively strip the geometric phase error independent of the rotation direction and restore the high-fidelity Doppler phase information; further analysis of the data in Table 1 shows that when the signal-to-noise ratio is improved to , the RMSE of the control group is only slightly improved to , which shows that the error is mainly caused by the multipath structure rather than random noise, and it is a systematic error floor. The RMSE of the sample group of the application is further converged to , which proves that the differential mechanism can extract the Doppler component more purely when the signal-to-noise ratio is improved, and the direction-finding accuracy of the system presents a good linear gain with the improvement of the signal-to-noise ratio, and the performance saturation phenomenon in the control group does not appear; in order to verify the effectiveness of the standing wave trap avoidance mechanism, the amplitude monitoring data is further introduced, and in the above multipath scene, the instantaneous amplitude response of the 3rd and 7th antenna elements is long lower than the array average amplitude , and the phase variance is higher than that of other elements, and after the standing wave trap avoidance function is turned on, the logic controller automatically removes the sampling data of the two elements in the timing, and it is found by comparing the data before and after the avoidance function is turned on that the jitter variance of the azimuth angle solution is reduced by about , which proves that by cutting off low-quality sampling points at the physical layer, the disturbance of phase singularity caused by deep fading on the overall direction-finding result can be effectively suppressed.

[0047] Embodiment 3: This embodiment combines Figs. 1 to 3 , a kind of Doppler radio direction finding system is described, as shown in Fig. 1 , the spatial electromagnetic wave signal containing multipath and direct wave components is incident to the antenna array unit composed of single-layer uniform circular array and even elements, the radio frequency switch matrix responds to the timing control instruction containing forward and reverse scanning and skipping certain element information issued by the logic controller, performs forward and reverse alternating scanning action and transmits the selection signal to the single-channel receiver through the radio frequency transmission channel, the single-channel receiver down-converts the radio frequency signal to baseband signal and transports to the signal processing unit, the signal processing unit extracts differential phase and standing wave trap decision for azimuth solution and outputs the incident signal azimuth angle, and the shielding instruction and environmental error are fed back to the logic controller according to the decision result, to trigger timing scheduling and dynamic reconstruction of scanning sequence.

[0048] As shown in Fig. 2 , wherein the ordinate represents the direction-finding error root mean square value unit in degrees, and the abscissa covers two typical test scenes of 10dB signal-to-noise ratio and 3 multipaths and 20dB signal-to-noise ratio and 3 multipaths, the data column of one-way scanning RMSE and two-way differential scanning RMSE is distinguished by the legend, and the intuitive data shows that the error amplitude of two-way differential scanning mode is lower than that of one-way scanning mode in the two scenes, which confirms the effective suppression of differential algorithm to static environmental error.

[0049] As shown in Fig. 3As shown, the overall hardware architecture of the system is specifically divided into an antenna array subsystem deployed in an external complex electromagnetic environment and a direction finding host processing subsystem located indoors, wherein the antenna array subsystem is usually installed outdoors or on the roof of a vehicle, including a single-layer uniform circular array antenna group receiving target radiation source signals and multipath reflection interference, and a radio frequency switch matrix module composed of PIN diode high-speed switching circuit, the subsystem is connected to the direction finding host processing subsystem through a low-loss radio frequency transmission cable and a timing control bus, the host includes a radio frequency receiving channel integrated with down-conversion and analog-to-digital conversion functions and a digital logic and signal processing board, the processing board further integrates a logic controller, a signal processing unit and an environment fingerprint memory, for performing timing generation, sector masking and differential calculation, and finally transmitting the calculated azimuth and channel quality map to a human-computer interaction terminal for display through a data interface.

[0050] Embodiment 4: This embodiment aims to target the technical repair and deepening disclosure of the variable rate scanning physical true value checking mechanism in the Doppler radio direction finding system, in the foregoing specific embodiments and embodiments, although the principle of differential checking by the reference angular velocity and the rate angular velocity is described, there are potential timing logic black boxes and parameter adaptive black boxes for measurement synchronization, checking tolerance dynamic calibration logic and specific frequency aliasing decision flow in non-stationary signal environment, this embodiment will eliminate the above technical ambiguities by constructing a time division duplexing (TDD) dual-speed scanning frame structure and an adaptive linearity decision model, to ensure the effectiveness and stability of the key checking mechanism in the real complex spectrum environment; this embodiment constructs a dual-speed scanning frame structure based on time division duplexing (TDD) to solve the time synchronization problem of dual-speed measurement under a single receiving channel, the logic controller defines a checking period containing two subframes, wherein the first subframe performs scanning at the reference angular velocity , and the second subframe performs scanning at the rate angular velocity , in order to ensure that the same signal environment is sampled by the two subframes, the time interval between the two subframes is set to be less than the channel coherence time , for the vehicle-mounted mobile direction finding scene (maximum moving speed ), is strictly limited to not more than , in the first subframe, the logic controller drives the antenna array to perform the forward and reverse interleaved scanning at the angular velocity , and the signal processing unit extracts and temporarily stores the first differential result ; then in the second subframe, the antenna array is driven at the angular velocity (set to ​) performing forward and backward interlaced scanning to extract the second difference result .

[0051] On this basis, the embodiment clearly defines the linearity check tolerance of the dynamic adaptive calibration procedure. Instead of using a fixed decision tolerance, the system adjusts in real time according to the current received signal SNR and frequency stability. The signal processing unit estimates the SNR of the current signal and calculates the theoretical direction finding error variance based on the CRLB principle , and the linearity check tolerance is constructed as a function of the theoretical error, that is , where is the confidence coefficient, usually taking the value of (corresponding to a confidence interval), which means that when the signal quality is poor and the direction finding jitter is large, the system automatically relaxes the check tolerance to avoid excessive discarding of valid data; when the signal quality is excellent, the tolerance is automatically tightened to improve the discrimination ability of weak interference. The final frequency aliasing decision logic performs the following atomic level operations: the system calculates the ratio deviation , when , the system determines that the current extracted Doppler component satisfies the physical reality constraint, that is, its frequency shift strictly changes linearly with the scanning speed, and confirms it as a real spatial azimuth signal. If , it is determined that the signal component is caused by the instantaneous frequency deviation of the non-cooperative target's own modulation such as FM modulation or co-frequency interference, and the system directly discards the data frame and triggers the frequency agile or anti-interference processing flow. Through the explicit timing frame structure and adaptive decision model, this embodiment completely eliminates the technical black box of the variability scanning check, and ensures the physical true value discrimination ability of the system in the coexistence environment of non-cooperative targets and complex interference.

[0052] Embodiment 5: This embodiment aims to target the standing wave trap decision logic of the signal processing unit in the Doppler radio direction finding system for technical repair and deepening disclosure. In the foregoing specific embodiments, although the description of the standing wave trap decision logic gives the calculation principle and decision formula of the instantaneous amplitude response eigenvalue and the forward and backward scanning phase consistency eigenvalue , the specific extraction algorithm, normalization processing procedure, and decision threshold and The dynamic adaptive generation mechanism has potential algorithm path black boxes and parameter setting black boxes. This embodiment will eliminate the above-mentioned technical ambiguities by embedding pseudocode-level operation flow description and parameter adaptive logic, ensuring the reproducibility and engineering stability of this key logic. This embodiment constructs a real-time decision module for standing wave traps based on sliding window statistics and dynamic thresholds, which is embedded in the FPGA or DSP of the signal processing unit and executed in parallel with the phase difference calculation process. The input data stream of this module is a baseband complex signal sequence after being switched by an RF switch matrix and down-converted and analog-to-digital converted by the receiver. The decision-making process is designed as a closed-loop pipeline that includes feature extraction, statistical normalization, and dual threshold verification.

[0053] Execute instantaneous amplitude response characteristic value Extraction and normalization, the system sets the length to be [length]. A sliding time window that covers the conduction time slot of a single antenna element, for the first... The antenna element is at the... Sampling sequence within a measurement period The processor calculates the root mean square (RMS) value of the power envelope, i.e. To eliminate global amplitude fluctuations caused by receiver gain fluctuations and changes in signal source distance, the system maintains a global average amplitude reference value. This value is composed of all values ​​within the current measurement period. The average power envelope of each antenna element is calculated, i.e. Perform normalization operation to obtain the first... Normalized amplitude response of antenna element This step converts the amplitude characteristics from absolute level values ​​to relative strength ratios, ensuring that the decision logic is insensitive to fluctuations in the total signal energy, and simultaneously performs forward and reverse scanning of phase consistency characteristics. The calculation, for the first The system extracts the phase mean of each antenna element within the forward scanning time slot. Phase average within the reverse scan time slot Considering the sign reversal characteristic introduced by the Doppler frequency shift in both forward and reverse scanning, the system performs sign compensation or conjugate processing on the reverse scanning phase to align it with the forward phase under ideal error-free conditions, and calculates the phase residual between the two. To enhance the statistical stability of the judgments, Defined as the phase residual in the most recent The weighted moving average over a measurement period, i.e. ,in The forgetting factor typically takes a value between 100 and 1500. to This is used to balance sensitivity and noise immunity.

[0054] On this basis, the embodiment further determines the threshold and adaptive setting procedures to solve the adaptability problem of the fixed threshold in the non-stationary electromagnetic environment, for the amplitude fading coefficient , the system no longer uses a fixed constant, but is dynamically adjusted according to the multipath severity index of the current environment, derived from the amplitude distribution of the aforementioned environment error component, specifically, the system calculates the standard deviation of the amplitude response of all antennas in the current period , and sets to , wherein is a preset sensitivity coefficient, which means that when the environmental multipath effect is weak and the amplitudes of the antennas tend to be consistent, the value approaches , and the system remains sensitive to small amplitude drops; when the multipath effect is strong and the amplitude fluctuates greatly, the value is automatically reduced to avoid misjudgment, and for the same reason, the phase dispersion threshold is set to a multiple of the phase noise level of the system, that is, , wherein is the measured value of the phase noise base of the receiver in the idle channel, and the final decision logic performs double verification: when and are satisfied at the same time, the antenna element is determined to be in a standing wave trap, and the logic controller generates a shielding mask for the element and takes effect in the control command of the next scanning period. Through the specific digital signal processing flow and parameter adaptive rules, this embodiment eliminates the technical black box of the standing wave trap decision logic, ensures that the system can accurately identify and avoid failed antennas under different signal-to-noise ratios and multipath intensities, and thus guarantees the direction-finding accuracy.

[0055] Example 6: In the actual engineering deployment of the Doppler radio direction finding system, to solve the problem of deviation between system performance in different channel environments and simulation design, a set of offline calibration and data filling procedures for channel environment characteristics can be used. The procedure aims to obtain and solidify the nonlinear mapping relationship between multipath fading factor, noise power spectral density and direction finding error through standardized offline tests, to construct a lookup table or neural network model for online correction. In the calibration process, a multi-channel vector signal generator is used to simulate radio frequency signals under different combinations of multipath delay, Doppler shift and signal-to-noise ratio. The signal is fed into the receiver front-end through a precision step attenuator. The system iterates through the preset channel parameter grid one by one, records the statistical values of the environmental error components and the real azimuth angle residuals corresponding to each test point, and establishes a correlation model between channel characteristic parameters and error compensation through regression analysis of massive measured data. The model parameters are written into the non-volatile memory of the signal processing unit as a reference for online operation.

[0056] To ensure the rapid adaptability of the system in diversified field environments, this embodiment also defines a set of pre-deployment calibration and debugging procedures. After the initial installation or replacement of major components, the procedure is executed to calibrate the amplitude and phase consistency of the radio frequency channels and the mutual coupling effect of the antenna array. The calibration process uses an internal or external standard reference source that emits a single carrier signal with known orientation, frequency and power. The logic controller drives the antenna array to perform omnidirectional scanning, and the signal processing unit collects the response data of each antenna element. The least squares method is used to solve the amplitude and phase error coefficient matrix between channels. The system loads the coefficient matrix as pre-distortion parameters into the digital beamforming or phase extraction module for channel equalization and mutual coupling compensation of subsequent real-time signals. This procedure ensures that the hardware channel characteristics of the system in different physical deployment states can converge to the design indicators, ensuring the long-term stability of the direction finding accuracy.

[0057] Example 7: This embodiment provides a set of pre-deployment calibration and engineering parameter calibration procedures for the Doppler radio direction finding system, aiming to ensure that the system can adaptively determine key control parameters and establish a reliable initial working baseline according to the electromagnetic environment characteristics of specific application scenarios and hardware batch differences before being put into actual operation. The system performs radio frequency channel consistency calibration. When the system starts, the logic controller drives the radio frequency switch matrix to switch all antenna channels to the internal standard reference source. The reference source generates a single carrier signal with a frequency of the system center frequency and a power of The signal processing unit collects the baseband signals of each channel and calculates the amplitude ratio and phase difference of the remaining channels relative to the reference channel based on the first antenna channel. The system generates a set of complex calibration coefficients accordingly and writes them into the pre-distortion filter of the digital front-end to compensate for the hardware inconsistency of the radio frequency link, ensuring that the amplitude and phase errors of the array response are less than and .

[0058] Environmental noise baseline calibration is performed. During quiet periods when no target signals are emitted, the system performs a full-band scan, and the signal processing unit... Within the bandwidth, To achieve the stepping, the noise power spectral density of the receiver is measured. Based on this measurement result, the system establishes a noise baseline model of the current environment and sets a phase dispersion threshold. Calculation baseline parameters Set as the root mean square value of phase noise in this frequency band This step establishes the system's sensitivity boundaries and decision thresholds under the current electromagnetic background. Then, a dynamic adaptation test of the scan rate and calibration tolerance is performed. The logic controller drives the antenna array at a series of preset angular velocities (ranging from...). to Step The virtual scan is performed, and the signal processing unit analyzes the system response stability at each scan rate. Combined with the expected Doppler frequency shift range of the target signal, the optimal reference angular velocity is determined. With angular velocity magnification The system generates a set of test signals with known linearity characteristics using a built-in analog signal source, and automatically adjusts the linearity verification tolerance. Until that tolerance can be met. It has a high probability of correctly identifying the linear characteristics of analog signals, and its false negative rate for nonlinear interference signals is lower than that of analog signals. Finally, to establish the initial filling of the environmental error fingerprint database, the system, with the assistance of several beacon sources at known azimuths, performs long-term bidirectional scanning in both directions. The signal processing unit extracts the environmental error components in each direction and uses interpolation algorithms to construct an omnidirectional fingerprint database. The initial environmental error map is stored in the environmental fingerprint register as the cold start data basis for subsequent transient compensation mode. Through the above standardized procedures, the system completes the complete initialization process from hardware calibration and environmental awareness to parameter optimization, ensuring reliable operation under non-ideal engineering conditions.

[0059] Example 8: The signal processing unit maintains a dynamic mapping table corresponding to the conduction time slot index and the physical azimuth angle of the antenna element. When the logic controller responds to the shielding command and performs timing reconstruction, the signal processing unit synchronously updates the mapping table, incorporating the measured phase data of each sampling point in the reconstructed conduction sequence. Physical azimuth angle of the actual connected antenna element When rematching, performing differential phase extraction or sliding correlation operations, the signal processing unit calls the updated... Sequence construction utilizes non-uniform Discrete Fourier Transform (NDFT) kernel functions or reconstructs steering vectors to counteract spatial sampling non-uniformity introduced by physical skipping of specific oscillators or time slot redistribution, maintaining the mathematical linearity of azimuth angle calculation; standing wave trap decision logic amplitude fading coefficient and phase dispersion threshold Based on the field environment noise floor calibration process during the system power-on initialization phase, the system scans the entire operating frequency band during the quiet period when there is no useful signal input on the RF channel, and calculates the standard deviation of the phase noise floor for each logic channel. ,Will Set as Statistical confidence upper bound, amplitude fading coefficient Based on the receiver's linear dynamic range and the statistical characteristics of multipath Rayleigh fading in the current scene, the 20th percentile of the mean amplitude of all effective array elements in the current measurement frame is taken to define the physical boundary between deep fading nodes and normal signal amplitude fluctuations in a strong multipath environment.

[0060] To suppress transient disturbances caused by high-speed switching of the RF switch matrix, the logic controller inserts a fixed-duration guard interval between adjacent conduction time slots. The duration is set to 1.5 to 2.0 times the nominal rise time of the PIN diode switching device, and the receiver is in... During this period, the analog-to-digital converter sampling is paused to shield switching noise. Environmental error component updates follow a sliding window weighting mechanism, and the signal processing unit only updates the check ratio. The deviation from the preset scaling factor constant is less than the linearity tolerance. Environmental errors are extracted from the measurement frame and written into a non-volatile memory environmental fingerprint database. The fingerprint database stores static phase error correction values ​​at different frequencies using frequency points as indexes, which can be directly called by the system in transient measurement mode.

[0061] The parts of this invention not described in detail are prior art.

[0062] The embodiments selected herein for the purpose of disclosing the inventive objectives are currently considered suitable; however, it should be understood that the invention is intended to include all variations and modifications of the embodiments that fall within the scope of this concept and invention.

Claims

1. A Doppler radio direction finding system characterized by: The antenna array unit, the radio frequency switch matrix, the logic controller, the single-channel receiver and the signal processing unit are connected in series. The antenna array unit comprises a plurality of circumferentially distributed antenna elements, and is configured to sense spatial electromagnetic wave signals and output the signals to the radio frequency switch matrix. The logic controller is configured to send time sequence control instructions to the radio frequency switch matrix to drive the radio frequency switch matrix to alternately perform a first scanning action of turning on the antenna elements in a first rotation direction and a second scanning action of turning on the antenna elements in a second rotation direction in a single measurement period, wherein the first rotation direction is opposite to the second rotation direction. The single-channel receiver is configured to transmit baseband signals obtained by down-converting radio frequency signals received by the antenna array unit selected by the radio frequency switch matrix to the signal processing unit. The signal processing unit is configured to extract a first phase slope corresponding to the first scanning action and a second phase slope corresponding to the second scanning action, and perform summation operation on the first phase slope and the second phase slope to generate an environment error component representing a degree of multipath scattering in a current electromagnetic environment. The signal processing unit is further configured to inversely map the environment error component to each physical position of the antenna array unit, identify a specific antenna element at a standing wave node position, and feed a shielding instruction containing an address of the specific antenna element to the logic controller. The logic controller is configured to dynamically reconstruct time sequence control instructions of a subsequent measurement period in response to the shielding instruction, and physically skip the turning on operation of the specific antenna element in the turning on sequence of the first scanning action and the second scanning action.

2. The Doppler radio direction finding system of claim 1, wherein: The signal processing unit is configured to use differential phase data obtained based on the reconstructed time sequence control instructions to calculate an incident signal azimuth angle.

3. The Doppler radio direction finding system of claim 1, wherein: The logic controller is configured to divide the first scanning action and the second scanning action into a plurality of time slices, and drive the radio frequency switch matrix in a time slice interleaving order to construct a time sequence conjugate sampling sequence in a single measurement period. The signal processing unit is configured to perform orthogonalization processing on the sampling sequence, and separate a dynamic Doppler component containing real physical azimuth information from a static phase error component containing the environment error component by using physical asymmetry that is sensitive to the rotation direction but not sensitive to the rotation direction of the environment standing wave geometric phase error.

4. The Doppler radio direction finding system of claim 1, wherein: The signal processing unit is configured to identify the specific antenna element according to a preset standing wave trap judgment logic, which includes calculating an instantaneous amplitude response eigenvalue of the specific antenna element and a forward-backward scanning phase consistency eigenvalue and checking whether the following condition is satisfied: wherein is a normalized amplitude response of the specific antenna element in a current scanning period, is a preset amplitude fading coefficient, is an average amplitude of all effective antenna elements of the antenna array unit, is a phase residual modulus value of the specific antenna element between a first scanning action and a second scanning action, is a preset phase dispersion threshold.

5. The Doppler radio direction finding system of claim 1, wherein: The signal processing unit comprises an environment fingerprint register configured to store and update the environment error component in real time. The signal processing unit is configured to call historical environment error components stored in the environment fingerprint register, perform subtraction correction operation on the transient phase feature, and output an azimuth angle data based on a corrected operation result. The logic controller is configured to generate time sequence control instructions based on a preset pseudo-random code sequence, and control the antenna elements in the antenna array unit to be turned on in a non-continuous hopping order to apply spread spectrum Doppler modulation to the received signal. The signal processing unit is configured to generate a local reference phase function corresponding to the pseudo-random code sequence, and perform a sliding correlation operation on the demodulated baseband signal and the local reference phase function, and perform extraction of differential phase data based on peak phase information output by the correlation operation.

6. The Doppler radio direction finding system of claim 1, wherein: The logic controller is configured to drive the antenna array unit to perform first and second scanning actions in adjacent measurement frames at a first scanning angular velocity and a second scanning angular velocity, respectively, wherein a ratio of the second scanning angular velocity to the first scanning angular velocity is a preset scaling constant; and the signal processing unit is configured to calculate a first difference value at the first scanning angular velocity and a second difference value at the second scanning angular velocity, respectively, and check whether a ratio of the second difference value to the first difference value meets the scaling constant. The signal processing unit is configured to determine that the difference values contain real physical azimuth information and output an azimuth angle only when the ratio meets the scaling constant.

7. The Doppler radio direction finding system of claim 1, wherein: The signal processing unit is configured to generate an interference alarm signal and discard current measurement data when the ratio deviates from the scaling constant and the deviation exceeds a preset linearity tolerance; and the logic controller is configured to adjust a scanning angular velocity combination of a next measurement period in response to the interference alarm signal until measurement data obtained satisfies a linear constraint relationship of the scaling constant.

8. The Doppler radio direction finding system of claim 1, wherein: The logic controller is configured to, after receiving a shielding instruction, re-allocate an on-time originally allocated to a specific antenna element to a healthy antenna element that is physically adjacent to the specific antenna element and has not been identified as the specific antenna element, so as to increase a resampling frequency of the healthy antenna element while keeping a total scanning period unchanged.

9. The Doppler radio direction finding system of claim 1, wherein: The signal processing unit is further configured to construct an environmental channel quality map representing a multipath reflection intensity of an electromagnetic wave in a current detection area based on an amplitude distribution characteristic of the environmental error component; and the logic controller is configured to dynamically adjust a switching frequency of the first and second scanning actions according to a gradient change of the environmental channel quality map.

10. The Doppler radio direction finding system of claim 1, wherein: The antenna array unit is composed of an even number of monopole antenna elements to form a single-layer uniform circular array; and the RF switch matrix includes a plurality of PIN diode switches configured to complete RF channel switching between the antenna elements within a microsecond level in response to a timing control instruction of the logic controller.

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