Land-based navigation channel monitoring method and system based on ZYNQ

Abstract

The invention belongs to the technical field of interference signal identification, and discloses a land-based navigation channel monitoring method and system based on ZYNQ. The method comprises the following steps: carrying out channel scanning to obtain channel information corresponding to VOR, ILS and DME systems, and receiving radio frequency signals in corresponding channels; the radio frequency signals are processed to obtain IQ signals corresponding to a VOR system, an ILS system and a DME system; receiving signals, without navigation signals, of the ILS system, the VOR system and the DME system are obtained; the existence interval of interference is judged through an energy detection method; and in an interval in which the interference signal exists, identifying the pulse signal, and judging the bandwidth of the interference signal through FFT (Fast Fourier Transform) so as to judge the type of the interference signal. Receiving and interference recognition of the land-based navigation system are integrated, and receiving, processing and interference monitoring of the three land-based navigation systems of VOR, ILS and DME are included, so that the integration level is greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of interference signal identification, and in particular relates to a ZYNQ-based land-based navigation channel monitoring method and system. Background Art

[0002] In the field of aircraft navigation, land-based navigation systems hold significant engineering value. Distance Measuring Equipment (DME), also known as a pulse short-range navigation system, provides straight-line distance information between the aircraft and the ground station. The Instrument Landing System (ILS) is a crucial navigation device for safe landings in inclement weather and low visibility. It provides precise positioning at the approach altitude and guides the aircraft on approach. The Very High Frequency Omnidirectional Range (VOR) provides information such as aircraft azimuth, heading, VOR azimuth, and relative azimuth.

[0003] Through the above analysis, the problems and defects of the existing technology are as follows: due to the regional shortage of aviation frequency band resources, the land-based navigation system faces threats from multiple interference sources and is easily affected by AM broadcasting, FM broadcasting and linear FM signals of civil aviation primary radar, resulting in reduced accuracy of the land-based navigation system and poor aircraft safety. Summary of the Invention

[0004] To overcome the problems existing in the related art, the embodiments disclosed in the present invention provide a land-based navigation channel monitoring method and system based on ZYNQ (Zynq-7000 All Programmable SoC, i.e. FPGA+ARM).

[0005] The technical solution is as follows: A ZYNQ-based land-based navigation channel monitoring method includes the following steps:

[0006] S1, using the radio frequency transceiver to scan the land-based navigation channels including the VOR system, ILS system and DME system in sequence, obtain the channel information corresponding to the VOR system, ILS system and DME system, and receive the radio frequency signals in the channels;

[0007] S2, the RF transceiver processes the received RF signal to obtain the IQ signals corresponding to the VOR system, ILS system and DME system respectively;

[0008] S3: The RF transceiver estimates the frequency of the received IQ signals corresponding to the ILS and VOR systems through the ARM, and processes the signals through the FPGA to obtain the received signals corresponding to the ILS and VOR systems without navigation signals. The RF transceiver sends the received IQ signals of the DME system to the FPGA for signal processing to obtain the received signal of the DME system without navigation signals.

[0009] S4, for the received signals without navigation signals corresponding to the ILS system and VOR system, and for the received signals without navigation signals obtained from the DME system, the interference existence interval is determined by the energy detection method; within the interval where the interference signal exists, the pulse signal is identified; and the bandwidth of the interference signal is determined by FFT, thereby determining the type of the interference signal.

[0010] In step S1, the radio frequency transceiver is used to sequentially scan the land-based navigation channels including the VOR system, ILS system, and DME system, including:

[0011] The ARM side configures the RF transceiver in the RF front-end receiving unit; for the received signal, it scans the channels in sequence, scanning each channel for 2 seconds, and calculates and records the received power of the channel; after all channels have been scanned, it checks that the channel with the highest received power is the channel currently in use. The ARM side adjusts the RF transceiver to adjust the receiving frequency to the corresponding channel bandwidth, and returns data at the same time to obtain the current channel information; the received signal power is judged and adaptively adjusted.

[0012] In step S2, the RF transceiver processes the received RF signal to obtain IQ signals corresponding to the VOR system, ILS system, and DME system, respectively, including:

[0013] The envelope detection method is used to demodulate the received signal. The square sum of the in-phase and quadrature branches is calculated, and then the square root is calculated. The calculation formula is as follows:

[0014] x 11 (n) = x(n)cos(ωn) (1)

[0015] x 21 (n) = x(n)sin(ωn) (2)

[0016]

[0017] Where x 11 (n) and x 21 (n) is the IQ signal, ω is the carrier frequency, m(n) is the baseband signal, x(n) is the received signal, and n is the sampling point number;

[0018] The baseband signal passes through a FIR low-pass filter with a sampling frequency of 40 MHz and a passband frequency of 1 MHz. The FIR filter equation is:

[0019]

[0020] Where h(k) is the coefficient of the filter, x(nk) is x(n) delayed by k cycles, y(n) is the filter output signal, N is the filter order, and k is the number of delay cycles.

[0021] The transfer function H(z) of the system is expressed as:

[0022]

[0023] Where h(0) is the first-order filter coefficient, h(1) is the second-order filter coefficient, h(N-1) is the N-order filter coefficient, and z -1 is the unit delay, z -(N-1) The delay is N-1 sampling periods.

[0024] In step S3, obtaining received signals corresponding to the ILS system and the VOR system without navigation signals includes: the RF transceiver estimates the frequency of the received IQ two-way signals corresponding to the ILS system and the VOR system through the ARM to obtain the corresponding specific carrier frequency, performs envelope detection and demodulation on the IQ two-way signals to obtain baseband signals, and parses the navigation information carried in the received IQ two-way navigation signals;

[0025] The corresponding specific carrier frequency is sent to FPGA to generate a corresponding filter to filter out the navigation signal in the received signal and obtain the received signal without navigation signal corresponding to the ILS system and VOR system;

[0026] Obtaining a received signal of a DME system without a navigation signal includes: a radio frequency transceiver sending the received IQ two-way signals of the DME system to an FPGA for signal processing, identifying a DME pulse signal in the IQ two-way signals of the DME system, parsing the navigation information contained therein through one way, and suppressing the identified DME pulse signal through the other way to remove the navigation signal from the received signal, thereby obtaining a received signal of the DME system without a navigation signal.

[0027] Furthermore, the RF transceiver estimates the frequency of the IQ signals received from the ILS system and the VOR system through the ARM to obtain the corresponding specific carrier frequency, including: for the IQ signals received by the ILS system and the VOR system, when the system initially receives the signal, determining the frequency of the carrier component of the signal through zero-crossing detection;

[0028] The IQ signals are subjected to envelope detection and demodulation to obtain baseband signals, and the navigation information carried in the received IQ navigation signals is parsed, including:

[0029] For the ILS system, the signal is downsampled and transmitted to the ARM end. In the ARM end, the amplitude values of the 90Hz component and the 150Hz component of the signal carrier are calculated using the Goertzel algorithm to obtain the corresponding DDM value and determine the heading angle or glide angle of the current position. The expression is:

[0030] M 90 =A / V0 (6)

[0031] M 150 =B / V0 (7)

[0032] DDM=M 150 -M 90 (8)

[0033] Where M 90 is the modulation index of the 90Hz signal, M 150 is the modulation index of the 150Hz signal, A is the amplitude of the 90Hz component, B is the amplitude of the 150Hz component, and V0 is the DC component;

[0034] For the VOR system, the signal is downsampled and transmitted to the ARM end. The ARM end compares the phase difference between the 30Hz reference and the variable phase signal to obtain the magnetic azimuth of the aircraft relative to the VOR station. The expression is:

[0035]

[0036] Where Δθ is the time at t s The phase difference between the two signals, u1(t s ) is the 30Hz reference phase signal, u2(t s ) is a 30Hz variable phase signal, t s For time.

[0037] Furthermore, for the DME system, the slant range between the aircraft and the ground DME station is calculated by calculating the time difference between sending the interrogation signal and receiving the reply signal. The expression is:

[0038]

[0039] Where R is the slant distance between the aircraft and the ground DME station, T0 is the fixed delay of the reply, T is the time difference between sending the interrogation signal and receiving the reply signal, and c is the speed of light.

[0040] Furthermore, the corresponding specific carrier frequency is sent to the FPGA to generate a corresponding filter, including:

[0041] Based on the obtained carrier frequency, a corresponding filter is designed to generate IIR notch filter coefficients corresponding to the bandwidth of the carrier and subcarrier carrying the navigation information on the carrier; this is to filter out the navigation signal components contained in the received signal, including the carrier, the subcarrier carrying the navigation information, and the 1020Hz identification code component;

[0042] The transfer function of the IIR notch filter is as follows:

[0043]

[0044] Where w n is the notch frequency, k1 and k2 are notch factors, Y(s) is the output signal of the notch filter in the complex frequency domain, s is a complex variable, and X(s) is the input signal of the notch filter in the complex frequency domain;

[0045] For the DME system, the identified DME pulse signal is suppressed to remove the navigation signal from the received signal. The received signal without the navigation signal of the DME system is obtained by:

[0046] For the DME system, the validity of the pulse signal in the signal received by the RF transceiver is judged. If the pulse width is within 3.5us±0.5us and the pulse interval is within 12us±0.5us, it is valid. The pulse is a DME pulse signal. When the DME pulse pair is detected, the signal is regarded as an interference-free interval, and the DME pulse is suppressed to obtain a signal with the DME signal pulse pair removed.

[0047] In step S4, for the received signals without navigation signals corresponding to the ILS system and the VOR system, and for the received signals without navigation signals corresponding to the DME system, an energy detection method is used to determine the interference existence interval, including:

[0048] To determine whether interference exists in the received signal after the navigation signal is removed, an interference presence test is performed on the signal. For the signal without the navigation signal, the average amplitude over a period of time in the system's initial state is regarded as the noise floor. A threshold value of twice the noise floor is set, and the envelope of the signal is extracted. If the envelope exceeds the threshold value for a period of time, it is considered to be an interference-existing interval.

[0049] In the interval where the interference signal exists, the DME system determines whether there is interference for every 1ms of data within 1s. If interference exists, the interference is counted. If the interference count exceeds the threshold value, it is determined that continuous wave interference exists; if the interference count is lower than the threshold value, it is determined that pulse interference exists, and linear frequency modulation interference occurs in the interval.

[0050] In step S4, the bandwidth of the interference signal is determined by FFT, including:

[0051] The frequency domain characteristics of the interference signal are obtained through FFT. The navigation signal contained in the signal is removed by filtering or suppressing it. The time domain signal is transferred from the FPGA to the ARM through DMA. The FFT function in the DSP function library is called by the ARM to perform continuous 2048-point FFT operations on the received signal segments. In the output result, the signal in the channel of the FFT result within a period of time under the initial state of the system is regarded as the noise floor. The frequency point with an amplitude exceeding the threshold set to 2 times the noise floor is the frequency of the interference signal. The difference between the highest and lowest frequencies of the interference signal is converted into a frequency, and this frequency is regarded as the bandwidth of the interference signal. The formula is as follows:

[0052]

[0053] Where B is the bandwidth of the interference signal, N1 and N2 are the highest and lowest frequency points respectively, and F s is the sampling rate, N is the number of FFT points;

[0054] For DME signals, multiple 2048-point FFT operations are performed on the time domain signal. In the output results, the frequency points with amplitudes exceeding the threshold set to 2 times the noise floor are the frequencies of the interference signal. In the multiple FFT results during the time when the interference exists, the difference between the highest frequency point and the lowest frequency point where the interference signal is judged is the bandwidth of the interference signal.

[0055] Determine the type of interference including:

[0056] When there is an interference signal in the DME system, if there is a pulse signal, the interference signal is judged to be a linear frequency modulation signal; otherwise, if the bandwidth of the interference signal exceeds the bandwidth threshold, the interference signal is judged to be an frequency modulation signal; if the bandwidth of the interference signal is lower than the bandwidth threshold, the interference signal is judged to be an amplitude modulation signal;

[0057] In VOR and ILS systems, if the bandwidth of the interference signal exceeds the bandwidth threshold, the interference signal is judged to be an FM signal; if the bandwidth of the interference signal is lower than the bandwidth threshold, the interference signal is judged to be an AM signal.

[0058] Another object of the present invention is to provide a ZYNQ-based land-based navigation channel monitoring system, which implements the ZYNQ-based land-based navigation channel monitoring method, and the system includes:

[0059] The channel scanning module is used to use the radio frequency transceiver to sequentially scan the land-based navigation channels including the VOR system, ILS system and DME system, obtain the channel information corresponding to the VOR system, ILS system and DME system, and receive the radio frequency signal in the channel;

[0060] The RF signal processing module is used for the RF transceiver to process the received RF signals and obtain the IQ signals corresponding to the VOR system, ILS system and DME system respectively;

[0061] The non-navigation signal acquisition module is used for the RF transceiver to estimate the frequency of the IQ two-way signals corresponding to the ILS system and VOR system through the ARM, and perform signal processing through the FPGA to obtain the received signals of the ILS system and VOR system without navigation signals; the RF transceiver sends the received IQ two-way signals of the DME system to the FPGA for signal processing to obtain the received signal of the DME system without navigation signals;

[0062] The interference signal type judgment module is used to determine the interference existence interval by energy detection method for the received signals without navigation signals corresponding to the ILS system and VOR system, and the received signals without navigation signals corresponding to the DME system; identify the pulse signal within the interval where the interference signal exists; and determine the bandwidth of the interference signal by FFT to determine the type of the interference signal.

[0063] In combination with all the above technical solutions, the beneficial effects of the present invention are as follows: the RF transceiver AD9361 provided by the present invention sequentially scans land-based navigation channels including VOR, ILS and DME systems to obtain specific channel information and receive corresponding in-channel signals; the RF transceiver AD9361 performs a series of processing on the received RF signals to obtain IQ two-way signals, which are received by the front end and sent to the FPGA for signal processing; the signals received by the front end are subjected to envelope detection and demodulation to obtain baseband signals, and the navigation information carried in the received navigation signals is calculated.

[0064] At the same time, the frequency of the front-end signals received by the ILS system and the VOR system is estimated to obtain the specific carrier frequency, and the corresponding filter is generated to filter out the navigation signal in the received signal; the pulses in the front-end signal received by the DME system are identified and suppressed to remove the navigation signal in the received signal; for the received signal without the navigation signal, the energy detection method is used to determine the existence interval of the interference, and the instantaneous frequency of the interference signal is calculated. At the same time, the bandwidth of the interference signal is determined by FFT, so as to determine the type of interference signal.

[0065] The present invention integrates the reception of land-based navigation systems and the identification of interference, and includes the reception, processing and interference monitoring of three land-based navigation systems: VOR, ILS and DME, thereby greatly improving the integration level. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure;

[0067] Figure 1 This is a flow chart of a ZYNQ-based land-based navigation channel monitoring method provided by an embodiment of the present invention;

[0068] Figure 2 1. It is a schematic diagram of a VOR channel interference detection method for ZYNQ provided in an embodiment of the present invention;

[0069] Figure 3 1. It is a schematic diagram of the ILS channel interference monitoring method for ZYNQ provided by an embodiment of the present invention;

[0070] Figure 4 This is a schematic diagram of the DME channel interference monitoring method for ZYNQ provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0071] To make the above-mentioned objects, features, and advantages of the present invention more readily apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. The following description sets forth numerous specific details to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art may make similar modifications without departing from the scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0072] The innovation of the present invention lies in that the present invention uses FPGA+ARM to realize the monitoring of land-based navigation channels, which has outstanding advantages in signal monitoring and can well realize the reception and analysis of land-based navigation signals and the identification of the existence and type of interference.

[0073] Example 1, as Figure 1 As shown, an embodiment of the present invention provides a ZYNQ-based land-based navigation channel monitoring method, including:

[0074] S1, using the radio frequency transceiver to scan the land-based navigation channels including the VOR system, ILS system and DME system in sequence, obtain the channel information corresponding to the VOR system, ILS system and DME system, and receive the radio frequency signals in the channels;

[0075] Among them, the RF transceiver uses AD9361;

[0076] S2, the RF transceiver processes the received RF signal to obtain the IQ signals corresponding to the VOR system, ILS system and DME system respectively;

[0077] S3: The RF transceiver estimates the frequency of the received IQ signals corresponding to the ILS and VOR systems through the ARM, and processes the signals through the FPGA to obtain the received signals corresponding to the ILS and VOR systems without navigation signals. The RF transceiver sends the received IQ signals of the DME system to the FPGA for signal processing to obtain the received signal of the DME system without navigation signals.

[0078] S4, for the received signals without navigation signals corresponding to the ILS system and VOR system, and for the received signals without navigation signals obtained from the DME system, the interference existence interval is determined by the energy detection method; within the interval where the interference signal exists, the pulse signal is identified; and the bandwidth of the interference signal is determined by FFT, thereby determining the type of the interference signal.

[0079] Exemplarily, in step S1, using a radio frequency transceiver to sequentially scan land-based navigation channels including VOR, ILS, and DME systems, obtain channel information corresponding to the VOR, ILS, and DME systems, and receive radio frequency signals in the corresponding channels specifically include:

[0080] The ARM is used to set up and adjust the RF transceiver AD9361 so that it scans all the channels for land-based navigation in sequence and records the receiving power of all the channels. The channel with the highest receiving power is obtained by comparison and regarded as the working channel in the current environment. The ARM is then used to adjust the RF transceiver AD9361 to adjust the receiving bandwidth to the current working channel.

[0081] In another exemplary embodiment, in step S1, the radio frequency transceiver sequentially scans the land-based navigation channels, specifically including:

[0082] The RF transceiver scans a range of channels, each for 2 seconds, and calculates the received power for each channel. Once all channels have been scanned, the channel with the highest received power is identified as the currently active channel. The AD9361 RF transceiver is then adjusted to the corresponding channel bandwidth and returns data indicating the current channel.

[0083] In another exemplary embodiment, specifically, step S1 includes:

[0084] The ARM configures the AD9361 RF transceiver in the RF front-end receiving unit. The default initial values for the receive channel bandwidth and receive gain can be adjusted via the serial port. The received signal is scanned sequentially, each channel lasting 2 seconds. The received power for each channel is calculated and recorded. After all channels have been scanned, the channel with the highest received power is identified as the currently active channel. The ARM then adjusts the AD9361 RF transceiver to the corresponding channel bandwidth and returns data indicating the current channel. The received signal power is then determined and adaptively adjusted to within an appropriate range.

[0085] Exemplarily, in step S2, the RF transceiver processes the received RF signal to obtain the IQ signals corresponding to the VOR, ILS, and DME systems, respectively. Specifically, the following steps are performed:

[0086] The RF transceiver AD9361 performs analog-to-digital conversion on the received RF interrogation signal, digitizes the interrogation pulse to obtain two IQ signals, and then sends them to the FPGA for processing. First, the envelope detection method is used to demodulate the received signal. The square sum of the in-phase and quadrature branches is calculated, and then the square root is calculated. The calculation formula is as follows:

[0087] x 11 (n) = x(n)cos(ωn) (1)

[0088] x 21 (n) = x(n)cos(ωn) (2)

[0089]

[0090] Where x 11 (n) and x 21 (n) is the IQ signal, ω is the carrier frequency, m(n) is the baseband signal, x(n) is the received signal, and n is the sampling point number;

[0091] The baseband signal passes through a FIR low-pass filter with a sampling frequency of 40MHz and a passband frequency of 1MHz. The equation of the FIR filter is:

[0092]

[0093] Where h(k) is the coefficient of the filter, x(nk) is x(n) delayed by k cycles, y(n) is the filter output signal, N is the filter order, and k is the number of delay cycles.

[0094] The transfer function H(z) of the system is expressed as:

[0095]

[0096] Where h(0) is the first-order filter coefficient, h(1) is the second-order filter coefficient, h(N-1) is the N-order filter coefficient, and z -1 is the unit delay, z -(N-1) The delay is N-1 sampling periods.

[0097] Exemplarily, in step S3, obtaining received signals corresponding to the ILS system and the VOR system without navigation signals includes: the RF transceiver estimates the frequency of the received IQ two-way signals corresponding to the ILS system and the VOR system through ARM to obtain corresponding specific carrier frequencies, performs envelope detection and demodulation on the corresponding IQ two-way signals to obtain baseband signals, and parses the navigation information carried in the received IQ two-way signals (navigation signals);

[0098] At the same time, the corresponding specific carrier frequency is sent to FPGA to generate a corresponding filter to filter out the navigation signal in the received signal and obtain the received signal without navigation signal corresponding to the ILS system and VOR system;

[0099] Obtaining a received signal of a DME system without a navigation signal includes: the RF transceiver sends the received IQ two-way signals of the DME system to the FPGA for signal processing, identifying the DME pulse signal in the IQ two-way signals of the DME system, parsing out the navigation information contained therein on one way, and suppressing the identified DME pulse signal on the other way to remove the navigation signal from the received signal, thereby obtaining a received signal of a DME system without a navigation signal.

[0100] Exemplarily, the RF transceiver estimates the frequency of the received IQ signals corresponding to the ILS system and the VOR system through the ARM to obtain the corresponding specific carrier frequency, specifically including:

[0101] For the IQ signals received by the ILS and VOR systems, when the system initially receives the signals, the FPGA performs zero-crossing detection on the pre-processed received signals, detects and counts the number of times the signal amplitude passes through zero within 1 second, and transmits this value to the ARM. The ARM calculates and converts the count to obtain the specific carrier frequency. The formula is as follows:

[0102]

[0103] Where, F c is the carrier frequency, N c is the number of zero crossings, T c is the counting duration;

[0104] For example, Figure 3As shown, in step S3, envelope detection and demodulation processing is performed on the corresponding IQ two-way signal to obtain a baseband signal, and the navigation information carried in the received IQ two-way signal (navigation signal) is parsed, specifically including:

[0105] For the ILS system, the signal is downsampled and transmitted to the ARM. In the ARM, the amplitude values of the 90Hz component and the 150Hz component of the signal carrier are calculated using the Goertzel algorithm to obtain the corresponding DDM value, which is used to determine the heading angle or glide angle of the current position. The formula is as follows:

[0106] M 90 =A / V0 (6)

[0107] M 150 =B / V0 (7)

[0108] DDM=M 150 -M 90 (8)

[0109] Where M 90 is the modulation index of the 90Hz signal, M 150 is the modulation index of the 150Hz signal, A is the amplitude of the 90Hz component, B is the amplitude of the 150Hz component, and V0 is the DC component;

[0110] like Figure 2 As shown, for the VOR system, the signal is downsampled and transmitted to the ARM. In the ARM, the magnetic azimuth of the aircraft relative to the VOR station can be obtained by comparing the phase difference between the 30Hz reference and the variable phase signal. The formula is as follows:

[0111]

[0112] Where Δθ is the time at t s The phase difference between the two signals, u1(t s ) is the 30Hz reference phase signal, u2(t s ) is a 30Hz variable phase signal, t s For time.

[0113] like Figure 4 As shown in the figure, for the DME system, the slant distance between the aircraft and the ground DME station can be calculated by calculating the time difference between sending the inquiry signal and receiving the reply signal. The formula is as follows:

[0114]

[0115] Where R is the slant distance between the aircraft and the ground DME station, T0 is the fixed delay of the reply, T is the time difference between sending the interrogation signal and receiving the reply signal, and c is the speed of light.

[0116] Furthermore, in step S3, the corresponding specific carrier frequency is sent to the FPGA to generate a corresponding filter, which specifically includes:

[0117] Based on the obtained carrier frequency, a corresponding filter is designed, and further IIR notch filter coefficients are designed to generate the bandwidths of the carrier and subcarrier corresponding to the navigation information carried on the carrier. This is to filter out the navigation signal components contained in the received signal, including the carrier, the subcarrier carrying the navigation information, the 1020 Hz identification code, and other components.

[0118] The transfer function of the IIR notch filter is as follows:

[0119]

[0120] Where w n is the notch frequency, k1 and k2 are notch factors, Y(s) is the output signal of the notch filter in the complex frequency domain, s is a complex variable, and X(s) is the input signal of the notch filter in the complex frequency domain;

[0121] Exemplarily, in step S3, filtering out the navigation signal from the received signal in a time division multiplexing manner specifically includes:

[0122] By using the IIR notch filter coefficients obtained above, the signals are filtered at high speed in a time-division multiplexing manner to obtain the received signal of the VOR system without the navigation signal and the received signal of the ILS system with the primary ILS signal filtered out.

[0123] As another example, the sampling rate of the signals received by the VOR system and the ILS system is low at this time, while the FPGA operation rate is high. Therefore, time division multiplexing is used to save the operation resources of the IIR filter and reduce the delay caused by filtering. Using the resources of the same set of IIR notch filters, after each filtering of the current signal, the coefficient of the notch filter is replaced to filter out the components of the next signal. In the VOR system and the ILS system, there are 7 signal components that need to be filtered out respectively. Therefore, in the implementation, within one data clock, time division multiplexing is used to filter out the 7 signal components of each. Before the next data arrives, the filtering process within the previous data clock can be completed to obtain the received signal of the VOR system without the navigation signal and the received signal of the ILS system after filtering out the ILS signal once.

[0124] For the ILS system's received signal, after filtering out the primary ILS signal, the system performs zero-crossing detection and frequency estimation to obtain a second carrier frequency. Using this carrier frequency, IIR notch filter coefficients are designed and generated to correspond to the carrier and subcarrier bandwidths of the navigation information carried on the carrier. These IIR notch filter coefficients are then applied to the received signal to obtain the ILS system's received signal without the navigation signal.

[0125] Exemplarily, in step S3, for the DME system, suppressing the identified DME pulse signal to remove the navigation signal from the received signal, and obtaining a received signal without the navigation signal of the DME system includes:

[0126] For the DME system, when a DME pulse pair is detected in the signal received by the RF transceiver, a delay is added to the original signal and the DME pulse is suppressed to obtain a signal with the DME signal pulse pair removed.

[0127] Exemplarily, in step S4, for the received signal without navigation signal obtained after signal processing received by the ILS system, the VOR system, and the DME system, determining the interference existence interval by the energy detection method specifically includes:

[0128] In order to determine whether there is interference in the received signal after the navigation signal is removed, it is necessary to perform interference detection on the signal. For the signal after the navigation signal is removed, if its envelope exceeds the threshold value for a period of time, it is considered to be interference.

[0129] Exemplarily, within the interval where the interference signal exists, a pulse signal is identified, and if a pulse signal is detected in a received signal without a navigation signal in the DME system, it is determined that linear frequency modulation interference has occurred;

[0130] Exemplarily, in step S4, determining the bandwidth of the interference signal through FFT includes:

[0131] The frequency domain characteristics of the interference signal are obtained through FFT. The signal after filtering or suppression has the navigation signal contained in it removed. For VOR and ILS signals, a 2048-point FFT operation is performed on the time domain signal. In the output results, the frequency points with an amplitude exceeding the threshold set to 2 times the noise floor are regarded as the frequencies of the interference signal. The difference between the highest and lowest frequencies of the interference signal is determined to be the bandwidth of the interference signal. For DME signals, due to the high frequency of the signal, multiple 2048-point FFT operations are performed on the time domain signal. In the output results, the frequency points with an amplitude exceeding the threshold set to 2 times the noise floor are regarded as the frequencies of the interference signal. The difference between the highest and lowest frequencies of the interference signal is determined to be the bandwidth of the interference signal in the multiple FFT results during the time when the interference exists.

[0132] For example, in land-based navigation channels, the FM signals commonly found are FM broadcast signals, which typically utilize broadband FM broadcasting. Therefore, in the frequency domain, FM interference, due to its characteristics, has a wider signal bandwidth, while AM interference generally has a narrower bandwidth. Therefore, AM and FM interference can be distinguished based on bandwidth characteristics.

[0133] Determining the interference type in step S4 includes:

[0134] When there is an interference signal in the DME system, if there is a pulse signal, the interference signal is judged to be a linear frequency modulation signal; otherwise, if the bandwidth of the interference signal exceeds the bandwidth threshold, the interference signal is judged to be an frequency modulation signal; if the bandwidth of the interference signal is lower than the bandwidth threshold, the interference signal is judged to be an amplitude modulation signal.

[0135] In VOR and ILS systems, if the bandwidth of the interference signal exceeds the bandwidth threshold, the interference signal is judged to be an FM signal; if the bandwidth of the interference signal is lower than the bandwidth threshold, the interference signal is judged to be an AM signal.

[0136] The above examples demonstrate that the present invention utilizes an FPGA + ARM processor to monitor land-based navigation channels, demonstrating significant advantages in signal monitoring. This system can effectively receive and analyze land-based navigation signals, as well as identify the presence and type of interference. Furthermore, the integration of the AD9361 RF front-end and signal baseband components significantly reduces the complexity of design and signal processing.

[0137] The present invention adopts ZYNQ as the core and completes the design of functions such as reception and analysis of land-based navigation new signals, land-based navigation channel monitoring, and interference identification based on the signal characteristics of AM broadcasting, FM broadcasting, and linear FM broadcasting. It has the advantage of integration in application and good flexibility.

[0138] The present invention adopts ARM to complete the output functions of the serial port and the network port, and can realize the modification and adjustment of multiple functions such as switching of working modes, selection of channels, receiving frequency, gain control, threshold setting, etc. At the same time, it can realize the output of signal data acquisition, scanning channels, navigation information, interference status, interference type, etc., and has the advantages of flexibility, low cost, small size and easy operation by technicians.

[0139] The present invention can be designed as a convenient receiving device and a wave channel monitor; it can meet the requirements of experimental researchers and has important significance in the field of wave channel monitoring.

[0140] Currently, there is no public use of ZYNQ chips in the existing technology to design a land-based navigation channel monitoring system.

[0141] The present invention adopts a design scheme based on FPGA+ARM, which can reduce the complexity of hardware circuits and effectively solve the problem of complex design.

[0142] The present invention proposes a simple and effective method for implementing a land-based navigation channel monitoring system, which can achieve the desired functions using FPGA + ARM. This is a technical solution that is not easily conceived by those skilled in the art and breaks through technical prejudice.

[0143] Example 2: A ZYNQ-based land-based navigation channel monitoring system provided by the present invention includes:

[0144] The channel scanning module is used to sequentially scan the land-based navigation channels including the VOR, ILS and DME systems using the RF transceiver, obtain the channel information corresponding to the VOR, ILS and DME systems, and receive the RF signals in the corresponding channels;

[0145] The RF signal processing module is used by the RF transceiver to process the received RF signals and obtain the IQ signals corresponding to the VOR, ILS and DME systems respectively;

[0146] The non-navigation signal acquisition module is used for the RF transceiver to estimate the frequency of the received IQ signals corresponding to the ILS system and VOR system through the ARM, and perform signal processing through the FPGA to obtain the received signals of the ILS system and VOR system without navigation signals; and the RF transceiver sends the received IQ signals of the DME system to the FPGA for signal processing to obtain the received signal of the DME system without navigation signals;

[0147] The interference signal type judgment module is used to determine the interference existence interval through the energy detection method for the received signals without navigation signals corresponding to the ILS system and VOR system, and the received signals without navigation signals obtained from the DME system; within the interval where the interference signal exists, the pulse signal is identified, and the bandwidth of the interference signal is determined by FFT, thereby determining the type of the interference signal.

[0148] The present invention was tested in a certain airport environment. In the actual environment, by receiving the real land-based navigation signal sent by the airport, it can correctly perform the analysis to obtain the channel information, carrier frequency and corresponding navigation information. At the same time, it can detect different types of interference added by humans, identify the corresponding interference type, and return the correct data and information to the user.

[0149] The above description is only a preferred specific implementation method of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A ZYNQ-based land-based navigation channel monitoring method, characterized in that: The method comprises the following steps: S1, using the radio frequency transceiver to scan the land-based navigation channels including the VOR system, ILS system and DME system in sequence, obtain the channel information corresponding to the VOR system, ILS system and DME system, and receive the radio frequency signals in the channels; S2, the RF transceiver processes the received RF signal to obtain the IQ signals corresponding to the VOR system, ILS system and DME system respectively; S3: The RF transceiver estimates the frequency of the received IQ signals corresponding to the ILS and VOR systems through the ARM, and processes the signals through the FPGA to obtain the received signals corresponding to the ILS and VOR systems without navigation signals. The RF transceiver sends the received IQ signals of the DME system to the FPGA for signal processing to obtain the received signal of the DME system without navigation signals. S4, for the received signals without navigation signals corresponding to the ILS system and VOR system, and for the received signals without navigation signals obtained from the DME system, the interference existence interval is determined by the energy detection method; within the interval where the interference signal exists, the pulse signal is identified; and the bandwidth of the interference signal is determined by FFT, thereby determining the type of the interference signal.

2. The ZYNQ-based land-based navigation channel monitoring method according to claim 1, characterized in that: In step S1, the radio frequency transceiver is used to sequentially scan the land-based navigation channels including the VOR system, ILS system, and DME system, including: The ARM side configures the RF transceiver in the RF front-end receiving unit; for the received signal, it scans the channels in sequence, scanning each channel for 2 seconds, and calculates and records the received power of the channel; after all channels have been scanned, it checks that the channel with the highest received power is the channel currently in use. The ARM side adjusts the RF transceiver to adjust the receiving frequency to the corresponding channel bandwidth, and returns data at the same time to obtain the current channel information; the received signal power is judged and adaptively adjusted.

3. The ZYNQ-based land-based navigation channel monitoring method according to claim 1, characterized in that: In step S2, the RF transceiver processes the received RF signal to obtain IQ signals corresponding to the VOR system, ILS system, and DME system, respectively, including: The envelope detection method is used to demodulate the received signal. The square sum of the in-phase and quadrature branches is calculated, and then the square root is calculated. The calculation formula is as follows: x 11 (n)=x(n)cos(ωn)(1) x 21 (n)=x(n)sin(ωn)(2) Where x 11 (n) and x 21 (n) is the IQ signal, ω is the carrier frequency, m(n) is the baseband signal, x(n) is the received signal, and n is the sampling point number; The baseband signal passes through a FIR low-pass filter with a sampling frequency of 40 MHz and a passband frequency of 1 MHz. The FIR filter equation is: Where h(k) is the coefficient of the filter, x(nk) is x(n) delayed by k cycles, y(n) is the filter output signal, N is the filter order, and k is the number of delay cycles. The transfer function H(z) of the system is expressed as: Where h(0) is the first-order filter coefficient, h(1) is the second-order filter coefficient, h(N-1) is the N-order filter coefficient, and z -1 is the unit delay, z -(N-1) The delay is N-1 sampling periods.

4. The ZYNQ-based land-based navigation channel monitoring method according to claim 1, characterized in that: In step S3, obtaining received signals corresponding to the ILS system and the VOR system without navigation signals includes: the RF transceiver estimates the frequency of the received IQ two-way signals corresponding to the ILS system and the VOR system through the ARM to obtain the corresponding specific carrier frequency, performs envelope detection and demodulation on the IQ two-way signals to obtain baseband signals, and parses the navigation information carried in the received IQ two-way navigation signals; The corresponding specific carrier frequency is sent to FPGA to generate a corresponding filter to filter out the navigation signal in the received signal and obtain the received signal without navigation signal corresponding to the ILS system and VOR system; Obtaining a received signal of a DME system without a navigation signal includes: a radio frequency transceiver sending the received IQ two-way signals of the DME system to an FPGA for signal processing, identifying a DME pulse signal in the IQ two-way signals of the DME system, parsing out the navigation information contained therein through one way, and suppressing the identified DME pulse signal through the other way to remove the navigation signal from the received signal, thereby obtaining a received signal of the DME system without a navigation signal.

5. The ZYNQ-based land-based navigation channel monitoring method according to claim 4, characterized in that: The RF transceiver estimates the frequency of the IQ signals received from the ILS and VOR systems through the ARM to obtain the corresponding specific carrier frequency, including: for the IQ signals received by the ILS and VOR systems, when the system initially receives the signal, it determines the frequency of the carrier component of the signal through zero-crossing detection; The IQ signals are subjected to envelope detection and demodulation to obtain baseband signals, and the navigation information carried in the received IQ navigation signals is parsed, including: For the ILS system, the signal is downsampled and transmitted to the ARM end. In the ARM end, the amplitude values of the 90Hz component and the 150Hz component of the signal carrier are calculated using the Goertzel algorithm to obtain the corresponding DDM value and determine the heading angle or glide angle of the current position. The expression is: M 90 =A / V0(6) M 150 =B / V0(7) DDM=M 150 -M 90 (8) Where M 90 is the modulation index of the 90Hz signal, M 150 is the modulation index of the 150Hz signal, A is the amplitude of the 90Hz component, B is the amplitude of the 150Hz component, and V0 is the DC component; For the VOR system, the signal is downsampled and transmitted to the ARM end. The ARM end compares the phase difference between the 30Hz reference and the variable phase signal to obtain the magnetic azimuth of the aircraft relative to the VOR station. The expression is: Where Δθ is the time at t s The phase difference between the two signals, u1(t s ) is the 30Hz reference phase signal, u2(t s ) is a 30Hz variable phase signal, t s For time.

6. The ZYNQ-based land-based navigation channel monitoring method according to claim 4, characterized in that: For the DME system, the slant distance between the aircraft and the ground DME station is calculated by calculating the time difference between sending the interrogation signal and receiving the reply signal. The expression is: Where R is the slant distance between the aircraft and the ground DME station, T0 is the fixed delay of the reply, T is the time difference between sending the interrogation signal and receiving the reply signal, and c is the speed of light.

7. The ZYNQ-based land-based navigation channel monitoring method according to claim 4, characterized in that: The corresponding specific carrier frequency is sent to the FPGA to generate the corresponding filter, including: Based on the obtained carrier frequency, a corresponding filter is designed to generate IIR notch filter coefficients corresponding to the bandwidth of the carrier and subcarrier carrying the navigation information on the carrier; this is to filter out the navigation signal components contained in the received signal, including the carrier, the subcarrier carrying the navigation information, and the 1020Hz identification code component; The transfer function of the IIR notch filter is as follows: Where w n is the notch frequency, k1 and k2 are notch factors, Y(s) is the output signal of the notch filter in the complex frequency domain, s is a complex variable, and X(s) is the input signal of the notch filter in the complex frequency domain; For the DME system, the identified DME pulse signal is suppressed to remove the navigation signal from the received signal. The received signal without the navigation signal of the DME system is obtained by: For the DME system, the validity of the pulse signal in the signal received by the RF transceiver is judged. If the pulse width is within 3.5us±0.5us and the pulse interval is within 12us±0.5us, it is valid. The pulse is a DME pulse signal. When the DME pulse pair is detected, the signal is regarded as an interference-free interval, and the DME pulse is suppressed to obtain a signal with the DME signal pulse pair removed.

8. The ZYNQ-based land-based navigation channel monitoring method according to claim 1, characterized in that: In step S4, for the received signals without navigation signals corresponding to the ILS system and the VOR system, and for the received signals without navigation signals corresponding to the DME system, an energy detection method is used to determine the interference existence interval, including: To determine whether interference exists in the received signal after the navigation signal is removed, an interference presence test is performed on the signal. For the signal without the navigation signal, the average amplitude over a period of time in the system's initial state is regarded as the noise floor. A threshold value of twice the noise floor is set, and the envelope of the signal is extracted. If the envelope exceeds the threshold value for a period of time, it is considered to be an interference-existing interval. In the interval where the interference signal exists, the DME system determines whether there is interference for every 1ms of data within 1s. If interference exists, the interference is counted. If the interference count exceeds the threshold value, it is determined that continuous wave interference exists; if the interference count is lower than the threshold value, it is determined that pulse interference exists, and linear frequency modulation interference occurs in the interval.

9. The ZYNQ-based land-based navigation channel monitoring method according to claim 1, characterized in that: In step S4, the bandwidth of the interference signal is determined by FFT, including: The frequency domain characteristics of the interference signal are obtained through FFT. The navigation signal contained in the signal is removed by filtering or suppressing it. The time domain signal is transferred from the FPGA to the ARM through DMA. The FFT function in the DSP function library is called by the ARM to perform continuous 2048-point FFT operations on the received signal segments. In the output result, the signal in the channel of the FFT result within a period of time under the initial state of the system is regarded as the noise floor. The frequency point with an amplitude exceeding the threshold set to 2 times the noise floor is the frequency of the interference signal. The difference between the highest and lowest frequencies of the interference signal is converted into a frequency, and this frequency is regarded as the bandwidth of the interference signal. The formula is as follows: Where B is the bandwidth of the interference signal, N1 and N2 are the highest and lowest frequency points respectively, and F s is the sampling rate, N is the number of FFT points; For DME signals, multiple 2048-point FFT operations are performed on the time domain signal. In the output results, the frequency points with amplitudes exceeding the threshold set to 2 times the noise floor are the frequencies of the interference signal. In the multiple FFT results during the time when the interference exists, the difference between the highest frequency point and the lowest frequency point where the interference signal is judged is the bandwidth of the interference signal. Determine the type of interference including: When there is an interference signal in the DME system, if there is a pulse signal, the interference signal is judged to be a linear frequency modulation signal; otherwise, if the bandwidth of the interference signal exceeds the bandwidth threshold, the interference signal is judged to be an frequency modulation signal; if the bandwidth of the interference signal is lower than the bandwidth threshold, the interference signal is judged to be an amplitude modulation signal; In VOR and ILS systems, if the bandwidth of the interference signal exceeds the bandwidth threshold, the interference signal is judged to be an FM signal; if the bandwidth of the interference signal is lower than the bandwidth threshold, the interference signal is judged to be an AM signal.

10. A ZYNQ-based land-based navigation channel monitoring system, characterized in that: The system implements the ZYNQ-based land-based navigation channel monitoring method according to any one of claims 1 to 9, and the system comprises: The channel scanning module is used to use the radio frequency transceiver to sequentially scan the land-based navigation channels including the VOR system, ILS system and DME system, obtain the channel information corresponding to the VOR system, ILS system and DME system, and receive the radio frequency signal in the channel; The RF signal processing module is used for the RF transceiver to process the received RF signals and obtain the IQ signals corresponding to the VOR system, ILS system and DME system respectively; The non-navigation signal acquisition module is used for the RF transceiver to estimate the frequency of the IQ two-way signals corresponding to the ILS system and VOR system through the ARM, and perform signal processing through the FPGA to obtain the received signals of the ILS system and VOR system without navigation signals; the RF transceiver sends the received IQ two-way signals of the DME system to the FPGA for signal processing to obtain the received signal of the DME system without navigation signals; The interference signal type judgment module is used to determine the interference existence interval by energy detection method for the received signals without navigation signals corresponding to the ILS system and VOR system, and the received signals without navigation signals corresponding to the DME system; identify the pulse signal within the interval where the interference signal exists; and determine the bandwidth of the interference signal by FFT to determine the type of the interference signal.

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