Method and system for evaluating radio altimeter immunity tolerance under 5g interference

Abstract

The present application relates to a kind of method and system for evaluating radio altimeter interference tolerance under 5G interference, belong to electromagnetic compatibility test equipment field.It includes the following steps: step one, obtain 5G signal path loss:step two, configure height simulator:step three, configure interference simulation module:step four, execute single frequency point power increment test:step five, calculate the interference tolerance of the radio altimeter under test:step six, 5G signal full-band interference tolerance scanning:through the above steps, complete the interference tolerance test of the radio altimeter under test under 5G signal interference, determine the interference tolerance of the radio altimeter under test;So as to help improve the overall level of aviation safety.

Description

TECHNICAL FIELD

[0001] The present application relates to a method and system for evaluating the radio altimeter interference margin under 5G interference, belonging to the field of electromagnetic compatibility test equipment. BACKGROUND

[0002] The radio altimeter is a key avionics equipment for measuring flight altitude on civil aircraft, and is widely used in the take-off, approach and landing stages of the aircraft. It not only provides the basis for the pilot to operate, but also provides key signal input for the near-ground warning system, instrument landing system, etc., which is crucial to ensure flight safety. The initial research and application of radio altimeter was in the 1970s, because there were few interference systems working near the altimeter frequency at that time, so the current international radio altimeter standards, including DO-155, ED-30, etc., do not constrain the anti-interference ability of the equipment. However, in recent years, through a series of researches by the International Civil Aviation Organization, the Aviation Radio Technology Committee and other institutions, it has been shown that there is a possibility that the radio altimeter will be affected by 5G signal electromagnetic interference. Interference margin is a key indicator to measure the anti-interference ability of radio altimeter, especially when evaluating the interference effect of 5G signal, the specific value of interference margin is crucial. However, there is currently no relevant scheme on how to accurately measure the radio altimeter interference margin under 5G signal interference. For example, for the patent application "Radio Altimeter Electromagnetic Interference Evaluation Method, Device and Medium" (Application Publication No.: CN118433761A), the patent application discloses a method, device and medium for evaluating the electromagnetic interference of radio altimeter. The main purpose is to evaluate the possible interference effect of 5G base station on aviation radio altimeter. The "front-end overload interference protection threshold" mentioned in its scheme is an input parameter needed to be obtained in the model, but it does not provide a specific scheme on how to measure or obtain the threshold value of a specific model of radio altimeter. SUMMARY

[0003] With the application of 5G communication technology in adjacent frequency bands, the safe operation of radio altimeters has faced potential electromagnetic interference risks, and accurate performance evaluation is urgently needed. The existing technology mainly relies on high-altitude equivalent disturbed tests to evaluate this influence, but such tests have problems such as difficulty in accurately controlling test conditions, high cost, and difficulty in implementation, leading to a lack of methods for quantifying the impact of 5G signals on radio altimeter performance. The present invention proposes a method and system for evaluating the interference tolerance of radio altimeters under 5G interference. The invention simulates the actual working state of the radio altimeter (such as a specific flight altitude) and various potential interference scenarios (for example, simulating the basic transmission interference of the same frequency interference signal and the 5G signal or the spurious emission interference of the 5G signal) in a controlled laboratory test environment, injects 5G signals and same frequency interference signals into the signal input end of the radio altimeter under test, and gradually changes the power parameters of the injected 5G interference signals. During the process, the computer monitors the change of the altitude value of the radio altimeter in real time, and determines the 5G signal power P vsgout that reaches the disturbed state according to the interference tolerance threshold standard, and then quantifies the interference tolerance of the radio altimeter under the interference of the 5G signal with the simulated altitude and center frequency according to the system path loss parameter through the interference tolerance calculation formula. The test results can provide key technical support and scientific data for the planning and deployment of 5G signals in sensitive areas such as airports, the optimization of radio altimeter anti-interference design, airworthiness certification, and aviation operation risk assessment, thereby helping to improve the overall level of aviation safety.

[0004] The technical solution adopted by the present invention is: a method for evaluating the interference tolerance of radio altimeters under 5G interference, comprising the following steps:

[0005] Step one, obtain the 5G signal path loss: measure the path loss with a vector network analyzer to obtain the path loss value L cable of the 5G signal in the set frequency range;

[0006] Step two, configure the height simulator: power the entire test system, start the height simulator, calibrate the delay of the height simulator, and complete the setting of the height parameter and the loop loss parameter;

[0007] Step three, configure the interference simulation module: according to the same frequency interference scenario, set the interference simulation module to obtain the required same frequency interference signal; according to the 5G signal interference scenario, set the parameters of the vector signal generator to obtain the required 5G signal;

[0008] Step four, perform single frequency point power increment test: after the height simulator and the interference simulation module are configured, control the interference simulation module to perform single frequency point power increment test, and when the disturbed judgment index is reached, record the current 5G signal power as P vsgout ;

[0009] Step five, calculate the measured radio altimeter interference margin: according to the path loss value L of 5G signal obtained in step one cable And according to the 5G signal power P obtained in step four vsgout , calculate the measured radio altimeter interference margin IT;

[0010] Step six, 5G signal full band interference margin scanning: after waiting for the measured radio altimeter to be stable, modify the frequency parameter of the vector signal generator set in step three, perform the test of step four and step five, and comprehensively evaluate the interference margin of the measured radio altimeter under the interference of 5G signal preset working frequency band under the simulation height of height simulator;

[0011] Through the above steps, the interference margin test of the measured radio altimeter under the interference of 5G signal is completed, and the interference margin of the measured radio altimeter is determined.

[0012] The method for measuring path loss by the vector network analyzer in step one is to set the frequency range of the vector network analyzer, complete the vector network analysis calibration, then disconnect the directional coupler output cable from the input end of the measured radio altimeter, connect it with cable A of the vector network analyzer, disconnect the input end cable of the combiner I in the interference simulation module from the output end of the vector signal generator, connect it with cable B of the vector network analyzer, observe the vector network analyzer, and obtain the path loss value L cable from the output end of the vector signal generator in the interference simulation module to the input end of the measured radio altimeter in the set frequency range.

[0013] The method for configuring the height simulator in step two is to install the measured radio altimeter on the test bench, then disconnect the directional coupler output cable from cable A and connect it with the input end of the measured radio altimeter, disconnect the input end cable of the combiner I in the interference simulation module from cable B and connect it with the output end of the vector signal generator, power the measured radio altimeter, computer I, vector signal generator, waveform generator, computer II and voltage controlled oscillator in the interference simulation module of the test system, manually start the automatic delay calibration program of the height simulator, manually set the predetermined flight height parameter on the height simulator, and set the loop loss of the height simulator according to the path loss.

[0014] The method for configuring the interference simulation module in step three is: according to the same-frequency interference scene corresponding to the flight height set by the height simulator, the parameters of the waveform generator in the interference simulation module are set to obtain a modulated signal, the fixed attenuator and the programmable attenuator in the interference simulation module are used in combination, the attenuation of each channel of the programmable attenuator in the interference simulation module is set, and a same-frequency interference signal with a required power is obtained; according to the 5G signal interference scene corresponding to the test frequency band, the waveform, the center frequency and the bandwidth parameters of the signal loaded by the vector signal generator are set, if the test frequency band is a basic transmission interference scene, the 5G NR TM1.1 waveform signal is set to be loaded by the vector signal generator, the center frequency is the center frequency of the test frequency band, and the bandwidth is 100 MHz, if the test frequency band is a stray transmission interference scene, the Gaussian white noise signal is set to be loaded by the vector signal generator, the center frequency is 4300 MHz, and the bandwidth is 160 MHz, and a required 5G signal is obtained.

[0015] The method for performing the single-frequency point power increment test in step four is: after the height simulator and the interference simulation module are configured, the height indicator data serial port software is opened by starting the computer I to establish the connection between the computer I and the radio altimeter to be tested; then the height indicator data serial port software is opened by starting the computer II to establish the connection between the computer II and the vector signal generator, after the above-mentioned connection is established, the interference injection and scanning are started: the vector signal generator is controlled by the height indicator data serial port software to set the initial power as -80 dBm and perform power scanning, the power scanning is specifically: the signal output is turned on for 10 seconds at the initial power of -80 dBm, and then turned off for 5 seconds; then the power is increased by 1 dBm, and the cycle of turning on for 10 seconds and turning off for 5 seconds is repeated, in the stepping process, if the height data of the radio altimeter to be tested displayed by the height indicator data serial port software on the computer I reaches the interference tolerance threshold standard, the power stepping increase is stopped and the 5G signal power P vsgout is recorded, if the stepping signal power reaches 20 dBm, the radio altimeter to be tested does not satisfy the interference tolerance threshold standard, it is determined that the interference tolerance cannot be tested at this frequency point, and it is considered that the 5G signal interference power at this time is P vsgout = 20 dBm;

[0016] The interference tolerance threshold standard: the height measured in each complete cycle of the 5G signal power satisfies any one of the following two standards, that is, the computer recognizes any one standard as true, and then it is determined that the radio altimeter to be tested is disturbed, and it is considered that the current 5G signal power reaches the interference tolerance threshold, when multiple standards are satisfied at the same time, the minimum value of the 5G signal power satisfying any standard is taken;

[0017] 1) Average error criterion: Calculate the average height of each 5G signal power complete cycle, which includes 10 seconds of interference and 5 seconds of interference off, and normalize the average height to the percentage of undistorted height to give the average error. When the average error exceeds 0.5%, it is determined that the measured radio altimeter is disturbed, and it is considered that the current 5G signal power reaches the interference tolerance threshold; when the 5G signal power increases to 20dBm, if the average error does not exceed 0.5%, it is determined that the 5G signal power does not interfere with the radio altimeter;

[0018] Average error calculation formula:

[0019] (| MeanHeight 5GON -MeanHeight 5GOFF |) / MeanHeight 5GOFF * 100%>0.5%;

[0020] Where MeanHeight 5GON is the average height of each 5G signal power on period, and MeanHeight 5GOFF is the average height of the 5G signal power off period;

[0021] 2) Percentage criterion: This criterion determines whether the interference tolerance threshold is reached by evaluating the impact of interference on the dispersion of measurement data distribution. Specifically, if the percentage of data points that do not fall within the confidence interval centered on the average height MeanHeight 5GOFF is greater than 2% during the 5G signal interference on period, it is determined that the measured radio altimeter is disturbed, and it is considered that the current 5G signal power reaches the interference tolerance threshold; when the 5G signal power increases to 20dBm, if the average error does not exceed 0.5%, it is determined that the 5G signal power does not interfere with the radio altimeter;

[0022] In algorithm implementation, when the 5G signal power reaches the interference tolerance threshold, it is equivalent to checking the 1st percentile H 1% and the 99th percentile H 99% of the measurement height during the 5G signal power complete cycle. If the percentage criterion judgment formula is met, it is considered that the interference tolerance threshold standard is reached:

[0023] (| H 1% -MeanHeight 5GOFF |) / MeanHeight 5GOFF >2% or

[0024] (| H 99%MeanHeight 5GOFF MeanHeight 5GOFF >2%;

[0025] wherein MeanHeight 5GOFF is the average of the heights during the 5G signal power off period, H 1% is the 1st percentile of the measured heights during the 5G signal power on period, H 99% is the 99th percentile of the measured heights during the 5G signal power on period.

[0026] The IT formula for calculating the interference tolerance of the tested radio altimeter in step five is:

[0027] IT = P vsgout - L cable ;

[0028] wherein IT is the interference tolerance of the tested radio altimeter, P vsgout is the 5G signal power, and L cable is the path loss value of the signal.

[0029] The method for scanning the full-band interference tolerance of the 5G signal in step six is: waiting for the tested radio altimeter to run stably for 30 seconds, and then testing point by point in the frequency range from 3300 MHz to 5000 MHz with a frequency step value of 100 MHz; for each center frequency test point in the range, first set the center frequency of the interference signal output by the vector signal generator in the interference simulation module to the frequency value corresponding to the current center frequency test point according to the method in step three, and then perform the test operations in steps four and five to determine and record the single-frequency point interference tolerance value at the current center frequency; by traversing all the center frequency test points in the frequency range from 3300 MHz to 5000 MHz and recording the single-frequency point interference tolerance value of each point, the full-band interference tolerance covering the frequency range from 3300 MHz to 5000 MHz at the height simulated by the height simulator is finally obtained, which is composed of a series of single-frequency point interference tolerance values.

[0030] A system for evaluating the interference tolerance of a radio altimeter under 5G interference, comprising a tested radio altimeter, characterized in that it further comprises a height simulator, a directional coupler, an ARINC429 data converter, a computer I, and an interference simulation module; the interference simulation module is connected with the height simulator and the tested radio altimeter through the directional coupler, the tested radio altimeter is connected with the height simulator in one way and with the computer I through the ARINC429 data converter in the other way;

[0031] The specific circuit of the interference simulation module is that the waveform generator is connected with the voltage-controlled oscillator I, the voltage-controlled oscillator II, the voltage-controlled oscillator III, the voltage-controlled oscillator IV, the voltage-controlled oscillator V, the voltage-controlled oscillator VI, the voltage-controlled oscillator VII, the voltage-controlled oscillator VIII, the voltage-controlled oscillator IX, the voltage-controlled oscillator X, the voltage-controlled oscillator XI, the voltage-controlled oscillator XII, the voltage-controlled oscillator XIII, the voltage-controlled oscillator XIV, the voltage-controlled oscillator XV and the voltage-controlled oscillator XVI respectively, the voltage-controlled oscillator I is connected with the combiner I through the fixed attenuator I, the voltage-controlled oscillator II is connected with the combiner I through the fixed attenuator II, the voltage-controlled oscillator III and the voltage-controlled oscillator IV are connected with the combiner I through the combiner III, the programmable attenuator and the combiner II in sequence respectively, the voltage-controlled oscillator V, the voltage-controlled oscillator VI, the voltage-controlled oscillator VII and the voltage-controlled oscillator VIII are connected with the combiner I through the combiner IV, the programmable attenuator and the combiner II in sequence respectively, the voltage-controlled oscillator IX is connected with the combiner I through the fixed attenuator III, the combiner V, the programmable attenuator and the combiner II in sequence, the voltage-controlled oscillator X is connected with the combiner I through the fixed attenuator IV, the combiner V, the programmable attenuator and the combiner II in sequence, the voltage-controlled oscillator XI and the voltage-controlled oscillator XII are connected with the combiner I through the combiner V, the programmable attenuator and the combiner II in sequence respectively, the voltage-controlled oscillator XIII, the voltage-controlled oscillator XIV, the voltage-controlled oscillator XV and the voltage-controlled oscillator XVI are connected with the combiner I through the combiner VI, the programmable attenuator and the combiner II in sequence respectively, the computer II is connected with the combiner I through the vector signal generator, and the combiner I is connected with the combiner II.

[0032] The measured radio altimeter is used for outputting height data; the height simulator is used for receiving the signal transmitted by the measured radio altimeter and sending the processed signal to the measured radio altimeter through the directional coupler; the interference simulation module is used for generating 5G signals and other radio altimeter same-frequency interference signals; the directional coupler is used for coupling the interference signals emitted by the interference simulation module into the signal transmission path from the height simulator to the measured radio altimeter; the ARINC429 data converter is used for converting the output height data of the measured radio altimeter into serial port signals and transmitting the serial port signals to the computer I; the computer I is used for storing the "altimeter data serial port software", collecting the serial port signals transmitted by the ARINC429 data converter; and the "altimeter data serial port software" is used for calculating the height data and the interference periodic average error value and displaying.

[0033] The technical beneficial effects generated by the present application are as follows: the present application can realize flexible setting of the simulated height during testing by adopting a high simulator to receive the transmission signal of the measured radio altimeter and generate a return signal, accurately simulate the signal transmission characteristics of the measured radio altimeter under different working height environments, and has the characteristics of customization.

[0034] By loading a 5G NR TM1.1 signal or a Gaussian white noise signal by using the vector signal generator of the interference simulation module, outputting the signal to the input end of the radio altimeter, simulating the two interference situations of 5G base station basic transmission interference and stray transmission interference faced by the radio altimeter, measuring different types of interference respectively, and determining the interference margin of the radio altimeter under the corresponding interference environment, the two main types of interference that the radio altimeter may encounter in actual application can be covered, and the industry standards and technical specifications are conformed to, so that the comprehensiveness and accuracy of the test results are ensured.

[0035] By using the waveform generator and the voltage-controlled oscillator of the interference simulation module to generate a frequency-modulated continuous wave signal, setting the channel attenuation of the programmable attenuator, and combining the use of the combiner, the fixed attenuator and the cable, a co-frequency interference signal is generated, the co-frequency interference environment that the radio altimeter may face at the worst landing scene of 200 feet height or above 200 feet height is simulated, the co-frequency interference of the radio altimeter under different height scenes is fully considered, so that the test results are closer to the actual application and have more reference value.

[0036] The test system and method provided by the present application can measure the interference margin of the measured radio altimeter in the laboratory, the experimental device is simple, and the test process is efficient. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The system circuit structure schematic diagram for realizing the present application;

[0038] Figure 2 The circuit structure schematic diagram of the interference simulation module for realizing the present application;

[0039] Figure 3 The schematic diagram of the vector network analyzer for measuring the 5G signal path loss of the present application;

[0040] Figure 4 The serial port software running diagram of the embodiment of the present application;

[0041] Figure 5 The 200 feet height time traversal diagram under the center frequency 3500MHz of the embodiment 1 of the present application;

[0042] Figure 6 Statistical chart of 200-foot height error at a center frequency of 3500MHz in Embodiment 1 of the present invention;

[0043] Figure 7 This is a time traversal diagram of a center frequency of 3500MHz at an altitude of 1000 feet in Embodiment 2 of the present invention;

[0044] Figure 8 This is a statistical chart of the altitude error at a center frequency of 3500MHz at 1000 feet in Embodiment 2 of the present invention.

[0045] Figure 9 This is a time traversal diagram of a center frequency of 4300MHz at a height of 200 feet in Embodiment 3 of the present invention;

[0046] Figure 10 This is a statistical chart of the 200-foot height error at a center frequency of 4300MHz in Embodiment 3 of the present invention.

[0047] Figure 11 This is a flowchart of the implementation method of an embodiment of the present invention. Detailed Implementation

[0048] like Figure 1 As shown, a system for evaluating the interference tolerance of a radio altimeter under 5G interference includes a radio altimeter under test, an altitude simulator, a directional coupler, an ARINC429 data converter, a computer I, and an interference simulation module. One path of the altitude simulator is connected to the signal output terminal of the radio altimeter under test via a cable; the other path is connected to the input terminal of the directional coupler. The output terminal of the directional coupler is connected to the signal input terminal of the radio altimeter under test, and the coupling terminal of the directional coupler is connected to the interference simulation module. The ARINC429 data converter is connected to the ARINC 429 interface of the radio altimeter under test via an aviation wire. The computer I is connected to the ARINC429 data converter via a USB interface.

[0049] The tested radio altimeter is used as a test object for testing the test interference tolerance in the system, and outputs the altitude data in ARINC429 format; the altitude simulator is used to receive the signal transmitted by the tested radio altimeter in response to the altitude setting request of the operator, and to perform attenuation and delay processing on the signal to simulate the signal power in the channel transmission under various altitudes, and to send the processed signal to the signal input end of the tested radio altimeter; the interference simulation module is used to generate a 5G signal and other radio altimeter co-frequency interference signals; the directional coupler is used to couple the interference signals emitted by the interference simulation module into the signal transmission path from the altitude simulator to the tested radio altimeter; the ARINC429 data converter is used to convert the altitude data signal in ARINC429 format output by the tested radio altimeter into RS-232 format serial port signal that can be collected by computer I, and to perform data transmission with computer I; computer I is used to store "altitude table data serial port software", and to collect the RS-232 format serial port data output by the ARINC429 data converter, to calculate and display the altitude data; the "altitude table data serial port software" is used to process the RS-232 format serial port signal collected by computer I, to calculate and display the altitude data according to the ARINC429 protocol, and to calculate and display the error value according to the altitude average value of the interference period.

[0050] As Figure 2As shown, the interference simulation module includes a vector signal generator, a waveform generator, a programmable attenuator, a computer II, a combiner I, a combiner II, a combiner III, a combiner IV, a combiner V, a combiner VI, a voltage-controlled oscillator I, a voltage-controlled oscillator II, a voltage-controlled oscillator III, a voltage-controlled oscillator IV, a voltage-controlled oscillator V, a voltage-controlled oscillator VI, a voltage-controlled oscillator VII, a voltage-controlled oscillator VIII, a voltage-controlled oscillator IX, a voltage-controlled oscillator X, a voltage-controlled oscillator XI, a voltage-controlled oscillator XII, a voltage-controlled oscillator XIII, a voltage-controlled oscillator XIV, a voltage-controlled oscillator XV, a voltage-controlled oscillator XVI, a fixed attenuator I, a fixed attenuator II, a fixed attenuator III, a fixed attenuator IV; the output end of the vector signal generator is connected to the input end of the combiner I through a cable, the output end of the computer II is connected to the input end of the vector signal generator through a network cable, the output end of the waveform generator is connected to the input end of the voltage-controlled oscillator I, the voltage-controlled oscillator II, the voltage-controlled oscillator III, the voltage-controlled oscillator IV, the voltage-controlled oscillator V, the voltage-controlled oscillator VI, the voltage-controlled oscillator VII, the voltage-controlled oscillator VIII, the voltage-controlled oscillator IX, the voltage-controlled oscillator X, the voltage-controlled oscillator XI, the voltage-controlled oscillator XII, the voltage-controlled oscillator XIII, the voltage-controlled oscillator XIV, the voltage-controlled oscillator XV, and the voltage-controlled oscillator XVI through cables respectively, the output end of the voltage-controlled oscillator I and the voltage-controlled oscillator II is connected to the input end of the fixed attenuator I and the fixed attenuator II through cables respectively, the output end of the fixed attenuator I and the fixed attenuator II is connected to two input ends of the combiner I through a cable, the output end of the voltage-controlled oscillator III and the voltage-controlled oscillator IV is connected to two input ends of the combiner III through a cable respectively, the output end of the voltage-controlled oscillator V, the voltage-controlled oscillator VI, the voltage-controlled oscillator VII, and the voltage-controlled oscillator VIII is connected to four input ends of the combiner IV through a cable respectively, the output end of the voltage-controlled oscillator IX and the voltage-controlled oscillator X is connected to two input ends of the fixed attenuator III and the fixed attenuator IV through a cable respectively, the output end of the fixed attenuator III and the fixed attenuator IV is connected to two input ends of the combiner V through a cable respectively, the output end of the voltage-controlled oscillator XI and the voltage-controlled oscillator XII is connected to two input ends of the combiner V through a cable respectively, the output end of the voltage-controlled oscillator XIII, the voltage-controlled oscillator XIV, the voltage-controlled oscillator XV, and the voltage-controlled oscillator XVI is connected to four input ends of the combiner VI through a cable respectively, the output end of the combiner III, the combiner IV, the combiner V, and the combiner VI is connected to four input ends of the programmable attenuator through a cable respectively, four output ends of the programmable attenuator is connected to four input ends of the combiner II through a cable respectively, the output end of the combiner II is connected to one input end of the combiner I through a cable, and the output end of the combiner I is connected to the coupling end of the directional coupler through a cable.

[0051] Computer II is used to store the control program of the vector signal generator, drive the vector signal generator to generate 5G NR-FR1-TM1.1 and Gaussian white noise signal, and control the initial power of the signal to be-80dBm, and increase the power by 1dBm step; the vector signal generator is used to generate signals in the working frequency band of 5G signals, support loading 5G NR-FR1-TM1.1 waveform for 5G basic transmission interference test, and generate 4300MHz as the center of 100MHz bandwidth Gaussian white noise signal for 5G stray emission interference test, and the output signal power can be stepped to adjust; the waveform generator is used to generate a triangular wave signal to regulate the frequency of the voltage-controlled oscillator I to the voltage-controlled oscillator XVI; the combiner is used for I to VI to combine two or more input signals into an output signal; the fixed attenuator I to IV is used to provide a fixed attenuation amount to accurately adjust the power of the co-frequency interference signal of each channel.

[0052] The voltage-controlled oscillator I and the voltage-controlled oscillator II are used to generate a frequency-modulated continuous wave waveform for the operation of the radio altimeter, simulate interference signals from other two radio altimeters inside the aircraft; the voltage-controlled oscillator III to XVI are used to generate a frequency-modulated continuous wave waveform for the operation of the radio altimeter, simulate interference signals from the radio altimeter outside the aircraft; the programmable attenuator is used to adjust the attenuation value of the signal path in the port.

[0053] The altitude simulator uses ALT-8000 produced by VIAVI, which can be used for testing radio altimeter of frequency-modulated continuous wave, providing simulation of radio altitude from-20 feet to 5500 feet; the radio altimeter to be tested, which measures and indicates the real altitude of the aircraft relative to the ground or water surface in real time, is usually used in the aircraft take-off, landing and low-altitude flight stages, and is used as the test object in this test to test the test interference tolerance, and outputs the altitude data in ARINC 429 format; the directional coupler uses ZADC-10-63-S+ produced by Mini-Circuits, with a 50-ohm matching load, a working frequency from 2500 MHz to 6000 MHz, a trunk loss of 0.3 dB and a coupling loss of 11.2 dB; the vector signal generator uses E8267D produced by Keysight, with a frequency range from 50 kHz to 44 GHz, a frequency resolution of 0.001 Hz, an output power range from-130 dBm to 25 dBm, a resolution of 0.01 dB, an amplitude accuracy of 0.5 dB, a phase noise less than or equal to-101 dBc / Hz and sequence generation capability; the waveform generator uses 33500B produced by Keysight, which can generate a voltage amplitude of 1 mVpp to 10 Vpp; the programmable attenuator uses RC4DAT-6G-95 produced by Mini-Circuits, with a 50-ohm matching load and an attenuation range of 0 to 95 dB, and an accuracy of 0.25dB, working frequency from 1MHz to 6000MHz; combiner II, combiner III, combiner IV, combiner V, combiner VI adopt ZN4PD1-63HP-S+ produced by Mini-Circuits company, 50Ω matching load, working frequency from 250MHz to 6000MHz, four-way combination, phase balance is zero degree; combiner I adopts ZN2PD-63-S+ produced by Mini-Circuits company, 50Ω matching load, working frequency from 250MHz to 6000MHz, two-way combination, phase balance is zero degree; fixed attenuator I, fixed attenuator II adopt VAT-34+ produced by Mini-Circuits company, 50Ω matching load, working frequency from direct current to 6000MHz, attenuation is-34dB; fixed attenuator III, fixed attenuator IV adopt VAT-23+ produced by Mini-Circuits company, 50Ω matching load, working frequency from direct current to 6000MHz, attenuation is-23dB; voltage-controlled oscillator I, voltage-controlled oscillator II, voltage-controlled oscillator III, voltage-controlled oscillator IV, voltage-controlled oscillator V, voltage-controlled oscillator VI, voltage-controlled oscillator VII, voltage-controlled oscillator VIII, voltage-controlled oscillator IX, voltage-controlled oscillator X, voltage-controlled oscillator XI, voltage-controlled oscillator XII, voltage-controlled oscillator XIII, voltage-controlled oscillator XIV, voltage-controlled oscillator XV, voltage-controlled oscillator XVI adopt ZX95-4403-S+ voltage-controlled oscillator produced by Mini-Circuits company, 50Ω matching load, 5V direct current power supply voltage, linear frequency modulation working frequency is 4200MHz to 4360MHz, power output is 4dBm; ARINC429 data converter adopts USB429-1T1R-P produced by OLYMPUS, supporting continuous reception of at least 120 429 data per second; the aviation wire connected between the measured radio altimeter and the ARINC429 data converter adopts M22759 / 16-22-922AWG aviation wire produced by Cable USA, single core, the insulation layer has good shielding and insulation; the cable for connection adopts RG142 coaxial cable produced by Jinxinuo company, 50Ω matching load, working frequency 0MHz to 6000MHz.

[0054] As shown in Figure 3 , the vector network analyzer Port1 end is connected with the directional coupler output end cable through cable A, the vector network analyzer Port2 end is connected with the combiner I input end cable in the interference simulation module through cable B, and the combiner I output end is connected with the directional coupler coupling end through cable; the vector network analyzer is used for measuring the path loss of 5G signal from the vector signal generator transmitting end to the input end of the measured radio altimeter.

[0055] Example 1: as Figure 11As shown, a method for evaluating the interference tolerance of a radio altimeter under 5G interference is used to evaluate the basic transmission interference tolerance of the tested radio altimeter when the 5G signal center frequency is 3500MHz, and the test is conducted in a 200-foot simulated altitude scenario. The specific test steps are as follows:

[0056] Step one, get the 5G signal path loss: set the frequency range of the vector network analyzer to 3000MHz to 5000MHz, complete the vector network analyzer calibration, then establish the connection relationship as shown in Figure 3 to get the 5G signal path loss;

[0057] Specifically: First, disconnect the directional coupler output cable from the input end of the tested radio altimeter, connect it to cable A of the vector network analyzer, disconnect the input cable of the combiner I in the interference simulation module from the output end of the vector signal generator, and connect it to cable B of the vector network analyzer. After the connection is completed, observe the vector network analyzer to get the path loss value L cable = 22.6dB at 3500MHz frequency from the output end of the vector signal generator in the interference simulation module to the input end of the tested radio altimeter.

[0058] Step two, configure the height simulator: after the path loss measurement is complete, install the tested radio altimeter on the test bench, then disconnect the directional coupler output cable from cable A and connect it to the input end of the tested radio altimeter. Disconnect the input cable of the combiner I in the interference simulation module from cable B and connect it to the output end of the vector signal generator. After the hardware connection is restored, provide 115V, 400Hz AC power to the tested radio altimeter of the test system, provide 220V, 50Hz AC power to computer I and the vector signal generator, waveform generator computer II in the interference simulation module, and provide 5V DC power to the voltage-controlled oscillator in the interference simulation module. After the system is powered on and stable, perform parameter setting, manually start the automatic delay calibration program of the height simulator, then manually set the predetermined flight height parameter to 200 feet on the height simulator, and set the loop loss of the height simulator according to the path loss as 8.7dB and 9.6dB. Specifically, the loop loss from the output end of the tested radio altimeter to the input end of the height simulator is 9.6dB, and the loop loss from the input end of the tested radio altimeter to the output end of the height simulator is 8.7dB.

[0059] Optionally, if other altitudes are to be tested, configuring the altitude simulator further comprises: modifying the altitude parameter of the altitude simulator to the test altitude, and setting the loop loss parameter corresponding to the test altitude; when the test altitude is set to be higher than 200 feet, the setting operation further comprises disconnecting the connecting cable between combiner I and combiner II in the interference simulation module, and only enabling voltage-controlled oscillator I and voltage-controlled oscillator II, to simulate the co-frequency interference signal from the inside of the aircraft.

[0060] Step three, configure the interference simulation module: according to the co-frequency interference scenario corresponding to the 200 feet simulated altitude set by the altitude simulator, generate the required co-frequency interference signal, set the waveform of the waveform generator in the interference simulation module to a triangular wave, the frequency to 150 Hz, the peak voltage to 1.5 V, and the direct current bias to 0.5 V to obtain a modulation signal, and then set the attenuation amount of each channel of the programmable attenuator in the interference simulation module by using a fixed attenuator and a programmable attenuator in combination, so that the power at the input end of the radio altimeter under test is as shown in Table 1, to obtain the required co-frequency interference signal;

[0061] Each signal transmission path is specifically configured as follows: for the voltage-controlled oscillator I and the voltage-controlled oscillator II simulating the co-frequency interference inside the aircraft, fixed attenuator I and fixed attenuator II with an attenuation amount of -34 dB are connected in series in the output path, so that the signal power reaching the input end of the radio altimeter under test is -58 dBm;

[0062] For the voltage-controlled oscillator Ix and the voltage-controlled oscillator X simulating the co-frequency interference outside the aircraft, fixed attenuator III and fixed attenuator IV with an attenuation amount of -23 dB and a programmable attenuator are connected in series in the output path, so that the signal power reaching the input end of the radio altimeter under test is -85 dBm, and for other voltage-controlled oscillators, the attenuation amount of each channel of the programmable attenuator is adjusted to -58 dB, -28 dB, -28 dB, and -51 dB respectively, to ensure that the signal power of each voltage-controlled oscillator reaching the input end of the radio altimeter under test is consistent with the target value shown in Table 1.

[0063] Table 1: Power setting of the output signal path of the co-frequency interference source voltage-controlled oscillator

[0064]

[0065] According to the 5G signal interference scenario corresponding to the 3500 MHz test frequency band, which is a basic transmission interference scenario, the vector signal generator is set to a 5G NR TM1.1 waveform signal with a center frequency of 3500 MHz and a bandwidth of 100 MHz, to obtain the required 5G signal.

[0066] According to the 5G signal interference scene, the potential interference of the 5G base station to the radio altimeter under test comes from two aspects: the first type is the interference in the frequency range of 4200-4400 MHz (i.e. the working frequency range of the radio altimeter under test); the second type is the interference outside the working frequency range of the radio altimeter under test, i.e. 3000-4200 MHz and 4400-5000 MHz, but due to the frequency proximity or signal strength, etc. factors, it may still interfere with it. Generally, the basic transmission of the 5G base station is one of the main sources of the above-mentioned out-of-band interference, and the spurious emission of the 5G base station may cause in-band interference.

[0067] Step four, perform single frequency point power increment test: after the height simulator and the interference simulation module are configured, first start computer I, run the altimeter data serial port software as shown in the figure, establish the connection between computer I and the radio altimeter under test by clicking the "open serial port" button on the software interface; Figure 4

[0068] Then, start computer II, run the altimeter data serial port software as shown in the figure, establish the connection between computer II and the vector signal generator by clicking the "connect" button on the software interface. Figure 4

[0069] Figure 4 The altimeter data serial port software as shown in the figure has the following interface layout and functions:

[0070] The left panel, from top to bottom, is: the receiving window, used to display the height data received from the radio altimeter under test and decoded in real time. The computer program decodes the serial data received by the computer to obtain specific height data, and displays the decoded height data in the receiving window of the software main interface.

[0071] The sending window is used to edit SCPI control instructions, and send the instructions to the vector signal generator through the "send data" button below to control the vector signal generator to set the initial power and perform power scanning. It also includes a "clear receiving" button to clear the height data in the receiving window.

[0072] The middle panel, from top to bottom, is: the controls of port number, baud rate, data bits, check bits and stop bits, used to configure the information of the serial port; the "encoding method: 68.7 BCD" and "encoding method: 68 BNR" buttons, used to manually start the computer program to send and receive automatically, to verify whether the computer program can normally send and receive; the port input box and the Internet protocol address input box, used for the computer program to make network connection, to change the IP address according to the actual situation, while the port number (such as 8080 in the above) is defined in cooperation with the Internet protocol address; Figure 4

[0073] ​​​"Connect" and "Disconnect" buttons are used to open and control the connection between the computer and the vector signal generator; "Open serial port" button is used to manually open and close the connection between the computer and the radio altimeter under test.

[0074] The right panel is a graphical display area of height data, specifically: the area is a coordinate graph, the horizontal axis is time, unit s, and the vertical axis is height, unit feet. The area dynamically draws the trend of height data in the form of line chart. Since the height data has two decoding forms of BCD and BNR, the display area has two kinds of height data, of which height_BCD is the height data in BCD form and height_BNR is the height data in BNR form.

[0075] The upper left corner also contains a menu bar, including the following menu items: "File": provides the function of saving data or images, saving time traversal graph and height error statistical graph.

[0076] "Serial port": provides the function of configuring serial communication parameters, including selecting serial port number, setting baud rate, data bits, check bits and stop bits.

[0077] The "Connect" menu item provides the function of configuring network connection parameters, including setting the IP address and network port number of the target server.

[0078] After establishing the above connection, start to perform interference injection and scanning: input SCPI command in the "send window" on the software interface of computer II, and send the SCPI command to the vector signal generator by clicking the "send data" button, control the vector signal generator to set the initial power-80dBm and perform power scanning; the specific process of power scanning is: open the signal output for 10 seconds with the initial power of-80dBm, and then close for 5 seconds; then increase the power by 1dBm, repeat the cycle of opening for 10 seconds and closing for 5 seconds.

[0079] During the power scanning process, the height data graphical display area of the altimeter data serial port software of computer I is observed in real time. It is observed that during the whole process of increasing the power of 5G signal from-80dBm to 20dBm, the height data does not appear to meet the interference tolerance threshold standard, the power step increase is stopped, and the upper left menu bar is opened, and the file is saved as Figure 5 The time traversal graph can be observed in the graph that the height data does not appear significant fluctuation during the step increase of 5G signal power;

[0080] In Figure 5In the figure, the horizontal axis is time, in ms, the main (left) vertical axis is the measured radio altimeter output height, in feet, and the secondary (right) vertical axis is the interference power of the 5G signal output by the vector signal generator, in dBm. Figure 5 The jagged solid line in the figure represents the height data, and the dashed line represents the 5G interference.

[0081] Further, the collected data can be statistically analyzed and saved as a height error statistical chart such as Figure 6 to accurately obtain the power of the 5G signal that meets the interference tolerance threshold standard from the data. According to the average error formula in the analysis chart data:

[0082] (| MeanHeight 5GON -MeanHeight 5GOFF |) / MeanHeight 5GOFF * 100%>0.5%;

[0083] wherein MeanHeight 5GON is the average height of each 5G signal power on period, and MeanHeight 5GOFF is the average height of the 5G signal power off period.

[0084] The calculation shows that the average error of all 5G signal power test points does not exceed 0.5%, and therefore does not meet the average error standard.

[0085] According to the percentage standard judgment formula:

[0086] (| H 1% -MeanHeight 5GOFF |) / MeanHeight 5GOFF >2% or

[0087] (| H 99% -MeanHeight 5GOFF |) / MeanHeight 5GOFF >2%;

[0088] wherein MeanHeight 5GOFF is the average height of the 5G signal power off period, H 1% is the 1st percentile of the measured height in the 5G signal power on period, and H 99% is the 99th percentile of the measured height in the 5G signal power on period.

[0089] Calculations show that for all 5G signal power test points, the first percentile value of the percentage standard does not exceed 2%, therefore the first percentile requirement of the percentage standard is not met; the 99th percentile value of the percentage standard does not exceed 2%, therefore the 99th percentile requirement of the percentage standard is not met.

[0090] exist Figure 6 In the diagram, the horizontal axis represents 5G interference power in dBm, and the vertical axis represents the error percentage in %. Figure 6 The zigzag solid line in the figure represents the average height error, which is the percentage standard error of the measured height calculated according to the average error formula. Figure 6 The topmost dotted line represents the 1% height data error. The 1% height data error is the first percentile error of the measured height during the 5G signal power activation period, calculated according to the percentage standard formula. Figure 6 The other dashed line represents the 99% height data error. The 99% height data error is the 99th percentile error of the height measurement during the 5G signal power activation cycle, calculated according to the percentage standard judgment formula.

[0091] When the 5G power reached the upper limit of 20dBm, none of the conditions of the interference tolerance threshold standard were met, and it was determined that interference tolerance could not be tested at the current altitude and frequency. Finally, the 5G signal power obtained in this test was recorded as P. vsgout >20dBm.

[0092] Step 5, calculate the interference tolerance of the measured radio altimeter: based on the path loss L obtained in Step 1. cable =22.6dB and the 5G signal power P obtained according to step four vsgout >20dBm, calculate the interference tolerance of the measured radio altimeter.

[0093] IT = P vsgout - L cable >20dBm - 22.6dB = -2.6dBm, where IT is the interference tolerance of the measured radio altimeter, P vsgout For 5G signal power, L cable The path loss value of the signal is used to obtain the interference tolerance of the measured radio altimeter greater than -2.6dBm. In Example 1, only the interference tolerance at 3500MHz is considered, so step six, the full-band interference tolerance scan of the 5G signal, is not performed.

[0094] The basic emission interference of the measured radio altimeter at the center frequency of 3500 MHz and the interference margin under the 200-foot analog height scenario are measured by the above steps, and the measured interference margin value can be used as a key technical performance parameter, for example, the "front-end overload interference protection threshold" of the measured radio altimeter, which provides a specific and quantitative scientific basis for evaluating the electromagnetic compatibility of the 5G base station deployment near the airport on the radio altimeter.

[0095] Embodiment 2: A method for evaluating the interference margin of a radio altimeter under 5G interference, for evaluating the basic emission interference margin of the measured radio altimeter when the center frequency of the 5G signal is 3500 MHz, and the test is conducted at a 1000-foot analog height scenario; the specific test steps are as follows:

[0096] Step one, obtain the path loss of the 5G signal: the test steps are the same as step one of embodiment 1, and the path loss of the cable at 4300 MHz is obtained, denoted as L cable = 22.6 dB.

[0097] Step two, configure the height simulator: after completing the test step one, before the test step two, modify the interference simulation module, disconnect the connection cable between the combiner I and the combiner II in the interference simulation module, and only enable the voltage-controlled oscillator I and the voltage-controlled oscillator II to simulate the same frequency interference signal from the inside of the aircraft. Then the test steps are the same as step two of embodiment 1.

[0098] Step three, configure the interference simulation module: the test steps are the same as step three of embodiment 1.

[0099] Step four, perform single frequency point power increment test: the test steps are the same as step four of embodiment 1, when the 5G signal power is stepped up to 5 dBm, it is observed that the height data of the measured radio altimeter starts to fluctuate significantly, and the time traversal graph is saved as Figure 7 , and in Figure 7 , it can be observed that the height data fluctuates significantly when the 5G signal power reaches 5 dBm;

[0100] In Figure 7 , the horizontal axis is time in ms, the primary (left) vertical axis is the output height of the measured radio altimeter in feet, and the secondary (right) vertical axis is the interference power of the 5G signal output by the vector signal generator in dBm, Figure 7 , the jagged solid line represents the height data, and the dashed line represents the 5G interference.

[0101] Further save the height error statistical graph as Figure 8 ,

[0102] In Figure 8In the figure, the horizontal axis is the 5G interference power, in dBm, and the vertical axis is the error percentage, in %, Figure 8 The zigzag solid line in the figure represents the average height error, which is the percentage standard error of the measured height calculated according to the average error calculation formula, Figure 8 The uppermost dotted line in the figure represents the 1% height data error, which is the 1st percentile error of the measured height in the 5G signal power-on period calculated according to the percentage standard judgment formula, Figure 8 The other dotted line in the figure represents the 99% height data error, which is the 99th percentile error of the measured height in the 5G signal power-on period calculated according to the percentage standard judgment formula.

[0103] Analysis Figure 8 In the figure, the horizontal axis is the 5G interference power, in dBm, and the vertical axis is the error percentage, in %,

[0104] (| MeanHeight 5GON -MeanHeight 5GOFF |) / MeanHeight 5GOFF * 100%>0.5%;

[0105] wherein MeanHeight 5GON is the average height of each 5G signal power-on period, and MeanHeight 5GOFF is the average height of the 5G signal power-off period;

[0106] It can be calculated that when the 5G signal power is -9 dBm, the average error is 0.904%, which is greater than 0.5%, meeting the average error standard;

[0107] According to the percentage standard judgment formula:

[0108] (| H 1% -MeanHeight 5GOFF |) / MeanHeight 5GOFF >2% or

[0109] (| H 99% -MeanHeight 5GOFF |) / MeanHeight 5GOFF >2%;

[0110] wherein MeanHeight 5GOFF is the average height of the 5G signal power-off period, H 1% is the 1st percentile of the measured height in the 5G signal power-on period, and H 99%The 99th percentile of the height measured in the on period of the 5G signal power;

[0111] The calculation shows that when the 5G signal power is -9 dBm, the 1st percentile of the percentage standard is -2.539%, which is greater than 2% and meets the 1st percentile requirement of the percentage standard. When the 5G signal power is increased in steps from -80 to 8 dBm, the 99th percentile of the percentage standard does not exceed 2%, so it does not meet the 99th percentile requirement of the percentage standard.

[0112] According to the definition of the interference tolerance threshold standard, the smallest value of the 5G signal power that meets any standard is taken, so the 5G signal power P vsgout = -9 dBm obtained in this test is recorded.

[0113] Step five, calculate the interference tolerance of the measured radio altimeter: according to the path loss L cable = 22.6 obtained in step one and the 5G signal power P vsgout = -9 dBm obtained in step four, calculate the interference tolerance

[0114] IT = P vsgout - L cable = -9 dBm - 22.6 dB = -31.6 dBm, where IT is the interference tolerance of the measured radio altimeter, P vsgout is the 5G signal power, and L cable is the path loss value of the signal; in embodiment 2, only the interference tolerance at 3500 MHz is concerned, so step six, 5G signal full-band interference tolerance scanning, is not performed.

[0115] Embodiment 3: A method for evaluating the interference tolerance of a radio altimeter under 5G interference, which is used to evaluate the interference tolerance of the measured radio altimeter under the 5G signal spurious emission interference at the center frequency of 4300 MHz and the 200-foot analog height scenario.

[0116] The specific test steps are as follows:

[0117] Step one, obtain the 5G signal path loss: the test steps are the same as those in step one of embodiment 1, and the path loss of the cable at 4300 MHz is obtained, denoted as L cable = 22.4 dB.

[0118] Step two, configure the height simulator: the test steps are the same as those in step two of embodiment 1.

[0119] Step three, configure the interference simulation module: the test steps are basically the same as those in step three of embodiment 1, only the settings of the vector signal generator need to be changed, the vector signal generator is set to load a Gaussian white noise signal, the center frequency is 4300 MHz, and the bandwidth is 160 MHz, so as to obtain the required 5G signal; in this embodiment 3, in order to test the interference tolerance of the radio altimeter receiver in the frequency band of 4200-4400 MHz, a Gaussian white noise signal with a sufficient bandwidth of 160 MHz is selected to cover the entire receiving bandwidth of the radio altimeter receiver, which is a suitable waveform for simulating 5G stray emission.

[0120] Step four, perform single frequency point power increment test: the test steps are the same as those in step four of embodiment 1, when the power of the 5G signal is stepped up to -6 dBm, it is observed that the height data of the radio altimeter under test begins to fluctuate significantly, and the time traverse graph as shown in Figure 9 is saved;

[0121] In Figure 9 , the horizontal axis is time, in ms, the main (left) vertical axis is the output height of the radio altimeter under test, in feet, and the secondary (right) vertical axis is the interference power of the 5G signal output by the vector signal generator, in dBm, Figure 9 , the jagged solid line in Figure 9 represents the height data, and the dotted line represents the 5G interference.

[0122] Further save the height error statistical graph as shown in Figure 10 ,

[0123] In Figure 10 , the horizontal axis is the 5G interference power, in dBm, and the vertical axis is the error percentage, in %, Figure 10 , the jagged solid line in Figure 10 represents the average height error, which is the percentage standard error of the measured height calculated according to the average error calculation formula, Figure 10 , the uppermost dotted line in Figure 10 represents the 1% height data error, which is the 1st percentile error of the measured height within the 5G signal power-on period calculated according to the percentage standard judgment formula, Figure 10 , the other dotted line in Figure 10 represents the 99% height data error, which is the 99th percentile error of the measured height within the 5G signal power-on period calculated according to the percentage standard judgment formula.

[0124] Analysis Figure 10 of the data shows that during the power stepping-up process, according to the average error formula:

[0125] (| MeanHeight 5GON -MeanHeight 5GOFF |) / MeanHeight 5GOFF* 100%>0.5%;

[0126] where MeanHeight 5GON is the average height of each 5G signal power on period, MeanHeight 5GOFF is the average height of 5G signal power off period; it can be calculated that when the 5G signal power is -23dBm, the average error is -1.685%, which is greater than 0.5%, meeting the average error standard; according to the percentage standard judgment formula:

[0127] (| H 1% -MeanHeight 5GOFF |) / MeanHeight 5GOFF >2% or

[0128] (| H 99% -MeanHeight 5GOFF |) / MeanHeight 5GOFF >2%;

[0129] where MeanHeight 5GOFF is the average height of 5G signal power off period, H 1% is the 1st percentile of the measured height in the 5G signal power on period, H 99% is the 99th percentile of the measured height in the 5G signal power on period;

[0130] It can be calculated that when the 5G signal power is -25dBm, the 1st percentile value of the percentage standard is -2.212%, which is greater than 2%, meeting the 1st percentile requirement of the percentage standard; during the step-by-step increase of the 5G signal power from -80 to -23dBm, the 99th percentile value of the percentage standard does not exceed 2%, so the 99th percentile requirement of the percentage standard is not met.

[0131] According to the definition of the interference tolerance threshold standard, the minimum value of the 5G signal power meeting any standard is taken, so the 5G signal power P vsgout = -25dBm obtained in this test is recorded.

[0132] Step five, calculate the interference tolerance of the measured radio altimeter: according to the path loss L cable = 22.4dB obtained in step one and the 5G signal power P vsgout = -25dBm obtained in step four, calculate the interference tolerance

[0133] IT = P vsgout - L cable= -25dBm - 22.4dB = -47.4dBm, where IT is the interference tolerance of the radio altimeter under test, P vsgout P5G is the 5G signal power, L cable L is the path loss value of the signal; in embodiment 3, only the interference tolerance at 4300MHz is concerned, so step six of 5G signal full-band interference tolerance scanning is not performed.

[0134] Embodiment 3 measures the interference tolerance of the radio altimeter under test at the center frequency 4300MHz by the above steps, and the interference tolerance of the radio altimeter under test in the 200-foot analog height scenario is -28.4dBm. The measured interference tolerance value can be used as a key technical performance parameter, for example, the "front-end overload interference protection threshold" of the radio altimeter under test, which provides a specific and quantitative scientific basis for evaluating the electromagnetic compatibility of 5G base station deployment near the airport area on the radio altimeter.

[0135] Embodiments 1, 2 and 3 take the radio altimeter under test as the research object, and quantitatively measure the interference tolerance of the radio altimeter under test in two typical interference scenarios, i.e. the basic transmission interference and the spurious emission interference of the 5G base station. In this way, the interference tolerance of the radio altimeter under test in the corresponding interference environment is obtained, which can cover the main interference types of the radio altimeter in actual application, realize the quantification of the interference tolerance of the radio altimeter under the interference of 5G, and has important practical significance for ensuring the safe flight of civil aviation aircraft and promoting the deep integration and coordinated development of 5G technology and aviation industry. It solves the technical problem of lacking a quantitative evaluation method for the interference tolerance of the radio altimeter under the interference of 5G in the prior art.

Claims

1. A method for evaluating the interference tolerance of a radio altimeter under 5G interference, characterized in that, One cable from the altitude simulator is connected to the signal output of the radio altimeter under test, and the other cable is connected to the input of a directional coupler. The output of the directional coupler is connected to the signal input of the radio altimeter under test, and the coupling end of the directional coupler is connected to the interference simulation module. The ARINC429 data converter is connected to the ARINC 429 interface of the radio altimeter under test via an aviation wire. Computer I is connected to the ARINC429 data converter via a USB interface. The process includes the following steps: Step 1: Obtain 5G signal path loss: The vector network analyzer is used to measure the path loss of the 5G signal from the transmitter of the vector signal generator in the interference simulation module to the input of the radio altimeter under test, and obtain the path loss value L of the 5G signal within the set frequency range. cable ; Step 2, Configure the height simulator: Power on the entire test system, start the height simulator, perform delay calibration on the height simulator, and complete the setting of height parameters and loop loss parameters; Step 3, Configure the interference simulation module: Based on the co-channel interference scenario, set the interference simulation module to obtain the required co-channel interference signal; based on the 5G signal interference scenario, set the vector signal generator parameters to obtain the required 5G signal; Step 4: Perform a single-frequency power increment test: After configuring the altitude simulator and interference simulation module, control the interference simulation module to perform a single-frequency power increment test. When the interference judgment index is reached, record the current 5G signal power as P. vsgout ; Step 5, calculate the interference tolerance of the tested radio altimeter: based on the path loss value L of the 5G signal obtained in Step 1. cable And the 5G signal power P obtained from step four vsgout Calculate the interference tolerance IT of the measured radio altimeter; Step 6, 5G signal full-band interference tolerance scan: After the radio altimeter under test stabilizes, modify the frequency parameters of the vector signal generator set in Step 3, and execute the tests in Step 4 and Step 5 to comprehensively evaluate the interference tolerance of the radio altimeter under test under the interference of the preset working frequency band of 5G signal at the simulated altitude of the altitude simulator. By following the above steps, the interference tolerance test of the tested radio altimeter under 5G signal interference is completed, and the interference tolerance of the tested radio altimeter is determined.

2. The method for evaluating the interference tolerance of radio altimeters under 5G interference according to claim 1, characterized in that, The method for measuring path loss using a vector network analyzer in step one is as follows: First, set the frequency range of the vector network analyzer and complete the vector network analysis calibration. Then, disconnect the output cable of the directional coupler from the input of the radio altimeter under test and connect it to cable A of the vector network analyzer. Next, disconnect the input cable of combiner I in the interference simulation module from the output of the vector signal generator and connect it to cable B of the vector network analyzer. Observe the vector network analyzer and obtain the path loss value L within the set frequency range, from the output of the vector signal generator in the interference simulation module to the input of the radio altimeter under test. cable .

3. The method for evaluating the interference tolerance of radio altimeters under 5G interference according to claim 1, characterized in that, The method for configuring the altitude simulator in step two is as follows: Install the radio altimeter under test on the test bench, then disconnect the output cable of the directional coupler from cable A and connect it to the input of the radio altimeter under test. Disconnect the input cable of combiner I in the interference simulation module from cable B and connect it to the output of the vector signal generator. Power the radio altimeter under test, computer I, vector signal generator, waveform generator, computer II, and voltage-controlled oscillator in the interference simulation module. Manually start the automatic delay calibration program of the altitude simulator, manually set the predetermined flight altitude parameters on the altitude simulator, and set the loop loss of the altitude simulator according to the path loss.

4. The method for evaluating the interference tolerance of radio altimeters under 5G interference according to claim 1, characterized in that, Step 3 describes the method for configuring the interference simulation module as follows: Based on the altitude simulator, set the co-channel interference scenario corresponding to the flight altitude. Set the parameters of the waveform generator in the interference simulation module to obtain the modulation signal. By combining the fixed attenuator and programmable attenuator in the interference simulation module, set the attenuation of each channel of the programmable attenuator in the interference simulation module to obtain the co-channel interference signal with the required power. Based on the 5G signal interference scenario corresponding to the test frequency band, set the waveform, center frequency, and bandwidth parameters of the signal loaded by the vector signal generator. If the test frequency band is a basic transmission interference scenario, set the vector signal generator to load a 5G NR TM1.1 waveform signal with the center frequency of the test frequency band and a bandwidth of 100MHz. If the test frequency band is a spurious transmission interference scenario, set the vector signal generator to load a Gaussian white noise signal with a center frequency of 4300MHz and a bandwidth of 160MHz to obtain the required 5G signal.

5. The method for evaluating the interference tolerance of radio altimeters under 5G interference according to claim 1, characterized in that, Step four describes the single-frequency power increment test method as follows: After configuring the altitude simulator and interference simulation module, start computer I, open the altimeter data serial port software, and establish a connection between computer I and the radio altimeter under test; then start computer II in the interference simulation module, open the altimeter data serial port software, and establish a connection between computer II and the vector signal generator; after establishing the above connection, begin interference injection and scanning: computer II controls the vector signal generator through the altimeter data serial port software to set the initial power to -80dBm and perform a power scan. The power scan is specifically as follows: turn on the signal output with an initial power of -80dBm for 10 seconds, then turn it off for 5 seconds; then increase the power in steps of 1dBm, repeating the cycle of turning on for 10 seconds and turning off for 5 seconds. During the stepping process, if the altitude data of the radio altimeter under test displayed by the altimeter data serial port software on computer I reaches the interference tolerance threshold standard, stop the power stepping increase, and record the 5G signal power as P. vsgout If the step signal power reaches 20dBm, and the measured radio altimeter does not meet the interference tolerance threshold standard, it is determined that the interference tolerance cannot be tested at this frequency point, and the 5G signal interference power at this time is considered to be P. vsgout =20dBm; The interference tolerance threshold standard is as follows: the height measurement of each complete cycle of 5G signal power meets either of the following two standards. If the computer recognizes either standard as true, it determines that the measured radio altimeter is disturbed and considers that the current 5G signal power has reached the interference tolerance threshold. When multiple standards are met at the same time, the value of the 5G signal power that meets any standard is taken. 1) Average Error Standard: Calculate the average measured height for each complete 5G signal power cycle. A complete 5G signal power cycle includes 10 seconds of interference enabled followed by 5 seconds of interference disabled. Normalize the average measured height to the percentage of undistorted height to give the average error. If the average error exceeds 0.5%, the measured radio altimeter is considered to be interfered with, and the current 5G signal power is considered to have reached the interference tolerance threshold. When the 5G signal power increases to 20dBm, if the average error does not exceed 0.5%, it is determined that the 5G signal power does not interfere with the radio altimeter. Formula for calculating average error: (| MeanHeight 5GON -MeanHeight 5GOFF |) / MeanHeight 5GOFF * 100% > 0.5%; MeanHeight 5GON MeanHeight is the average height for each 5G signal power-on cycle. 5GOFF The height average of the 5G signal power shutdown cycle; 2) Percentage Standard: This standard determines the percentage by assessing the impact of interference on the dispersion of the measured data distribution. When 5G signal interference causes the statistical distribution of the measured height values ​​to become excessively dispersed, it is considered to have reached the interference tolerance threshold. Specifically, if the measured height values ​​do not fall within the mean height during the 5G signal interference period, the percentage is considered to be within the mean height. 5GOFF If the percentage of data points within the central confidence interval is greater than 2%, the measured radio altimeter is considered to be disturbed, and the current 5G signal power is considered to have reached the interference tolerance threshold. When the 5G signal power increases to 20 dBm, if the measured height value does not fall within the MeanHeight value... 5GOFF If the percentage of data points within the confidence interval centered on the signal does not exceed 0.5%, it is determined that the 5G signal does not interfere with the radio altimeter. In terms of algorithm implementation, the 5G signal power reaching the interference tolerance threshold is equivalent to checking the first percentile H of the measured altitude within a complete cycle of the 5G signal power. 1% and the 99th percentile H 99% If the percentage standard judgment formula is met, then the interference tolerance threshold standard is considered to have been met. (|H 1% -MeanHeight 5GOFF |) / MeanHeight 5GOFF > 2% or (| H 99% -MeanHeight 5GOFF |) / MeanHeight 5GOFF >2%; MeanHeight 5GOFF H represents the average height of the 5G signal power shutdown period. 1% H represents the first percentile of the measured height during the 5G signal power activation period. 99% This is the 99th percentile of the measured height during the 5G signal power activation period.

6. The method for evaluating the interference tolerance of a radio altimeter under 5G interference according to claim 1, characterized in that: The formula for calculating the interference tolerance IT of the measured radio altimeter in step five is as follows: IT=P vsgout - L cable ; Where IT is the interference tolerance of the measured radio altimeter, and P... vsgout For 5G signal power, L cable This represents the path loss value of the signal.

7. The method for evaluating the interference tolerance of radio altimeters under 5G interference according to claim 1, characterized in that: The method for scanning the full-band interference tolerance of 5G signals in step six is ​​as follows: wait for the radio altimeter under test to run stably for 30 seconds, and test point by point in the frequency range from 3300MHz to 5000MHz with a frequency step value of 100MHz; for each center frequency test point in the range, first set the center frequency of the interference signal output by the vector signal generator in the interference simulation module to the frequency value corresponding to the current center frequency test point according to the method in step three, and then perform the test operations in steps four and five to determine and record the single-frequency interference tolerance value at the current center frequency; by traversing all center frequency test points in the frequency range from 3300MHz to 5000MHz and recording the single-frequency interference tolerance value of each point, the full-band interference tolerance covering the frequency range from 3300MHz to 5000MHz under the simulated altitude of the altimeter is finally obtained, consisting of a series of single-frequency interference tolerance values.

8. A system for evaluating the interference tolerance of a radio altimeter under 5G interference, used to implement the method for evaluating the interference tolerance of a radio altimeter under 5G interference as described in any one of claims 1 to 7, comprising the radio altimeter under test, characterized in that: It also includes an altitude simulator, a directional coupler, an ARINC429 data converter, computer I, and an interference simulation module; the interference simulation module is connected to the altitude simulator and the radio altimeter under test respectively through the directional coupler, and the radio altimeter under test is connected to the altitude simulator on one side and to computer I through the ARINC429 data converter on the other side. The specific circuit of the interference simulation module is as follows: a waveform generator is connected to voltage-controlled oscillators (VCOs) I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII, XIII, XIV, XV, and XVI respectively. VCO I is connected to combiner I via a fixed attenuator I. VCO II is connected to combiner I via a fixed attenuator II. VCOs III and IV are connected to combiner I via combiner III, a programmable attenuator, and combiner II respectively. VCOs V, VI, VII, and XVI are connected to voltage-controlled oscillators (VCOs). The oscillator VIII is connected to combiner I in sequence via combiner IV, programmable attenuator, and combiner II. The voltage-controlled oscillator IX is connected to combiner I in sequence via fixed attenuator III, combiner V, programmable attenuator, and combiner II. The voltage-controlled oscillator X is connected to combiner I in sequence via fixed attenuator IV, combiner V, programmable attenuator, and combiner II. The voltage-controlled oscillators XI and XII are connected to combiner I in sequence via combiner V, programmable attenuator, and combiner II. The voltage-controlled oscillators XIII, XIV, XV, and XVI are connected to combiner I in sequence via combiner VI, programmable attenuator, and combiner II. The computer II is connected to combiner I via a vector signal generator. Combiner I is connected to combiner II.

9. The system for evaluating the interference tolerance of radio altimeters under 5G interference according to claim 8, characterized in that: It also includes a vector network analyzer. The Port1 end of the vector network analyzer is connected to the output end of the directional coupler via cable A, and the Port2 end of the vector network analyzer is connected to the input end of the combiner I in the interference simulation module via cable B. The output end of the combiner I is connected to the coupling end of the directional coupler via cable. The vector network analyzer is used to measure the path loss of the 5G signal from the transmitter of the vector signal generator to the input end of the measured radio altimeter.

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