CN116106886B - Airborne radio altimeter device based on frequency modulation continuous wave - Google Patents
Airborne radio altimeter device based on frequency modulation continuous wave Download PDFInfo
- Publication number
- CN116106886B CN116106886B CN202310377585.8A CN202310377585A CN116106886B CN 116106886 B CN116106886 B CN 116106886B CN 202310377585 A CN202310377585 A CN 202310377585A CN 116106886 B CN116106886 B CN 116106886B
- Authority
- CN
- China
- Prior art keywords
- module
- frequency
- signal
- frequency hopping
- time
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
- G01S13/06—Systems determining position data of a target
- G01S13/08—Systems for measuring distance only
- G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C5/00—Measuring height; Measuring distances transverse to line of sight; Levelling between separated points; Surveyors' levels
- G01C5/005—Measuring height; Measuring distances transverse to line of sight; Levelling between separated points; Surveyors' levels altimeters for aircraft
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Abstract
The invention discloses an airborne radio altimeter device based on frequency modulation continuous waves, and relates to the technical field of radio distance measurement. The device comprises a transmitting unit and a receiving unit, wherein the transmitting unit comprises a waveform generating module, a spread spectrum module, a linear frequency modulation module, a frequency hopping module, a time control module and a transmitting antenna module; the receiving unit comprises a receiving antenna module, a despreading module, a frequency hopping and debonding module, a synchronizing module, a difference frequency module and a height measuring module; the spread spectrum module is used for generating a pseudo random sequence to form a pulse modulation signal; the linear frequency modulation module forms a broadband frequency modulation signal under the action of the time control module; the frequency hopping module is used for converting the broadband frequency modulation signal into a frequency hopping signal; the beat frequency module forms a beat signal after mixing and low-pass filtering the debounced signal and the broadband frequency modulation signal so as to realize height measurement. The invention improves the anti-interference and Doppler shift resistance of the radio altimeter and improves the altimeter high resolution.
Description
Technical Field
The invention relates to the field of radio altimeter distance measurement, in particular to an airborne radio altimeter device with anti-interference capability for height measurement.
Background
The airborne radio altimeter is used for determining the height of a flight carrier by measuring the principle of propagation delay time of electromagnetic waves in the air, and is important navigation equipment for a conveyor, a helicopter, a civil aircraft and the like. Radio altimeters play an important role on aircraft, such as take-off, landing, and autopilot of aircraft. In on-board radio altimeter devices, the altimeter technical regime based on frequency modulated continuous waves dominates. The radio altimeter based on the frequency modulation continuous wave system has the advantages of no distance blind area, high measurement precision, small volume, light weight, low transmitting power and the like, and is also based on the advantages, so that the radio altimeter based on the frequency modulation continuous wave machine-carried radio altimeter is widely applied.
Since radio altimeter signals are always transmitted in an open space, interference is always accompanied by radio signals. The electronic interference equipment is utilized to radiate unnecessary noise or other interference signals to a receiver of the electronic system on a wireless channel, so that the normal operation of the electronic system is destroyed, the transmission of radio signals is blocked, and finally the electronic system cannot work normally. The openness of the wireless channel inevitably presents vulnerability issues, making the on-board radio altimeter vulnerable to attack, fraud and interference. In particular, with the development of radar theory and radio technology and the increasing complexity of modern applied electromagnetic environmental conditions, higher demands are placed on the development of airborne radio altimeter equipment. However, the existing radio altimeter equipment based on the frequency modulation continuous wave technology system adopts fixed frequency transmitting signals, the signals are easy to intercept and have poor anti-interference capability, and the influence of Doppler frequency shift is large, so that the height measurement precision is low, and the modern application requirements are difficult to meet. Therefore, the in-depth research of the anti-interference capability of the airborne radio altimeter has important significance, and the research of developing an airborne radio altimeter device based on a novel anti-interference system of the frequency modulation continuous wave is imperative.
Disclosure of Invention
The invention aims to: in order to overcome the defects in the prior art, the invention provides an airborne radio altimeter device based on frequency modulation continuous waves, so as to improve the anti-interference capability and the height measurement precision of the device.
The technical scheme is as follows: in order to achieve the above object, the present invention provides an airborne radio altimeter device based on frequency modulation continuous wave, which comprises a transmitting unit and a receiving unit, wherein the transmitting unit comprises a waveform generating module, a time control module, a linear frequency modulation module, a spread spectrum module, a frequency hopping module and a transmitting antenna module; the receiving unit comprises a receiving antenna module, a despreading module, a frequency hopping and debonding module, a synchronizing module, a difference frequency module and a height measuring module;
the waveform generation module is used for generating pulse waveform to be modulatedγ(t) And output to the chirp module;
the time control module is used for timing and setting the cycle time of the altitude meter height measurement signalT s The cycle time is set toT s Divided into 2NTime slots and outputs to the chirp module and the frequency hopping moduleA time control signal;
the linear frequency modulation module generates an envelope function as follows under the action of the time control signalγ(t) Is output to the spread spectrum module and the difference frequency module; before the front partNWithin each of the time slots, the chirp signal is
At the rearNWithin each of the time slots, the chirp signal is
The saidf 0 Is the carrier frequency of the chirp signal,μis the frequency modulation slope;
the spread spectrum module is used for generating a pseudo-random sequence and outputting the pseudo-random sequence to the despreading module; multiplying each chip amplitude of the pseudo-random sequence with the linear frequency modulation signal according to the chip sequence from low to high to form a broadband frequency modulation signal, and outputting the broadband frequency modulation signal to the frequency hopping module;
the frequency hopping module adjusts the carrier frequency of the broadband frequency modulation signal under the action of the time control signal to form a frequency hopping signal, and outputs the frequency hopping signal to the transmitting antenna module;
the despreading module performs despreading processing on the echo signals received by the receiving antenna module based on the pseudo-random sequence to form despread signals and outputs the despread signals to the frequency hopping and frequency hopping module;
the synchronization module is used for realizing frequency synchronization of the frequency hopping signals, generating synchronization signals and outputting the synchronization signals to the frequency hopping de-hopping module;
the frequency hopping and frequency hopping module performs frequency hopping and frequency hopping demodulation processing on the despread signals based on the synchronous signals to form frequency hopping signals and outputs the frequency hopping signals to the difference frequency module;
the beat frequency module mixes the debounced signal and the linear frequency modulation signal, performs low-pass filtering processing on the debounced signal and the linear frequency modulation signal, forms a beat signal and outputs the beat signal to the height measurement module;
the height measurement module is used for measuring the beat frequency of the beat signal, obtaining a height measurement value according to the corresponding relation between the beat frequency and the height to be measured, and outputting and displaying the height measurement value.
Further, in the technical scheme disclosed by the invention, the method for forming the frequency hopping signal by adjusting the carrier frequency of the broadband frequency hopping signal by the frequency hopping module comprises the following steps:
under the action of the time control signalNThe carrier frequencies of the chirp signals of each time slot are respectively adjusted to
Said->
Represent the firstiThe frequency hopping frequency of each time slot, to be laterNThe carrier frequencies of the chirped signals of the individual time slots are each adjusted to +.>
Said->
Represent the firstN+iFrequency hopping frequency of a time slot, said frequency hopping +.>
And->
From frequency hopping sequences [f 1 ,f 2 ,…,f V ]Is selected in a pseudo-random manner,Vthe total number of frequency hopping points in the frequency hopping sequence is the same as that of the frequency hopping sequenceiTake 1 toNIs a positive integer of (2);
the frequency hopping module is at the firstiEach time slot
The generated frequency hopping signal->
Can be expressed as:
The frequency hopping module is at the firstN+iEach time slot
The generated frequency hopping signal->
Can be expressed as:
wherein, the liquid crystal display device comprises a liquid crystal display device,
the method comprises the steps of carrying out a first treatment on the surface of the The saidc j For the number of chipsMPseudo-random sequence of (c)jA chip amplitude of the codeτ pulse For the pulse waveform to be modulatedγ(t) Pulse cycle time width of (a), saidμIs the frequency modulation slope.
Further, in the technical scheme disclosed by the invention, the pseudo-random sequence is a pseudo-random sequence with good autocorrelation characteristicsc 1 ,c 2 ,c 3 ,…,c j , …,c M ]The saidc j For the number of chipsMPseudo-random sequence of (c)jThe chip amplitude.
Further, in the technical scheme disclosed in the invention, the time control module controls the cycle timeT s Divided into 2NThe method for each time slot is as follows: the cycle time is set toT s Divided into 2NTime slots with equal time length; the front partNThe time slots are expressed as:
、/>
、…、/>
、…、/>
wherein, said->
And->
Respectively represent the firstiStarting time and ending time of each time slot; the rear part is provided withNThe time slots are expressed as: />
、/>
、…、/>
、…、/>
Wherein, said->
And->
Respectively represent the firstN+iThe starting time and the ending time of each time slot.
Further, in the technical scheme disclosed by the invention, the corresponding relation between the beat frequency and the height to be detected is as follows:
wherein the saidhFor the height value to be measured, C is the transmission rate of electromagnetic waves,f b in order to be a beat frequency,μis the frequency modulation slope.
Further, in the technical scheme disclosed in the invention, the chirp signal
Is associated with the chirp signal +.>
The frequency modulation bandwidth of (c) is the same.
Further, in the technical scheme disclosed in the invention, the frequency modulation slopeμThe method comprises the following steps:
wherein the saidBFor the frequency modulation bandwidth of the chirp signal, theT s And detecting the cycle time of the high signal for the aviation altimeter.
Preferably, in the technical scheme disclosed in the invention, the pulse waveform to be modulatedγ(t) As a 0 th order long spherical wave function with a time-bandwidth product of 4pi, where the time-bandwidth product is the integration interval T p And the angular frequency omega.
Preferably, in the technical scheme disclosed in the present invention, the frequency hopping frequency
And->
From frequency hopping sequences [f 1 ,f 2 ,…,f V ]Pseudo-randomly selected, the hopping sequence [f 1 ,f 2 ,…,f V ]Preset in microwave band, the frequency hopping sequence [f 1 ,f 2 ,…,f V ]The frequency interval between the adjacent frequency points is more than or equal to 3MHz.
Preferably, in the disclosed embodiment of the present invention, the pseudo-random sequence [c 1 ,c 2 ,c 3 ,…,c j , …,c M ]Is a barker code with the number of chips being 11.
Compared with the prior art, the invention has the following beneficial effects:
(1) The radio altimeter is improved in the capability of resisting system interference.
In the prior art, an airborne radio altimeter signal generally adopts fixed frequency to transmit an altimeter signal, is easily intercepted by electronic reconnaissance equipment and performs high-power suppression type interference on the altimeter signal, so that the altimeter cannot work normally. In the technical scheme disclosed by the invention, the frequency hopping module adjusts the carrier frequency of the broadband frequency modulation signal under the action of the time control signal, and thenNCarrier frequency adjustment of a time-slotted chirp signal to
Will laterNCarrier frequency of chirped signal of each time slot is adjusted to +.>
The frequency hopping frequency ∈>
And->
From frequency hopping sequences [f 1 ,f 2 ,…,f V ]The frequency hopping signal is formed, frequency agility of the altimetric signal is realized, and the airborne radio altimeter altimetric signal is difficult to capture by the reconnaissance equipment, so that high-power suppression interference cannot be realized on the reconnaissance equipment. Compared with the prior art, the technical scheme disclosed by the invention improves the capacity of the airborne radio altimeter for resisting the system interference.
(2) The concealment capability of the radio altimeter to detect high signals is improved.
In the prior art, radio altimeter signals based on frequency modulation continuous waves have high peak power characteristics, are easy to intercept and have poor hiding capability of altimeter signals. In the technical scheme disclosed by the invention, the spread spectrum module generates a pseudo-random sequence, and each chip amplitude of the pseudo-random sequence is multiplied with the linear frequency modulation signal generated by the linear frequency modulation module according to the sequence of chips from low to high to form a broadband frequency modulation signal, so that the frequency spectrum of the high-power spectrum altimeter signal is widened through the pseudo-random sequence, and the aim of reducing the power spectrum of the high-power spectrum of the radio altimeter signal is fulfilled. Compared with the prior art, the technical scheme disclosed by the invention reduces the power spectrum density of the radio altimeter high-frequency signal and improves the concealment capability and the interception resistance.
(3) The capability of the radio altimeter to resist the forward interference is improved.
In the prior art, a height measurement signal of an airborne radio altimeter based on frequency modulation continuous waves is a fixed-frequency broadband signal, and a continuous wave system is adopted, so that the signals are easy to be subjected to repeated interference by electronic reconnaissance equipment, and the height measurement cannot work normally. In the technical scheme disclosed by the invention, the time control module measures the cycle time of the high signal of the aviation altimeterT s Divided into 2NAnd the frequency hopping module is controlled to change the carrier frequency of the broadband linear frequency modulation signal, so that the carrier frequency of the generated height measurement signal in each time slot is different. Further, by reasonably controlling the time length of the time slot, it is difficult for the interfering party to implement the forward interference on the altimetric signal. Therefore, compared with the prior art, the technical scheme disclosed by the invention has better capability of resisting forwarding interference.
(4) The ability of the radio altimeter to resist doppler shift is improved.
In the prior art, an airborne radio altimeter signal based on a frequency modulation continuous wave is used for realizing height measurement by adopting a frequency method, and the height measurement is realized according to the corresponding relation between the beat frequency and a height measurement value by transmitting the height measurement signal and utilizing the beat frequency between an echo signal and the height measurement signal at the same moment. In the technical proposal disclosed by the invention, theThe time control module detects the cycle time of the high signal of the aviation altimeterT s Divided into 2NA time slot, wherein the chirp module generates an envelope function as follows under the action of the time control signalγ(t) Is a linear frequency modulated signal of the precedingNWithin each of the time slots, the chirp signal is
At the rearNWithin each of the time slots, the chirp signal is
To construct a symmetric triangle wave frequency signature. The beat frequencies of the positive slope modulation interval and the negative slope modulation interval of the constructed symmetrical triangular wave are different, so that the beat frequency after the addition processing is equal to the beat frequency corresponding to the stationary target, thereby eliminating the influence of Doppler frequency shift on height measurement and improving the capability of resisting Doppler frequency shift.
Additional advantages and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following and practice of the invention.
Drawings
FIG. 1 is a schematic diagram of the apparatus according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of time slot division disclosed in an embodiment of the present invention.
Detailed Description
The present invention is described in further detail below with reference to examples and drawings to enable those skilled in the art to practice the same and to refer to the description.
In the prior art, the prior radio altimeter device based on the frequency modulation continuous wave technical system adopts a fixed frequency transmitting signal, the signal is easy to intercept and has poor anti-interference capability, and the beat frequency is greatly influenced by frequency parameters, so that the height measurement accuracy is greatly influenced by Doppler frequency shift, and the height measurement accuracy is low, so that the modern application requirements are difficult to meet.
In order to solve the problems in the prior art, the embodiment of the invention discloses an airborne radio altimeter device based on frequency modulation continuous waves. As shown in fig. 1, the device comprises a transmitting unit and a receiving unit, wherein the transmitting unit comprises a waveform generating module, a time control module, a linear frequency modulation module, a spread spectrum module, a frequency hopping module and a transmitting antenna module; the receiving unit comprises a receiving antenna module, a despreading module, a frequency hopping and debonding module, a synchronizing module, a difference frequency module and a height measuring module;
the waveform generation module is used for generating pulse waveform to be modulatedγ(t) And output to the chirp module;
the time control module is used for timing and setting the cycle time of the altitude meter height measurement signalT s The cycle time is set toT s Divided into 2NTime slots, and outputting time control signals to the linear frequency modulation module and the frequency hopping module;
the linear frequency modulation module generates an envelope function as follows under the action of the time control signalγ(t) Is output to the spread spectrum module and the difference frequency module; typically, the time control signal includes a timing signal and a time slot count signal, which are used to control the duration or the time slot count of the chirp signal generated by the chirp module; further, in the frontNWithin each of the time slots, the chirp signal is
At the rearNWithin each of the time slots, the chirp signal is +.>
The saidf 0 Is the carrier frequency of the chirp signal;
the spread spectrum module is used for generating a pseudo-random sequence and outputting the pseudo-random sequence to the despreading module; multiplying each chip amplitude of the pseudo-random sequence with the linear frequency modulation signal according to the chip sequence from low to high to form a broadband frequency modulation signal, and outputting the broadband frequency modulation signal to the frequency hopping module;
the frequency hopping module is used for adjusting the carrier frequency of the broadband frequency modulation signal to form a frequency hopping signal and outputting the frequency hopping signal to the transmitting antenna module;
the despreading module performs despreading processing on the echo signals received by the receiving antenna module based on the pseudo-random sequence to form despread signals and outputs the despread signals to the frequency hopping and frequency hopping module;
the synchronization module is used for realizing frequency synchronization of the frequency hopping signals, generating synchronization signals and outputting the synchronization signals to the frequency hopping de-hopping module;
the frequency hopping and frequency hopping module performs frequency hopping and frequency hopping demodulation processing on the despread signals based on the synchronous signals to form frequency hopping signals and outputs the frequency hopping signals to the difference frequency module;
the beat frequency module mixes the debounced signal and the linear frequency modulation signal, performs low-pass filtering processing on the debounced signal and the linear frequency modulation signal, forms a beat signal and outputs the beat signal to the height measurement module;
the height measurement module is used for measuring the beat frequency of the beat signal, obtaining a height measurement value according to the corresponding relation between the beat frequency and the height to be measured, and outputting and displaying the height measurement value.
In the prior art, radio altimeter devices based on frequency modulated continuous waves use a frequency method for the altimetry, and the envelope function of the altimetric signal typically uses rectangular pulses. As known from the prior art, the rectangular pulse is an envelope function with a small time-bandwidth product, and when the rectangular pulse is used for radio altimetry, the small time-bandwidth product can cause the echo signal energy to be not concentrated, so that the detection capability of a receiving unit of the altimeter device on the echo signal is weak. Therefore, in order to improve the detection capability of the airborne radio altimeter receiving unit on the altimeter echo signals and improve the resolution of the altimeter at the same time so as to solve the limitation of the altimeter detection of the existing radio altimeter device based on the frequency modulation continuous wave, in the technical scheme disclosed by the embodiment of the invention, the pulse signals with large time-bandwidth product characteristics are adoptedγ(t) The envelope function of the airborne radio altimeter height signal is designed.
Further, in the technical scheme disclosed by the embodiment of the inventionThe waveform generation module is used for generating a pulse waveform to be modulatedγ(t) The pulse waveform to be modulatedγ(t) The pulse waveform to be modulated is a 0 th order long spherical wave function (Prolate Spheroidal Wave Functions, PSWFs) with a time-bandwidth product of 4 piγ(t) For 0 th order long spherical wave function, in a given time interval [ cavity [ ]T p /2，T p /2]In, the saidγ(t) The following integral equation is satisfied:
in the method, in the process of the invention,
for the 0 th order long spherical wave function +.>
And omega is the angular frequency of the corresponding characteristic value.
In the technical scheme disclosed in the embodiment of the invention, the pulse waveform to be modulated generated by the waveform generation moduleγ(t) The method has the characteristics of large time bandwidth product, optimal energy aggregation and the like, can enable the main lobe energy aggregation of the height measurement signal to reach more than 99% when used for the envelope function of the height measurement signal of the radio altimeter, can greatly increase the capability of the height measurement signal to resist channel noise, has stronger anti-interference capability, and is beneficial to improving the resolution of the height measurement when used for the height measurement.
In the prior art, a radio altimeter based on a frequency modulation continuous wave has the characteristics of large peak power, is easy to intercept and has poor hiding capability. In order to solve the problems in the prior art, in the technical scheme disclosed by the embodiment of the invention, the spread spectrum module is used for generating a pseudo-random sequence, multiplying each chip amplitude of the pseudo-random sequence with the linear frequency modulation signal according to the sequence of chips from low to high to form a wideband frequency modulation signal, so that the spectrum spreading of the altimetric signal is realized, and the frequency spectrum of the altimetric signal with high power spectrum characteristics is widened through the pseudo-random sequence and pulse modulation, so that the aim of reducing the power spectrum of the high signal of the radio altimeter is fulfilled, and the concealment of the altimetric signal in the channel transmission process is improved. Compared with the prior art, the technical scheme disclosed by the embodiment of the invention reduces the power spectrum density of the radio altimeter to detect the high signal and improves the concealment capability and the anti-interception performance.
When receiving echo signals, a despreading module of the receiving system performs autocorrelation despreading processing on the echo signals received by the receiving antenna module based on the pseudorandom sequence output by the spreading module and good autocorrelation thereof, and the despreading processing process can accumulate echo signal energy of all chip time and convert the echo signals with broadband low-power spectral density into narrow-band high-power spectral density signals, thereby improving signal-to-noise ratio, being beneficial to improving the capability of the echo signals of the airborne radio altimeter for resisting distortion, multipath, diffuse reflection and other distortion factors, and improving the height measurement precision of the airborne radio altimeter. The received echo signals are subjected to autocorrelation processing based on the autocorrelation characteristics of the pseudo-random sequence, and methods such as serial acquisition, parallel acquisition, and hybrid acquisition in the prior art can be adopted, which are disclosed in the prior art, and can be implemented by those skilled in the art based on the prior art and conventional technical means, and are not repeated here.
In the prior art, the autocorrelation characteristics of the pseudo-random sequences have large differences due to different implementation manners. Although M sequences are easy to generate, their autocorrelation properties are weak. The autocorrelation characteristic of the pseudo-random sequence generated by the spreading module is related to the peak characteristic of the echo signal detected by the airborne radio altimeter. The sharper the autocorrelation of the pseudo-random sequence, the more favorable the accurate capturing of the peak value of the echo signal, and the higher the accuracy of the height measurement. Further, in the technical scheme disclosed in the embodiment of the invention, the number of the chips of the pseudo-random sequence generated by the spread spectrum module is closely related to the height measurement performance of the airborne radio altimeter. The more the number of chips of the pseudo-random sequence, the spectrum widening capability of the spread spectrum module to the altimetric signalThe stronger the hiding capability of the height measurement signal in channel transmission is, the larger the processing gain of the despreading module of the receiving unit in processing the echo signal is, which is more beneficial to improving the anti-interference capability of the echo signal; however, the number of chips is too large, the time for processing the echo signal is also increased, and the real-time performance of the height measurement is reduced. Based on the above analysis, the inventors optimized the number of chips of the pseudo-random sequence by theoretical analysis and by means of simulation calculation. Preferably, in order to improve the height measurement capability of the airborne radio altimeter, in the technical scheme disclosed in the embodiment of the invention, the pseudo-random sequence generated by the spreading module [c 1 ,c 2 ,c 3 ,…,c j , …,c M ]For a chip number of 11 barker codes, the respective chip magnitudes of the pseudo-random sequence [c 1 ,c 2 ,c 3 ,…,c 11 ]The method comprises the following steps of: [ -1, -1, -1,1,1,1, -1,1,1, -1,1]。
In the prior art, an airborne radio altimeter height measurement signal based on a frequency modulation continuous wave generally adopts a fixed frequency transmission signal, is easily intercepted by electronic reconnaissance equipment and carries out high-power suppression type interference on the electronic reconnaissance equipment, so that the height measurement cannot work normally. In order to solve the problems in the prior art, in the technical scheme disclosed by the embodiment of the invention, the frequency hopping module adjusts the carrier frequency of the broadband frequency modulation signal under the action of the time control signal to form a frequency hopping signal, and outputs the frequency hopping signal to the transmitting antenna module for transmission.
Further, in the technical solution disclosed in the embodiment of the present invention, the method for adjusting the carrier frequency of the wideband fm signal by the frequency hopping module to form a frequency hopping signal includes:
under the action of the time control signal, namely according to the timing or time slot counting signal output by the time control module, the method comprises the following steps ofNThe carrier frequencies of the chirp signals of each time slot are respectively adjusted to
Said->
Represent the firstiThe frequency hopping frequency of each time slot, to be laterNThe carrier frequencies of the chirped signals of the individual time slots are each adjusted to +.>
Said->
Represent the firstN+iFrequency hopping frequency of a time slot, said frequency hopping +.>
And->
From frequency hopping sequences [f 1 ,f 2 ,…,f V ]Pseudo-randomly selecting, the followingVThe total number of frequency hopping points in the frequency hopping sequence is the same as that of the frequency hopping sequenceiTake 1 toNIs a positive integer of (2);
the frequency hopping module is at the firstiEach time slot
The generated frequency hopping signal->
Expressed as:
wherein, the liquid crystal display device comprises a liquid crystal display device,
the saidc j For the number of chipsMPseudo-random sequence of (c)jA chip amplitude of the codeτ pulse For the pulse waveform to be modulatedγ(t) Pulse cycle time of (a) saidμIs the frequency modulation slope.
Further, the frequency hopping
And->
Slave hopping sequence under control of keyf 1 ,f 2 ,…,f V ]Pseudo-randomly selected. Therefore, since the interfering party does not know the key, the change rule of the frequency hopping frequency cannot be tracked. Further, the hopping sequence [f 1 ,f 2 ,…,f V ]Preset in microwave band, the frequency hopping sequence [f 1 ,f 2 ,…,f V ]The frequency interval between the adjacent frequency points is more than or equal to 3MHz, so that the frequency agility degree of the altimeter signals is further enhanced, the airborne radio altimeter signals are difficult to capture by the reconnaissance equipment, and high-power suppression interference cannot be realized on the reconnaissance equipment. Compared with the prior art, the technical scheme disclosed by the invention improves the capacity of the radio altimeter for resisting the system interference.
After the transmitting unit of the airborne radio altimeter transmits a height measurement signal through the transmitting antenna module, the receiving unit starts the synchronizing module, captures a frequency synchronizing signal of an echo signal under the control of a secret key, tracks the change of the carrier frequency of the echo signal, realizes the frequency synchronization of the frequency hopping signal, generates a synchronizing signal and outputs the synchronizing signal to the frequency hopping and debounce module; the synchronization module may be implemented by using a frequency hopping receiving technology in the prior art, which is a known and conventional technical means for those skilled in the art, and will not be described herein. The frequency hopping and despreading module performs frequency hopping and despreading processing on the despread signal generated by the despreading module based on the synchronous signal, and forming a debounce signal and outputting the debounce signal to the difference frequency module. The method for performing the frequency hopping processing on the frequency hopping signal can be implemented by using the frequency hopping receiving technology in the prior art, which is a known and conventional technical means for those skilled in the art, and is not described herein.
In the technical scheme disclosed by the embodiment of the invention, in order to reduce the influence of Doppler frequency shift on the height accuracy of the radio altimeter, the linear frequency modulation module generates an envelope function as follows under the action of the time control signalγ(t) Is a linear frequency modulated signal of the precedingNWithin each of the time slots, the chirp signal is
At the rearNWithin each of the time slots, the chirp signal is +.>
The method comprises the steps of carrying out a first treatment on the surface of the Further, the chirp signal
Is associated with the chirp signal +.>
The frequency modulation bandwidths of the two symmetrical triangular waves are identical to construct the frequency characteristics of the symmetrical triangular waves, and the beat frequencies of the positive slope modulation interval and the negative slope modulation interval of the constructed symmetrical triangular waves are different.
Further, in the technical solution disclosed in the embodiment of the present invention, under a static target condition, a frequency hopping signal output by the frequency hopping and frequency hopping module of the receiving unit is expressed as:
in the method, in the process of the invention,t d representing the transmission delay of the echo signal in the channel;
under static target conditions, the chirp signal output by the chirp module of the transmitting unit may be expressed as:
the beat frequency module mixes the debounce signal and the linear frequency modulation signal, and performs low-pass filtering treatment to form a beat signal which is output to the height measurement module, wherein the height measurement module can obtain beat frequency under a static target condition; in the same way, the beat frequency under the moving target condition can be obtained. As to how to obtain the beat frequencies of the static and moving targets, the knowledge of the triangular wave of the radio altimeter in the prior art can be used, and it is a known and conventional means for those skilled in the art, and will not be described here.
Further, in the technical solution disclosed in the embodiment of the present invention, the beat frequency of the moving object obtained by the beat frequency module in the triangular wave positive slope modulation interval may be expressed as:
the beat frequency of the moving object in the triangular wave negative slope modulation interval obtained by the beat frequency module can be expressed as follows:
in the method, in the process of the invention,
representing the beat frequency of the moving object in the positive slope modulation interval,/for the moving object>
Representing the beat frequency of the moving object in the negative slope modulation interval,/for the moving object>
Indicates the beat frequency corresponding to the stationary object, < +.>
Is the doppler frequency caused by the moving object. In the beat frequency module, after the moving target is subjected to addition processing in a positive slope modulation interval and a negative slope interval, the beat frequency is obtained by the following steps: />
The formula shows that the beat frequency after the addition processing is the beat frequency corresponding to the static target, so that the influence of Doppler frequency on the beat signal frequency can be avoided, and the influence of Doppler frequency on the height measurement accuracy of the radio altimeter is eliminated. Compared with the prior art, the technical scheme disclosed by the embodiment of the invention can eliminate the influence of Doppler frequency shift on the height accuracy of the radio altimeter and improve the height measurement performance.
Further, in the technical scheme disclosed by the embodiment of the invention, the height measurement module is used for measuring the beat frequency of the beat signal, obtaining a height measurement value according to the corresponding relation between the beat frequency and the height to be measured, and outputting and displaying the height measurement value; the corresponding relation between the beat frequency and the height to be measured is as follows:
wherein the saidhFor the height value to be measured, C is the transmission rate of electromagnetic waves,f b in order to be a beat frequency,μis the frequency modulation slope. The frequency modulation slopeμThe method comprises the following steps:
wherein the saidBFor the frequency modulation bandwidth of the chirp signal, theT s And detecting the cycle time of the high signal for the aviation altimeter.
In the field of radar electronics, in addition to interference suppression, interference with the form of repetition is one of the types of interference that are commonly used. Compared with the suppression type interference, the forwarding type interference does not need to obtain the parameters of the interfered signal, and the purpose of implementing interference is achieved by amplifying the power of the received interfered signal and forwarding the amplified signal to the interfered system.
In order to improve the capability of the airborne radio altimeter to detect the high signal to resist the forward interference, in the technical scheme disclosed by the embodiment of the invention, the time control module controls the cycle time to be equal to the timeT s Divided into 2NThe method for each time slot is as follows: the cycle time is set toT s Divided into 2NTime slots with equal time length; the front partNThe time slots are expressed as:
、/>
、…、/>
、…、
wherein, said->
And->
Respectively represent the firstiStarting time and ending time of each time slot; the rear part is provided withNThe time slots are expressed as: />
、/>
、…、/>
、…、/>
Wherein, saidSaid->
And->
Respectively represent the firstN+iThe starting time and the ending time of each time slot. The frequency hopping module adjusts the carrier frequency of the broadband frequency modulation signal to form a frequency hopping signal under the action of the time control signal, and the frequency hopping module is used for transmitting the time control signalNThe carrier frequencies of the chirped signals of the individual time slots are each adjusted to +.>
Will laterNThe carrier frequencies of the chirped signals of the individual time slots are each adjusted to +.>
The frequency hopping frequency ∈>
And->
From frequency hopping sequences [f 1 ,f 2 ,…,f V ]Pseudo-randomly selected. I.e. the carrier frequencies of the generated altimetric signals are different in each time slot. As known from the prior art, the forwarded interference is achieved by the interfering party amplifying the power of the received interfered signal and forwarding the amplified signal to the interfered party. Thus, if the interfering party achieves the purpose of interference, only the same frequency altimetric signal can be interfered, which makes the implemented forward interference necessary to be completed within one time slot. Further, in the technical scheme disclosed by the embodiment of the invention, the interference party can hardly implement the forward interference on the height measurement signal of a single time slot by reasonably controlling the time length of the time slot.
Preferably, in the technical solution disclosed in the embodiment of the present invention, the time slot time lengthδAt 0.2 μs, the ideal distance between the platform implementing the forward interference and the interfered platform is known according to the transmission theory of radio wavesThe separation is as follows: 0.1 microsecond by 3 by 10 8 Meter/second = 30 meters, which is obviously unreasonable in practical application scenarios, i.e. no repeater interference can be implemented. Therefore, compared with the prior art, the technical scheme disclosed by the embodiment of the invention has better capability of resisting forwarding interference.
Further, as shown in fig. 2, in the technical solution disclosed in the embodiment of the present invention, the aviation altimeter detects the cycle time of the high signalT s Divided into 2NTime slots with equal time length; the time slot time lengthδNumber of chips of the pseudo random sequenceMAnd the pulse waveform to be modulatedγ(t) Pulse cycle time of (2)τ pulse The three satisfy the relation:δ=M× τ pulse . Further, in the technical scheme disclosed in the embodiment of the present invention, the pulse waveform to be modulatedγ(t) Pulse cycle time of (2)τ pulse And said at least one ofT p The relation between them is satisfied:τ pulse >T p to reduce the pulse waveform to be modulatedγ(t) According to the transformation relation between the time domain and the frequency domain, the frequency spectrum of the high signal of the airborne radio altimeter can be further widened, under the condition that the total transmitting power is unchanged, the power spectrum density of the height measurement signal is further reduced, and the concealment and interception resistance of the height measurement signal are improved.
Although the embodiments of the present invention have been disclosed above, they are not limited to the modes of use listed in the specification and embodiments. It can be applied to various fields suitable for the present invention. Additional modifications will readily occur to those skilled in the art. Therefore, the invention is not to be limited to the specific details and illustrations shown and described herein, without departing from the general concepts defined in the claims and their equivalents.
Claims (10)
1. An airborne radio altimeter device based on frequency modulation continuous waves is characterized by comprising a transmitting unit and a receiving unit, wherein the transmitting unit comprises a waveform generating module, a time control module, a linear frequency modulation module, a frequency spreading module, a frequency hopping module and a transmitting antenna module; the receiving unit comprises a receiving antenna module, a despreading module, a frequency hopping and debonding module, a synchronizing module, a difference frequency module and a height measuring module;
the waveform generation module is used for generating pulse waveform to be modulatedγ(t) and output to the chirp module; the time control module is used for timing and setting the cycle time of the altitude meter height measurement signalT s The cycle time is set toT s Divided into 2NTime slots, and outputting time control signals to the linear frequency modulation module and the frequency hopping module; the linear frequency modulation module generates an envelope function as follows under the action of the time control signalγ(t) Is output to the spread spectrum module and the difference frequency module; before the front partNWithin each of the time slots, the chirp signal is
At the rearNWithin each of the time slots, the chirp signal is +.>
Whereinf 0 Is the carrier frequency of the chirp signal, +.>
Is the frequency modulation slope;
the spread spectrum module is used for generating a pseudo-random sequence and outputting the pseudo-random sequence to the despreading module; multiplying each chip amplitude of the pseudo-random sequence with the linear frequency modulation signal according to the chip sequence from low to high to form a broadband frequency modulation signal, and outputting the broadband frequency modulation signal to the frequency hopping module;
the frequency hopping module adjusts the carrier frequency of the broadband frequency modulation signal under the action of the time control signal to form a frequency hopping signal, and outputs the frequency hopping signal to the transmitting antenna module;
the despreading module performs despreading processing on the echo signals received by the receiving antenna module based on the pseudo-random sequence to form despread signals and outputs the despread signals to the frequency hopping and frequency hopping module;
the synchronization module is used for realizing frequency synchronization of the frequency hopping signals, generating synchronization signals and outputting the synchronization signals to the frequency hopping de-hopping module;
the frequency hopping and frequency hopping module performs frequency hopping and frequency hopping demodulation processing on the despread signals based on the synchronous signals to form frequency hopping signals and outputs the frequency hopping signals to the difference frequency module;
the beat frequency module mixes the debounced signal and the linear frequency modulation signal, performs low-pass filtering processing on the debounced signal and the linear frequency modulation signal, forms a beat signal and outputs the beat signal to the height measurement module;
the height measurement module is used for measuring the beat frequency of the beat signal, obtaining a height measurement value according to the corresponding relation between the beat frequency and the height to be measured, and outputting and displaying the height measurement value.
2. The frequency modulated continuous wave based on-board radio altimeter device of claim 1, wherein the method for adjusting the carrier frequency of the wideband frequency modulated signal by the frequency hopping module to form a frequency hopped signal comprises:
under the action of the time control signalNThe carrier frequencies of the chirp signals of each time slot are respectively adjusted to
Said->
Represent the firstiThe frequency hopping frequency of each time slot, to be laterNThe carrier frequencies of the chirped signals of the individual time slots are each adjusted to +.>
Said->
Represent the firstN+iFrequency hopping of individual time slotsThe frequency hopping frequency ∈>
And->
From frequency hopping sequences [f 1 ,f 2 ,…,f V ]Is selected in a pseudo-random manner,Vthe total number of frequency hopping points in the frequency hopping sequence is the same as that of the frequency hopping sequenceiTake 1 toNIs a positive integer of (2);
the frequency hopping module is at the firstiEach time slot
The generated frequency hopping signal->
Expressed as:
The frequency hopping module is at the firstN+iEach time slot
The generated frequency hopping signal->
Can be expressed as:
wherein, the liquid crystal display device comprises a liquid crystal display device,
；c j for the number of chipsMPseudo-random sequence of (c)jIndividual chipsThe amplitude value of the amplitude value,τ pulse for the pulse waveform to be modulatedγ(t) Is used for the pulse cycle time of (a),μis the frequency modulation slope.
3. The frequency modulated continuous wave based on-board radio altimeter device of claim 2, wherein the pseudo-random sequence is a pseudo-random sequence with good auto-correlation properties [c 1 , c 2 , c 3 ,…,c j , …,c M ]The saidc j For the number of chipsMPseudo-random sequence of (c)jThe chip amplitude.
4. The fm continuous wave based on-board radio altimeter device of claim 3, wherein said time control module sets said cycle time toT s Divided into 2NThe method for each time slot is as follows: the cycle time is set toT s Divided into 2NTime slots with equal time length; the front partNThe time slots are expressed as:
、/>
、…、/>
、…、/>
wherein the said
And->
Respectively represent the firstiStarting time and ending time of each time slot; the rear part is provided withNThe time slots are expressed as: />
、
、…、/>
、…、/>
Wherein, said->
And->
Respectively represent the firstN+iThe starting time and the ending time of each time slot.
5. The fm continuous wave based on-board radio altimeter device of claim 3, wherein said beat frequency corresponds to the altitude to be measured by:
wherein, the liquid crystal display device comprises a liquid crystal display device,hfor the height value to be measured, C is the transmission rate of electromagnetic waves,f b in order to be a beat frequency,μis the frequency modulation slope.
6. An on-board radio altimeter device based on a frequency modulated continuous wave according to claim 3, characterised in that the chirp signal
Is associated with the chirp signal +.>
The frequency modulation bandwidth of (c) is the same.
7. An on-board radio altimeter apparatus based on a frequency modulated continuous wave according to claim 3, characterised in that the frequency modulation slopeμThe method comprises the following steps:
wherein, the liquid crystal display device comprises a liquid crystal display device,Bfor the frequency modulation bandwidth of the chirp signal, theT s And detecting the cycle time of the high signal for the aviation altimeter.
8. An fm continuous wave based on-board radio altimeter device according to claim 3, characterised in that the pulse waveform to be modulatedγ(t) As a 0 th order long spherical wave function with a time-bandwidth product of 4pi, where the time-bandwidth product is the integration interval T p And the angular frequency omega.
9. An fm continuous wave based on-board radio altimeter device according to claim 3, characterised in that said hopping frequency
And->
From frequency hopping sequences [f 1 ,f 2 ,…,f V ]Pseudo-randomly selected, the hopping sequence [f 1 ,f 2 ,…,f V ]Preset in microwave band, the frequency hopping sequence [f 1 ,f 2 ,…,f V ]The frequency interval between the adjacent frequency points is more than or equal to 3MHz.
10. An fm continuous wave based on-board radio altimeter apparatus according to claim 3, characterised in that said pseudo-random sequence [c 1 , c 2 , c 3 ,…,c j , …,c M ]Is a barker code with the number of chips being 11.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310377585.8A CN116106886B (en) | 2023-04-11 | 2023-04-11 | Airborne radio altimeter device based on frequency modulation continuous wave |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310377585.8A CN116106886B (en) | 2023-04-11 | 2023-04-11 | Airborne radio altimeter device based on frequency modulation continuous wave |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN116106886A CN116106886A (en) | 2023-05-12 |
| CN116106886B true CN116106886B (en) | 2023-06-23 |
Family
ID=86256459
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310377585.8A Active CN116106886B (en) | 2023-04-11 | 2023-04-11 | Airborne radio altimeter device based on frequency modulation continuous wave |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116106886B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116599546B (en) * | 2023-07-18 | 2023-09-29 | 烟台初心航空科技有限公司 | Anti-interference radio distance measuring device for short-range navigation |
| CN116699506B (en) * | 2023-08-02 | 2023-10-13 | 烟台初心航空科技有限公司 | Short-range radio navigation system ranging beacon response signal generating device |
| CN117250619B (en) * | 2023-11-08 | 2024-01-26 | 烟台初心航空科技有限公司 | Low false alarm high reliable anticollision radar device |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2007865A1 (en) * | 1990-01-03 | 1991-07-03 | John Studenny | Integrated altimeter and doppler velocity sensor arrangement |
| CN2914111Y (en) * | 2006-04-30 | 2007-06-20 | 中国科学院空间科学与应用研究中心 | Sub-aperture radar altimeter |
| CN108632988A (en) * | 2017-03-20 | 2018-10-09 | 霍尼韦尔国际公司 | Delay computing in wireless system |
| CN114978832A (en) * | 2022-08-01 | 2022-08-30 | 烟台初心航空科技有限公司 | Radar communication integrated modulation signal generation method with channel adaptability |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB0121491D0 (en) * | 2001-09-05 | 2001-10-24 | Thales Res Ltd | Position fixing system |
| US10281557B2 (en) * | 2005-12-15 | 2019-05-07 | Polte Corporation | Partially synchronized multilateration/trilateration method and system for positional finding using RF |
| US8175134B1 (en) * | 2009-04-29 | 2012-05-08 | L-3 Communications, Corp | Radio communications system and method having decreased capability for detection by an adversary |
| CN102707275B (en) * | 2012-05-25 | 2013-12-18 | 北京航空航天大学 | Digital processing method of altimeter of linear frequency modulation continuous wave radar |
| KR101289315B1 (en) * | 2013-03-05 | 2013-07-24 | 국방과학연구소 | Mcw radio altimeter having wide altitude range and low measurement error and altitude measuring method thereof |
| CN108845312B (en) * | 2018-06-04 | 2022-04-08 | 陕西长岭电子科技有限责任公司 | Height measurement method based on pulse system radio altimeter |
| CN109818648B (en) * | 2018-12-10 | 2021-07-30 | 中国人民解放军陆军工程大学 | Multi-sequence frequency hopping anti-interference communication method based on pseudorandom linear frequency modulation |
-
2023
- 2023-04-11 CN CN202310377585.8A patent/CN116106886B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2007865A1 (en) * | 1990-01-03 | 1991-07-03 | John Studenny | Integrated altimeter and doppler velocity sensor arrangement |
| CN2914111Y (en) * | 2006-04-30 | 2007-06-20 | 中国科学院空间科学与应用研究中心 | Sub-aperture radar altimeter |
| CN108632988A (en) * | 2017-03-20 | 2018-10-09 | 霍尼韦尔国际公司 | Delay computing in wireless system |
| CN114978832A (en) * | 2022-08-01 | 2022-08-30 | 烟台初心航空科技有限公司 | Radar communication integrated modulation signal generation method with channel adaptability |
Also Published As
| Publication number | Publication date |
|---|---|
| CN116106886A (en) | 2023-05-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN116106886B (en) | Airborne radio altimeter device based on frequency modulation continuous wave | |
| CN116087942B (en) | Method for generating modulating signal of aeronautical altimeter | |
| CN116068501B (en) | Method for generating anti-interference radio altimeter modulation signal | |
| KR100939276B1 (en) | UWB distance measurement system and driving method thereof | |
| US9664777B2 (en) | Radar device | |
| US5657021A (en) | System and method for radar-vision for vehicles in traffic | |
| US7342651B1 (en) | Time modulated doublet coherent laser radar | |
| CN104076352A (en) | Low-interception speed measurement method and radar device | |
| CN102998656B (en) | Frequency step based broadband distribution type radar time synchronizing method | |
| WO2018045594A1 (en) | Space-time adaptive processing method and apparatus based on co-prime pulse recurrence interval | |
| CN108132461B (en) | Method for inhibiting direct current leakage of frequency modulation continuous wave landing radar | |
| CN110988864B (en) | MTI radar speed measuring method with frequency agility | |
| CN104977567B (en) | A kind of adaptive launching beam forming method of OFDM monopulse radars | |
| CN103064065B (en) | Waveform design for double-cycle pinch-off type pseudo-random code and signal processing method for echo | |
| CN101256230A (en) | Continuous wave chaos phase-modulation radio fuse detection system and demodulation method | |
| WO2014201795A1 (en) | Method for generating and compressing multi-sweep-frequency radar signals | |
| CN104931946A (en) | Outer radiation source radar Doppler-time delay two-dimension double-threshold object detection method | |
| US20230273307A1 (en) | Method for radar ranging and transceiver therefor | |
| CN209765034U (en) | X-waveband vehicle-mounted detection radar receiving device | |
| CN116015343A (en) | Ultra-wideband narrow pulse detection and analog forwarding system and method | |
| CN114280532B (en) | Radar target angle estimation method and system based on in-band conjugate point multiplication | |
| RU2596229C1 (en) | Method for increasing range resolution of radar station | |
| Hao et al. | A high performance waveform and a new ranging method for the proximity detector | |
| CN110609264B (en) | Target echo Doppler frequency estimation method for pulse laser radar | |
| RU2444026C1 (en) | Radar station for ship navigation |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |