CN116087942B - Method for generating modulating signal of aeronautical altimeter - Google Patents

Method for generating modulating signal of aeronautical altimeter Download PDF

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CN116087942B
CN116087942B CN202310354297.0A CN202310354297A CN116087942B CN 116087942 B CN116087942 B CN 116087942B CN 202310354297 A CN202310354297 A CN 202310354297A CN 116087942 B CN116087942 B CN 116087942B
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pseudo
time
altimeter
signal
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CN116087942A (en
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李聪
吴志江
吴晨
唐晓雪
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Yantai Ima Technology Co ltd
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    • 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
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/882—Radar or analogous systems specially adapted for specific applications for altimeters
    • 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
    • G01S13/26—Systems for measuring distance only using transmission of interrupted, pulse modulated waves wherein the transmitted pulses use a frequency- or phase-modulated carrier wave
    • 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 a method for generating an aviation altimeter modulation signal, and relates to the field of radio altimetry. Dividing the time width of a repetition period into 2N time slots, and multiplying each chip amplitude of the pseudo-random sequence with the pulse waveform to be modulated according to the chip sequence from low to high by generating the pseudo-random sequence with good autocorrelation characteristics and the pulse waveform to be modulated to realize pulse amplitude modulation; multiplying the pulse amplitude modulated signal with a linear frequency modulation signal in each of the first N time slots to form a modulated signal; multiplying the pulse amplitude modulated signal with a linear frequency modulation signal in each time slot of the last N time slots to form a modulated signal; the carrier frequency of the chirp signal varies pseudo-randomly. The invention improves the anti-interference and Doppler shift resistance of the aviation altimeter and improves the height measurement resolution.

Description

Method for generating modulating signal of aeronautical altimeter
Technical Field
The invention relates to the field of radio measurement, in particular to a method for generating an aviation altimeter modulation signal with anti-interference capability.
Background
Altimetry is commonly used to measure the altitude of airborne carriers on land and on sea surfaces. The altimeter can be divided into laser, air pressure, gravitation, radio altimeter and the like according to different principles, and the altimeters have different characteristics and application occasions.
The radio altimeter is used for determining the altitude of a flying carrier by measuring the principle of propagation delay time of electromagnetic waves in air, and has two systems of continuous waves and pulses. The signal transmitted by the continuous wave radio altimeter is a variable frequency signal, and the received echo signal contains delayed time information. The pulse radio altimeter radiates pulse signals to the ground, measures the delay time of the relative transmitting pulse in the echo of the received signals, and further calculates the altitude value. Because of the problem of altitude ambiguity in pulse radio altimeters, current aircraft altimeters mainly employ continuous wave technology systems. In the existing continuous wave altimeter technical system, the altitude distance measurement is mainly realized by adopting a frequency method. The frequency method height measurement is to determine the height by using the frequency difference between the echo signal and the transmitting signal at the same time, i.e. by the frequency of the beat signal. However, since the method is greatly influenced by frequency parameters, the height measurement accuracy is greatly influenced by Doppler frequency shift.
Particularly, with the development of radar theory and technology and the increasing complexity of modern applied electromagnetic environment conditions, aviation altimeter signals based on a continuous wave technology system are easy to intercept, have poor anti-interference capability and are greatly influenced by Doppler frequency shift, so that the height measurement precision is low, the modern application requirements are difficult to meet, and the aviation altimeter based on the novel anti-interference system is imperative to be studied.
Disclosure of Invention
The invention aims to: in order to overcome the defects in the prior art and improve the anti-interference capability and the height measurement precision of the aviation altimeter, the invention provides a method for generating an aviation altimeter modulation signal.
The technical scheme is as follows: in order to achieve the above object, the present invention provides a method for generating an air altimeter modulation signal, comprising the steps of:
step one: width of period time to be repeatedT s Divided into 2NA time slot;
step two: generating pulse period time width ofτ pulse Is to be modulated with a pulse waveformγ(t)；
Step three: generating pseudo-random sequences with good autocorrelation propertiesc 1 ,c 2 ,c 3 ,…,c j , …,c M ]，c j For the number of chipsMPseudo-random sequence of (c)jThe chip magnitudes;
step four: before the front partNWithin each of the time slots, each of the chip magnitudes of the pseudo-random sequence are sequentially from low to highc j Respectively and uniformly modulating pulse waveformγ(t) Multiplying to realize pulse amplitude modulation; then the pulse amplitude modulated signal and the linear frequency modulation signal
Figure SMS_1
Multiplying to form a modulated signal->
Figure SMS_2
Represent the firstiCarrier frequency of individual time slots, from hopping sequence [f 1 ,f 2 ,…,f V ]Is selected in a pseudo-random manner,irepresent the firstiEach time slot has a value ranging from 1 to 1NIs a positive integer of (2);
step five: at the rearNWithin each of the time slots, each of the chip magnitudes of the pseudo-random sequence are sequentially from low to highc j Respectively and uniformly modulating pulse waveformγ(t) Multiplying to realize pulse amplitude modulation; then the pulse amplitude modulated signal and the linear frequency modulation signal
Figure SMS_3
Multiplying to form a modulated signal->
Figure SMS_4
Represent the firstN+iCarrier frequency of individual time slots, from hopping sequence [f 1 ,f 2 ,…,f V ]Is selected in a pseudo-random manner,N+irepresent the firstN+iA number of time slots of a time slot,ithe value range is 1-1NIs a positive integer of (2);
step six: time width of repetition period according to aeroaltimeterT s Time width at next repetition periodT s In the process, the first to fifth steps are repeatedly executed for a period of repetitionT s In, the generated air altimeter modulation signal is:
Figure SMS_5
，
wherein, the liquid crystal display device comprises a liquid crystal display device,s 1 (t)、s 2 (t)、…、s i (t)、…、s N (t)、s N+1 (t)、…、s N i+ (t) 、…s N2 (t) For the modulated signal of each time slot,μfor the frequency modulation slope,γ(t) In order to be able to modulate the pulse waveform,τ pulse for the period time width of the pulse waveform to be modulated,c j for the number of chipsMPseudo-random sequence of (c)jThe amplitude of the individual chips is determined,
Figure SMS_6
、/>
Figure SMS_7
、…、/>
Figure SMS_8
、…、/>
Figure SMS_9
、/>
Figure SMS_10
、…、
Figure SMS_11
、…/>
Figure SMS_12
modulating the carrier frequency of the signal for each time slot from a hopping sequence [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.
Further, in the technical proposal disclosed by the invention, the time width of the repetition period isT s Divided into 2NTime slots with equal time length.
Further, in the technical scheme disclosed by the invention,γ(t) For 0 th order long spherical wave function, in a given time interval [ cavity [ ]T p /2，T p /2]In the inner part of the inner part,γ(t) The following integral equation is satisfied:
Figure SMS_13
，
in the method, in the process of the invention,
Figure SMS_14
is 0 th order long spherical wave function +.>
Figure SMS_15
And omega is the angular frequency of the corresponding characteristic value.
Further, in the technical proposal disclosed by the invention, the time width of the repetition period isT s Divided into 2NTime slots with equal time lengthδIs 0.2 microseconds.
Further, in the technical scheme disclosed in the invention, the frequency hopping sequencef 1 ,f 2 ,…,f V ]Preset in microwave S band, frequency hopping sequence [f 1 ,f 2 ,…,f V ]The interval between the adjacent frequency points is more than or equal to 2MHz.
Preferably, in the technical scheme disclosed in the invention, the pseudo-random sequence is a pseudo-random sequence with the number of chips being 11, and the amplitude of each chip of the pseudo-random sequence is [ [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]。
Preferably, in the technical scheme disclosed in the invention, the time slot time lengthδNumber of pseudo-random sequence chipsMAnd the cycle time width of the pulse waveform to be modulatedτ pulse The three satisfy the relation:δ=M×τ pulse 。
preferably, in the technical scheme disclosed in the invention, the cycle time width of the pulse waveform to be modulatedτ pulse Comprising a pulse transmission time width and a pulse stop time width, wherein the pulse transmission time width occupies the period time width of the pulse waveform to be modulatedτ pulse Fifty percent of (f).
Preferably, in the technical scheme disclosed by the invention, the time bandwidth product factor of the 0 th order long spherical wave function is 4 pi.
The method for generating the modulation signal of the aviation altimeter has at least the following beneficial effects:
(1) The resistance to blocking interference is improved.
In the prior art, aviation altimeter signals are usually transmitted by adopting fixed frequency, are easily intercepted by reconnaissance equipment and realize high-power blocking interference on the reconnaissance equipment, and have poor anti-interference capability. In the technical proposal disclosed by the invention, the pulse amplitude modulated signal and the linear frequency modulated signal are processed in each time slot
Figure SMS_16
Or chirped signals
Figure SMS_17
Multiplying to form a modulated signal; the carrier frequency of the chirp signal is controlled by a key from the hopping sequence [f 1 ,f 2 ,…,f V ]The frequency agility is performed by pseudo-random selection in the aircraft, so that the scout equipment is difficult to capture the aerial altimeter signal, and high-power blocking interference cannot be realized on the scout equipment. Therefore, compared with the prior art, the technical scheme disclosed by the invention improves the anti-blocking type interference capability.
(2) The capability of resisting the forwarding interference is improved.
In the technical proposal disclosed by the invention, the time width of the repetition period isT s Divided into 2NTime slots with equal time lengthδFor 0.2 microsecond, in each time slot, the pulse amplitude modulated signal is multiplied by a chirp signal to form a modulated signal, the carrier frequency of the chirp signal is multiplied by a hopping sequencef 1 ,f 2 ,…,f V ]The carrier frequencies of the modulated signals are different from each other. This allows the interference party to implement the repeater interference to interfere with only the modulated signal of a single time slot, but not with the modulated signal of an adjacent time slot. So that the total time for implementing the repeater interference must be less than or equal to one time slot duration, i.e. the signal is received from the beginningThe whole process to the completion of the signal forwarding must be completed in the same time slot. According to the theory of radio wave transmission, the maximum distance between the platform for implementing the forward interference and the interfered platform 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 invention has better capability of resisting forwarding interference.
(3) The concealment performance of the signal is improved.
In the prior art, aviation altimeter signals usually adopt a single modulation waveform (continuous wave modulation or pulse modulation), have larger peak power and are easy to intercept. In the technical proposal disclosed by the invention, the pseudo-random sequence with good autocorrelation characteristic is generated, and each chip amplitude of the pseudo-random sequence is respectively matched with the pulse waveform to be modulated according to the chip sequenceγ(t) The multiplication realizes pulse amplitude modulation, so that the high-power spectrum pulse signal is subjected to spectrum broadening through a pseudo-random sequence, and the purpose of reducing the power spectrum density of the aviation altimeter modulation signal is achieved. Compared with the prior art, the technical scheme disclosed by the invention reduces the power spectrum density of the signal and improves the concealment capability and the anti-interception performance.
(4) The Doppler shift resistance is improved.
In the prior art, an aviation altimeter based on frequency method height measurement utilizes the frequency difference between echo signals and transmitting signals at the same moment, namely, the height is determined by the frequency of beat signals, and the influence of frequency parameters is large, so that the height measurement accuracy is greatly influenced by Doppler frequency shift. In the technical proposal disclosed by the invention, the time width of the repetition period is divided into 2NTime slot, leadingNPulse amplitude modulated signal and positive slope chirp signal of a time slot
Figure SMS_18
Multiplying and thenNPulse amplitude modulated signal and negative slope chirp signal of a time slot
Figure SMS_19
Multiplying to form a modulated signal; when receiving echo signals, the obtained beat frequency presents the characteristic of symmetrical triangular waves, and the beat frequencies of a positive slope modulation section and a negative slope modulation section of the symmetrical triangular waves are different, so that the beat frequency after addition processing is equal to the beat frequency corresponding to a stationary target, thereby eliminating the influence of Doppler frequency shift on height measurement and improving the capability of resisting the Doppler frequency shift.
(5) The height measurement resolution is improved.
In the prior art, a rectangular pulse is generally used as an envelope function to form a modulation signal so as to realize height measurement, and the time bandwidth product of the rectangular pulse is smaller, so that the height measurement resolution of the aviation altimeter is difficult to improve. In the technical scheme disclosed by the invention, the pulse waveform to be modulated adopts a 0-order long spherical wave function, has the characteristic of large time bandwidth product, is used for modulating an envelope function of a signal, and can obviously improve the height measurement resolution of an aviation altimeter. Compared with the prior art, the technical scheme disclosed by the invention can solve the problem of low resolution of the existing single modulation waveform height measurement on the premise of not increasing the power of the transmitted signal, and greatly improves the height measurement performance of the aviation altimeter.
Drawings
Fig. 1 is a slot division diagram of the embodiment disclosure.
Detailed Description
The present invention will be described in further detail with reference to fig. 1, so that those skilled in the art can implement the present invention by referring to the description.
In the prior art, the aerial altimeter signal is usually measured by a frequency method, and the altitude is determined by using the frequency difference between the echo signal and the transmitting signal at the same time, i.e. the frequency of the beat signal. However, in the aviation altimeter signal based on the technical system, the problems of irregular reflection surface, multipath, diffuse reflection and the like are commonly existed, so that the echo signal distortion is serious, and the clutter interference of the echo signal is large; furthermore, the aviation altimeter modulation signal of the prior art system is a fixed frequency transmission signal, has a larger high-power main lobe peak value, is easy to intercept by reconnaissance equipment, has poorer anti-interception and anti-interference capabilities, is greatly influenced by Doppler frequency shift, and has low height measurement precision, 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 a method for generating an aviation altimeter modulation signal. At the repetition period time widthT s In this regard, the altimeter modulation signal is shown below. Wherein, the liquid crystal display device comprises a liquid crystal display device,s 1 (t)、s 2 (t)、…、s i (t)、…、s N (t)、s N+1 (t) 、…、s N i+ (t) 、…s N2 (t) For the modulated signal of each time slot,γ(t) In order to be able to modulate the pulse waveform,τ pulse for the period time width of the pulse waveform to be modulated,c j for the number of chipsMPseudo-random sequence of (c)jThe amplitude of the individual chips is determined,
Figure SMS_20
、/>
Figure SMS_21
、…、/>
Figure SMS_22
、…、/>
Figure SMS_23
、/>
Figure SMS_24
、…、/>
Figure SMS_25
、…/>
Figure SMS_26
modulating the carrier frequency of the signal for each time slot from a hopping sequence [f 1 ,f 2 ,…,f V ]Is selected in a pseudo-random manner,Vfor the total number of frequency hopping points in the frequency hopping sequence,μis the frequency modulation slope. Frequency modulation slopeμIs known to those skilled in the art and will not be described in detail herein.
Figure SMS_27
Generating the aeroaltimeter modulation signal comprises the steps of:
step one: width of period time to be repeatedT s Divided into 2NA time slot;
step two: generating pulse period time width ofτ pulse Is to be modulated with a pulse waveformγ(t)；
Step three: generating pseudo-random sequences with good autocorrelation propertiesc 1 ,c 2 ,c 3 ,…,c j , …,c M ]，c j For the number of chipsMPseudo-random sequence of (c)jThe chip magnitudes;
step four: before the front partNWithin each of the time slots, each of the chip magnitudes of the pseudo-random sequence are sequentially from low to highc j Respectively and uniformly modulating pulse waveformγ(t) Multiplying to realize pulse amplitude modulation; then the pulse amplitude modulated signal and the linear frequency modulation signal
Figure SMS_28
Multiplying to form a modulated signal->
Figure SMS_29
Represent the firstiCarrier frequency of individual time slots, from hopping sequence [f 1 ,f 2 ,…,f V ]Is selected in a pseudo-random manner,irepresent the firstiEach time slot has a value ranging from 1 to 1NIs a positive integer of (2);
step five: at the rearNWithin each time slot of each time slotThe chip amplitudes of the pseudo-random sequence are determined from the chip order from low to highc j Respectively and uniformly modulating pulse waveformγ(t) Multiplying to realize pulse amplitude modulation; then the pulse amplitude modulated signal and the linear frequency modulation signal
Figure SMS_30
Multiplying to form a modulated signal->
Figure SMS_31
Represent the firstN+iCarrier frequency of individual time slots, from hopping sequence [f 1 ,f 2 ,…,f V ]Is selected in a pseudo-random manner,N+irepresent the firstN+iA number of time slots of a time slot,ithe value range is 1-1NIs a positive integer of (2);
step six: time width of repetition period according to aeroaltimeterT s Time width at next repetition periodT s And repeatedly executing the processes from the first step to the fifth step.
In the prior art, radio wave energy of an aviation altimeter signal is generally concentrated in a limited spectrum bandwidth, the power spectrum density is large, the detection is easy, and the concealment performance is poor. In order to improve the concealment of the aeronautical altimeter signal, in the technical scheme disclosed by the embodiment of the invention, the inventor breaks through the limitation of the prior art for measuring the height based on the continuous wave frequency method, adopts a pseudo-random sequence with good autocorrelation characteristics and respectively combines each chip amplitude of the pseudo-random sequence with a pulse waveform to be modulated according to the chip sequenceγ(t) The high-power spectrum signals are modulated through the pseudo-random sequence, so that the power of the aviation altimeter modulation signals is distributed in a wider spectrum range, the purpose of reducing the power spectrum density of the aviation altimeter modulation signals is achieved, the high-power spectrum signals have stronger concealment, and the reconnaissance interference equipment is difficult to detect and intercept the aviation altimeter signals. Therefore, compared with the prior art, the technical scheme disclosed by the embodiment of the invention improves the interception resistance of the aviation altimeter signal.
Further, in the technical scheme disclosed by the embodiment of the invention, when the echo signals are received to measure the height, the received echo signals are subjected to autocorrelation processing based on the good autocorrelation characteristics of the pseudo-random sequence, and the capacity of resisting the influence of distortion factors such as distortion, multipath and diffuse reflection of the modulating signals of the aerial altimeter can be greatly improved by accumulating the echo signal energy of all the chip time, so that the height measurement precision of the aerial altimeter is improved. The received echo signals are subjected to autocorrelation processing based on the autocorrelation characteristics of the pseudo-random sequence, and methods such as serial capturing, parallel capturing, and hybrid capturing in the prior art are 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 described herein.
In the field of radar electronics, blocking interference, and repeating interference are one of the common types of interference. The blocking interference refers to that the interference transmitting equipment is used for transmitting high-power interference signals with the same frequency, so that the signal-to-noise ratio of receiving equipment of an interfered party is seriously reduced, and the information is covered, so that the information is difficult to detect, and the purpose of interference is achieved. Compared with the blocking type interference, the forwarding type interference does not need to obtain signal parameters, 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 the prior art, the aviation altimeter signal usually adopts a fixed frequency transmitting signal, is easily intercepted by the reconnaissance equipment and has poor anti-interference capability on the implementation of high-power blocking interference. In order to improve the anti-blocking interference capability of the aeroaltimeter, in the technical scheme disclosed by the embodiment of the invention, in each time slot, a pulse amplitude modulated signal and a positive slope linear frequency modulation signal are processed
Figure SMS_32
Or negative slope chirp->
Figure SMS_33
Multiplying to form a modulated signal; the carrier frequency of the chirp signal is controlled by a key from the hopping sequence [f 1 ,f 2 ,…,f V ]Pseudo-randomly selected, and frequency agility is performed. To implement effective blocking interference, the interfering party must enable the blocking interference signal to track the frequency variation of the aircraft altimeter signal in the frequency domain. However, since the carrier frequency of the aeroaltimeter modulated signal is derived from the hopping sequence [f 1 ,f 2 ,…,f M ]The pseudo-random selection of the pilot frequency is controlled by the secret key, so that an interfering party cannot grasp the change rule of the frequency and cannot track the carrier frequency change of the aviation altimeter signal, and effective blocking interference is difficult to implement. Therefore, compared with the prior art, the technical scheme disclosed by the invention improves the capacity of resisting blocking interference. How the carrier frequency of the aeroaltimeter modulated signal is derived from the hopping sequence [f 1 ,f 2 ,…,f V ]The pseudo-random selection of the code is usually controlled by a key, which can be realized by adopting a frequency hopping technology, and is a conventional technical means for those skilled in the art, and is not repeated here.
Preferably, in the technical scheme disclosed in the embodiment of the invention, the carrier frequency of the aviation altimeter modulation signal is selected from the frequency hopping sequences [f 1 ,f 2 ,…,f V ]The total number of frequency points in a typical frequency hopping sequence is greater than 20. Further, frequency hopping sequence [f 1 ,f 2 ,…,f V ]Preset in microwave S band, frequency hopping sequence [f 1 ,f 2 ,…,f V ]The interval between the adjacent frequency points is more than or equal to 2MHz, and the frequency interval between the carrier frequencies of the adjacent time slot modulation signals is more than or equal to 5MHz, so that the frequency agile span of the aviation altimeter signals between different time slots is increased, and the difficulty of implementing blocking interference by an interfering party is further improved. Even if the interferer uses wideband blocking interference to cover multiple frequency points, it is difficult to achieve effective interference. This is mainly due to the fact that after the frequency agile span of the air altimeter signal increases, the power of the blocking interference is forced to be distributed in a wider frequency spectrum range to reach the coverage of multiple frequency pointsThe purpose is that; however, in this case, the interference power at each frequency point is rapidly reduced with an increase in the spectrum width, and therefore, the present invention can be used only for short-range interference. Further, in the technical scheme disclosed by the embodiment of the invention, the interval between the carrier frequencies between the adjacent time slots is more than or equal to 5MHz, and the total number of the frequency points in the frequency hopping sequence is more, so that the carrier frequency of the aviation altimeter signal can cover a wider frequency spectrum range, thereby forcing an interfering party to be unable to achieve a useful effect even if broadband interference is adopted. After the aerial altimeter signals are transmitted, a synchronization module is started, under the control of a secret key, the synchronization signals of the echo signals are captured, the change of carrier frequencies is tracked, the synchronization of carrier frequency signal jump is completed, the tracking capture of the carrier frequencies of the echo signals is realized, and the height measurement is completed. The following of how to receive the frequency hopping signal can be implemented by using a frequency hopping receiving technology, which is a common technical means for those skilled in the art, and will not be described herein.
In order to improve the capability of the aeroaltimeter signal to resist the forwarding interference, in the technical scheme disclosed by the embodiment of the invention, the time width of the repetition period is as followsT s Divided into 2NTime slots with equal time lengthδ0.2 microsecond, will be preceded byNPulse amplitude modulated signal and positive slope chirp signal of a time slot
Figure SMS_34
Multiplying and thenNPulse amplitude modulated signal and negative slope chirp signal of one time slot +.>
Figure SMS_35
Multiplying to form a modulated signal, the carrier frequency of the chirp signal being derived from the hopping sequencef 1 ,f 2 ,…,f V ]Pseudo-randomly selected such that the carrier frequencies of the modulated signals for each time slot are different from each other. 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. Due to the technology disclosed in the embodiments of the present inventionIn the scheme, the carrier frequencies of the aeroaltimeter signals are different from time slot to time slot, so that if the interference party carries out the forward interference, the interference party can only forward the modulated signals interfering with the same time slot and cannot interfere with the modulated signals crossing the time slot, and the total time for carrying out the forward interference is less than or equal to one time slot duration, namely the whole process from the start of receiving the signals to the retransmission of the signals is required to be completed in the same time slot. Preferably, in the technical scheme disclosed in the embodiment of the present invention, the time slot time lengthδIs 0.2 microseconds. According to the theory of radio wave transmission, the maximum distance between the platform for implementing the forward interference and the interfered platform 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.
In the prior art, an aviation altimeter signal is usually measured by a frequency method, and the altitude is determined by utilizing the frequency difference between an echo signal and a transmitting signal at the same moment, namely, the frequency of a beat signal, which is greatly influenced by Doppler frequency shift, so that the altitude measurement precision is low. In the technical scheme disclosed by the embodiment of the invention, under the action of the frequency hopping synchronous signal, signal processing such as frequency mixing is performed after the carrier frequency tracking capture of the echo signal, so as to obtain the beat signal of the echo signal. The frequency of the beat signal is different between the positive slope modulation section and the negative slope modulation section of the symmetric triangular wave.
Further, in the technical solution disclosed in the embodiment of the present invention, the beat signal frequency of the moving object in the positive slope modulation interval may be expressed as:
Figure SMS_36
the beat signal frequency of the moving object in the negative slope modulation section can be expressed as:
Figure SMS_37
in the method, in the process of the invention,
Figure SMS_38
beat signal frequency representing positive slope modulation interval, < >>
Figure SMS_39
Beat signal frequency representing negative slope modulation interval, < >>
Figure SMS_40
Indicates the frequency of the beat signal corresponding to the stationary object, < >>
Figure SMS_41
Is the doppler frequency caused by the moving object. By adding the two formulas, the following can be obtained: />
Figure SMS_42
The formula shows that the added and processed beat frequency signal frequency is the beat signal 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 height measurement is eliminated. Compared with the prior art, the technical scheme disclosed by the embodiment of the invention can eliminate the influence of Doppler frequency on altimetry and improve the altimetry performance.
In the case of noise power spectrum determination, the detection capability of the altimeter to receive echo signals depends on the energy of the pulse waveform transmitted by the altimeter. In the case of constant transmit power of an aeroaltimeter, the prior art generally uses an increase in the spectral width of the transmitted signal in order to increase the energy of the transmitted signal. However, as the spectral width of the transmitted signal increases, this can lead to a significant decrease in the altimetric resolution. In the prior art, when the frequency method is used for measuring the height, the envelope function of the modulated signal usually adopts rectangular pulses, the time bandwidth product of the rectangular pulses is about 1, and the smaller time bandwidth product can not meet the requirement of improving the echo signal detection capability. Thus, at the transmitter powerUnder the condition of unchanged upper limit, in order to improve the detection capability of echo signals and meet higher height measurement resolution at the same time so as to solve the limitation of the existing continuous wave frequency method for measuring the height, in the technical scheme disclosed by the embodiment of the invention, a pulse signal with a large time-bandwidth product characteristic is adoptedγ(t) And designing an aeroaltimeter modulation signal.
Further, in the technical scheme disclosed in the embodiment of the invention, the pulse waveform to be modulatedγ(t) Is a 0 th order long spherical wave function (Prolate Spheroidal Wave Functions, PSWFs), in a given time interval [ - ] isT p /2，T p /2]In the inner part of the inner part,γ(t) The following integral equation is satisfied:
Figure SMS_43
，
in the method, in the process of the invention,
Figure SMS_44
is 0 th order long spherical wave function +.>
Figure SMS_45
And omega is the angular frequency of the corresponding characteristic value.
The long spherical wave function has the characteristics of large time-bandwidth product, optimal energy aggregation and the like, so that the long spherical wave function has wide application. In the technical proposal disclosed by the embodiment of the invention, the pseudo random sequence with good autocorrelation property participates in the pulse waveform of pulse amplitude modulationγ(t) Adopting a long spherical wave function; preferably, the method comprises the steps of,γ(t) The time bandwidth product factor is 4 pi for the 0-order long spherical wave function, and at the moment, the main lobe energy aggregation of the aviation altimeter modulation signal can reach more than 99%, so that the capability of the modulation signal for resisting channel noise is greatly improved, and the modulation signal has stronger anti-interference capability when being used for height measurement. Furthermore, 0 th order long spherical wave functionγ(t) The device also has the characteristic of large time bandwidth, and has high energy aggregation, so that the device is beneficial to improving the resolution of height measurement when being used for height measurement of an aeroaltimeter.
In the state of the art,the autocorrelation properties of pseudo-random sequences also have a large variance due to the different implementation. Although M sequences are easy to generate, their autocorrelation properties are weak. The autocorrelation characteristic of the pseudo-random sequence is related to the peak characteristic of the echo signal detected by the aviation altimeter. The sharper the autocorrelation of the pseudo-random sequence, the more advantageous it is for accurately capturing the peak of the echo signal, the higher the accuracy for the altimetry. Further, in the technical scheme disclosed by the embodiment of the invention, the number of the chips of the pseudo-random sequence is closely related to the height measurement performance of the aviation altimeter, and the more the number of the chips of the pseudo-random sequence is, the larger the energy of the accumulated received echo signal is, namely the larger the power of the useful signal is, the more the signal to noise ratio is favorably improved, so that the detection capability is favorably improved; 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. Therefore, in order to improve the altitude measurement capability of the altitude meter, in the technical scheme disclosed by the embodiment of the invention, the pseudo-random sequence adopts a pseudo-random sequence with 11 chips, and the amplitude of each chip of the pseudo-random sequence is [ [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]At this time, the pseudo-random sequence has sharp autocorrelation peaks, which is favorable for capturing echo signals and improving the height measurement precision.
Further, as shown in fig. 1, in the technical scheme disclosed in the embodiment of the invention, as shown in fig. 1, the cycle time width is repeatedT s Divided into 2NTime slots with equal time length; time slot time lengthδNumber of pseudo-random sequence chipsMAnd the cycle time width of the pulse waveform to be modulatedτ pulse The three satisfy the relation:δ=M×τ pulse . Further, in the technical scheme disclosed in the embodiment of the invention, the pulse period time width to be modulatedτ pulse And (3) withT p The relation between them is satisfied:τ pulse >T p to reduce the modulation to be performedPulse waveformγ(t) According to the transformation relation between the time domain and the frequency domain, the frequency spectrum of the aviation altimeter signal can be further widened, and the power spectrum density of the signal is further reduced under the condition that the total transmitting power is unchanged, so that the concealment and interception resistance of the Gao Hang empty altimeter signal can be improved.
In the technical scheme disclosed by the embodiment of the invention, the cycle time width of the pulse waveform to be modulatedτ pulse Comprising a pulse transmission time width and a pulse stop time width, wherein the pulse transmission time width occupies the period time width of the pulse waveform to be modulatedτ pulse Fifty percent of (f).
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 (9)

1. A method of generating an air altimeter modulation signal, the method comprising the steps of:
step one: width of period time to be repeatedT s Divided into 2NA time slot;
step two: generating pulse period time width ofτ pulse Is to be modulated with a pulse waveformγ(t)；
Step three: generating pseudo-random sequences with good autocorrelation propertiesc 1 , c 2 , c 3 ,…,c j , …,c M ]，c j For the number of chipsMPseudo-random sequence of (c)jThe chip magnitudes;
step four: before the front partNIn each of the time slots, the chip sequences from low to highIndividual chip magnitudes of a pseudo-random sequencec j Respectively and uniformly modulating pulse waveformγ(t) Multiplying to realize pulse amplitude modulation; multiplying the pulse amplitude modulated signal with the linear frequency modulation signal to form a modulated signal, representing the firstiCarrier frequency of individual time slots, from hopping sequence [f 1 ,f 2 ,…,f V ]Is selected in a pseudo-random manner,irepresent the firstiEach time slot has a value ranging from 1 to 1NIs a positive integer of (2);
step five: at the rearNWithin each of the time slots, each of the chip magnitudes of the pseudo-random sequence are sequentially from low to highc j Respectively and uniformly modulating pulse waveformγ(t) Multiplying to realize pulse amplitude modulation; multiplying the pulse amplitude modulated signal with the linear frequency modulation signal to form a modulated signal, representing the firstN+iCarrier frequency of individual time slots, from hopping sequence [f 1 ,f 2 ,…,f V ]Is selected in a pseudo-random manner,N+irepresent the firstN+iA number of time slots of a time slot,ithe value range is 1-1NIs a positive integer of (2);
step six: time width of repetition period according to aeroaltimeterT s Time width at next repetition periodT s In the process, the first to fifth steps are repeatedly executed for a period of repetitionT s In, the generated air altimeter modulation signal is:
Figure QLYQS_1
，
wherein, the liquid crystal display device comprises a liquid crystal display device,s 1 (t)、s 2 (t)、…、s i (t)、…、s N (t)、s N+1 (t)、…、s N i+ (t) 、…s N2 (t) For the modulated signal of each time slot,μfor the frequency modulation slope,γ(t) In order to be able to modulate the pulse waveform,τ pulse for the period time width of the pulse waveform to be modulated,c j for the number of chipsMPseudo-random sequence of (c)jThe amplitude of the individual chips is determined,
Figure QLYQS_2
、/>
Figure QLYQS_3
、…、/>
Figure QLYQS_4
、…、/>
Figure QLYQS_5
、/>
Figure QLYQS_6
、…、/>
Figure QLYQS_7
、…/>
Figure QLYQS_8
modulating the carrier frequency of the signal for each time slot from a hopping sequence [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.
2. The method of generating an air altimeter modulation signal according to claim 1, wherein the repetition period time width is set to beT s Divided into 2NTime slots with equal time length.
3. The method of generating an air altimeter modulation signal according to claim 2, wherein,γ(t) For 0 th order long spherical wave function, in a given time interval [ cavity [ ]T p /2，T p /2]In the inner part of the inner part,γ(t) The following integral equation is satisfied:
Figure QLYQS_9
，
in the method, in the process of the invention,
Figure QLYQS_10
is 0 th order long spherical wave function +.>
Figure QLYQS_11
And omega is the angular frequency of the corresponding characteristic value.
4. A method of generating an air altimeter modulation signal according to claim 3, wherein the repetition period time is of a widthT s Divided into 2NTime slots with equal time lengthδIs 0.2 microseconds.
5. The method of generating an air altimeter modulation signal according to claim 4, wherein the hopping sequence [f 1 ,f 2 ,…,f V ]Preset in microwave S band, frequency hopping sequence [f 1 ,f 2 ,…,f V ]The interval between the adjacent frequency points is more than or equal to 2MHz.
6. The method of generating an air altimeter modulation signal according to claim 4, wherein the pseudo-random sequence is a pseudo-random sequence having a chip number of 11, and each chip amplitude 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]。
7. The method of generating an air altimeter modulation signal of claim 4 wherein the slot time lengthδNumber of pseudo-random sequence chipsMAnd the cycle time width of the pulse waveform to be modulatedτ pulse The three satisfy the relation:δ= M×τ pulse 。
8. the method of generating an air altimeter modulation signal according to claim 4, wherein the period time width of the pulse waveform to be modulatedτ pulse Comprising a pulse transmission time width and a pulse stop time width, wherein the pulse transmission time width occupies the period time width of the pulse waveform to be modulatedτ pulse Fifty percent of (f).
9. The method of generating an air altimeter modulation signal of claim 4 wherein the time bandwidth product factor of the 0 th order long spherical wave function is 4pi.
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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110703279A (en) * 2019-09-16 2020-01-17 西安空间无线电技术研究所 Satellite navigation signal generation method based on chip-level pulse time hopping

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5477226A (en) * 1994-05-09 1995-12-19 Honeywell Inc. Low cost radar altimeter with accuracy enhancement
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US7064703B2 (en) * 2004-02-17 2006-06-20 Honeywell International Inc. Methods and apparatus for randomly modulating radar altimeters
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
CN113534145A (en) * 2021-09-16 2021-10-22 北京安达维尔航空设备有限公司 Altimeter height measurement method and system based on linear frequency modulation continuous wave system
CN113820669A (en) * 2021-09-30 2021-12-21 中国人民解放军63892部队 Coherent noise interference signal optimization generation method based on genetic algorithm
CN114427871B (en) * 2022-04-07 2022-07-01 烟台初心航空科技有限公司 Aviation altimeter application efficiency detection method based on dynamic continuous detection
CN114442058B (en) * 2022-04-07 2022-07-01 烟台初心航空科技有限公司 Application efficiency detection device for aviation altimeter
CN114978832B (en) * 2022-08-01 2022-10-21 烟台初心航空科技有限公司 Radar communication integrated modulation signal generation method with channel adaptability

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110703279A (en) * 2019-09-16 2020-01-17 西安空间无线电技术研究所 Satellite navigation signal generation method based on chip-level pulse time hopping

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