CN108845312B - Height measurement method based on pulse system radio altimeter - Google Patents
Height measurement method based on pulse system radio altimeter Download PDFInfo
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- CN108845312B CN108845312B CN201810564185.7A CN201810564185A CN108845312B CN 108845312 B CN108845312 B CN 108845312B CN 201810564185 A CN201810564185 A CN 201810564185A CN 108845312 B CN108845312 B CN 108845312B
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- 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
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- G01S13/10—Systems for measuring distance only using transmission of interrupted, pulse modulated waves
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Abstract
The invention discloses a height measuring method of a pulse system altimeter, which mainly solves the problem that the prior art is easy to generate same frequency interference when formation flying. The implementation scheme is as follows: transmitting a random pulse time sequence signal, processing an echo signal to generate two paths of video signals when receiving, wherein the amplitude and noise of a first path of signal are greater than those of a second path of signal; performing related accumulation on the first path of signals through a plurality of nanosecond range gates, and generating a stop pulse according to the coincidence of the range gates and the video pulse when the number of accumulated pulses is greater than a tracking threshold value; calculating the height by adopting a mathematical statistic method according to the delay time of the trigger pulse and the stop pulse; the sensitivity of the receiver is controlled through the second path of signals, so that the amplitude of the second path of signals under different loop attenuation is controlled to be close to the sampling threshold, and the amplitude of the first path of signals is larger than the sampling threshold and is kept stable. The invention can avoid signal interference with other aircrafts, improve the height measurement precision of multi-aircraft formation and can be used for aerospace aircrafts.
Description
Technical Field
The invention belongs to the technical field of radar ranging, and particularly relates to a radio altimeter which can be used for high-precision tracking measurement of flying height in an aerospace aircraft under multi-machine formation or a complex environment.
Background
The measurement of the real height of the aircraft from the ground and the water surface is mainly realized by a radio altimeter which mainly comprises three working systems at present, namely a pulse system, a frequency modulation continuous wave system and a pseudo code continuous wave height measurement system, wherein:
the pulse system altimeter has the working principle that: the pulse generating circuit generates transmitting pulses, the microwave transmitting equipment modulates pulse signals to radio frequency, the radio frequency signals are radiated to the ground through the transmitting antenna, the radio frequency signals returned from the ground enter a microwave receiving system through the receiving antenna, the radio frequency signals are subjected to low-noise amplification and frequency mixing to generate intermediate frequency signals, the intermediate frequency signals are output through the gain control and analog signal tracking circuit to form video echo pulse signals, and the height data processing and calculating circuit and the interface circuit output height and state information to other equipment on the aircraft.
The existing method for measuring height based on the impulse radio altimeter mainly comprises three interconnected parts of searching, capturing and automatically tracking echo signals. The echo signal is processed into a video pulse signal satisfying the amplitude requirement after being output by the receiver, and the signal is compared with the tracking pulse in terms of time to obtain the time interval between the signal and the tracking pulse. The output error voltage is zero if the tracking pulse coincides in time exactly with the echo pulse, i.e. the delay times of the two are the same. Otherwise, an error voltage is output, the magnitude of the error voltage is in direct proportion to the difference value of time, and the front-back correlation of the tracking pulse and the echo pulse is represented by positive and negative values of the error voltage. A control signal is generated according to the magnitude of the positive and negative values of the error voltage, the control signal having the function of controlling the time and direction of movement of the tracking pulse, the purpose of which is to change the delay time of the tracking pulse with respect to the reference pulse in the same direction as the delay time of the video pulse with respect to the reference pulse, to make the tracking pulse and the video pulse completely coincide, and the current height is calculated by measuring the time delays of the transmission pulse and the tracking pulse.
The existing height measurement method applied to the radio altimeter for height measurement has the following defects:
with the increasing of equipment equipped on aircrafts, the electromagnetic environment is increasingly complex, most aircrafts need to be formed into a formation for flying, each aircraft is equipped with at least one radio altimeter, interference exists between the inside of the equipment and the equipment, and co-frequency interference of other airborne radars exists.
Therefore, how to solve the problem of normal tracking when a plurality of machines are formed into a formation to fly is a difficult problem which needs to be solved urgently by the pulse system radio altimeter.
Disclosure of Invention
The invention aims to provide a height measurement method based on a pulse system altimeter aiming at the defects of the prior art, so as to avoid signal interference with other machines, ensure the flight safety and normal tracking of airplane formation and improve the height measurement precision and stability of multi-machine formation.
The technical idea of the invention is as follows: transmitting a random pulse time sequence signal, processing an echo signal to generate two paths of video signals when receiving, wherein the amplitude and noise of a first path of signal are greater than those of a second path of signal; performing related accumulation on the first path of signals through a plurality of nanosecond range gates, and generating a stop pulse according to the coincidence of the range gates and the video pulse when the number of accumulated pulses is greater than a tracking threshold value; calculating the height by adopting a mathematical statistic method according to the delay time of the trigger pulse and the stop pulse; the sensitivity of the receiver is controlled through the second path of signals, so that the amplitude of the second path of signals under different loop attenuation is controlled to be close to the sampling threshold, the amplitude of the first path of signals is larger than the sampling threshold and is kept stable, and the pulse front edge tracking and the height measurement accuracy under echo signals with different strengths are ensured.
According to the technical idea, the implementation steps of the invention comprise the following steps:
(1) initializing and reading the residual height H of the altimeter with pulse systemAParameter, preset binary sampling accumulation threshold detection value K0Height gain control AGC curve voltage and initial pulse repetition period TiDelay time T of the tracking gate to be searched relative to the transmission trigger pulseGInitializing to zero, and controlling a tracking gate to search from zero height; simultaneously, AGC curve voltage parameter is controlled according to height gain, and gain control is outputAGC voltage, which controls the receiving sensitivity of the pulse system altimeter and switches the working mode of the altimeter into a search mode;
(2) according to the initial pulse repetition period TiGenerating a new pulse repetition period TFAccording to the new pulse repetition period TFGenerating a radio frequency modulated trigger pulse T0Controlling the pulse system altimeter to generate a radio frequency pulse signal and transmit the radio frequency pulse signal to the ground;
(3) the echo pulse signal output by the pulse system altimeter is filtered and amplified to generate a first video pulse signal P1Outputting, and generating a second video pulse signal P by denoising and blocking the first video pulse signal2Outputting;
(4) selecting a pure noise time sequence interval without echo signals, and carrying out comparison on the first path of video pulse signal P1Sampling, obtaining the average noise of the echo signal sampling circuit through accumulation and averaging, and accumulating the accumulated threshold detection value K according to the average noise and the preset binary sampling0Determining a tracking threshold value K;
(5) reading tracking gate relative emission trigger pulse signal T0Generating a relative emission trigger pulse delay tracking gate according to the delay time digital quantity, wherein the width of the tracking gate is 10ns, inputting the tracking gate into a range gate shift register with the width of 30 bits, the clock frequency of the range gate shift register is 100MHz, and respectively generating 30 adjacent range gates R with the height distance sequentially increased by the width of 10nsN；
(6) At a distance gate RNPosition-to-position first video pulse signal P10/1 quantization is performed, and the shift register SRM is accumulated by M bit pulseNReading the quantized result and then accumulating the pulse into the shift register SRMNValue of (SRQ)NCounting the number of bits of 1 to obtain M pulse repetition periods at a distance gate RNFirst path video pulse signal P sampled by position1The number of (2);
if it is a distance gate RNFirst path of video pulse P sampled at M repeated cycles1Large number ofWhen tracking threshold K, then distance gate RNPosition tracking status signal STN1, in the range gate RNSampling the position to obtain a valid echo signal;
otherwise, STN0 denotes a range gate RNEcho signals are not sampled from the positions;
(7) based on the tracking state signal STNDoor R for judging distanceNAnd a distance gate RNM-bit pulse accumulation at location shift register SRMNThe direction of movement of the value;
if tracking status signal STNSatisfies the following conditions: ST (ST)N＝0,1<＝N<For distance gate R of 11NAnd a distance gate RNM-bit pulse accumulation at location shift register SRMNShifting the value to the right;
if tracking status signal STNSatisfies the following conditions: ST (ST)N1, N1, 2, … 10, for the range gate RNAnd a distance gate RNM-bit pulse accumulation at location shift register SRMNShifting the value to the left;
(8) according to the distance RNThe first video pulse P1 is coincided to generate a stop pulse T1;
(9) transmitting a trigger pulse T according to (2)0Leading edge and stop pulse T1The delay time between the leading edges is calculated by adopting a mathematical statistics method to calculate the average height H of 512 times2According to the residual height HAParameters, correcting the average height to obtain the true height HRAnd output to the pulse system altimeter;
(10) determining the working state of the altimeter, and outputting a gain control voltage according to the working state of the altimeter:
if all tracking state signals STNAre all zero, namely: ST (ST)N＝0,1<＝N<If not, the altimeter works in a tracking state;
if the altimeter works in a searching state, outputting a gain control AGC voltage according to the altitude gain control AGC curve, controlling the sensitivity of the altimeter, and returning to the step 2;
if the altimeter is operated in tracking mode, then at the range gate RNWithin range to the second path of video pulse P2Quantizing (0/1), counting the quantized pulses of M repetition periods, generating signal gain control AGC voltage according to the counted pulse number of M repetition periods, and controlling the second path of video pulse P2The output amplitude is equal to the sampling threshold value;
and (3) comparing the signal gain control AGC voltage with the height gain control AGC curve voltage, if the gain controlled by the signal gain control AGC voltage is smaller than the gain controlled by the height gain control AGC curve voltage, outputting a signal gain control AGC voltage to control the sensitivity of the altimeter, otherwise, outputting the height gain control AGC curve voltage to control the sensitivity of the altimeter, and returning to the step (2).
Compared with the prior art, the invention has the following advantages:
1. the invention can effectively identify local signals and other signals or noise during receiving by transmitting random pulse time sequence signals, and can not track other signals or interference signals, thereby realizing high stability and high reliability distance measurement of the pulse radio altimeter and solving the problem that the altimeter can not stably measure the height when a plurality of machines form a team and a plurality of bombs are simultaneously transmitted;
2. the invention carries out signal detection and tracking and AGC control through multiple thresholds, can still realize stable tracking of signals even under complex terrain environment and low signal-to-noise ratio, and ensures the reliability of high output;
3. according to the invention, binary sampling is adopted, and signal detection and tracking and AGC (automatic gain control) are carried out through multiple thresholds, so that amplitude quantization errors of binary sampling processing are effectively solved, the amplitude of an echo signal can be stabilized during signal tracking, and the height measurement precision is ensured;
4. the invention solves the problems of low resolution and low precision of the altimeter caused by the limitation of sampling frequency in a digital processing method through a height measurement mode of double-leading-edge coincidence and mathematical statistics.
Drawings
FIG. 1 is a schematic block diagram of a pulse system altimeter used in the present invention;
FIG. 2 is a general flow chart of an implementation of the present invention;
Detailed Description
The present invention is described in detail below with reference to the attached drawings.
Referring to fig. 1, the pulse system used in the present invention includes a receiving antenna, a transmitting antenna, a receiving antenna high frequency cable, a transmitting antenna high frequency cable, a microwave transmitting unit, a microwave receiving unit, a signal processing unit, an interface unit and a power supply unit. The microwave transmitting unit generates 4300MHz high frequency pulse signal under the control of the random trigger pulse generated by the signal processing unit, and the high frequency pulse signal is transmitted to the transmitting antenna by the transmitting antenna through the high frequency cable and radiated to the ground. The receiving antenna transmits the received echo signal to the microwave receiving unit through the high-frequency cable, and the microwave receiving unit controls the gain of the echo signal under the control of AGC control voltage generated by the signal processing unit and outputs a video pulse signal to the signal processing unit. The signal processing unit tracks and positions the video pulse signal, calculates the height, and converts the height and state information into signals meeting EIA-RS-422A bus standard and HB 6096 bus standard. The interface unit modulates signals of HB 6096 bus standard and EIA-RS-422A bus standard output by the signal processing unit into signals conforming to HB 6096 bus level signals and EIA-RS-422A bus level signals, and transmits the signals to equipment on an external machine. The power supply unit filters 28V direct current power supply input on an external machine, converts the 28V direct current power supply into +5V direct current power supply and +/-12V direct current power supply through the DC/DC power supply module, respectively supplies the +5V direct current power supply to the signal processing unit and the interface unit, and respectively supplies the +/-12V direct current power supply to the microwave transmitting unit, the microwave receiving unit and the interface unit.
Referring to fig. 2, the method for measuring height based on the pulse system altimeter of the present invention includes the following steps:
step 1, initializing a pulse system altimeter, and switching the altimeter into a search mode.
Reading the remaining height H of the altimeterAA preset binary sampling accumulation threshold detection value K0Height gain control AGC curve voltage and initial pulse repetition period Ti；
Tracking gate relative transmission trigger pulse T to be searched0Delay time T ofGInitialised to zero, i.e. TGAnd (5) controlling the tracking gate to search from zero height, controlling the AGC curve voltage according to the gain of the height, outputting the gain control AGC voltage, and controlling the receiving sensitivity of the altimeter by the gain control AGC voltage.
And 2, generating a radio frequency modulation trigger pulse.
According to the initial pulse repetition period TiGenerating a random offset TSWherein, 0<TS<Ti*30％；
Generating a new pulse repetition period TF：TF＝Ti+TS；
According to the new pulse period TFGenerating a radio frequency modulated trigger pulse T0And controlling the pulse system altimeter to generate a radio frequency pulse signal and transmit the radio frequency pulse signal to the ground.
And 3, generating a first path of video pulse signal and a second path of video pulse signal.
The receiving antenna receives the ground echo signal, the ground echo signal is converted into a video echo signal through the receiving unit, and the video echo signal is filtered and amplified to generate a first path of video pulse signal P1；
For the first video pulse signal P1De-noising and blocking processing are carried out to generate a second path of video pulse signal P2。
And 4, generating a tracking threshold value K.
4a) Selecting a pure noise time sequence interval without echo signals, and carrying out comparison on the first path of video pulse signal P1Binary sampling is carried out, and a first path of video pulse signal P is obtained through M pulse repetition period accumulation1Is sampled by averaging the noise values KN：
4a1) Selecting to generate trigger pulse T0In the former pure noise time sequence interval, generating 8 noise sampling detection gates with different positions, wherein the width of each detection gate is 10 ns;
4a2) respectively on the positions of the above 8 noise sampling detection gatesThe first path of input video pulse signal P10/1 quantization is carried out;
4a3) reading the first path of video pulse signals with quantized noise sampling detection gate positions through an M-bit pulse accumulation shift register respectively, and counting the number of bits of the pulse accumulation shift register which is 1 to obtain the noise quantity detected by binary accumulation in M pulse repetition periods of the noise sampling detection gate positions;
4a4) averaging the noise number detected by the 8 noise sampling detection gates to obtain an average noise sampling value KN；
4b) At the mean noise sampling value KNAdding a preset binary sampling accumulation threshold detection value K0And obtaining a tracking threshold value K.
Step 5, 30 adjacent distance gates R are generatedN。
Reading tracking gate relative emission trigger pulse signal T0Delay time T ofGAccording to the delay time TGGenerating a tracking gate delayed relative to the transmit trigger pulse, the tracking gate having a width of 10 ns;
inputting the tracking gate into 30 stages of range gate shift registers, and respectively generating 30 adjacent range gates R with the height distance sequentially increased by 10ns by the range gate shift registers through the 100MHz clock frequencyN，1<＝N<＝30。
Step 6, for the distance door RNPosition first video pulse signal P1And carrying out pulse accumulation detection.
6a) At a distance gate RNPosition-to-position first video pulse signal P10/1 quantization is performed, and the shift register SRM is accumulated by M bit pulseNReading the quantized result and then accumulating the pulse into the shift register SRMNCounting the number of bits of 1 to obtain M pulse repetition periods at a distance gate RNFirst path video pulse signal P sampled by position1The number of (2);
6b) for distance door RNFirst path of video pulse P sampled at M repeated cycles1Number of and tracking thresholdComparing the value K and outputting a distance gate RNPosition tracking status signal STN：
If it is a distance gate RNFirst path of video pulse P sampled at M repeated cycles1If the number is greater than K, STN1, in the range gate RNSampling the position to obtain a valid echo signal;
otherwise, STN0 denotes a range gate RNThe location is not sampled to an echo signal.
Step 7, controlling the distance door RNAnd a distance gate RNM-bit pulse accumulation at location shift register SRMNThe value is shifted.
7a) Judging the range gate R according to the tracking state signalNMoving direction:
if tracking status signal STNSatisfies the following conditions: ST (ST)N＝0,1<＝N<When the distance is 11, the distance gate RNMoving right, and executing the step 7 b;
if tracking status signal STNSatisfies the following conditions: ST (ST)N1, N1, 2, … 10, distance gate RNMoving left, and executing the step 7 c;
7b) for distance door RNAnd a distance gate RNM-bit pulse accumulation at location shift register SRMNThe values are shifted to the right:
7b1) will track the delay time T of the gate relative to the trigger pulseGIncreasing one clock period Δ T, the right shift of the tracking gate is realized, i.e.:
TG＝TG+ΔT，TG<Tiif T isG＝TiThen, the right shift is not performed any more;
wherein T isiAn initial pulse repetition period defined for step 1;
due to the distance from the door RNIs synchronously generated by the tracking door, so that the distance door R is realized when the tracking door moves to the rightNRight shift;
7b2) will be at a distance from the door RNPosition M-bit pulse accumulation shift register SRMNValue of (SRQ)NTo the right, i.e. to accumulate the next M-bit pulse into the shift register SRMN+1Value of (SRQ)N+1The previous M-bit pulse accumulation shift register is given
SRMNTo obtain each range gate RNPosition M-bit pulse accumulation shift register SRMNThe value of (c):
SRQ1＝SRQ2，
SRQ2＝SRQ3，
……
SRQN＝SRQN+1，
……
SRQ29＝SRQ30；
SRQ30＝0，
wherein, 1< ═ N < ═ 30;
7c) for distance door RNAnd a distance gate RNM-bit pulse accumulation at location shift register SRMNThe values are shifted to the left.
7c1) Will track the delay time T of the gate relative to the trigger pulseGReducing one clock period Δ T, a left shift of the tracking gate is achieved, i.e.: t isG＝TG-ΔT，TG>0; if TGIf the value is 0, the left shift is not performed any more;
due to the distance from the door RNIs synchronously generated by a tracking door, so that the distance door R is realized when the tracking door moves leftwardsNMoving left;
7c2) will be at a distance from the door RNPosition M-bit pulse accumulation shift register SRMNIs left shifted, i.e. the previous M-bit pulse is accumulated in the shift register SRMN-1Value of (SRQ)N-1SRM (sequence reference register) assigned to the next M-bit pulse accumulation shift registerNTo obtain each range gate RNPosition M-bit pulse accumulation shift register SRMNThe value of (c):
SRQ30＝SRQ29；
SRQ29＝SRQ28；
……
SRQN＝SRQN-1；
……
SRQ2＝SRQ1；
SRQ1＝0；
wherein, 1< N < 30.
Step 8, generating a stop pulse T1
The 11 th distance gate R11And a 12 th distance gate R12Phase-or-after-phase with the first video pulse P1Carrying out superposition;
the overlapped result is compared with a 13 th range gate R13Then phase-OR is carried out to obtain a stop pulse T1：
T1＝P1&(R11 or R12)or R13，
Wherein, P1For the first video pulse signal, R11Is the 11 th range gate, R12Is the 12 th range gate, R13Is the 13 th range gate, T1In order to stop the pulse, the pulse is stopped,&is an AND gate, or is an OR gate.
Step 9. according to the emission trigger pulse T0And a stop pulse T1And calculating the average height according to the delay time, correcting the average height according to the residual height parameters to obtain the real height, and outputting the real height to a pulse system altimeter.
9a) Calculating the height by adopting a mathematical statistic method, and calculating the average height H for 512 times2：
9a1) In generating a transmission trigger pulse T0Starts counting the counter until a stop pulse T is generated1Stopping counting, recording the number n of counting pulses of the counter during the period1Calculating the stop pulse T according to the number of counting pulses and the clock period of the counter1With respect to the transmit pulse T0Delay time t ofH：
tH＝n1*T＝n1/f，
Wherein T is the clock period of the counter, and f is the clock frequency of the counter;
9a2) according to delay time tHAnd the propagation speed c of the electromagnetic wave, and calculating to obtain the single measurement height H1:
H1＝(c*tH)/2＝(c*n1)/(2f)；
9a3) For stop pulse T1Dividing the frequency of the pulse by 512 times to generate a divided pulse TABy dividing the pulse TAReading the pulse number n of a counter with 512 pulse repetition periods2Meanwhile, the counter is cleared, and the average height H of 512 pulse repetition periods is calculated2：
H2＝(c*n2)/(2*f*512)。
9b) According to the residual height HAAnd (3) correcting the average height for 512 times according to the parameters, and calculating the real height:
9b1) calculating the residual height HA:
HA＝(c*tA)/2，
Wherein, tATime delay generated when a signal transmitted by the altimeter passes through a device and a cable is indicated;
9b2) calculating the true height HR：
HR＝H2-HA
Wherein H2Is the average height of 512 pulse repetition periods.
And step 10, determining the working state of the altimeter, and outputting the gain control voltage according to the working state of the altimeter.
10a) Determining the working state of the altimeter according to the tracking state signal:
if all tracking state signals STNAre all zero, namely: ST (ST)N＝0,1<＝N<If not, the altimeter works in a tracking state;
10b) outputting a gain control voltage according to the working state of the altimeter:
if the altimeter works in a searching state, outputting a gain control AGC voltage according to the altitude gain control AGC curve, controlling the sensitivity of the altimeter, and returning to the step 2;
if the altimeter is operated in tracking mode, then at the range gate RNSecond path of video within rangePulse P2Quantizing (0/1), counting the quantized pulses of M repetition periods, generating signal gain control AGC voltage according to the counted pulse number of M repetition periods, and controlling the second path of video pulse P2The output amplitude is equal to the sampling threshold value;
and (3) comparing the signal gain control AGC voltage with the height gain control AGC curve voltage, if the gain controlled by the signal gain control AGC voltage is smaller than the gain controlled by the height gain control AGC curve voltage, outputting a signal gain control AGC voltage to control the sensitivity of the altimeter, otherwise, outputting the height gain control AGC curve voltage to control the sensitivity of the altimeter, and returning to the step (2).
The foregoing description is only an example of the present invention and is not intended to limit the invention, so that it will be apparent to those skilled in the art that various changes and modifications in form and detail may be made therein without departing from the spirit and scope of the invention, and these changes and modifications are within the scope of the appended claims.
Claims (6)
1. A height measurement method based on a pulse system radio altimeter is characterized by comprising the following steps:
(1) initializing and reading the residual height H of the altimeter with pulse systemAParameter, preset binary sampling accumulation threshold detection value K0Height gain control AGC curve voltage and initial pulse repetition period TiDelay time T of the tracking gate to be searched relative to the transmission trigger pulseGInitializing to zero, and controlling a tracking gate to search from zero height; simultaneously, controlling AGC curve voltage parameters according to altitude gain, outputting gain control AGC voltage, controlling the receiving sensitivity of a pulse system altimeter, and switching the working mode of the altimeter into a search mode;
(2) according to the initial pulse repetition period TiGenerating a new pulse repetition period TFAccording to the new pulse repetition period TFGenerating a radio frequency modulated trigger pulse T0Controlling the height of the pulse systemThe meter generates a radio frequency pulse signal and transmits the radio frequency pulse signal to the ground;
(3) the echo pulse signal output by the pulse system altimeter is filtered and amplified to generate a first video pulse signal P1Outputting, and generating a second video pulse signal P by denoising and blocking the first video pulse signal2Outputting;
(4) selecting a pure noise time sequence interval without echo signals, and carrying out comparison on the first path of video pulse signal P1Sampling, obtaining the average noise of the echo signal sampling circuit through accumulation and averaging, and accumulating the accumulated threshold detection value K according to the average noise and the preset binary sampling0Determining a tracking threshold value K;
(5) reading tracking gate relative emission trigger pulse signal T0Generating a relative emission trigger pulse delay tracking gate according to the delay time digital quantity, wherein the width of the tracking gate is 10ns, inputting the tracking gate into a range gate shift register with the width of 30 bits, the clock frequency of the range gate shift register is 100MHz, and respectively generating 30 adjacent range gates R with the height distance sequentially increased by the width of 10nsN；
(6) At a distance gate RNPosition-to-position first video pulse signal P10/1 quantization is performed, and the shift register SRM is accumulated by M bit pulseNReading the quantized result and then accumulating the pulse into the shift register SRMNValue of (SRQ)NCounting the number of bits of 1 to obtain M pulse repetition periods at a distance gate RNFirst path video pulse signal P sampled by position1The number of (2);
(7) according to the first video pulse signal P1Determine at the range gate RNWhether the position samples an echo signal:
if it is a distance gate RNFirst path of video pulse P sampled at M repeated cycles1When the number is larger than the tracking threshold K, the distance gate RNPosition tracking status signal STN1, in the range gate RNSampling the position to obtain a valid echo signal;
otherwise, STN0 denotes a range gate RNEcho signals are not sampled from the positions;
(8) based on the tracking state signal STNDoor R for judging distanceNAnd a distance gate RNM-bit pulse accumulation at location shift register SRMNThe direction of movement of the value;
if tracking status signal STNSatisfies the following conditions: ST (ST)N＝0,1<＝N<For distance gate R of 11NAnd a distance gate RNM-bit pulse accumulation at location shift register SRMNShifting the value to the right;
if tracking status signal STNSatisfies the following conditions: ST (ST)N1, N1, 2, … 10, for the range gate RNAnd a distance gate RNM-bit pulse accumulation at location shift register SRMNShifting the value to the left;
(9) will be at a distance from the door RNThe first video pulse P1 is coincided to generate a stop pulse T1;
(10) transmitting a trigger pulse T according to (2)0Leading edge and stop pulse T1The delay time between the leading edges is calculated by adopting a mathematical statistics method to calculate the average height H of 512 times2According to the residual height HAParameters, correcting the average height to obtain the true height HRAnd output to the pulse system altimeter;
(11) determining the working state of the altimeter, and outputting a gain control voltage according to the working state of the altimeter:
if all tracking state signals STNAre all zero, namely: ST (ST)N＝0,1<＝N<If not, the altimeter works in a tracking state;
if the altimeter works in a searching state, outputting a gain control AGC voltage according to the altitude gain control AGC curve, controlling the sensitivity of the altimeter, and returning to the step (2);
if the altimeter is operated in tracking mode, then at the range gate RNWithin range to the second path of video pulse P20/1 quantization, counting the quantized pulse of M repetition periods, counting the pulses according to the M repetition periodsThe digital generated signal gain controls AGC voltage and controls the second path of video pulse P2The output amplitude is equal to the sampling threshold value;
and (3) comparing the signal gain control AGC voltage with the height gain control AGC curve voltage, if the gain controlled by the signal gain control AGC voltage is smaller than the gain controlled by the height gain control AGC curve voltage, outputting a signal gain control AGC voltage to control the sensitivity of the altimeter, otherwise, outputting the height gain control AGC curve voltage to control the sensitivity of the altimeter, and returning to the step (2).
2. The method of claim 1, wherein step (8) is performed with respect to a range gate RNAnd a distance gate RNM-bit pulse accumulation at location shift register SRMNThe values are shifted to the right by the following steps:
(8.1) will track the delay time T of the gate relative to the trigger pulseGIncreasing one clock period Δ T, the right shift of the tracking gate is realized, i.e.:
TG＝TG+ΔT，TG<Tiif T isG＝TiThen, the right shift is not performed any more;
wherein T isiAn initial pulse repetition period defined for step 1;
due to the distance from the door RNIs synchronously generated by a tracking door, so that the distance door R is realized when the tracking door moves rightwardsNRight shift;
(8.2) will be apart from the door RNPosition M-bit pulse accumulation shift register SRMNValue of (SRQ)NTo the right, i.e. to accumulate the next M-bit pulse into the shift register SRMN+1Value of (SRQ)N+1SRM (sequence reference register) assigned to previous M-bit pulse accumulation shift registerNTo obtain each range gate RNPosition M-bit pulse accumulation shift register SRMNThe value of (c):
SRQ1＝SRQ2，
SRQ2＝SRQ3，
……
SRQN＝SRQN+1，
……
SRQ29＝SRQ30；
SRQ30＝0，
wherein, 1< ═ N < ═ 30;
3. the method of claim 1, wherein step (8) is performed with respect to a range gate RNAnd a distance gate RNM-bit pulse accumulation at location shift register SRMNThe values are shifted to the left by the following steps:
(8.3) will track the delay time T of the gate relative to the trigger pulseGReducing one clock period Δ T, a left shift of the tracking gate is achieved, i.e.: t isG＝TG-ΔT，TG>0; if TGIf the value is 0, the left shift is not performed any more;
due to the distance from the door RNIs synchronously generated by a tracking door, so that the distance door R is realized when the tracking door moves leftwardsNMoving left;
(8.4) will be apart from the door RNPosition M-bit pulse accumulation shift register SRMNIs left shifted, i.e. the previous M-bit pulse is accumulated in the shift register SRMN-1Value of (SRQ)N-1SRM (sequence reference register) assigned to the next M-bit pulse accumulation shift registerNTo obtain each range gate RNPosition M-bit pulse accumulation shift register SRMNThe value of (c):
SRQ30＝SRQ29；
SRQ29＝SRQ28；
……
SRQN＝SRQN-1；
……
SRQ2＝SRQ1；
SRQ1＝0；
wherein, 1< N < 30.
4. The method of claim 1, wherein the gate R is based on distance in step (9)NThe method is coincident with the first path of video pulse to generate a stop pulse, and comprises the following steps:
(9.1) put the 11 th range gate R11And a 12 th distance gate R12Phase-or-after-phase with the first video pulse P1Carrying out superposition;
(9.2) the result of the superposition is compared with the 13 th range gate R13Then phase-OR is carried out to obtain a stop pulse T1：
T1＝P1&(R11 or R12)or R13，
Wherein, P1For the first video pulse signal, R11Is the 11 th range gate, R12Is the 12 th range gate, R13Is the 13 th range gate, T1In order to stop the pulse, the pulse is stopped,&is an AND gate, or is an OR gate.
5. The method according to claim 1, wherein the step (10) of calculating the height by using a mathematical statistical method comprises the following steps of calculating 512 average heights:
(10.1) generating a trigger pulse T0Starts counting the counter until a stop pulse T is generated1Stopping counting, recording the number n of counting pulses of the counter during the period1The clock period of the counter is T, the frequency is f, and the delay time T of the echo pulse relative to the transmission pulse is calculatedH：
tH＝n1*T，
(10.2) according to the delay time tHAnd the propagation speed c of the electromagnetic wave to obtain the target height H of a single pulse1:
H1＝(c*tH)/2＝(c*n1)/(2f)；
(10.3) for stop pulse T1Dividing the frequency of the pulse by 512 times to generate a divided pulse TABy dividing the pulse TAReading the pulse number n of a counter with 512 pulse repetition periods2Meanwhile, the counter is cleared, and the average height H of 512 pulse repetition periods is calculated2：
H2＝(c*n2)/(2*f*512)。
6. The method of claim 1, wherein step (10) is performed according to a residual height HAThe parameters are corrected for the average height of 512 times, and the method comprises the following steps:
(10.4) calculating the residual height HA:
HA＝(c*tA)/2
Wherein, tATime delay is generated when a signal transmitted by the altimeter passes through a device and a cable, and c is the propagation speed of electromagnetic waves;
(10.5) calculating the true height HR：
HR＝H2-HA
Wherein H2Is the average height of 512 pulse repetition periods.
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