1. High-tech ammunition

The so-called high-tech ammunition refers to the use of terminal sensitive projectile technology, terminal guidance technology, trajectory correction technology and so on. , with a certain target detection function.

2. Three strikes and three defenses

The so-called "three strikes" refers to hitting armed helicopters, cruise missiles and stealth aircraft.

"Three defenses" refers to anti-reconnaissance, anti-electronic interference and anti-precision strike.

3. The principle of intelligent mine bombs

It uses acoustic sensors to detect the noise generated by helicopter propellers around 1000m m, and once this signal is analyzed, lightning locks its frequency. When the signal or noise increases to a certain extent, the second detection system (infrared or ground motion starts) works. It can detect the approaching distance of the helicopter or be sensitive to the atmospheric pressure change caused by the descending airflow of the helicopter propeller. Once a predetermined distance or pressure change is reached, lightning can be ejected to a certain height and explode, damaging the helicopter.

4. Intelligent precision guided weapons have two key core technologies.

One is the sensitive technology of millimeter wave or infrared detection with high resolution and sensitivity, and the other is the technology of information processing and identification.

Second, the target characteristics

1. The main characteristics of tanks are shown in three aspects.

Infrared radiation characteristics, sound propagation characteristics and ground vibration characteristics generated during driving.

2. Infrared atmospheric window

In 0.72~ 14? There are 8 atmospheric windows in the m wavelength range.

There are four kinds of infrared radiation sources on a jet plane.

As the hot metal cavity of the engine combustion chamber, the exhausted hot gas, the self-radiation of the aircraft shell surface and the environmental radiation (including the radiation of sunlight, atmosphere and the earth) reflected by the aircraft surface.

4. The skin radiation is between 8~ 14? M accounts for an important proportion.

1. The peak wavelength of skin radiation (for example, its temperature is 80K) is about 10? M, just at 8~ 14? In the m-band range; Second, the width of this band is wide; Thirdly, the area of aircraft skin is very large, and its radiation area is many times larger than that of nozzle.

5. The advantages of armed helicopters are strong maneuverability and protection, low requirements for landing sites and strong battlefield application ability.

6. Acoustic detection technology uses the sound waves emitted or reflected by the target to measure it, and then identifies, locates and tracks it.

7. Bending propagation of sound: Because of the great temperature difference at different heights in the air and the different propagation speed of sound at different heights, the sound at high altitude is constantly refracted when it propagates to the microphone. The refraction angle of its curvature radius is related to the increase of sound velocity in the atmosphere. If the speed of sound increases with height, the sound waves will be refracted downwards, and vice versa, which is the curve propagation phenomenon of sound.

8. Microphone array can be divided into linear array, area array and stereo array. An array of n microphones can obtain N- 1 independent time delays.

9. Generalized correlation method is to add a generalized weight function to the frequency domain of cross-correlation function method.

10. Sound pressure, sound intensity and sound intensity level

① Sound is longitudinal wave, and its propagation causes the change of air density, thus causing the change of air pressure. The difference between pressure and atmospheric pressure is sound pressure p.

(2) Sound intensity I is the average rate of change of the energy of sound waves propagating in a unit area perpendicular to the propagation direction with time, that is, the average power propagating in a unit area.

(3) Sound intensity level of sound wave β=20㏒P/P0.

1 1. The influence of sound propagation speed, temperature and humidity.

In the process of sound propagation, the speed of sound is related to the temperature of the medium.

Attenuation of sound waves in air

The acoustic energy e received by the sensor decays exponentially.

13 Doppler effect

When the sound source or both are heard moving relative to the air, the tone (i.e. frequency) heard by the listener is usually different from that heard by the sound source and the listener when they are stationary.

14. Realize the target positioning

Generally, there are three ways: guiding cylinders, synthesizing patterns, and using geometric relations.

15. Microphone array

Microphone array can be divided into line array, plane array and stereo array.

16. ternary linear array

The ternary linear sensor array can not only be oriented, but also be fixed in distance.

Fixed distance formula:

cosφ=(D2-d 1)/2L r = lsin 2φ/(D2-d 1)

17. The most typical post-processing method is Kalman filter.

18. Kalman filter is an ideal least squares recursive estimator.

Third, the ground motion detection technology

1. Seismic wave classification

Body wave and surface wave.

2. Composition of ground motion signal detection system

Ground motion sensor → signal pre-amplification processing circuit → automatic gain amplification → 12 bit A/D converter → computer memory.

3. The structure and working principle of the magnetoelectric speed sensor.

Magnetoelectric sensor is a kind of sensor that can convert the change of non-electric quantity (such as mechanical energy) into induced electromotive force.

4. Sensitivity K of sensor

K=e/V=ωdBdL0

Fourthly, laser detection technology.

1. Characteristics of laser

Strong directionality, good monochromaticity, good coherence and high brightness.

2. Special requirements of laser proximity fuze

① Short-range and ultra-short-range detection.

② Only a single point "ranging" is needed, and a large spatial range "ranging" is not needed.

③ Small size and low power consumption.

④ High overload environment.

⑤ There is high-speed motion between the missile and the target.

3. Pulse phase discrimination and ranging system

(1) principle:

The laser pulse power supply excites the pulsed semiconductor laser to emit light pulses, which are collimated by the optical system and irradiated to the target surface. After the reflected light is received by the proximity optical system, a part of it is focused on the photosensitive surface of the detector, and an electric pulse signal is output, which is amplified and shaped and sent to the pulse phase detector. In addition, while the laser pulse power supply excites the semiconductor laser, the excitation signal is appropriately delayed by the delay device and sent to the pulse phase detector, which is used as a reference pulse and an echo pulse for leading-edge phase comparison, and the leading edges of the two pulses coincide, that is, when the target is at a predetermined distance, the initial signal is given.

② Features:

High precision, small loss of leading-edge phase information, simple and flexible structure, good anti-interference and low false alarm rate.

4. Pseudo-random coded distance system

5. Main functions of transmitting and receiving optical system

(1) By adjusting the laser beam, the emission optical system makes the final emitted beam have a specific field of view, which is beneficial to complete the function of the system.

(2) Using an optical receiving system with a larger photosensitive area than the photoelectric sensor, most of the light emitted by the target is collected and concentrated on the optical detector, which greatly improves the sensitivity of the fuze.

6. The influence of laser pulse waveform quality on laser fuze is shown in the following aspects.

① The energy utilization ratio of large pulse width signal is much lower than that of small pulse width signal.

② The waveform quality of laser pulse, especially the rising time of pulse front, plays a decisive role in the ranging accuracy of pulse laser fuze.

③ It is of great significance to determine the appropriate pulse repetition frequency to reduce the system power consumption and the practical application of laser ranging technology in fuze.

④ The anti-backscattering interference characteristics of laser fuze are related to the laser pulse width. The smaller the pulse width, the stronger the anti-backscattering interference ability.

7. What method does the phase detector consist of?

① 74S74 D flip-flop

② Ultra-high speed comparator

Verb (abbreviation of verb) capacitance detection technology

1. Understand the essence of capacitance detection technology.

Capacitance detection technology is to use the appearance of the detected object to cause the change of capacitor capacitance, and realize the detection of the object by detecting the capacitance value or its change rate, which belongs to the non-contact measurement range.

2. Advantages and disadvantages of capacitance detection technology

Capacitance detection has the advantages of simple structure, non-contact measurement, high ranging accuracy and strong anti-interference ability, but its disadvantages are short detection distance and nonlinear error.

3. The expression and significance of capacitance in capacitive sensing.

C=ε0εrS∕d=εS∕d

4. Capacitance detection principle

The electrode and detection circuit of the detector are designed to detect the change of capacitance caused by the appearance of the detected object, so that the characteristics of the circuit change, thus realizing the detection of the detected object.

5. Derivation of capacitance detection formula in two-electrode mode

6. Three-electrode capacitance detection principle

The three-electrode capacitance detector itself has three electrodes, and when the target appears, a capacitance network is formed between the three electrodes. As the projectile approaches the target, the parameters of the capacitance network will change, and the short-range detection of the target can be realized by detecting the network parameters.

7. Processing circuit for capacitance detection

The capacitance detection and processing circuit extracts the variation of capacitance δ с and converts it into voltage or current signal.

8. Application and working principle of capacitance detection in proximity fuze

Capacitive proximity fuze uses a detector to establish a quasi-electrostatic field in the space around the electrode. When the fuze approaches the target, the electric field will be disturbed and the charge will be redistributed, thus changing the equivalent capacitance between the electrodes of the fuze-extracting the voltage change through signal formation to realize the detection of the target.

Six, millimeter wave detection technology

1. The characteristics of millimeter wave and its application principle in detection are expounded.

1 mm band is extremely wide, 2 mm beam is narrow, directivity is good, and resolution is extremely high.

High Doppler frequency, high measurement accuracy and low noise.

2. Understand the influence of millimeter wave propagation of atmospheric team.

The influence of the atmosphere on millimeter wave propagation includes the absorption, scattering and refraction of millimeter waves by the atmosphere, in which the absorption is often formed by the transition of electrons in molecules, and various particles in the atmosphere can scatter or refract electromagnetic waves.

3. Understand the components of millimeter wave radiation equation.

4. Millimeter wave temperature model and the influence of various factors on the temperature model.

5. The principle of millimeter wave detection of metal targets.

The radiation characteristics of various substances in nature are different. At the same physical temperature, the radiation temperature of high conductivity materials is lower than that of low conductivity materials. For a smooth surface with ideal conductivity, its reflectivity is close to 1, which is independent of incident angle and polarization. Without Yun Tiankong, it can be considered that the emissivity is small and the reflectivity is high. These differences can be used for identification.

6. Understand the distance equation of millimeter wave radiometer and the influence of multiple factors.

r=[ηaaδt∕ωaδtmin]

The detection distance is directly related to the working frequency of the antenna diameter. The antenna diameter increases. Increase the action distance

The detection distance is proportional to the fourth square root of IF amplifier bandwidth.

The detection distance is inversely proportional to the square root of the receiver noise number.

The detection distance is inversely proportional to the fourth root of the signal-to-noise ratio in the output bandwidth.

7. Master the type and working principle of millimeter wave radiometer.

The most typical radiometers are full power radiometer and Dick comparison radiometer.

Millimeter wave radiometer uses the millimeter wave radiation difference between ground target and background to detect and identify targets. Millimeter wave is essentially a high-sensitivity receiver, which is used to receive millimeter wave radiation energy from targets and backgrounds.

8. Understand the typical millimeter wave detection system.

Millimeter wave radar: mixer → IF amplifier → video detector → video amplifier → signal processor.

↑ ↑ ↓

Transmitter/local oscillator ignition control signal

Millimeter wave radiometer: → IF amplifier → filter → detector.

↑ ↓

Local oscillator video amplifier

↓

Ignition control signal/signal processor

Seven, detection technology

1. Generation principle of infrared radiation and its distribution in electromagnetic spectrum

The movement of matter is the source of infrared rays.

2. Master the similarities and differences between infrared radiation and visible light.

Infrared rays are not sensitive to human eyes, so they must be received by infrared detectors sensitive to infrared rays.

The quantum energy of infrared light is less than that of visible light.

The thermal effect of infrared light is much stronger than that of visible light.

Infrared rays are more easily absorbed by substances, but for mist, long-wave infrared rays are easier to pass through.

3. Grasp the band distribution of infrared radiation

The near infrared wavelength range is 0.75~3 NIR.

Mid-infrared 3~6 MIR far infrared 6~ 15 FIR far infrared 15~ 1000 XIR

4. The research significance of infrared detection technology.

Based on infrared physics, infrared detection studies and analyzes the characteristics and laws of the generation, transmission and detection of infrared radiation, providing theoretical and experimental basis for detecting and identifying the targets that generate infrared radiation.

5. Understand the concepts of radiometry, radiant energy, radiant energy flux, radiant energy intensity, emissivity and irradiance.

Generally, the energy emitted, transmitted or received in the form of electromagnetic waves is called radiant energy.

The radiant energy flux is the radiant energy passing through a certain area in unit time.

The radiant energy flux emitted by a point radiation source in a unit solid angle in a certain direction is called radiation intensity.

Expand the radiant energy flux emitted by the light source in a certain direction from the unit projection area a to the unit solid angle θ.

Radiant energy flux received per unit area of illuminated object surface.

6. Understand the basic law of infrared radiation and Kirchhoff's law.

Kirchhoff's Law Planck's Formula Wien's Displacement Law Stephen Boltzmann's Law

Under the condition of thermal balance, the ratio of emission capacity to absorption capacity of all objects at a given temperature has nothing to do with the properties of the objects themselves, and is constant for all objects.

7. Infrared detection principle

Working principle of thermal detector: Infrared radiation irradiates the sensitive surface of the detector, which makes its temperature rise and some physical properties change. By measuring them, the incident radiation power can be determined.

Photon detector: When infrared radiation is absorbed, the electronic state of the material on the sensitive surface of the detector changes, resulting in photon effect. By measuring these effects, the power of the incident radiation can be determined.

8. Master the efficacy and function of infrared detectors.

9. Composition and classification of infrared detectors

A complete infrared detector includes an infrared sensitive element, an infrared radiation incident window, a housing, electrode leads, an aperture, a cold screen, a field mirror, a light cone, an immersion lens, a filter and the like. It also includes a dewar bottle and some preamplifiers working at low temperature. According to the working mechanism of detectors, infrared detectors can be divided into thermal detectors and photon detectors.

10. Similarities and differences, advantages and disadvantages of thermal detectors and photon detectors

The main advantages of thermal detector are wide response band, working at room temperature and easy to use. Thermal detectors generally do not need refrigeration, so they are convenient to use, simple to maintain and reliable. The spectral response is independent of wavelength, and it is a non-selective detector with simple preparation process and low cost. Disadvantages: long response time and low sensitivity.

The disadvantages of photon detector are high sensitivity, fast response speed and high response frequency. It works at low temperature and has a narrow detection band.

1 1. Performance comparison between thermal detector and photon detector

12. Influencing factors of infrared detector performance

1 response rate 2 noise voltage 3 noise equivalent power 4 detection rate 5 spectral response 6 response time 7 frequency response

13. characteristics that determine infrared detection capability

Radiation source temperature, modulation frequency and amplifier bandwidth.

14. Principles for the use and selection of infrared detectors

1 Select the response band of the detector according to the spectral range of the target radiation; 2. Determine the detection rate and response rate of the detector according to the temperature resolution of the system; 3. Determine the response time of the detector according to the requirements of the scanning rate of the system; 4. According to the requirements of the spatial resolution of the system and the focal length of the optical system, the acceptance area of the detector is determined.

15. Understand the working principle of typical infrared detection system.

16. Working principle of thermal detector

Eight, target recognition technology

1. Flow chart and working process of target identification

Sensor array → signal acquisition → feature extraction and feature selection → classification and identification → output results.

The first two are target detection, and the last two are target recognition.

2. Basic concepts of target recognition, such as pattern and pattern recognition.

Target recognition is a process that human beings analyze, describe and judge various things or phenomena.

We should scientifically abstract the classified recognition object and establish its mathematical model to describe and replace the recognition object. We call the description of this object a pattern.

Pattern recognition refers to using a computer-centered machine system with a certain analysis algorithm to identify the category of the research object according to the characteristics or attributes of the research object, and the system should make the results of classification and recognition conform to the real situation as much as possible.

3. Block diagram and principle description of pattern recognition system (such as license plate recognition)

Object to be recognized → data acquisition and preprocessing → feature extraction and selection → classification and recognition → recognition results.

Input the two-dimensional image of the license plate sample into the computer, represent the two-dimensional image by matrix or vector through measurement, sampling and quantization, remove noise, strengthen useful information, transform the original data caused by measuring instruments or other factors, get the features that best reflect the essence of classification, and then test the accuracy. Constantly correct mistakes and improve deficiencies, so that the correct rate of license plate recognition meets the design requirements.

4. Basic tasks of feature extraction and selection

The basic task of feature extraction and selection is how to find the most effective feature from many features.

5. Why do you want to extract and select the features of the target?

The quality of feature extraction and selection greatly affects the design and performance of classifier, which should be paid enough attention to.

6. Feature classification

Physical structure mathematics

7. Process and steps of feature extraction and selection

1 feature formation. According to the identified objects, a set of basic features is generated, which can be measured by instruments or sensors.

2 feature extraction. The sample is in a high-dimensional space, and we can express the sample in a low-dimensional space by mapping or transformation.

3 feature selection. Select some of the most effective features from a set of features to reduce the dimension of feature space.

8. Basic methods of feature extraction and selection

1 When the number of features d used for classification and recognition is given, D features x 1, x2…xd are directly selected from the obtained N original features so that the value of separability criterion J satisfies J(x 1, X2 … XD) = Max [J (XI 1, xi2 .. xid. This is the direct method, and the main branches are BAB method, SFS method, GSFS method, SBS method and GSBS method.

2. Under the condition of maximization criterion J, transform the N original features to reduce dimensions, that is, transform the coordinates of the original N-dimensional feature space, and then take the subspace.

9. What types of pattern recognition include?

1 statistical pattern recognition 2 syntactic structure pattern recognition 3 neural network pattern recognition 4 fuzzy pattern recognition 5 data fusion recognition technology

10. Understanding Minimum Error Bayesian Decision and Its Application

In order to reduce the error rate of classification, Bayesian estimation based on minimum error rate is proposed by applying Bayesian formula from the perspective of probability theory.

1 1. Steps, advantages and disadvantages of Bayesian decision-making

At step 1, predictive analysis is performed to determine whether it is worth searching for this information.

Search data, scientific experiments, research, statistical analysis, and obtain experimental probability.

3 Calculate posterior probability with Bayesian formula

4. Determine the decision-making scheme of judgment.

Advantages 1 scientific analysis method is adopted to reduce subjective influence.

It is more objective to make statistical analysis of the survey results and adopt quantitative means.

3 Combination of subjective and objective investigation.

Prior knowledge can be continuously updated, and it can be an adaptive decision-making system with continuous learning.

What is data fusion technology?

The data and information from many sensors and information sources are combined, correlated and combined to obtain accurate position estimation and identity estimation, as well as battlefield situation and threat, and their importance, and the evaluation levels are regularly divided: decision-making and fusion, feature-level fusion and data-level fusion.

13. Block diagram and description of data fusion identification

Objective → sensor 1→ special → identification → shutdown → feature-based identity fusion.

The reasoning of → sensor 2→ sign → recognition is based on recognition model → physical model → fusion recognition.

Mention ↓

Tag → sensor 3→ access → identification → connection → target document: database of known targets.

14. Hierarchy and interpretation of data fusion

Data fusion includes decision-level fusion, feature-level fusion and data-level fusion.

1 Decision-level fusion: In the decision-level fusion method, each sensor completes the transformation to obtain independent identity estimation, and then fuses the attribute classification from each sensor.

2 Feature level fusion: each sensor observes a target and completes feature extraction to obtain feature vectors from each sensor, then fuses these feature vectors and generates identity estimation based on joint feature vectors.

Data level fusion: the original data from the same level of sensors are directly fused, and then the logo is extracted and the identity is estimated according to the fused sensor data.

Specific theme

1. the essence of capacitance sensor

The detection of the target is realized by detecting the capacitance value or its change rate.

2. The difference and classification of capacitance detection and processing circuits.

According to the different detection and processing circuits, there are generally two-electrode and three-electrode detection methods.

Electromagnetic wave is a frequency band between microwave and light wave.

4. Types of capacitive sensors

Variable gap type, variable area type and variable medium type.

5. Influence factors of atmosphere on millimeter wave radiometer

In a clear atmosphere, the influence of the atmosphere on millimeter wave propagation includes the absorption, scattering and refraction of millimeter waves by the atmosphere.

6. The nature of infrared radiation

The physical essence of infrared radiation is thermal radiation.

7. The basic theory of infrared technology.

The theoretical basis of infrared technology is Planck's law describing thermal radiation.

8. Classification of infrared detectors

According to the working mechanism of detectors, infrared detectors can be divided into two categories: thermal detectors and photon detectors.

9. Types of photon detectors

According to the working principle, photon detectors can be generally divided into two types: external photodetectors and built-in photodetectors.

10. The core of target recognition technology

Target recognition is a process that human beings analyze, describe and judge various things or phenomena.

1 1. Basic tasks of signal feature extraction and selection

Levels and Classification of Data Fusion

① Decision-level fusion

② Feature level fusion

③ Data level fusion

13 radiation intensity

Radiation intensity is used to describe the spatial distribution characteristics of radiant energy flux emitted by point radiation sources. It is defined as the radiant energy flux emitted by a point radiation source in a unit solid angle in a certain direction.

14. Thermal effect

The phenomenon that an object absorbs radiation and changes its temperature, thus causing corresponding changes in its physical and mechanical properties is called thermal effect.

15. blackbody radiation

Black body means that the incident electromagnetic wave is completely absorbed, neither reflected nor transmitted.

Basic concepts of pattern recognition.

The so-called pattern recognition means that the computer-centered machine system uses certain analysis algorithms to identify the categories of the research objects according to their characteristics or attributes, and the system should make the results of classification and recognition conform to the real situation as much as possible.

17. Data fusion technology

Data and information from many sensors (homogeneous or heterogeneous) and information sources are integrated, correlated and combined to obtain accurate position estimation, identity estimation and timely evaluation of battlefield situation and threats and their importance.

65438+

Its principle is to design the electrode and detection circuit of the detector to detect the change of capacitance caused by the appearance of the detected object, so as to change the characteristics of the circuit and realize the detection of the detected object.

19. Capacitance change of double-electrode capacitance detection

Total capacitance c = c12+c10c20/(c10+C20)

When the target is far away from the detector, it can be C 10, C 12≈0, C=C 12.

When the target enters the sensitive area of the detector, C 10 and C20 gradually increase.

Let δ c = c10c20/(c10+C20), then c = c12+δ c.

By detecting the increment or growth rate of δC, the distance to the target can be obtained.

20. Using radiation differences to identify metal targets

The radiation characteristics of various substances in nature are different. Generally speaking, substances with relatively high dielectric constant have lower emissivity and higher reflectivity. Under the same physical humidity, the radiation temperature of high conductive materials is lower than that of low conductive materials. These differences can be used to identify different targets.

Working principle of 2 1. Millimeter radiometer

Millimeter wave radiometer uses the millimeter wave radiation difference between ground target and background to detect and identify targets. When the radiometer beam scans between the ground background and the target, the radiometer outputs a bell-shaped pulse because the millimeter wave radiation temperature of the target and the background is different, and the existence of the ground target can be identified by using the characteristics such as the height and width of this pulse.

22. Similarities and differences between infrared and visible light

(1) infrared ray is insensitive to human eyes;

② The quantum energy of infrared light is less than that of visible light;

③ The thermal effect of infrared ray is much stronger than that of visible light;

(4) Infrared rays are more easily absorbed by substances, but for mist, long-wave infrared rays are easier to pass through.

23. The main task of infrared detector

Convert infrared radiation energy into electric energy.

24. The working principle of temperature detector

The incident infrared radiation is used to cause the temperature change of the sensitive element, and then the related physical parameters or performance are changed accordingly.

25. The working principle of photon detector

Some semiconductor materials are irradiated by infrared radiation to produce photon effect, which changes the electrical properties of materials.

26. Taking license plate recognition as an example, the block diagram of pattern recognition and the principle of each part are explained.

Object to be recognized → data acquisition and preprocessing → feature extraction and selection → classification and recognition → recognition results.

The license plate is the object to be recognized, and the camera collects the data of the license plate. After preprocessing, noise is removed and effective information is recovered. In order to classify and recognize effectively, we transform the pattern represented in high-dimensional metric space into the pattern represented in low-dimensional feature space.

27. Target feature extraction and selection process steps

(1) When the number of features actually used for classification and recognition is given, the d features X 1, X2, ..., XD are directly selected from the n original features that have been obtained, so that the value of the classifiable data j satisfies the following formula.

J(x 1，x2，…，xd)=max[J(x 1，x2，…，xd)]

In the formula, xi 1, xi2, ..., xid are any d features of n original features, that is, the d-dimensional subspace can be directly found in the n-dimensional feature space. This method is called direct method.

(2) Under the condition of maximizing criterion J, the dimensionality of n original features is reduced by transformation, that is, the original N-dimensional feature space is transformed to the left, and then the subspace is taken. This method is called transformation.

28. Apply Bayesian minimum error estimation to make decisions.

(1) First, analyze the prognosis and decide whether it is worth collecting this information.

② Collect data, conduct scientific experiments, investigate and analyze, and get the experimental probability.

③ Calculate posterior probability with Bayesian formula.

(4) Determine the decision-making scheme of discrimination.