What is radar?

Question 1: What is radar? Radar is an electronic device that uses electromagnetic waves to find targets from a distance and determine their positions. Because of its fast target detection and all-weather work, it has been widely used in the fields of vigilance, guidance, weapon control, investigation, navigation support, meteorological observation, friend or foe identification and so on. Radar can be divided into warning radar guidance radar, weapon control radar, reconnaissance radar and navigation support radar. In addition, according to the different installation positions, radars can be divided into ground radars, airborne radars and shipborne radars.

Question 2: What is radar radar? This is a kind of radio equipment that uses radio waves to determine the position of objects.

Electromagnetic waves, like sound waves, will be reflected when encountering obstacles, and radar works by using this characteristic of electromagnetic waves. The shorter the wavelength of electromagnetic wave, the better the linearity of propagation and the stronger the reflection performance. Therefore, radar uses radio waves in the microwave band.

The radar has a special rotatable radio that can emit discontinuous radio waves in a certain direction. The time of each transmission is about one millionth of a second, and the time interval between two transmissions is about one millionth of a second. In this way, when the transmitted radio waves encounter obstacles, they can be reflected back and received wirelessly within this time interval.

According to the formula 2S=ct, the distance s of the obstacle can be determined, and then the position of the obstacle can be determined according to the direction and elevation angle of the emitted radio wave.

Radar can be used to detect planes, ships, missiles and other military targets. Besides military use, radar can also be used to navigate planes and ships in traffic, study stars in astronomy and detect typhoons, thunderstorms and dark clouds in meteorology. [

Question 3: What is a driving radar? Reversing radar:

A sensor is installed on the rear bumper of the vehicle to detect the distance between the objects behind the vehicle, and when the objects approach the vehicle, the driver will be reminded by a warning signal. The reversing radar is only an auxiliary safety device. When reversing, the driver must observe the situation behind the car, and the warning signal of the reversing radar will be different due to different obstacles.

Question 4: What is the working principle of radar? After the radar sends a signal, it will return when it meets an object. The echo signal received by the radar contains the distance information and speed information of the target, and even the angle of the target can be calculated according to the beam emitted by the radar. The landlord can look at the number of radar principles and understand the radar equation.

Question 5: What is radar? Radar was originally an English abbreviation for "radio detection and positioning". The basic task of radar is to detect the target of interest and measure the state parameters such as distance, direction and speed of the target. Radar is mainly composed of antenna, transmitter, receiver (including signal processor) and display. The radar transmitter generates enough electromagnetic energy and transmits it to the antenna through the transceiver switch. The antenna radiates these electromagnetic energies into the atmosphere, concentrates them in a narrow direction to form a beam and propagates forward. After the electromagnetic wave meets the target in the beam, it will reflect in all directions, and part of the electromagnetic energy will reflect back to the direction of the radar and be acquired by the radar antenna. The energy obtained by the antenna is sent to the receiver through the transceiver switch to form a radar echo signal. Because the electromagnetic wave will decay with the propagation distance, the radar echo signal is very weak and almost drowned by noise. The receiver amplifies the weak echo signal, which is processed by the signal processor to extract the information contained in the echo and send it to the display to show the distance, direction and speed of the target. In order to measure the distance of the target, the radar accurately measures the delay time from transmitting electromagnetic waves to receiving echoes. The delay time is the propagation time of electromagnetic wave from transmitter to target and then from target to radar receiver. According to the propagation speed of electromagnetic waves, the distance of the target can be determined as: S=CT/2, where S: the target distance T: the round-trip propagation time of electromagnetic waves from radar to target C: the light-speed radar uses microwaves.

Question 6: What is radar? 5-point radar is an electronic device that uses electromagnetic waves to detect targets. The emitted electromagnetic wave irradiates the target and receives its echo, so as to obtain information such as the distance from the target to the electromagnetic wave emission point, the rate of change of distance (radial speed), azimuth, altitude, etc.

Radar functions like eyes and ears. Of course, it is no longer a masterpiece of nature, and its information carrier is radio waves. In fact, visible light and radio waves are essentially the same thing, both electromagnetic waves, and their propagation speed is C. The difference between radar is that they occupy different frequencies and wavelengths. Its principle is that the transmitter of radar equipment emits electromagnetic wave energy to a certain direction in space through an antenna, and the object in this direction reflects the electromagnetic wave it encounters; The radar antenna receives this reflected wave and sends it to the receiving equipment for processing, and extracts some information about the object (the distance from the target object to the radar, the change rate of distance or radial speed, azimuth, altitude, etc.). ).

Measuring the distance is actually measuring the time difference between the transmitted pulse and the echo pulse. Since electromagnetic waves travel at the speed of light, they can be converted into the exact distance of the target.

Measuring the target azimuth is a sharp azimuth beam measurement using an antenna. Narrow elevation beam measurement. According to the elevation and distance, the target height can be calculated.

Velocity measurement is the principle that radar produces frequency Doppler effect according to its relative motion with the target. The target echo frequency received by radar is different from the radar transmission frequency, and the difference between them is called Doppler frequency. One of the main information that can be extracted from Doppler frequency is the range change rate between radar and target. When the target and jamming clutter exist in the same spatial resolution unit of the radar, the radar can detect and track the target from the jamming clutter by using the difference of their Doppler frequencies.

The advantage of radar is that it can detect long-distance targets day and night, and it is not blocked by fog, clouds and rain. It has the characteristics of all-weather and all-day, and has certain penetration ability. Therefore, it is not only an indispensable military electronic equipment, but also widely used in social and economic development (such as weather forecast, resource exploration, environmental monitoring, etc.). ) and scientific research (celestial research, atmospheric physics, ionospheric structure research, etc. Spaceborne and airborne synthetic aperture radars have become very important sensors in remote sensing. A radar targeting the ground can detect the precise shape of the ground. Its spatial resolution can reach several meters to tens of meters, and it has nothing to do with distance. Radar has shown good application potential in flood monitoring, sea ice monitoring, soil moisture measurement, forest resources survey, geological survey and so on.

Types of radar: (1) According to the types of radiation sources, it can be divided into active radar and passive radar. (2) According to the platform, it can be divided into: ground radar, shipborne radar, airborne radar, spaceborne radar, etc. (3) According to the waveform, it can be divided into pulse radar and continuous wave radar. (4) According to the working band, it can be divided into meter wave radar, decimeter wave radar, centimeter wave radar and millimeter wave radar. (5) It can be divided into surveillance radar, search radar, fire control radar, guidance radar, weather radar and navigation radar. (6) According to the scanning mode, it can be divided into mechanical scanning radar and electric scanning radar. Electric scanning radar refers to a radar using an electric scanning antenna. The typical method is to control the feed phase of antenna elements to achieve the purpose of flexible and controllable beam pointing, also known as phased array radar, which is an important development direction of radar in the future.

Question 7: What is the radar system istis.sh/list/list.asp?? ? Id = 1068 According to the waveform, radar can be divided into two categories: pulse radar and continuous wave radar. At present, the most commonly used radar is pulse radar. Traditional pulse radar periodically emits high-frequency pulses. Relevant parameters are pulse repetition period (pulse repetition frequency), pulse width and carrier frequency. Carrier frequency is the high-frequency oscillation frequency of a signal within a pulse, which is also called the working frequency of radar. The ability of radar antenna to concentrate electromagnetic energy in this direction is described by beam width. The narrower the beam, the better the directivity of the antenna. However, in the process of design and manufacture, it is impossible for radar antenna to concentrate all energy in the ideal beam, and there is energy leakage in other directions. The energy is concentrated in the main beam, which is usually called the main lobe visually, while the sidelobe is formed by leakage in other directions. In order to cover a wide space, it is necessary to scan the radar beam in the detection area by mechanical rotation or electronic control of the antenna. To sum up, the technical parameters of radar mainly include working frequency (wavelength), pulse repetition frequency, pulse width, transmission power, antenna beam width, antenna beam scanning mode, receiver sensitivity and so on. The technical parameters are selected and designed according to the tactical performance and index requirements of the radar, and their values reflect the functions of the radar to some extent. For example, in order to improve the detection ability of long-range targets, early warning radar uses relatively low operating frequency and pulse repetition frequency, while airborne radar uses relatively high operating frequency and pulse repetition frequency for the purpose of reducing volume and weight. This shows that if we know the technical parameters of radar, we can identify the type of radar to some extent. Radar is widely used and its classification method is very complicated. Generally speaking, radars can be classified according to their uses, such as early warning radar, search and warning radar, radio altimetry radar, weather radar, air traffic control radar, guidance radar, artillery aiming radar, radar fuze, battlefield surveillance radar, airborne interception radar, navigation radar, anti-collision and IFF radar, etc. In addition to its use, radar can also be distinguished from the working system. Some new radar systems are briefly introduced here. (To sum up, the technical parameters of radar mainly include working frequency (wavelength), pulse repetition frequency, pulse width, transmission power, antenna beam width, antenna beam scanning mode, receiver sensitivity, etc. The technical parameters are selected and designed according to the tactical performance and index requirements of the radar, and their values reflect the functions of the radar to some extent. For example, in order to improve the detection ability of long-range targets, early warning radar uses relatively low operating frequency and pulse repetition frequency, while airborne radar uses relatively high operating frequency and pulse repetition frequency for the purpose of reducing volume and weight. This shows that if we know the technical parameters of radar, we can identify the type of radar to some extent. Radar is widely used and its classification method is very complicated. Generally speaking, radars can be classified according to their uses, such as early warning radar, search and warning radar, radio altimetry radar, weather radar, air traffic control radar, guidance radar, artillery aiming radar, radar fuze, battlefield surveillance radar, airborne interception radar, navigation radar, anti-collision and IFF radar, etc. In addition to its use, radar can also be distinguished from the working system. Some new radar systems are briefly introduced here. (Military observation? Warii) Bistatic/Multistatic Radar The transmitter and receiver of ordinary radar are installed in the same place, while the transmitter and receiver of bistatic/multistatic radar are installed in two or more places far apart, which can be located on the ground, air platform or space platform. Because the shape design of stealth aircraft is mainly to prevent the incident radar wave from directly reflecting back to the radar, it is very effective for monostatic radar. However, incident radar waves will be reflected in all directions, and in bistatic/multistatic radar, some reflected waves will always be received by one receiver. The U.S. Department of Defense has been developing and testing bistatic/multistatic radars since 1970s. The famous "Temple" project is specially designed for the research of bistatic radar, and the receiver and transmitter have been completed. & gt

Question 8: What does radar mean? Electronic equipment that uses electromagnetic waves to detect targets.

The emitted electromagnetic wave irradiates the target and receives the echo reflected by the target, so as to obtain the information such as the distance from the target to the electromagnetic wave emission point and the change rate of the distance (radial speed, azimuth, height, etc.). ).