"The so-called millimeter wave is a paragraph in radio waves, and we call electromagnetic wavelengths of 1 to 10 mm, which is located in the wavelength range overlapping the microwave and far-infrared wave, and thus the characteristics of two spectrum. Mm The theory and techniques are the development of microwave to high frequency and the development of optical wave to low frequency.
The so-called millimeter wave is a paragraph in radio waves, and we call a wavelength of 1 to 10 mm, which is located in the wavelength range of microwave and far-infrared wave, thereby compatible with two spectrum characteristics. The theory and techniques of millimeter waves are the development of microwave to high frequency and the development of light wavelet low frequency. Be
The so-called millimeter wave radar means the radar of the working frequency section in the millimeter wave band, the genital ranging principle is like general radar, that is, the radio wave (radar wave) is sent, and then the echo is received according to the time difference between the delivery. The location data of the target. The millimeter wave radar is the frequency of this radio wave is a millimeter wave band. Since the wavelength of millimeter waves is between centimeter and optical waves, the advantages of millimeter waves and microwave guidance and photoelectric guidance are therefore. Compared with the same cm waveguide header, the millimeter waveguide head has a small size, high quality and high spatial resolution. Compared to optical guides such as infrared, laser, TV, millimeter waveguide leads to fog, smoke, dust, and has the characteristics of all-day (except heavy rain days). In addition, the anti-interference of the millimeter waveguide header is superior to other microwave guide. Millimeter wave radar is a high-precision sensor that measures the relative distance of the measuring object, the speed, orientation of high-precision sensors, early usage to the military field, with the development and progress of radar technology, the millimeter wavelet sensor began to apply in automotive electronics, drone , Intelligent transportation and other areas. Temporal characteristics of millimeter wave radar
1. The band is extremely wide, and the bandwidth can be used in the two atmospheres, and the bandwidth is 16G and 23G, and various broadband signal processing can be used in the two atmospheres.
2, can get a narrow beam in a small antenna aperture, good direction, high spatial resolution, high tracking accuracy;
3, there is a high Doppler bandwidth, Doppler effect is obvious, with good Doppler resolution, high speed accuracy;
4, the ground clutter and multipath effect have little effect, good tracking performance;
5, millimeter wave scattering characteristics are sensitive to the detail of the target shape, and thus improve the ability to distinguish between multi-objective resolution and the ability to identify the target and imaging quality;
6. Because the millimeter wavelet is transmitted with a narrow beam, it has low intercept performance, anti-electronic interference performance;
7, millimeter wave radar has a certain anti-stick function.
8, millimeter wave has the ability to penetrate smoke, dust and fog, and work all day. The advantageous precision of millimeter radar ranging is high-resistant interference with the microwave guide header, the millimeter waveguide head has a small size, high quality and high spatial resolution. In the case where the antenna diameter is the same, millimeter wave radar has a narrower beam (generally a millimetric order), which improves the angular resolution of the radar, and facilitates anti-electron interference, clutter interference and multiplies. Reflective interference, etc. Compared with infrared, video, laser and other optical guide heads all day, the millimeter waveguide heads are strong, and the smoke and dust are strong, with the characteristics of all-day all day. High-resoluled multi-objective due to high operating frequency, large signal bandwidth (such as Ghth magnitude) and Doppler frequency shift, which facilitates improving distance and speed measurement accuracy and resolution capability and analyzing the target details. At the same time, millimeter radar can distinguish a small target, and can simultaneously identify multiple targets, so there is a strong spatial resolution and imaging capabilities. Sensitive is highly sensitive and low system, and the error is low, and it is not easy to interfere with external electromagnetic noise. High frequency low power has higher emission frequencies, lower transmit power. The speedable speed can be measured by FMCW FM, and multiple target distances and speeds can be measured simultaneously, and can be tracked for targets, and even reactive targets can be kept. The distance from the distance is far from the distance, reaching two-way 12 lanes 200 meters long, while the detection frequency of 38Hz 26ms has strong real-time. The working principle of millimeter wave radar is taken as an example, and the radar transmits millimeters through the antenna, receives the target reflection signal. Fast and accurately obtain physical environment information around the car body after the rear process (such as the car and other objects. The relative distance, relative speed, angle, motion direction, etc.), and then performs target tracking and identification classification according to the detected object information, and then combines the body dynamic information to perform data fusion, ultimately intelligent through the central processing unit (ECU). After determination, it is informed or warned the driver in a variety of ways such as sound, light and haptic, or to make active interventions to the car in time, thereby ensuring the safety and comfort of the driving process, and reducing the chance of accidents. Be
Be
In the automotive safety field, the car millimeter wave radar sensor is one of the core components, of which 77GHz millimeter radar is an indispensable key component in smart cars, which is a rapid perception of 0-200 meters in the range of 0-200 meters. Sensing device for information such as distance, speed, azimuth. The position millimeter wave radar emits the directional millimeter wave of the corresponding band by the transmitting antenna, and when the millimeter wave is reflected back, the reflected millimeter wave is received by the receiving antenna. According to the wave band of millimeter waves, the time of the millimeter wave is flying through the formula, and then combined with the driving speed of the front car and the driving speed factor of the car, the relative distance between the millimeters (this car) and the target, At the same time, you will know the location of the target. In addition, according to the Doppler effect, the frequency of millimeter waverada changes, the relative speed of the vehicle and the tracking target is closely related, according to the change in the millimeter wave frequency reflected, you can learn the obstacle objective for real-time tracking in front. The relative motion speed compared to the vehicle. Therefore, when the sensor has issued a safe distance alarm, if the vehicle continues to accelerate, or before monitoring the target deceleration, or before monitoring the target stationary, the frequency of millimeter wave reflection echoes will be higher and higher. The frequency is getting lower and lower. The degree angle measurement problem of the migratory target, the principle of mm radar is: After emitting millimeter waves by the transmitting antenna of millimeter wave, it encounters the monitored object, reflects back, and receives the received antenna in parallel with millimeter wave radar. By receiving the phase difference of the millimeter wave reflected back from the same monitoring target, the azimuth angle of the monitored target can be calculated. The schematic is as follows:
The azimuth αAZ is a geometric distance D between the antenna RX1 and the receiving antenna RX2 through the millimeter wave radar, and the phase difference B receiving the reflected echo is received by the two millimeters of the radar antenna, and then the azimuth αaz is calculated by the triangular function. Value, this can know the azimuth of the monitored target. Location, speed and azimuth monitoring is a matter of millimeter wave radar, and then combined with a strong anti-interference ability of millimeter waves, it can be stabilized all day, so millimeter wave radar is selected as car core sensing technology. Millimeter wave radar and laser radar With the hot driving, laser radar is sought after because it has high precision, large information, and is not subject to visible. But we can notice that the mainstream automatic driving plan is not completely abandoned with millimeters, what is the reason?
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Compared to laser radar, the detection distance of millimeter waves can be easily more than 200 meters, while laser radar is generally less than 150 meters. In the scene of high-speed driving, millimeter wave radar is more suitable. Second, since the laser radar is high in the transceiver and assembly process, the cost is more difficult. The millimeter wavelet is no particularly expensive and complex process because it is a silicon-based chip, so millimeters is more advantageous. The current price of millimeter Poe Radad is about 1.5,000, and the price of laser radar is still calculated as units. And due to the amount of data acquired by the laser radar, it is necessary for more performance processor to process data, and higher performance processors also means higher prices. Therefore, for engineers, in simple scenes, millimeter wave radar is still the best choice. However, the disadvantage of millimeter wave radar is also very intuitive, and the detection distance is protected from the frequency band loss, and the pedestrians cannot be perceived, and all obstacles around the surrounding obstacles cannot be accurately modeled. For the market prospects of millimeter wave radar, a car will be equipped with 3-8 millimeter waves, and 7 are already installed on the high-end bus in Mercedes. In the next few years, the market size of car millimeter-wave radar will not be underestimated. The laser radar is currently a very important technology to solid-state laser radar. It is actually with traditional radar, millimeter wave radar is a pulse, solid-state laser radar is essentially adjusted each launch and receiving unit, millimeter wave radar is also the same The principle, only millimeter wave radar is to operate electromagnetic waves, and the difficulty of the device is difficult to perform phase changes over the frequency band of light. In the future, solid laser radar is combined with millimeter waves perhaps a good choice. In short, millimeter wave radar is a hard-replaced sensor, although there is a deficiency, but the full-time working status is the biggest advantage. Its speed, the accuracy of the ranging is much higher than the visual sensor, and the penetration will be better than the laser radar. But overall, this does not conflict, because the future will go to the trend of integration, especially for automatic driving, there is no doubt that the three major sensors will integrate with each other. Main application classification of millimeters 1, guided radar, fire-controlled radar, this type of radar currently has some main reason for improving detection capabilities, reducing radar volume, reducing weight and volume, easy integration. 2. Target detection radar, the type radar is mainly through mechanical / electron beam scanning, realizing detection of target distance, speed and angle of observation region, with respective data processing units, can implement identification (scattering characteristics), tracking And prediction (Kalman filtering, particle filtering, etc.). Be
3, millimeter wave pair observed radar, the type of radar is mainly a millimeter wave synthetic aperture radar, which mainly realizes the field imaging observation to obtain SAR images of the ground area. Be
4, millimeter wave proximity detection radar, this type of radar mainly achieves two-dimensional or three-dimensional imaging detection within 2 meters, and the band of this type system is from 30 to 37.5 GHz, and there are 94 ~ 200 GHz or THz bands. For example, the human body security inspection of the US airport is three-dimensionally scanned radar, and the detection imaging of the target between the human body is realized by the millimeter wave instead of X-rays, to strengthen security; there is also a 35GHz wave band radar or 94GHz and THz band radar realization No loss of three-dimensional testing for some special materials. Be
5, car radar, install the radar sensor on the car, realize the anti-collision, automatic parking, pedestrian testing, etc., the mainstream automotive radar is 24GHz radar, but is limited to frequency band control, the radio astronomy 5km does not allow the band radar The use and self-volume (mainly antenna volume is large). At present, 77GHz car radar is gradually productive and equipped with some high-end cars. The main advantages of 77GHz automotive radar are wider, and the distance resolution is higher. Compared to 24GHz radar, the target detection capacity is strong, but the production and processing process of 77GHz radar is higher, but it is not currently, this problem is no longer a industry barrier. Be
Millimeter wave radar in military typical application "long bow" "No matter after launch" anti-tank system is one of the US Army's 20th-90s major weapon system development plan, the AH-64D attack helicopter manufactured in Boeing It is the aim to make AH-64D's ability to detect, classify and operate in bad weather and low energy conditions such as rain, fog, smoke, dust. The military's radar and missile search instruments require light weight, small size, high resolution, all-weather work, so only millimeter wave bands can only be selected. In 1992, the US Army decided to develop a new type of "Hell Fire" missile with a millimeter wave active radar. Later, it was called "long bow Hell" missile, the code is AGM-114L, used for "long Bow Apa Odd "weapon system, used to combat the ground tank armored troops. The millimeter waveguide header operating frequency of the "Long Bow Hell" missile is 94 GHz, the distance is 12 ~ 16 km, and the APG-78 radar or helicopter can be utilized for the proximity target or moving target, AGM-114L mm wave. The target capture with the calibration sight (TADS) is locked in the transmitted target; when the remote fixed target is combined, the target direction is transmitted, and the target is launched in the millimeter wave to lock the target (final aim) Prior to, the missile is controlled by the inertial navigation system.
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The application of millimeter wave radar in the field of drone, in the military, the military has a manner, and the drone has long been largely applied. Its first application in the drone is also the largest market, which is the high application of plant protection drones. Be
We know that GPS and pneumatic measures are altitude, while plant protection, we hope that the drone is fixed above the crop, regardless of whether the ground and vegetation fluctuates. This is also called imitationly. This application has a lot of solutions, such as our ultrasound, laser, infrared, double objects, and more. However, due to most of the plant protection environment, there is a lot of dust, but also water fog, so ultrasound and optical-based are very disturbed. At present, it is the most stable performance based on millimeter wave radar. First, he can wear the dust of the water, and it is basically unsearched. Based on beam instead of point reflection, the height is highly reflected by the vegetation blade height. The second application of drone is avoiding. This is also a battlefield for a variety of sensors. However, we will talk about millimeter-wave radar, and the role is very large, reliable, etc., and these advantages have been proven in military personnel, cars and drones. Of course, the resolution of millimeter waves is relatively low. However, due to the advantages of array antennas, this can be greatly improved. Therefore, millimeter wave radar has a large adjustment space, such as beam width, action distance, price, etc. Millimeter wave radar is high in drone, and the advantage of avoidance is obvious, but there are also places that need to be added. Millimeter wave radar in automatic driving function is automatically driving mainly with a camera, millimeter wave radar, laser, ultrasonic, infrared, and so on. The transfer distance of millimeter wave radar is far, in the transmission window, low attenuation, low penetration, can meet the requirements of the vehicle's adaptability of the whole day, and the characteristics of the millimeter wave itself determines the millimeter waveradid sensor.The devices are small, and the weight is light. It is very good to make up for other sensors such as cameras, lasers, ultrasound, infrared, and use scenarios in vehicle applications. Be
Installing millimeter wave radar on a car, you can measure distance, angle, and relative speed from the thunder to the measured object. AdaptiveCruiseControl, pre-anti-collision alarm, auxiliary, auxiliary, auxiliary, auxiliary, auxiliary Driving Assist System (ADAS) function. Comparative automotive millimeter wave radar is around 24GHz and 77GH. The 24GHz radar system mainly implements near-distance detection (SRR), and the 77GHz system mainly achieves long-distance detection (LRR). Currently, millimeter wave radar is mainly 24GHz and 77GHz. 24GHz radar measurement distance is shorter (5 ~ 30m), mainly used in the rear of the car; 77GHz radar measurement distance is longer (30 ~ 70m), mainly applied to the front of the car and both sides. Millimeter wave radar mainly includes radar radio front end, signal processing system, and rear end algorithm. In existing products, the patent licensing cost of the radar rear end algorithm accounts for about 50% of the cost, and the front of RF is approximately 40% of the cost, and the signal processing system accounts for 10% of the cost. 1. RF front end: The radio frequency front end is transmitted and received by millimeter waves to obtain an intermediate frequency signal, from which the distance, speed and the like are extracted. Therefore, the radio front end directly determines the performance of the radar system. The current millimeter wave radar radio frequency front end is mainly planar integrated circuit, and there are two forms of mixed microwave integrated circuit (HMIC) and single-chip microwave integrated circuit (MMIC). Among them, the MMIC form of radio frequency front end is low, and the finished product is high, suitable for large-scale production. In the production process, it is generally employed by delay MESFET, HEMT, and HBT and other device processes. Among them, the GaAS-based HEMT process is most mature and has excellent noise performance. 2. Signal processing system: The signal processing system is also an integral part of the radar. By embedding different signal processing algorithms, extract the intermediate frequency signal acquired from the radio front end to obtain a specific type of target information. The signal processing system typically uses DSP as the core, realizes complex digital signal processing algorithm to meet real-time needs of radar. 3, the rear end algorithm: the backend algorithm accounts for the highest proportion of the entire millimeter wavelere. For millimeter wave radar, domestic researchers have proposed a large number of algorithms from the frequency domain, time domain, and time-frequency analysis, and the accuracy of offline experiments is also high. However, domestic radar products mainly use the frequency domain-based fast Fourier transform and its improved algorithm for analysis, measurement accuracy and application ranges have certain limitations and foreign algorithms are strictly protected by patents, and the price is very expensive. The application of millimeter wave radar in the field of intelligent traffic management system 4D millimeter wave visible radar is a multi-lane multi-objective tracking 4D video radar designed for intelligent transportation system, which uses the world's first intelligent three-dimensional spatial mm wave detection technology to provide Accurate X, Y, Z 3D coordinates and one-dimensional speed of 4D multi-objective real-time tracking track information, ensuring precise detection and statistics of various information of each driving vehicle.
Be
The radar has a new millimeter wave detector that completely independently intellectual property rights. Using FM continuous wave and Doppler technology principle, the radio continuous wave and Doppler technology principle are used to transmit millimeter waves on the road surface. By performing high-speed real-time digital processing analysis of the echo signal, the cycle speed, average Non-contact traffic detector for traffic flow basic information such as speed, traffic, lane occupancy, model, queuing length, and event analysis. 4D millimeter wave Visual Radar Series Integrated HD video camera that simultaneously monitors 4-12 lanes and provides 128 target high-resolution four-dimensional radar trajectory information and synchronously overlapping in video. 4D millimeter wave visible radar's four-dimensional identification technology enables it to accurately speed and track the target.
Reprinted from the virtual electronic information. "
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