Indoor millimeter wave radar has module advantages and functions, millimeter band definition is generally 30~300GHz frequency domain (wavelength is 1~10mm) electromagnetic wave called millimeter wave, located in the wavelength range of microwave and far infrared wave overlap, with the characteristics of two spectrum. The theory and technology of millimeter wave is the extension of microwave to high frequency and the development of light wave to low frequency.
What are the advantages of millimeter wave radar human presence module? The advantages of millimeter wave:
1) Extremely wide bandwidth
It is generally believed that the MMW frequency range is 26.5 ~ 300GHz and the bandwidth is up to 273.5GHz. More than 10 times from DC to microwave. Even allowing for atmospheric absorption, only four main Windows can be used in the atmosphere, and the total bandwidth of these four Windows can reach 135GHz, which is five times the bandwidth of the sub-microwave bands combined. This is undoubtedly very attractive when frequency resources are tight.
2) Narrow beam
Millimeter wave radar human presence module millimeter wave beam is much narrower than microwave beam at the same antenna size. For example, a 12cm antenna has a beam width of 18 degrees at 9.4GHz and a wave speed width of only 1.8 degrees at 94ghz. As a result, we can distinguish between smaller targets that are closer or see the details of the target more clearly.
3) Strong detection ability
The wide-band broad-spectrum capability of the human presence module of millimeter wave radar can be used to suppress multipath effect and disorder echo. Large use frequency, effectively eliminate mutual interference. A large Doppler shift can be obtained at the radial velocity of the target, which improves the detection and recognition ability of low-speed moving objects or vibrating objects.
Millimeter waves are essentially electromagnetic waves. The millimeter wave band is more specific than radio, visible light and infrared light. At present, there are two main millimeter-wave radar bands used indoors.
1. 24GHz This frequency band has low frequency and narrow Bandwidth of 250MHz, which has the advantage of low cost.
2, 77GHz the frequency band is high, the international allowable bandwidth up to 800MHz. The performance of radar in this band is better than 24GHz radar, and of course, the cost is high.
Millimeter wave radar human existence module principle: The oscillator will produce a signal with increasing frequency over time. When the signal hits an object in front of it, it bounces, with a delay twice the distance/speed of light. There is a frequency difference between the returned waveform and the emitted waveform. The frequency difference is linearly related to the delay: the farther away the object is, the later the return wave is received, and the greater the frequency difference between it and the incident wave. Millimeter wave radar human presence module By subtracting these two frequencies, we can get the difference frequency of the two frequencies (difference frequency). By judging the difference frequency, we can judge the distance of the object in front of us.
What is the "startup time" of the radar module? When the MMW radar human presence module starts to work, it is necessary to completely reset the internal circuit of the module and fully evaluate the environmental noise to ensure the normal operation of the module. Module initialization takes about 30 seconds to ensure the validity and accuracy of subsequent output parameters.
In extreme cases, the electromagnetic noise of some users is high, which is easy to cause state misjudgment. If the current environment is harsh, the existing module of MMW radar can be placed in the current environment. The internal algorithm of the module supports the learning and adaptation of the existing environmental characteristics in the unmanned scene, so as to reduce the misjudgment of the module detection in the harsh environment.
