5.8G is a special distance/displacement measurement method. Sensing technologies such as microwave radar can solve the measurement problem of short-range targets, also known as short-range radar. It has been extended from the military field to the civilian field, and is used in positioning, character recognition, speed measurement, environmental monitoring, displacement monitoring, etc. Compared with other sensing technologies, 5.8G radar sensing technology has unique advantages such as non-contact, rain and fog protection, and dust resistance. It has gradually become an important detection method in short-range target displacement measurement.
There are many kinds of microwave radar sensing technologies, which can be divided into two categories according to the different transmitted signals: single-frequency radar and broadband radar. The signal sent by a single-frequency radar is a single-frequency microwave continuous wave (CW), which can also be called a Doppler radar, which is used for target velocity and high-precision displacement measurement; the wideband radar transmission signal has a certain bandwidth, depending on the difference of different transmission signals , Wideband radar can be divided into pulsed ultra-wideband (IRUWB), linear FMCW (FMCW), continuous frequency stepping (SFCW) and other steps. Compared with CW radar, it has higher resolution and can perform multiple steps simultaneously. Target measurement.
Although the microwave radar is used to measure the distance between the radar host and the measured target, it can measure the distance of the same target by multiple hosts, and use the spatial position relationship between the radar hosts to solve the space of the measured target. Three-dimensional coordinates, so as to realize the spatial positioning of the target. Because of the different signals sent, the measurement principle and structure of each radar system are different. The CW radar system is relatively simple. It only needs a single-frequency microwave source. By interfering with the demodulated target reflected signal and emission signal, and demodulating the frequency and phase shift of the interference signal, the target's velocity and displacement can be measured to obtain High-precision measurement results. The pulse width of the microwave pulse signal emitted by IR-UWB radar is narrow, and the time interval between the reflection of the target and the transmission signal is used to measure the distance of the target; when the target is moving, the measurement of the target displacement can be completed; When measuring from different targets, the response time to the target echo pulse is different, and the radar pulse resolution meets the multi-target resolution of the pulse resolution. FMCW radar has the characteristic that the periodic emission frequency changes linearly and continuously with time. This method obtains the beat signal reflecting the target distance by mixing the target reflected echo signal and the transmitted signal. The measurement of the target distance is based on the size of the beat frequency. When multiple targets at different distances are measured, the beat frequency of the target will be different, thus realizing the decomposition of multiple targets. SFCW radar is different from FMCW radar. SFCW radar is not a kind of microwave signal whose transmission frequency changes linearly and continuously with time. The microwave signal is used to increase the frequency spectrum stepwise with time. The radar receives the target reflected echo signal, which is used in the radar demodulation device. Interferes with the transmitted signal and outputs the interference phase (similar to the CW radar); this method uses the interference phase of the microwave stepping frequency in one cycle to achieve the measurement of the target distance; based on the interference phase information, the displacement target is achieved Measurement.
The above four types of microwave radars all have their own focus on application research fields, involving many aspects of social needs, and each has its own characteristics. At present, there are many researches on CW radar in short-range, high-precision displacement measurement, life signal detection, etc. IR-UWB radar is mainly reflected in indoor positioning, life signal detection, and wall detection; FMCW radar has speed, ranging, Intelligent transportation, space positioning, and SFCW radar have the advantages of multi-target recognition and phase high-precision displacement measurement, so they have the advantages of high-precision level measurement and target speed measurement. There have been reports on the application of structural monitoring products.
The FR58L4L8-2020S(A) microwave induction sensor of Ferry Smart uses the Doppler principle to transmit high-frequency electromagnetic waves through an antenna and receive and process the reflected waves to determine the movement of objects within the coverage area and give corresponding electrical signals. It is widely used in induction lighting, security, small household appliances, smart homes, automatic door control switches, welcome devices and other products, as well as garages, corridors, corridors, courtyards, balconies, toilets and other places that require automatic induction control. Longer sensing distance than infrared sensor module, wider angle, no dead zone, lens and lens aging problems are not affected by temperature, humidity, airflow, dust, noise, brightness, etc., strong anti-interference ability can penetrate acrylic, glass and thin The non-metallic material onboard MCU, embedded multiple digital filtering algorithms, has higher immunity. Because the chip has integrated 5.8G microwave circuit, intermediate frequency amplifier circuit, signal processing MCU, and peripheral components, the integration is high and the production consistency is good, which greatly reduces the overall size while ensuring the performance of the sensor. The 5.8G microwave radar sensor can be used to detect human presence or moving target sensing and other scenarios, including smart home, Internet of Things, smart lighting and other fields, especially in the home appliance and bathroom markets, and can be used to realize screen wake-up and gesture control functions. It is widely used because of its super high cost performance. The sensing distance of the radar can be configured through the MCU, and the sensing distance is up to 12 meters, and the actual sensing distance can be flexibly adjusted as required.
