Microwave technology in alarm motion detection
What's microwave and doppler effect
The wave length of 300MHz to 3000MHz frequency, we call them microwave. This wave lenght is between Ultrashort wave and Infrared wave. Due to Earth's outer ionosphere can totally reflect the microwave, Microwave is one of best communication method.
Doppler effect was found by the physicist Doppler in 1842. The changes of frequency of wave is related to the moving sources of wave. A simple example is a vehicle is approaching, the volume of horn will increase for the receiver, that means the frequency of wave is higher. When the vehicle is in recession, then the volume of horn will low, that means the frequency of wave is low.
What's Microwave sensor
Microwave sensor also are called Doppler Radar. It emits the continuously of microwave and receive the refelct microwave to detect the moving object. The microwave sensor with the advantages of low power consumption, constant/pulse wave operation mode, are sensitive to the reflect microwave from objects, without interference from temperature.There are three kinds of microwave sensor: planar Microstrip, Waveguide, Coaxial.
The frequency that microwave sensor can be used
X-band:
Frequency | Country | Regulations |
| 9.35 GHz | Germany | EN 300 440 |
| 9.9 GHz | French, Italy | EN 300 440 |
| 10.525 GHz | Belgium, Netherlands | EN 300 440 |
| 10.525 GHz | USA, other | FCC Part 15.245 |
| 10.587 GHz | UK | EN 300 440 |
| 10.687 GHz | UK | EN 300 440 |
K-band:
Frequency | Country | Regulations |
| 24.2 GHz | UK | MPT1394 |
| 24.125 GHz | Other | EN 300 440/FCC Part 15.245 |
Microwave sensor application
Since the development of microwave technology, Microwave sensors are widely used in industry, traffic, Civilian electronic devices such as Speed measure of vehicle, liquid level measure, automation door, automation light, alarm system, reversing radar...etc.
Compared to conventional PIR motion detector, the motion detector with microwave sensor combination is able to provide more reliable performance, Microwave based Motion detector are widely used for special guard places such as Prison, Bank, Military warehouse, Musemum, Transformer substation...etc.
The advantages of Microwave based PIR Motion detector as below:
1. Combined with PIR technology to reduce the false alarm, that we usually called as dual technology detection method.
2. Microwave is a wave that can not be interfered by the temperature, can composent the disadvantage of passive infrared detection technology.
3. Microwave can penetrate the objects, can prevent the indended damage of detector.
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Tags: Motion sensor, Microwave