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.

Microwave Sensor

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

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


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