Radar-type and wall-type microwave detector are divided into two kinds.
Microwave detector radar: radar is a microwave receiving and equipment reset detectors working principle is based on the Doppler effect. Microwave wavelengths are very short, in between 1mm~1000mm, so it is easy to object. Microwave signal encountered after you move the object will have a Doppler effect, that is, upon reflection, the microwave signal and launch wave frequency will have a small offset. At this time can be regarded as alarming.
Principle of using Doppler radar, microwave-transmitting antenna and the receiving antenna is mounted alongside. For microwave use-effect transistor solid state oscillator through a combination of waveguide, forming a small emission microwave signal source. The xiaojite detector in the probe tube with the same waveguide composed of single tube waveguide mixers as receiver and source-coupled signal mixing back, resulting in a frequency difference, and then sent to a low frequency amplifier control and alarm outputs. Microwave band due to the shorter wavelength of the electromagnetic wave, penetrating power, glass, non-metallic materials such as wood, brick walls are penetrable. Do not install outdoors, avoid outdoor was caused by false positives. Metal objects on the microwave reflected strong detectors guard in the region not to have a large area (or larger) object, such as tiegui and so on. Otherwise in shadow form to detect blind spots, causing preventing vulnerabilities. When more than one microwave detector are mounted together, firing frequency should be different, prevent interference from false positives. In addition, such as fluorescent lamps, mercury vapor lamps, gas discharge lamp 100Hz modulation signals due to ionized gas in the flashing lights easy sports reflector for microwave and cause false positives. Use microwave intrusion detector sensitivity is not too high, when adjusted to 2/3 is appropriate. High false-positives increases. With ultrasonic family can be used.