Brief introduction

Radar microwave detector is a kind of detector that combines microwave receiving and transmitting equipment, and the working principle is based on the Doppler effect. The wavelength of microwaves is very short, between 1mm~1000mm, so it is easily reflected by objects. The Doppler effect occurs when the microwave signal encounters the reflection of a moving object, that is, the frequency of the reflected microwave signal and the transmitted wave signal will be slightly offset. At this point, it can be considered that the alarm has been generated.

principle

Using the principle of Doppler radar, the microwave transmitting antenna and the receiving antenna are installed together. The bulk effect tube is used as the microwave solid-state oscillation source, and a small emission source emitting microwave signal is formed by combining with the waveguide. The Schokit detector tube in the probe and the same waveguide form a single-tube waveguide mixer as a signal mixed by the receiver coupled back to the transmitter source, so as to obtain a frequency difference, and then send it to the low-frequency amplifier to process and control the output of the alarm. Due to the short wavelength and strong penetration of electromagnetic waves in the microwave band, non-metallic materials such as glass, wood panels, and brick walls can penetrate. Therefore, do not face the outside during installation, so as not to cause false alarms caused by people passing outside. Metal objects have strong reflection on microwaves, and there should be no large-area (or large-volume) objects in the detector protection area, such as iron cabinets. Otherwise, the shadow behind it will form a detection blind zone, resulting in a protection loophole. When multiple microwave detectors are installed together, the emission frequency should be different to prevent false alarms caused by cross-interference. In addition, the 100Hz modulation signal generated by gas discharge light sources such as fluorescent lamps and mercury lamps is caused by the ionized gas in the flashing lamp that easily becomes a moving reflector of microwaves. The sensitivity of using microwave intrusion detectors should not be too high, and it is more appropriate to adjust to 2/3. Too high false positives increase. As with ultrasound, it can also be used in the home.

Scope of use

The detection range of the detector to the active target in the warning area is a three-dimensional defense space, the range is relatively large, can cover the horizontal radiation angle of 60 ° to 90 °, and the control area can reach tens to hundreds of square meters. The emission energy map of radar microwave detector is related to the antenna structure used, and the use of omnidirectional antennas (such as 1/4 wavelength unipolar antennas) can produce a nearly spherical or elliptical emission range, which is suitable for protecting large areas of rooms or warehouses. The use of directional antennas (such as horn antennas) can produce wide teardrop-shaped or narrow and long teardrop-shaped energy maps, suitable for protecting narrow and long locations, such as corridors or passages.

4 How it works

Radar-type microwave anti-theft detector is a kind of detector that combines microwave receiving and transmitting equipment, and the working principle is based on the Doppler effect. The wavelength of microwaves is very short, between 1mm~1000mm, so it is easily reflected by objects. The Doppler effect occurs when the microwave signal encounters the reflection of a moving object, that is, the frequency of the reflected microwave signal and the transmitted wave signal will be slightly offset. At this point, it can be considered that the alarm has been generated.

The detection range of the detector to the active target in the warning area is a three-dimensional defense space, the range is relatively large, can cover the horizontal radiation angle of 60 ° to 90 °, and the control area can reach tens to hundreds of square meters.

5 main advantages

1. High sensitivity.

2. The control range is relatively large, and its warning range is a three-dimensional prevention space, which can cover the horizontal radiation angle of 60 ° ~ 90 °, and the control area can reach tens to hundreds of square meters.

3. Using the penetration of microwave detectors to non-metallic substances, several rooms can be monitored with a microwave detector, and additional modifications can be added for camouflage, which is convenient for concealed installation.

Main disadvantages and precautions for installation and use

1. The probe of the microwave detector should not aim at potentially moving objects.

2. It is strictly forbidden to install on the exterior wall or exterior wall of the protected room. Because microwaves are penetrating to non-metals, people walking outside the wall or vehicles on the road may cause false alarms.

3. There should be no oversized and thick objects in the monitoring area, especially metal bodies, otherwise there will be a blind zone for detection behind these objects.

4. Microwave detectors should not be used for fluorescent lamps, mercury lamps and other gas discharge light sources. The 100Hz modulated signal directly generated by the fluorescent lamp can cause false alarms, especially if the faulty flickering fluorescent lamp is more likely to cause interference. This is because the ionized gas in the flashing lamp is more likely to become a microwave transported to the reflector and cause false alarms.

5. Should not be installed indoors.

6. When more than two microwave detectors need to be installed in the same room, it is easy to produce cross-interference and false alarms. Therefore, the microwave emission frequency between them should be different, generally about 25MHz, and should not be placed relative to each other.