Doppler motion detector units, or microwave sensors, operate at frequencies of 10
Mhz. They utilize a doppler radar signal which bounces microwaves off of an object,
then measures the frequency of the returning microwaves. If an object is
moving in the sensor's field, the returning microwave will be at a different frequency,
higher or lower than the original signal transmitted. Microwave sensors
offer a greater distance of coverage and are more reliable at greater distances.
Microwaves can also penetrate walls which means these security sensors can
be placed behind objects.
A drawback to using microwave sensors in a
home security setting is their strong sensitivity, which makes themhard to set
or adjust effectively, and makes them vulnerable to interference from other electrical
devices such as lighting and radios. |
