Recent advances in the field of theoretical developments and practical the application of microwave technology, and the development of the element base (including microprocessor technology) allow us to expect that in the very near future appears the design of detectors metal objects, which will used the principle of radar. The interest in devices that use the radar principle, due to the fact that the range of such metal detectors incomparably higher than that of other types of detectors.
Currently in various sources you can find very original circuit solutions such detectors. However, their practical implementation has been rather difficult.
The basis for constructing such devices is the principle used in radar (Fig. 1.5). As in radar, information about the presence in the zone of action of the device any object (distance, size, etc.) is estimated after treatment the parameters of the pulse signal reflected from the object.
Fig. 1.5. A simplified block diagram of radar detector
A pulse signal generated by pulse generator modulates the signal the transmitter is radiated by the antenna. With the attainment of the object passed the signal reflects from it. The reflected signal is received by the antenna, and then through antenna switch and the receiver is fed to the analyzer. To cascade analyzer also the signal generated by a pulse generator.
Both received at the signal analyzer compares, and then assessed differences with the subsequent formation data to the display unit. In this case information about the distance to the detected object is formed after evaluation the delay time of the reflected signal, and information about the magnitude of the object on the amplitude of this signal.
Author: M. V. Adamenko