## 3 Practical Implementation  
To detect a dielectric object in a conductive layer (Figure 1), a mobile object-monitoring device was developed and patented, which consists of a linear generator and a receiving EA with orthogonal axes. The generator EA is connected to the symmetrical output of a low-frequency alternating voltage generator, and the receiving EA is connected to the symmetrical input of a differential amplifier. We called such a device a module. To create a protected boundary, several independent modules are placed along it, which are close to the protected water area. Another implementation of an active electromagnetic system for the protection of a water area consists of two independent detection channels: electric and magnetic, complementing each other. This increases the reliability of object detection and their classification based on conductivity [5,12]. When developing the receiving part of the device, the following tasks were defined:  
1. Signal filtering in order to increase the signal-to-noise ratio;  
2. Amplification and conversion of the signal to a form convenient for further processing;  
3. Ensuring operational changes in the parameters of the electronic path for the purposes of the experiment. The basis of the experiment was an electrical circuit with two quadrature channels, which have wide functionality [8]. The functional diagram of the receiving part of the device is shown in Figure 2. The device contains a series-connected generator (1), amplifier (2) and linear EA (3) two identical receiving antennas (4) and (5) connected to the inputs of a differential amplifier (6), whose output through a pole filter is connected to the input of a phase shifter (8), whose output is connected in parallel to an amplifier with a variable coefficient of the amplifier (9) and to the amplifier with a constant gain of (10). The outputs of the amplifiers are connected to the signal inputs of two synchronous detectors (11) and (12).The inputs of the reference signals are connected to the sine and cosine outputs of the generator (1). The outputs of the detectors are connected to the outputs of the adder (13). The signal from the adder output was recorded in parallel using a digital voltmeter (V7-27/I) and an amplifier (I-37) with an output to the recorder (H37). The device works as follows. A harmonic signal \(U=A\sin\omega t\) (where \(A\) is the amplitude, \(\omega\) is the circular frequency) pre-amplified by a power amplifier (2) is fed to the transmitting antenna (3). In the absence of an object, there are harmonic signals \(U_{1}=A_{1}\sin(\omega t+\phi_{1})\) and \(U_{2}=A_{1}\sin(\omega t+\phi_{2})\) at the input terminals of the first and second receiving antennas (4) and (5). At the output of the differential amplifier (6), the difference signal has the form  
\[U_{p}=A_{p}K\sin(\omega t+\psi),\]  
where \(A_{p}=\sqrt{2\big{(}A_{1}^{2}+A_{2}^{2}-A_{1}A_{2}\cos\big{(}\varphi_{1}- \varphi_{2}\big{)}\big{)}}\) is the amplitude of the difference signal; \(K\) is the amplifier coefficient of the differential amplifier;  
\(\psi=arctg[(A_{1}\cos\varphi_{1}-A_{2}\cos\varphi_{2})/(A_{1}\sin\varphi_{1}- A_{2}\sin\varphi_{2})]\)--a phase of the difference signal. The presence of the object leads to the appearance of an additional useful signal at the output of the differential amplifier  
\[U_{c}=A_{c}K\sin(\omega t+Q),\]  
where \(A_{c}\) is the amplitude of the useful signal; \(Q\) is the phase of the useful signal. After passing the bandpass filter (7), the total signal is received at the input of the processing unit  
\[U=KA_{p}(\cos\psi\sin\omega t+\sin\psi\cos\omega t)+KA_{c}(\cos Q\sin\omega t +\sin Q\cos\omega t)\]  
After passing the phase shifter (8), the total signal is shifted in phase by an angle \(\varphi\). \[U(\varphi)=KA_{p}[\cos(\psi+\varphi)\sin\omega t+\sin(\psi+\varphi)\cos\omega t ]+KA_{c}[\cos(Q+\varphi)\sin\omega t+\sin(Q+\varphi)\cos\omega t].\]  
Further, signal processing is carried out in parallel channels.