Theoretical processing of passive filters, design and simulation of the same in MATLAB. When designing a low-pass, high-pass, band-pass, and band-stop filter, simulink was used. After calculating the transfer function of each filter, the operation of the filters with a monoharmonic continuous sinusoidal signal was simulated to show how they work. Subsequently, the operation of a filter with a multi-harmonic rectangular discrete signal was simulated where the results obtained were slightly different than expected. The low pass filter passes lower frequency harmonics from the cutoff frequency, while at frequencies above the cutoff frequency it cuts or blocks the signal harmonics and changes its shape from rectangular to pilasters. The high-pass filter cuts or blocks the harmonics of the lower frequency signals from the cutoff frequency and there is a jump in the signal amplitude at each transition from -1.1 V, and from 1, -1 V after which the amplitude returns to zero. At very high frequencies, the high-pass filter passes the harmonics of the signal completely with an almost identical shape as the input signal. The band-pass filter behaves at frequencies lower than the lower cut-off frequency as a high-pass filter, cuts or dampens the harmonics of the signal and with a noticeable jump in amplitude after which it returns to zero. In the region between the lower and upper cut-off frequency, the harmonics of the signal are passed and the signal shape is almost identical to the input signal. At very high frequencies higher than the upper cutoff frequency, the harmonics of the output signal are again blocked and the shape of the output signal looks like the output of a low-pass filter. The band-stop filter works opposite to the band-pass filter in such a way that it passes the harmonics of lower frequency signals from the lower cutoff frequency and the harmonics of the higher frequency signals from the upper cutoff frequency. In the region between the two cut-off frequencies, filter blocks signal harmonics and the signal amplitude is zero.