ANTI-ALIASING FILTERS WITH COMPLEX AMPLITUDE-FREQUENCY RESPONSES

A method for designing anti-aliasing filters for use in information and control systems is proposed. A distinctive feature of the filters under consideration is that their amplitude-frequency response has transmission zeros at critical (from the point of view of interference suppression) frequencies and a specified attenuation in the rest of the frequency range. This allows the use of the filters in question, both for the suppression of undesirable harmonics of the network (50 Hz and 100 Hz), and as spectrum limiters at the inputs of analog-to-digital converters and, in particular, at the inputs of discrete-analog filters made on switchable capacitors. It is shown that the found transfer function of the filter can be implemented on the basis of cascade or multi-loop structures, and the circuitry of such filters can be made on the basis of RC circuits and op-amps. The calculation of the parameters of the elements of the circuit diagrams of filters is carried out according to the coefficients of the specified transfer function. Cascade implementation is based on the principle of internal models, which ensures the greatest stability of the filter's critical frequencies.