Multiple‐critical‐pole coupled active filters

In this paper realizations of low sensitivity narrow BP active filters implementing multiple‐critical‐pole (MCP) approximation methods and coupled filter structures are studied. In the first part of the paper, a synthesis procedure particularly developed for the realization of MCP transfer functions is described. According to that procedure the portion of the MCP transfer function containing multiple poles is realized as a follow‐the‐leader feedback (FLF) network, and the remaining part as a cascade. It is shown that the lower sensitivities of MCP functions in comparison with standard approximating functions (Butterworth, Chebyshev, etc.) can be further decreased by applying the FLF configuration instead of the cascade. the synthesis procedure is straightforward and in some cases it can be performed using identical second‐order BP blocks. the final circuit sensitivities can be optimized according to given filter specifications and a user selected optimization criterion. In the second part of the paper, the MCP transfer functions are combined with the cascaded biquarts (CBQ), the shifted companion form (SCF), and the leap‐frog (LF) structures, and sensitivity analysis is performed. It is shown that applications of the above mentioned structures can improve the filter sensitivites in a way similar to that of the given FLF configuration.