Design of Three-Resonator Dissipative Band-Pass Filters Having Minimum Insertion Loss

The purpose of this paper is to present universal design curves for three-resonator band-pass filters having minimum insertion loss. This information is obtained by solving Dishal´s equations for a band-pass network uniquely for the condition of minimum insertion loss, the network here consisting of three synchronously tuned resonant circuits (coupled to a resistive generator and a resistive load) having the same finite value of unloaded Q. The general solution for the maximally flat response is presented in detail in the second half of this paper. The exact values of the circuit constants for a minimum-insertion-loss response are given both analytically and graphically in terms of the unloaded Q and the fractional bandwidth. Also, the deviation from the exact response shape of a maximally flat filter is discussed for varying values of circuit constants.