A synthesized method for minimum insertion loss bandpass filter design

An approach to designing a two λ/2 resonators bandpass filter is proposed. The synthesis method is based on the relationship between a lumped lowpass prototype, an equivalent circuit model of the two λ/2 resonators bandpass filter, and the corresponding physical layout. First, the parameter values in the equivalent circuit are determined during a condition of minimum equivalent network loss. Then, the initial value of the layout dimension is derived from the relationship between the equivalent circuit and the physical layout. Based on the initial values, a minimum insertion loss bandpass filter can be obtained by employing optimization. A 2.45 GHz two λ/2 resonators bandpass filter has been evaluated by using this method with 1.5 dB insertion loss, and adequate agreement is obtained between simulated and measured results.