A new synthesis method for equiripple dual-passband microwave filters

This paper introduces one new method to synthesize S parameters´ polynomials of dual-passband filters, which have two passbands separated by one stopband. Both symmetric and asymmetric dual-passband filters can employ this method. A serial of optimization procedures were carried on to optimize one function with the band edges of stopbands as variables. The band edges of stopbands have their own ranges reassured by the design specifications. The optimization procedures begin with initial values of transmission zeros, which are the function of stopbands edges, and reflection zeros according to specifications. A characteristic that in every frequency band is equiripple and the maximum return loss in passbands are optimum same is obtained after the optimization.