Crystal band-pass lattice filters with equal ripple pass bands and arbitrary stop bands

A design procedure is given for crystal lattice filters with the attenuation poles (frequencies of infinite attenuation) set to any value. Simple formulae are then provided in terms of the specification data. The designer selects the number of lattices and the distribution of attenuation poles in each lattice. This flexibility, which is not possible for designs resulting from modern insertion loss theory, is achieved here by returning to image parameter techniques. Different expressions for the image impedance function are given, including equal ripple solutions, to enable the pass-band characteristics to be altered as required with minimal effect on the stop-band response.