a microwave radial power divider / combiner device having desirably broad bandwidth response over a selected frequency range . the device includes a radial waveguide that has a number of adjoining annular sections , each of selected radial length and axial height , to provide lumped circuit parameters closely euqivalent to those of an ideal filter with the desired passband characteristics . the ideal filter is first designed using conventional synthesis techniques , then modified , if necessary , to allow its realization in radial waveguide form . the waveguide sections are selected to have lengths and uniform heights to approximate the lumped circuit parameters of the filter , and the dimensions are then optimized to provide the closest approach to the desired performance characteristics .