Novel synthesis methodology for ultra-wideband filters based on frequency transformation technique

A novel methodology is proposed for the design of ultra-wideband filters by the combination of the transmission-line-theory-based frequency-transformation technique to a recently-proposed Chebyshev-filter-based synthesis technique. Firstly, the frequency-transformation technique is mathematically formulated and applied to the basic distributed transmission-line elements — short-circuited shunt stubs, open-circuited series stubs and unit elements. Then, the procedure of the filter synthesis is described in detail and demonstrated by designing an example filter with an FBW of 67%. For confirmation, the designed filter is optimized by an EM simulator, practically fabricated and then characterized by a network analyzer. The measured results are compared with the simulated ones and the theoretical ones. Good agreements are found and the correctness and effectiveness of the proposed technique are validated accordingly.