New progress in the development of compact highperformance microwave ultra-wideband (UWB) filters

Because of the important performance benefits associated with ultra-wideband (UWB) communication systems, UWB bandpass filters (BPFs) are on the cutting edge of UWB technologies and are of great interest to researchers and engineers in the areas of RF filters and systems. This paper presents some of our recent research works in the development of compact high-performance microwave UWB BPFs. Our newly proposed synthesis techniques are described, which provide both theoretical filtering functions and practical structural parameters of the filters. Mechanisms of UWB filters employing microstrip multi-mode resonators loaded with open- and short-circuited stubs are described. Design examples provided are all verified well by measurements, and exhibit excellent performances such as a compact size, low return losses and a flat group delay in passband, and good stopband property.