| Ultra-wideband (UWB) communication has been widely used in modern wireless communication, because of its high transmission rate. With the rapid development of integrated communication systems, high performance and compact size are required for the concerned passive devices. This paper focuses on the design of UWB bandpass filters and power dividers with compact sizes and high performance, including that of extra notched bands in their passbands.The low-pass filter prototypes are discussed and the prototype which is more suitable to realize high performance is chosen. Then a folded bandpass filter structure is proposed to achieve high performance with a much more compact size. To obtain further miniaturization, a new type of UWB filter is designed and an electromagnetic bandgap structure is introduced to improve its upper stopband performance.The inveistigation about power dividers is as follows. The reasons that limit the bandwidths of traditional power dividers are discussed. A power divider with ultra-wideband and filtering property is suggested. The filtering property is achieved by adopting a stepped-impedance stub and parallel coupled structure. In this way, an UWB power divider is realized with compact size and high performance.Because of possible interference with existing applications, the research on UWB bandpass filters and power dividers with notched bands in their passbands has also been conducted. A notched band can be obtained by adding a coupled resonator on an UWB filter. It can also be produced by etching a Hilbert fractal curve slit on the filter without the necessity of readjusting the geometrical parameters. Finally, a new filter structure based on signal-interference concept is proposed and the notched band is realized by adjusting the structure size to produce a transmission zero in the passband. A power divider with notched band is achieved by using a coupled resonator and sharp rejection at the band edges is also realized. |
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