OTHER TYPES OF UWB FILTERS
To meet the prompt needs in exploration of UWB technology in recent years, studies on UWB bandpass filters have increasingly become an attractive research topic since it is one of indispensable circuit blocks in the whole UWB system. Besides the MMR-based UWB filters discussed in the previous chapters, there are a few other types of UWB filters reported so far based on other design methodologies. In this chapter, these UWB filters will be generally classified and comparatively discussed in terms of their filtering performance, geometrical characteristic, operating mechanism, design procedure, and so on. As a result, the readers can have a global view on the current development of a variety of UWB bandpass filters.
7.2 UWB FILTERS WITH HIGHPASS AND LOWPASS FILTERS
The most straightforward way to design a UWB bandpass filter is to simply cascade a highpass filter with a lowpass filter [1–5]. The lower and upper cutoff frequencies of the constituted UWB filter is predominantly determined by the cutoff frequencies of the highpass and lowpass filters, respectively. However, if the highpass and lowpass filters are directly connected, the overall circuitry area will be enlarged to a large extent. To circumvent this problem, a composite highpass–lowpass UWB filter was presented in Reference 1 by embedding a lowpass filter into a highpass filter. As shown in Figure 7.1a, the lowpass filter is made up of a stepped-impedance structure, ...