Transversal signal interaction

As one of the most important components in RF/microwave systems, high-performance wideband bandpass filters with low insertion loss within the passband and large attenuation in the stopband are extremely desirable [1], [2]. Moreover, as shown in Figure 1(a), the definition of the fractional bandwidth for the narrowband bandpass filter is less than 1%; and the fractional bandwidths for wideband/ultrawideband (UWB) bandpass filter are greater than 1% and 25%, respectively [2]. The main features of the high-performance wideband microstrip bandpass filters include simple design, compact size, low loss and good linearity, enhanced out-of-band rejection, and easy integration with other circuits/antennas etc. [3], [4]. Various microstrip wideband filters employing multimode resonators, complementary split-ring resonator (CSRR) and multilayer aperture-coupled patches have been designed and analyzed [3]-[10]. In [11]-[18], the cascaded low-pass/high-pass filters, electromagnetic (EM) loaded bandgap and T/Y-shaped resonators are used to extend the upper stopband bandwidth and improve the selectivity of the passband. © 2000-2012 IEEE.