Yu-Dan Wu, Guo-Hui Li, Wei Yang, Tong Mou
2016 Progress In Electromagnetics Research Letters  
A novel dual-band substrate integrated waveguide (SIW) filter with multiple transmission zeros and good out-of-band rejection performance is presented in this paper. For this purpose, an orthogonal input/output (I/O) feeding structure directly connected to the substrate integrated waveguide (SIW) cavity is designed to split the resonant frequencies of the degenerate pair of mode. The filter can be modeled with a multi-path circuit formed by three modes (TE 101 , TE 201 and TE 102 modes) and
more » ... cross coupling between I/O ports, thereby producing three transmission zeros which make the dual-band high selectivity. The offset of the input/output ports shifts the second transmission zero to a lower frequency from the upper passband. Several filter prototypes are designed and fabricated for demonstration, and the measured results validate the new structure for high selectivity applications. INTRODUCTION Microwave filters are key components in modern communication systems. Recent advances in communication technologies bring about the requirement of highly selective microwave filters with compact size, low cost, high power capability, etc. Transmission lines, such as microstrip, coplanar waveguide (CPW) and rectangular waveguide, have been used in the design of microwave filters. Compared with these structures, substrate integrated waveguide (SIW) has attracted much attention for its low cost, high performance and flexible integration with radio-frequency/microwave integrated circuits. Recently, half-mode SIW, folded half-mode SIW and quarter-mode SIW have been widely employed for designing filter with size reduction [1] [2] [3] [4] . For a bandpass response technology, slots loaded on SIW cavity attract lot of academic attention for its easy design and fabrication [5, 6] . Dual-band bandpass filter is an indispensable component for multi-band systems since it can be used as two separate single bandpass filters. So far, several ways have been used to acquire dual-band. Traditionally, a dual-band filter is based on degenerate modes of a cavity or the frequency transformation from normalized frequency domain [7] . In [8] , dual-band is realized by generating one transmission zero in the middle of a wide passband. Li et al. proposed a dual-band SIW filter based on spirality compact microstrip resonators cell [9] . A three-cavity dual-mode dual-band filter is designed using coupling matrix [10]. Dual-band filters using metamaterials [11] , defected ground structure (DGS) [12] and complementary split ring resonator (CSRR) [13, 14] are introduced. In this paper, a novel dual-band (SIW) filter is presented, and the dual-band response is realized by open loop resonators, TE 101 mode and the first degenerate modes (TE 201 and TE 102 ). By using an orthogonal input/output feeding line for perturbation, the generated TE 102 and TE 201 modes are split. Two open loop resonators etched on the substrate integrated waveguide (SIW) cavity not only are used as resonators but also generate inter-coupling. The proposed bandpass filter is analyzed and designed using full-wave EM simulator software (Ansoft HFSS). To validate the design and analysis, several filter prototypes are designed and fabricated. The measured results verify the performance of the proposed filters.
doi:10.2528/pierl16032401 fatcat:gc27uqx5vvbgxk4rhj72gzv7h4