This paper presents two novel different feeding and coupling schemes to solve the problem of generating transmission zeros (TZ) in lower stopband and their applications to design single-band filters. The designed two filters are based on substrate integrated waveguide (SIW) square cavity with orthogonal ports. In the design of Filter A, two L-shaped stubs are introduced to form an addition coupling path between two ports, which cause the generation of one TZ. Other two TZs are formed due to the resonance characteristics of L-shaped stubs and ports offset. Two metal vias are used to adjust center frequency slightly. In the design of Filter B, other two stubs are designed to form two additional coupling paths, thus forming a total of three coupling paths with the original path. Two TZs are obtained by utilizing the phase difference between different paths, and one TZ is generated for the resonance characteristics of the proposed stub 3. Simultaneously, an L-shaped slot is used to adjust center frequency. Both designed filters use the coplanar waveguide (CPW) structure to control bandwidth. Two filters are set to operate at 14.4 GHz with bandwidth of 800 MHz. Both filters are fabricated and measured. The simulation results of two filters are in good agreement with the measured ones.
2. Liu, Y. J., G. Zhang, S. C. Liu, and J. Q. Yang, "Compact triple-band filter with adjustable passbands on one substrate integrated waveguide square resonant cavity," Microwave and Optical Technology Letters, Vol. 62, No. 12, 3709-3715, Jun. 2020.
3. Azad, A. R. and A. Mohan, "Compact bandpass filter with wide-stopband using substrate integrated waveguide cavities and short-circuited coplanar line," International Journal of Microwave and Wireless Technologies, Vol. 12, No. 5, 1-7, Jun. 2020.
4. Kim, P. and Y. Jeong, "Compact and wide stopband substrate integrated waveguide bandpass filter using mixed quarter- and one-eighth modes cavities," IEEE Microwave and Wireless Components Letters, Vol. 30, No. 1, 16-19, Jan. 2020.
5. Becharef, K., K. Nouri, H. Kandouci, B. S. Bouazza, M. Damou, and T. H. C. Bouazza, "Design and simulation of a broadband bandpass filter based on complementary split ring resonator circular “CSRRs”," Wireless Personal Communications, Vol. 111, No. 3, 1341-1354, Apr. 2020.
6. Moitra, S., S. Nayak, R. Regar, S. Kumari, K. Kumari, F. Parween, and F. Naseem, "Circular complementary split ring resonators (CSRR) based SIW BPF," International Conference on Advanced Computational and Communication Paradigms, ICACCP, 1–5, 2019.
7. Moitra, S. and P. S. Bhowmik, "Analyses of combined DSRR and EBG structures over SIW and HMSIW for obtaining band pass response," Wireless Personal Communications, Vol. 111, No. 2, 1207-1218, Nov. 2019.
8. Khalil, M., M. Kamarei, J. Jomaah, and , "Miniaturized half-mode slow-wave substrate-integrated waveguide bandpass filter," Wireless Personal Communications, Vol. 107, No. 1, 283-290, Jul. 2019.
9. Azad, A. R. and A. Mohan, "Substrate integrated waveguide dual-band and wide-stopband bandpass filters," IEEE Microwave and Wireless Components Letters, Vol. 28, No. 8, 660-662, Aug. 2018.
10. Azad, A. R. and A. Mohan, "Single- and dual-band bandpass filters using a single perturbed SIW circular cavity," IEEE Microwave and Wireless Components Letters, Vol. 29, No. 3, 201-203, Mar. 2019.
11. Zhang, H., W. Kang, and W. Wu, "Miniaturized dual-band SIW filters using E-shaped slotlines with controllable center frequencies," IEEE Microwave and Wireless Components Letters, Vol. 28, No. 4, 311-313, Apr. 2018.
12. Zhang, H., W. Kang, and W. Wu, "Dual-band substrate integrated waveguide bandpass filter utilising complementary split-ring resonators," Electronic Letters, Vol. 54, No. 2, 85-87, Jan. 2018.
13. Dong, Y., W. Hong, H. Tang, and W. Ke, "Millimeter-wave dual-mode filter using circular high-order mode cavities," Microwave and Optical Technology Letters, Vol. 51, No. 7, 1743-1745, Jul. 2009.
14. Chen, F., K. Song, B. Hu, and Y. Fan, "Compact dual-band bandpass filter using HMSIW resonator and slot perturbation," IEEE Microwave and Wireless Components Letters, Vol. 24, No. 10, 686-688, Oct. 2014.
15. Rebenaque, D., F. Pereira, J. Garcia, A. Melcon, and M. Guglielmi, "Two compact configurations for implementing transmission zeros in microstrip filters," IEEE Microwave and Wireless Components Letters, Vol. 14, No. 10, 475-477, Oct. 2004.
16. Mandal, M., K. Divyabramham, and V. Velidi, "Compact wideband bandstop filter with five transmission zeros," IEEE Microwave and Wireless Components Letters, Vol. 22, No. 1, 4-6, Jan. 2012.
17. Xu, K.-D., D. Li, and Y. Liu, "High-selectivity wideband bandpass filter using simple coupled lines with multiple transmission poles and zeros," IEEE Microwave and Wireless Components Letters, Vol. 29, No. 2, 107-109, Feb. 2019.
18. Lee, B., T.-H. Lee, K. Lee, M.-S. Uhm, and J. Lee, "K-band substrate-integrated waveguide resonator filter with suppressed higher-order mode," IEEE Microwave and Wireless Components Letters, Vol. 25, No. 6, 367-369, Jun. 2015.