Wide Stopband Planar Microwave Bandpass Filter Design

Muhammad Riaz, Bal S Virdee

Abstract


This paper describes a high selectivity microstrip bandpass filter fabricated using microstrip integrated technology with a wide stopband. The proposed filter consists of electromagnetically coupled 50Ω input and output feedlines that are strategically loaded with spiral inductors in order to introduce transmission zeros in the filter’s stopband response. Simulation results reveal that the proposed design enables the upper and lower transmission zeros to be adjustable independently by (±16.5%) prior to fabrication. Moreover, the coupling scheme employed allows the filter’s centre frequency to be adjusted by 8.69% and 3dB fractional bandwidth by 7.1% with insignificant effect on the stopband characteristics. The measured result confirms the filter exhibits a relatively sharp roll-off skirt with a passband insertion-loss of 1.51 dB and return-loss that is better than 15 dB. The proposed filter is suitable for applications in high interference environments and cognitive radio systems.

Keywords


Planar filters, microstrip integrated technology, microwave filters, high selectivity filters, wide out-of-band rejection

Full Text:

PDF

References


REFERENCES

L. Athukorala and D. Budimir, "Design of compact dual-mode microstrip filters," IEEE Transactions on Microwave Theory and Techniques, vol. 58, no. 11, pp. 2888-2895, 2010.

S. Marín, J. D. Martínez, C. I. Valero, and V. E. Boria, "Microstrip filters with enhanced stopband based on lumped bisected pi-sections with parasitics," IEEE Microwave and Wireless Components Letters, vol. 27, no. 1, pp. 19-21, 2016.

R. Gómez-García, L. Yang, J.-M. Muñoz-Ferreras, and D. Psychogiou, "Selectivity-enhancement technique for stepped-impedance-resonator dual-passband filters," IEEE Microwave and Wireless Components Letters, vol. 29, no. 7, pp. 453-455, 2019.

C.-L. Hsu and J.-T. Kuo, "A two-stage SIR bandpass filter with an ultra-wide upper rejection band," IEEE microwave and wireless components letters, vol. 17, no. 1, pp. 34-36, 2007.

Y. Rao, H. J. Qian, R. Gómez-García, and X. Luo, "Dual-band bandpass filter with ultra-wide upper stopband using slow-wave dual-resonance cells," in 2018 IEEE/MTT-S International Microwave Symposium-IMS, 2018, pp. 537-539: IEEE.

J.-T. Kuo, S.-P. Chen, and M. Jiang, "Parallel-coupled microstrip filters with over-coupled end stages for suppression of spurious responses," IEEE Microwave and Wireless Components Letters, vol. 13, no. 10, pp. 440-442, 2003.

M. H. Ho and W. C. Lin, "Design of stepped‐impedance hairpins band‐pass filter with wide stopband performance," Microwave and Optical Technology Letters, vol. 52, no. 6, pp. 1405-1408, 2010.

J.-T. Kuo, W.-H. Hsu, and W.-T. Huang, "Parallel coupled microstrip filters with suppression of harmonic response," IEEE Microwave and Wireless Components Letters, vol. 12, no. 10, pp. 383-385, 2002.

J.-T. Kuo and E. Shih, "Microstrip stepped impedance resonator bandpass filter with an extended optimal rejection bandwidth," IEEE Transactions on microwave theory and techniques, vol. 51, no. 5, pp. 1554-1559, 2003.

M. Makimoto and S. Yamashita, "Bandpass filters using parallel coupled stripline stepped impedance resonators," IEEE Transactions on Microwave Theory and Techniques, vol. 28, no. 12, pp. 1413-1417, 1980.

J. García-García et al., "Spurious passband suppression in microstrip coupled line band pass filters by means of split ring resonators," IEEE Microwave and Wireless Components Letters, vol. 14, no. 9, pp. 416-418, 2004.

S.-Y. Lee and C.-M. Tsai, "New cross-coupled filter design using improved hairpin resonators," IEEE Transactions on Microwave theory and Techniques, vol. 48, no. 12, pp. 2482-2490, 2000.

W.-H. Tu and K. Chang, "Compact microstrip bandstop filter using open stub and spurline," IEEE Microwave and Wireless Components Letters, vol. 15, no. 4, pp. 268-270, 2005.

Q.-X. Chu and Z.-H. Li, "Dual-band filter using asymmetrical stub-loaded resonator with independently controllable frequencies and bandwidths," IET Microwaves, Antennas & Propagation, vol. 7, no. 9, pp. 729-734, 2013.

H. Jia-Sheng and M. Lancaster, "Microstrip filters for RF/microwave applications," New York: John Wiley&Sond. Inc, pp. 235-272, 2001.




DOI: http://dx.doi.org/10.22385/jctecs.v31i0.313