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Abstract

This paper proposes a compact stepped-impedance low-pass filter using coplanar open-circuited stubs. The coplanar open-circuited stubs, which are used to compensate for the capacitive effect of the stepped-impedance low-pass filter, are implemented underneath the stepped-impedance low-pass filter. Consequently, the size of the stepped-impedance low-pass filter can be significantly reduced from 11.1 mm × 23.4 mm to 5.6 mm × 9.4 mm without altering its performance, amounting to a reduction rate of 79.83%. In addition, The transmission coefficient is attenuated below -30 dB, which is less than -20 dB attenuation of the conventional stepped-impedance low-pass filter. To verify the simulation result, the conventional stepped-impedance low-pass filter and the compact stepped-impedance low-pass filter using coplanar open-circuited stubs are fabricated and measured where the measurement results agree well with the simulation ones.

1. Cohn, S. B., "Parallel-coupled transmission-line-resonator filters," IRE Transactions on Microwave Theory and Techniques, Vol. 6, No. 2, 223-231, Apr. 1958.

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

3. Tang, Ching-Wen and Ming-Guang Chen, "Wide stopband parallel-coupled stacked SIRs bandpass filters with open-stub lines," IEEE Microwave and Wireless Components Letters, Vol. 16, No. 12, 666-668, Dec. 2006.

4. Tang, Ching-Wen and Yen-Kuo Hsu, "Design of a wide stopband microstrip bandpass filter with asymmetric resonators," IEEE Microwave and Wireless Components Letters, Vol. 18, No. 2, 91-93, Feb. 2008.

5. Tang, Ching-Wen and Yen-Kuo Hsu, "A microstrip bandpass filter with ultra-wide stopband," IEEE Transactions on Microwave Theory and Techniques, Vol. 56, No. 6, 1468-1472, Jun. 2008.

6. Mandal, M. K. and S. Sanyal, "A novel defected ground structure for planar circuits," IEEE Microwave and Wireless Components Letters, Vol. 16, No. 2, 93-95, 2006.

7. El-Halabi, Heba, Soubhi Abou-Chahine, Darine Kaddour, Emmanuel Pistono, and Philippe Ferrari, "DGS-SMS compact fifth order low pass filter," 2017 International Conference on High Performance Computing & Simulation (HPCS), 274-277, Genoa, Italy, Jul. 2017.

8. Ahn, D., J.-S. Park, C.-S. Kim, J. Kim, Y. Qian, and T. Itoh, "A design of the low-pass filter using the novel microstrip defected ground structure," IEEE Transactions on Microwave Theory and Techniques, Vol. 49, No. 1, 86-93, 2001.

9. Boudaa, S., M. Challal, R. Mehani, and D. Rabahallah, "Miniaturized ultra-wide stopband microstrip low pass filter design," 2015 4th International Conference on Electrical Engineering (ICEE), 1-3, Boumerdes, Algeria, Dec. 2015.

10. Luo, Sha, Lei Zhu, and Sheng Sun, "Stopband-expanded low-pass filters using microstrip coupled-line hairpin units," IEEE Microwave and Wireless Components Letters, Vol. 18, No. 8, 506-508, 2008.

11. Hsieh, Lung-Hwa and Kai Chang, "Compact elliptic-function low-pass filters using microstrip stepped-impedance hairpin resonators," IEEE Transactions on Microwave Theory and Techniques, Vol. 51, No. 1, 193-199, 2003.

12. Zhang, Fan, Shuai Liu, Peng Zhao, Ming Du, Xiaochuan Zhang, and Jun Xu, "Compact ultra-wide stopband lowpass filter using transformed stepped impedance hairpin resonator," 2017 IEEE International Symposium on Antennas and Propagation & USNC/URSI National Radio Science Meeting, 2227-2228, San Diego, CA, USA, Jul. 2017.

13. Dahlan, Samsul Haimi and Mazlina Esa, "Miniaturized low pass filter using modified unifolded single hairpin-line resonator for microwave communication systems," 2006 International RF and Microwave Conference, 16-20, Putra Jaya, Malaysia, Sep. 2006.

14. Pozar, D. M., Microwave Engineering, 3nd Ed., John Wiley & Sons, 2005.

15. Matthaei, G. L., L. Young, and E. M. T. Jones, Microwave Filters, Impedance-Matching Networks, and Coupling Structures, Artech House, 1980.

16. Yan, Zih-Siang, "Reduction of common-mode and differential-mode noises for multilayers differential transmission line," Master’s degree thesis, National Taiwan University of Science and Technology, Taipei City, Taiwan, 2016.

Dr. Yi-Ruo Chen

Mr. Kuan-Wei Chen

Prof. Chun-Long Wang