本論文主要分成四大部份︰(a)非對稱截線負載共振器之三頻濾波器設計；(b)具有超寬止帶特性之低通濾波器設計；(c)微小化之超寬頻帶通濾波器設計；(d)具有窄頻與寬頻特性之雙頻帶通濾波器設計。
首先，本研究介紹了無線通訊系統之運作以及相關之通訊協定，並進一步介紹濾波器於無線通訊系統所提供之功能以及相關之基礎傳輸線理論。
接著，本研究提出一種三頻濾波器之設計，此三頻濾波器主要是由兩組非對稱截線負載共振器所組成。此非對稱截線負載共振器之結構是在一組抗均勻之微帶線上，額外附加一組具有相同阻抗之截線作為負載端；其中，額外附加之截線並非如傳統截線一般饋入於對稱面上，而本研究以此截線之饋入位置以及截線長度為變因，定義兩組比值參數(饋入位置比值與電子長度比值)以製作共振特性分析圖表，並加以評估與分析此非對稱截線負載共振器之共振特性，藉此有效控制與調整此共振器之倍頻響應，進而設計一三頻率波器。
接著，本研究提出一種低通濾波器之設計，此低通濾波器主要是由矩形截線共振器與開路截線共振器所組成。此矩形截線共振器是由平行耦合線兩端附加一矩形截線；其中，此矩形截線共振器具有低通濾波器之特性，根據輸入導納以及散射參數分析，其截止頻率主要受到平行耦合線與矩形截線之特性阻抗與電子長度所控制。因此，本研究定義兩組比值參數(電子長度比值與特性阻抗比值)，並根據此兩組比值參數進行共振特性圖表，藉此有效進行此矩形截線共振器之截止頻率之評估與預測，進而設計一具有超寬止帶範圍之低通濾波器。
接著，本研究提出兩種超寬頻帶通濾波器之設計，第一組超寬頻帶通濾波器是由平行耦合線與矩形截線共振器所組成，第二組超寬頻帶通濾波器是由矩形截線共振器所組成。在第一組超寬頻帶通濾波器中，透過平行耦合線與矩形截線共振器產生三組共振模態，並透過此三組共振模態激發超寬頻響應，此外，此矩形截線共振器亦可額外產生多組傳輸零點，透過電子長度比值與特性阻抗比值之調整，進而獲得良好之高頻雜訊抑制效果，藉此設計一具有超寬止帶範圍之超寬頻帶通濾波器。而在第二組超寬頻帶通濾波器中，本研究採用輸入導納與散射參數分析，說明此矩形截線共振器亦具有模態激發特性，並以其所激發之共振模態形成超寬頻帶通響應，並以此設計一超寬頻帶通濾波器。
最後，本研究提出一種具有窄頻與寬頻特性之雙頻帶濾波器之設計，此雙頻帶濾波器是由步階阻抗環形負載共振器與矩形截線共振器所組成。其中，此步階組抗環形負載共振器透過奇模態/偶模態等效電路分析，形成近似於步階式非對稱截線負載共振器，且根據本研究所定義之三組比值參數(饋入位置比值、電子長度比值與特性阻抗比值)，其共振模態之操作頻率可獲得有效之控制，並藉此激發一窄頻與一寬頻之通帶特性；此外，透過矩形截線共振器之附加，此雙頻帶濾波器於高頻區域之雜訊亦可獲得相當優良之抑制效果。該雙頻帶通濾波器具有相當良好之量測特性，如2.4 GHz之窄頻帶、3至5 GHz之寬頻帶、低插入損失、高通帶選擇性以及超寬止帶區域，而實際電路測量結果與模擬響應具有相當良好之一致性。

The dissertation is divided into four sections, comprising: (a) design of tri-band bandpass filter (BPF) by using asymmetric stub-loaded resonators (ASLR); (b) design of low-pass filter (LPF) with ultra broad stopband characteristic; (c) design of compact ultra-wideband (UWB) BPF; (d) design of dual-band BPF with narrow-bandwidth and wide-bandwidth responses.
Firstly, introductions about the operation of wireless communication system and relative protocol are proposed in this research. Moreover, the feature of filters in the wireless communication system and the basic transmission line theory are discussed.
Secondly, a tri-band BPF, constructed by ASLRs, is proposed. This ASLR is constructed by tapping a stub-loaded on the other uniform microstrip line. By properly tuning the electrical length ratios of the ASLRs (α and γ), the spurious modes of ASLR are controlled easily to form a tri-band response. In addition, a resonant chart of ASLR is provided to find the frequency of each spurious mode accurately.
Thirdly, a LPF, constructed by rectangular stub loaded resonator and open-circuited stubs, is proposed. The rectangular stub loaded resonator consists of a parallel coupled line and a rectangular stub patch, and it creates multiple transmission zeros at higher frequency side to form a low-pass response. It is noted that the cutoff frequency of rectangular resonators is dominated by the electrical length ratio and impedance ratio.
Fourthly, two UWB BPFs, basically constructed by rectangular stub loaded resonator, are fabricated and proposed. The resonant modes of one UWB BPF are excited by adopting parallel coupled line and rectangular stub loaded resonator, additionally, multiple transmission zeros created by rectangular stub loaded resonator are used to eliminate interference at the higher frequency side. And the resonant modes of the other UWB BPF are excited by using the mode-exciting technology. By properly tuning the electrical length ratio of the stub and parallel coupled-lines, a controllable resonant mode is excited and two transmission zeros are created in accordance with the results of imaginary-admittance analysis.
Finally, a dual-band BPF, constructed by stepped-impedance ring loaded resonator (SIRLR) and rectangular stub loaded resonator (RSLR), is fabricated and proposed. Based on even- and odd-mode analysis, the properties of SIRLR is analyzed and predicted. Herein, three parameters (two electrical length ratios and one impedance ratio) are defined and used to control the resonant modes of SIRLR. Moreover, Three transmission zeros, created by RSLR, are located near the passband edge to improve the band selectivity and achieve a sharp cutoff skirt. The fabricated dual-band BPF exhibits good performance, including a narrow passband at 2.4 GHz, a wide passband from 3 GHz to 5GHz, low insertion loss, high passband selectivity, and broad stopband region. The designed dual-band bandpass filter are fabricated and measured, and the measured results match the theoretical prediction.

Chapter 1
[1] Federal Communications Commission, “Revision of part 15 of the commission’s rules regarding ultra-wideband transmission systems,” Tech. Rep., ET-Docket 98–153, FCC02–48, Apr. 2002.
[2] https://electronicsnews.com.au/wireless-spectrum-is-for-sale-but-what-is-it
[3] http://mwrf.com/test-and-measurement/improve-accuracy-amplifier-aclr-and-acpr-measurements
[4] P.-H. Deng and J.-T. Tsai, “Design of microstrip cross-couple bandpass filter with multiple independent designable transmission zeros using branch-line resonators,” IEEE Microw. Wireless Compon. Lett., vol. 23, no. 5, pp. 249–251, May 2013.
[5] H. Di, B. Wu, X. Lai, and C.-H. Liang, “Synthesis of cross-coupled triple-passband filters based on frequency transformation,” IEEE Microw. Wireless Compon. Lett., vol. 20, no. 8, pp. 432–434, Aug. 2010.
[6] A. Garcia-Lamperez and M. Salazar-Palma, “Single-band to multiband frequency transformation for multiband filters,” IEEE Trans. Microw. Theory Tech., vol. 59, no. 12, pp. 3048–3058, Dec. 2011.
[7] Q. X. Chu, Z. H. Li, “Dual-band filter using asymmetrical stub-loaded resonator with independently controllable frequencies and bandwidths,” IET Proc. on Microw. Antennas Propag., vol. 7, Iss. 9, pp. 729–735, June 2013.
[8] J.-Z. Chen, N. Wang, Y. He, and C.-H. Liang, “ Fourth-order tri-band bandpass filter using square ring loaded resonators,” Electron. Lett., vol. 47, no. 15, pp. 858–859, July 2011.
[9] W.-Y. Chen, M.-H. Weng, and S.-J. Chang, “A new tri-band bandpass filter based on stub-loaded step-impedance resonator,” IEEE Microw. Wireless Compon. Lett., vol. 22, no. 4, pp. 179–181, Apr. 2012.
[10] M. Hayati, H. Asadbeigi, A. Sheikhi, “Microstrip lowpass filter with high and wide rejection band,” Electron. Lett., vol. 48, no. 19, pp. 1217–1219, Sep. 2012.
[11] J. Xu, Y. X. Ji, W. Wu, and C. Miao, “Design of miniaturized microstrip LPF and wideband BPF with ultra-wide stopband,” IEEE Microw. Wireless Compon. Lett., vol. 23, no. 8, pp. 397–399, Aug. 2013.
[12] R. Gomez-Garcia, M. A. Sanchez-Soriano, M. Sanchez-Renedo, G. Torregrosa-Penalva, E. Bronchalo, “Low-pass and bandpass filters with ultra-broad stopband bandwidth based on directional couplers,” IEEE Trans. Microw. Theory Tech., vol. 61, no. 12, pp. 4365–4366, Dec. 2013.
[13] X.-H. Wu, Q.-X. Chu, X.-K. Tian, and X. Quyang, “Quintuple-mode UWB bandpass filter with sharp roll-off and super-wide upper stopband,” IEEE Microw. Wireless Compon. Lett., vol. 21, no. 12, pp. 661–663, Dec. 2011.
[14] Z. Shang, X. Guo, B. Cao, B. Wei, X. Zhang, Y. Heng, G. Suo, and X. Song, “Design of a superconducting ultra-wideband (UWB) bandpass filter with sharp rejection skirts and miniaturized size,” IEEE Microw. Wireless Compon. Lett., vol. 23, no. 2, pp. 72–74, Feb. 2013.
[15] S. S. Gao and S. Sun, “Synthesis of wideband parallel-coupled line bandpass filters with non-equiripple responses,” IEEE Microw. Wireless Compon. Lett., vol. 24, no. 9, pp. 587–589, Sep. 2014.
[16] R. Zhang and L. Zhu, “Design of a wideband bandpass filter with composite short- and open-circuited stubs,” IEEE Microw. Wireless Compon. Lett., vol. 24, no. 2, pp. 96–08, Feb. 2014.

Chapter 2
[1] D. M. Pozar, 1998, Microwave engineering, 2nd ed., Wiley, New York.
[2] J. S. Hong, 2010, Microstrip filters for RF/microwave applications, 2nd ed., A John Wiley and Sons, New York.
[3] K. C. Gupta, R. Garg, I. Bahl, and P. Bhartia, 1996, Microstrip lines and slotlines, 2nd ed. Norwell, MA: Artech House.
[4] E. O. Hammerstard, “Equations for microstrip circuit design,” in Proceeding of the European Microwave Conference, 1975, Hamburg, Germany, pp. 286-272.
[5] S. Hong and K. Chang, “A 10–35-GHz six-channel microstrip multiplexer for wide-band communication systems,” IEEE Transactions on Microwave Theory & Techniques, vol. 54, no. 4, pp. 1370-1378, 2006.
[6] T. C. Edwards and M. J. Lancaster, 2000, Foundations of interconnect and microstrip design, Reading, John Wiley and Sons.
[7] R. A. Pucel, D. J. Masse, and C. P. Hartwig, “Losses in microstrip,” IEEE Transactions on Microwave Theory & Techniques, vol. 16, no. 6, pp. 342-350, 1968.

Chapter 3
[1] H. Di, B. Wu, X. Lai, and C.-H. Liang, “Synthesis of cross-coupled triple-passband filters based on frequency transformation,” IEEE Microw. Wireless Compon. Lett., vol. 20, no. 8, pp. 432–434, Aug. 2010.
[2] A. Garcia-Lamperez and M. Salazar-Palma, “Single-band to multiband frequency transformation for multiband filters,” IEEE Trans. Microw. Theory Tech., vol. 59, no. 12, pp. 3048–3058, Dec. 2011.
[3] Q. X. Chu, Z. H. Li, “Dual-band filter using asymmetrical stub-loaded resonator with independently controllable frequencies and bandwidths,” IET Proc. on Microw. Antennas Propag., vol. 7, Iss. 9, pp. 729–735, June 2013.
[4] X. Lai, C.-H. Liang, H. Di, and B. Wu, “Design of tri-band filter based on stub loaded resonator and DGS resonator,” IEEE Microw. Wireless Compon. Lett., vol. 20, no. 5, pp. 265–267, May 2010.
[5] X. Y. Zhang, Q. Xue, and B. J. Hu, “Planar tri-band bandpass filter with compact size,” IEEE Microw. Wireless Compon. Lett., vol. 20, no. 5, pp. 262–264, May 2010.
[6] J. Z. Chen, N. Wang, Y. He, and C. H. Liang, “Fourth-order tri-band bandpass filter using square ring loaded resonators”, Electron. Lett., vol. 47, no. 15, pp. 858–859, July 2011.
[7] L.-Y. Ren, “Tri-band bandpass filters based on dual-plane microstrip/DGS slot structure,” IEEE Microw. Wireless Compon. Lett., vol. 20, no. 8, pp. 429–431, Aug. 2010.
[8] W.-Y. Chen, M.-H. Weng, and S.-J. Chang, “A new tri-band bandpass filter based on stub-loaded step-impedance resonator,” IEEE Microw. Wireless Compon. Lett., vol. 22, no. 4, pp. 179–181, Apr. 2012.
[9] M.-H. Weng, S.-J. Chang, W.-Y. Chen, S.-W. Lan, C.-Y. Hung, Y.-H. Su, and H. Kuan, “A triband bandpass filter with low loss and high band selectivity using the split-end asymmetric stepped impedance resonators,” Microw. Opt. Tech. Lett., vol. 56, no. 6, pp. 1427–1430, June, 2014.
[10] J.-S. Hong and M.-J. Lancaster, Microstrip Filters for RF/Microwave Applications, Wiley, New York, 2001.
[11] M. Moradian and H. Oraizi, “Optimum design of microstrip parallel coupled-line band-pass filters for multi-spurious pass-band suppression,” IET Microw. Antennas Propag., vol. 1, iss. 2, pp. 488–495, Apr. 2007.

Chapter 4
[1] J.-S. Hong and M.-J. Lancaster, Microstrip Filters for RF/Microwave Applications, Wiley, New York, 2001.
[2] S. W. Ting, K. W. Tam, and R. P. Martins, “Miniaturize microstrip lowpass filter with wide stopband using double equilateral U-shaped defected ground structure,” IEEE Microw. Wireless Compon. Lett., vol. 16, no. 5, pp. 240–242, May 2006.
[3] M. Hayati, H. Asadbeigi, A. Sheikhi, “Microstrip lowpass filter with high and wide rejection band,” Electron. Lett., vol. 48, no. 19, pp. 1217–1219, Sep. 2012.
[4] J. Xu, Y. X. Ji, W. Wu, and C. Miao, “Design of miniaturized microstrip LPF and wideband BPF with ultra-wide stopband,” IEEE Microw. Wireless Compon. Lett., vol. 23, no. 8, pp. 397–399, Aug. 2013.
[5] R. Gomez-Garcia, M. A. Sanchez-Soriano, M. Sanchez-Renedo, G. Torregrosa-Penalva, E. Bronchalo, “Low-pass and bandpass filters with ultra-broad stopband bandwidth based on directional couplers,” IEEE Trans. Microw. Theory Tech., vol. 61, no. 12, pp. 4365–4366, Dec. 2013.
[6] M. Y. Hsieh and S. M. Wang, “Compact and wideband microstrip bandstop filter,” IEEE Microw. Wireless Compon. Lett., vol. 15, no. 7, pp. 472–474, July 2005.
[7] R. Li, D. I. Kim, and C. M. Choi, “Compact structure with three attenuation poles for improving stopband characteristics,” IEEE Microw. Wireless Compon. Lett., vol. 16, no. 12, pp. 663–665, Dec. 2006.
[8] C. Y. Hung, M. H. Weng, and R. Y. Yang, “A compact sharp-rejection lowpass filter,” Microw. Opt. Technol. Lett., vol. 50, no. 4, pp. 894–896, Apr. 2008.
[9] K. Ma and K. S. Yeo, “New ultra-wide stopband low-pass filter using transformed radial stubs,” IEEE Trans. Microw. Theory Tech., vol. 59, no. 3, pp. 604–611, Mar. 2011.
[10] C. Y. Hung, M. H. Weng, and R. Y. Yang, “A dual-mode bandpass filter with a wide stopband using a controllable bandstop structure,” Microw. Opt. Technol. Lett., vol. 50, no. 8, pp. 2214–2216, Aug. 2008.

Chapter 5
[1] Revision of Part 15 of the Commission’s Rules Regarding Ultra-Wideband Transmission Systems, Feb. Commun. Commiss., First Rep. Order, FCC02. V48, Apr. 2002.
[2] T. B. Lim, S. Sun, and L. Zhu, “Compact ultra-wideband bandpass filter using harmonic-suppressed multiple-mode resonator,” Electronics Lett., vol. 43, no. 22, pp. 1205–1205, Oct. 2007.
[3] H. N. Shaman and J.-S. Hong, “Compact wideband bandpass filter with high performance and harmonic suppression,” Proc. 37th Eur. Microw. Conf., pp. 528–531, 2007.
[4] J. Garcia-Garcia, J. Bonache, and F. Martin, “Application of electromagnetic bandgaps to the design of ultra-wide bandpass filters with good out-of-band performance,” IEEE Trans. Microw. Theory Tech., vol. 54, no. 12, pp. 4136–4140, Dec. 2006.
[5] C.-Y. Hung, M.-H. Weng, R.-Y. Yang, and Y.-K. Su, “Design of the compact parallel coupled wideband bandpass filter with very high selectivity and wide stopband,” IEEE Microw. Wireless Compon. Lett., vol. 17, no. 7, pp. 510–512, July 2007.
[6] M. Y. Hsieh and S. M. Wang, “Compact and wideband microstrip bandstop filter,” IEEE Microw. Wireless Compon. Lett., vol. 15, no. 7, pp. 472–474, July 2005.
[7] R. Li, D. I. Kim, and C. M. Choi, “Compact structure with three attenuation poles for improving stopband characteristics,” IEEE Microw. Wireless Compon. Lett., vol. 16, no. 12, pp. 663–665, Dec. 2006.
[8] C.-Y. Hung, M.-H. Weng, and R.-Y. Yang, “A compact sharp-rejection lowpass filter,” Microw. Opt. Technol. Lett., vol. 50, no. 4, pp. 894–896, Apr. 2008.
[9] L. Zhu, H. Bu, and K. Wu, “Aperture compensation technique for innovative design of ultra-broadband microstrip bandpass filter” in IEEE MTT-S Int. Dig., vol. 1, 2000, pp. 315–318.
[10] J.-S. Hong and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, New York, NY, USA: Wiley, 2001.

Chapter 6
[1] L. Zhu, S. Sun, and W. Menzel, “Ultra-wideband (UWB) bandpass filters using multiple-mode resonator,” IEEE Microw. Wireless Compon. Lett., vol. 15, no. 11, pp. 796–798, Nov. 2005.
[2] X.-H. Wu, Q.-X. Chu, X.-K. Tian, and X. Ouyang, “Quintuple-mode UWB bandpass filter with sharp roll-off and super-wide upper stopband,” IEEE Microw. Wireless Compon. Lett., vol. 21, no. 12, pp. 661–663, Dec. 2011.
[3] Z. Shang, X. Guo, B. Cao, B. Wei, X. Zhang, Y. Heng, G. Suo, and X. Song, “Design of a superconducting ultra-wideband (UWB) bandpass filter with sharp rejection skirts and miniaturized size,” IEEE Microw. Wireless Compon. Lett., vol. 23, no. 2, pp. 72–74, Feb. 2013.
[4] M.-Y. Hsieh and S.-M. Wang, “Compact and wideband microstrip bandstop filter,” IEEE Microw. Wireless Compon. Lett., vol. 15, no. 7, pp. 472–474, July 2005.
[5] R. Li, D. I. Kim, and C. M. Choi, “Compact structure with three attenuation poles for improving stopband characteristics,” IEEE Microw. Wireless Compon. Lett., vol. 16, no. 12, pp. 663–665, Dec. 2006.
[6] C.-Y. Hung, M.-H. Weng, and R.-Y. Yang, “A compact sharp-rejection lowpass filter,” Microw. Opt. Tech. Lett., vol. 50, no. 4, pp. 894–896, Apr. 2008.
[7] J.-S. Hong and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, New York, NY, USA: Wiley, 2001.
[8] L. Zhu, H. Bu, and K. Wu, “Aperture compensation technique for innovative design of ultra-broadband microstrip bandpass filter,” in IEEE MTT-S Int. Dig., vol. 1, 2000, pp. 315–318, June 2000.

Chapter 7
[1] L.-C. Tsai and C.-W. Hsue, “Dual-band bandpass filters using equal-length coupled-serial-shunted lines and Z-transform technique,” IEEE Trans. Microw. Theory Tech., vol. 52, no. 4, pp. 1111‒1117, Apr. 2004.
[2] X.-Y. Zhang and Q. Xue, “Novel dual-mode dual-band filters using coplanar-waveguide-fed ring resonators,” IEEE Trans. Microw. Theory Tech., vol. 55, no. 10, pp. 2183‒2190, Oct. 2007.
[3] B. Wu, C.-H. Liang, Q. Li, and P.-Y. Qin, “Novel dual-band filter incorporating defected SIR and microstrip SIR,” IEEE Microw. Wireless Compon. Lett., vol. 18, no. 6, pp. 392‒394, June 2008.
[4] H.-W. Wu, Y.-F. Chen and Y.-W. Chen, “Multi-layered dual-band bandpass filter using stub-loaded stepped-impedance and uniform-impedance resonators,” IEEE Microw. Wireless Compon. Lett., vol. 22, no. 3, pp. 114‒116, Mar. 2012.
[5] Y.-P. Zhang and M. Sun, “Dual-band microstrip bandpass filter using stepped-impedance resonators with new coupling schemes,” IEEE Trans. Microw. Theory Tech., vol. 54, no. 10, pp. 3779‒3785, Oct. 2006.
[6] M.-H. Weng, H.-W. Wu, and Y.-K. Su, “Compact and low loss dual-band bandpass filter using pseudo-interdigital stepped impedance resonators for WLANs,” IEEE Microw. Wireless Compon. Lett., vol. 17, no. 3, pp. 187‒189, Mar. 2007.
[7] R. Zhang and L. Zhu, “Design of a compact dual-band bandpass filter using coupled stepped-impedance resonators,” IEEE Microw. Wireless Compon. Lett., vol. 24, no. 3, pp. 155‒157, Mar. 2014.
[8] X.-Y. Zhang, J.-X. Chen, Q. Xue, and S.-M. Li, “Dual-band bandpass filter using stub-loaded resonators,” IEEE Microw. Wireless Compon. Lett., vol. 17, no. 8, pp. 583‒585, Aug. 2007.
[9] Y. Peng, L. Zhang, J. Fu, Y. Wang, and Y. Leng, “Compact dual-band bandpass filter using coupled lines multimode resonator,” IEEE Microw. Wireless Compon. Lett., vol. 25, no. 4, pp. 235‒237, Apr. 2015.
[10] C.-Y. Huang, M.-H. Weng, C.-Y. Hung, and S.-W. Lan, “Design of a dual-band bandpass filter for GSM and direct sequence ultra-wideband communication systems,” J. of Electromagn.Waves and Appl., vol. 25, pp. 1605‒1615, June 2011.
[11] S. Sun, “A dual-band bandpass filter using a single dual-mode ring resonator,” IEEE Microw. Wireless Compon. Lett., vol. 21, no. 6, pp. 298‒300, June 2011.
[12] J.-S. Hong and M. J. Lancaster, Microstrip Filters for RF/Microwave Applications, New York, NY, USA: Wiley, 2001.
[13] Zeland Software, Inc., IE3D Simulator, 1997.
[14] L. Zhu, H. Bu, and K. Wu, “Broadband and compact multi-pole microstrip bandpass filters using ground plane aperture technique,” IEE Proc.-Microw. Antenna Propag., vol. 149, no. 1, pp. 71‒77, Feb. 2002.
[15] L. Zhu, H. Bu, and K. Wu, “Aperture compensation technique for innovative design of ultra-broadband microstrip bandpass filter,” in IEEE MTT-S Int. Dig., vol. 1, 2000, pp. 315‒318.
[16] M.-Y. Hsieh and S.-M. Wang, “Compact and wideband microstrip bandstop filter,” IEEE Microw. Wireless Compon. Lett., vol. 15, no. 7, pp. 472‒474, July 2005.
[17] C.-Y. Hung, M.-H. Weng, and R.-Y. Yang, “A compact sharp-rejection lowpass filter,” Microw. Opt. Technol. Lett., vol. 50, no. 4, pp. 894‒896, Apr. 2008.
[18] C.-Y. Hung, M.-H. Weng, and R.-Y. Yang, “A dual-mode bandpass filter with a wide stopband using a controllable bandstop structure,” Microw. Opt. Technol. Lett., vol. 50, no. 8, pp. 2214‒2216, Aug. 2008.