Figure 8(c) shows the measured individual phase and PD of S 21 and S 31 of the squared Marchand balun. The measured PD is 184.2  at 80 GHz, and equal to 183.4  –184.3  for frequencies 75–85 GHz. That is, the measured DPD is smaller than 4.3  for frequencies 75–85 GHz. Figure 9(a) shows the measured input reflection coefficients S 11 , S 22 , and S 33 of the octagonal Marchand balun. S 11 is equal to 26.23 dB at 80 GHz, smaller than 26.02 dB for frequencies 75– 85 GHz, and smaller than 210 dB for frequencies 91.3–107 GHz. S 22 is equal to 26.13 dB at 80 GHz, and smaller than 25.68 dB for frequencies 75–85 GHz. In addition, S 33 is equal to 26.02 dB at 80 GHz, and smaller than 25.9 dB for frequencies 75–85 GHz. Figure 9(b) shows the measured gains S 21 and S 31 , and AI versus frequency characteristics of the octagonal Marchand balun. The measured S 21 is equal to 24.78 dB at 80 GHz, and larger than 25.04 dB for frequencies 75–85 GHz. The measured S 31 is equal to 24.82 dB at 80 GHz, and larger than 24.86 dB for frequencies 75–85 GHz. Besides, the measured AI is 20.043 dB at 80 GHz, and equal to 20.01 to 20.175 dB for frequencies 75–85 GHz. That is, the measured MAI is smaller than 0.175 dB for frequen- cies 75–85 GHz. Figure 9(c) shows the measured individual phase and PD of S 21 and S 31 of the octagonal Marchand balun. The measured PD is 180.3  at 80 GHz, and equal to 180.7  –182  for frequencies 75–85 GHz. That is, the measured DPD is smaller than 2  for frequencies 75–85 GHz. Table 1 is a summary of the implemented CMOS W-band Marchand baluns, and recently reported state-of-the-art Marchand baluns. As can be seen, our proposed Marchand baluns occupy the smallest chip area, and achieve the best S 21 , S 31 , MAI, and DPD. The result indicates that the proposed CMOS W-band Marchand baluns are very promising for W-band RFIC (radio frequency integrated circuits) applications. 4. 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Lu, Micromachined CMOS LNA and VCO By CMOS compatible ICP deep trench technology, IEEE Trans Microwave Theory Tech 54 (2006), 580–588. 13. Y.S. Lin, J.F. Chang, H.B. Liang, T. Wang, and S.S. Lu, High-per- formance transmission-line inductors for 30–60 GHz RFIC applica- tions, IEEE Trans Electron Devices, 54 (2007), 2512–2519. V C 2014 Wiley Periodicals, Inc. METAMATERIAL BASED DUAL-BAND BANDPASS FILTER DESIGN FOR WLAN/WiMAX APPLICATIONS Ali Kursad Gorur, 1 Ceyhun Karpuz, 2 Ahmet Ozek, 2 and Murat Emur 2 1 Department of Electrical and Electronics Engineering, Nevsehir Haci Bektas Veli University, Nevsehir, 50100, Turkey; Corresponding author: agorur@pau.edu.tr 2 Department of Electrical and Electronics Engineering, Pamukkale University, Denizli, 20070, Turkey Received 5 February 2014 ABSTRACT: This article proposes a dual-band bandpass filter exhibit- ing negative effective magnetic permeability as well as effective negative electric permittivity. The proposed filter is constructed by loaded open- loop resonators (OLR). Input and output ports are connected to each other with a grounded feedline having two via holes located at the tap- ping point alignments of loading elements. Dual-mode properties of OLRs are used to obtain the dual-band response. Hence, each passband can be controlled individually by means of the gap between the folded parts of the OLR and the dimensions of loading elements. Four loaded OLRs are placed at the upper and lower sides of the main feedline to obtain two poles in each passband. Center frequencies of the designed filter are adjusted to 2.45 GHz (WLAN) and 3.5 GHz (WiMAX). It has an electrical length of 0.414 k g 3 0.32 k g , where k g is the guided wave- length at the lowest center frequency, 2.45 GHz. Proposed filter has also been fabricated for the experimental verification of the design methodology. V C 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2211–2214, 2014; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.28564 Key words: dual-band; bandpass filter; metamaterial; open-loop; load- ing element DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 56, No. 10, October 2014 2211