This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination. IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS 1 Multiple Band Notched Filter Using C-Shaped and E-Shaped Resonator for UWB Applications Sandip Kumar, Ravi Dutt Gupta, Student Member, IEEE, and Manoj Singh Parihar, Member, IEEE Abstract—In this letter, a highly selective ultra wide band (UWB) band pass filter (BPF) with triple notch bands is proposed using C-Shaped and E-Shaped resonators along with a triangular ring loaded stub resonator (TRLSR) resting on a multi-mode resonator (MMR). The MMR is constructed using a uniform transmission line and parallel coupled lines connected to 50 Ω feed lines at both ends. Five even and odd modes are created to achieve an UWB passband response. Additionally, two transmission zeros at lower and upper cutoff frequencies of the passband are formed by TRLSR which helps to get a high skirt factor (SF) of 0.975. In addition, multiple notch bands are created using λ g /2 resonators to reject three interfering frequency bands named as WiMAX, WLAN, and X-Band. The center frequency of each notch can be controlled by tuning the length of the resonator. The proposed filter is simulated, fabricated, and tested experimentally. Both the predicted and the measured results are in good agreement and replicating the behavior of the proposed filter. Index Terms—Band pass filter (BPF), triangular ring loaded stub resonator, triple-notch, ultra wide band (UWB). I. I NTRODUCTION T HE FCC (Federal Communication Commission) has allo- cated an unlicensed commercial bandfrom 3.1 to 10.6 GHz in 2002 for short range high speed transmission [1]. Earlier, this technology was used for military applications, but as of now, UWB technology is very interesting and getting much attention. The UWB spectrum suffers an interference from other radio frequency (RF) bands such as 3.6, 5.2, and 8.4GHz used for other technologies. A number of designs and methods based on MMR using stepped impedance transmission lines have been proposed in [2]–[5]. All these designs reported an acceptable UWB passband response with reasonably good skirt factor, but without rejecting interferences at mentioned RF bands. In [6]–[9], several methods have been reported to reject these in- terferences. Nevertheless, rejecting the interfering bands with- out disturbing the actual UWB response and retaining high skirt factor in the stop band has been rather challenging. In this letter, a highly selective UWB filter with multiple notches has been proposed. This filter has the advantage to choose any combination of the notch bands at the designer’s perspective, such as: a single notch (3.6 GHz/5.2 GHz/8.4 GHz), dual notch (3.6 GHz Manuscript received December 28, 2015; revised January 29, 2016; accepted February 9, 2016. The authors are with the PDPM Indian Institute of Information Technology Design and Manufacturing Jabalpur, Madhya Pradesh, 482005, India (e-mail: sandip.iiit@gmail.com; ravidutt81@gmail.com; mscareiit@gmail.com). Color versions of one or more of the figures in this letter are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/LMWC.2016.2549700 Fig. 1. Schematic of the proposed design, Design Parameters: L 1 = 15.4, L 2 =9.3, L 3 = 15.0, L 5 =7.6, L 6 =8.2, L 7 =8.9, W 0 =2.25, W 1 = 1.75, W 2 =0.6, W 3 = W 4 =0.4, W 5 =0.3, W 6 =1.1, W 7 =3.6, L r1 = 14.0, L r2 =9.5, L r3 =6.5, L r4 = L r6 + L r7 =8.8, L r5 =1.5, L r6 =5.8, L r7 =3.0, L r8 =4.0, L r9 =1.5, W r1 = W r2 = W r3 =0.4, g 1 = 0.35, g 2 =0.2, D 1 =0.21, D 2 =0.5 (allin mm). & 5.2 GHz/5.2 GHz & 8.4 GHz/3.6 GHz & 8.4 GHz) and triple notch (3.6, 5.2, and 8.4 GHz) UWB filter. II. DESIGN OF TRIANGULAR RING LOADED STUB RESONATOR UWB FILTER As shown in Fig. 1, the triangular ring loaded stub resonator is centrally located on the uniform transmission line having an electrical length θ 1 and characteristic impedance Z 1 . Using the transmission line theory, an even and odd mode behav- ior is approximated. The uniform transmission line with the stepped transmission line having an electrical length θ 5 and impedance Z 5 behaves as an MMR. The MMR and TRLSR contribute five resonant modes (three even and two odd modes) in the passband and two sharp transmission zeros at lower and higher cutoff, respectively, thereby enhancing the filter’s skirt factor significantly. Aperture backed parallel coupled lines have been enacted to have better coupling in the passband [2]. The proposed UWB filter is simulated in Finite Integral Technique [FIT]-based CST Microwave Studio. The effect of introducing TRLSR and back side aperture is shown in Fig. 2(a). Two trans- mission zeros are created at 2.96 and 11.1 GHz, which provide a highly selective UWB band pass response. The transmission zero frequencies depend on the stub length L 2 and perimeter L 3 of the triangle. The governing equation of transmission zeros could be obtained by making the transmission coefficient (S 21 ) 1531-1309 © 2016 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.