A Novel Design Of Microstrip Diplexer Using Triangular Loop Resonators A
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A Novel Design Of Microstrip Diplexer Using Triangular Loop Resonators A

Chinig JZbitou AErrkik L El Abdellaoui A Tajmouati M Latrach A Tribak 1 LITEN Laboratory FST of Settat Hassan 1st Univer sity of SettatMorocco 2 FPK LITEN Laboratory Hassan 1st University of Sett at Morocco 3 Microwave Group ESEO France 4 Nati

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A Novel Design Of Microstrip Diplexer Using Triangular Loop Resonators A

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1 A Novel Design Of Microstrip Diplexer Using Triangular Loop Resonators A.Chinig , J.Zbitou , A.Errkik , L .El Abdellaoui , A. Tajmouati , M. Latrach , A. Tribak . 1 LITEN Laboratory, FST of Settat, Hassan 1st Univer sity of Settat-Morocco 2 FPK LITEN Laboratory, Hassan 1st University of Sett at- Morocco 3 Microwave Group, ESEO France. 4 National Institute of Posts and Telecommunications Rabat Morocco Abstract This paper presents a new structure of microstrip diplexer based on triangular loop resonators. The di plexer is composed of two bands pass filters for the WiMAX ap

plications at 3.2 GHz (IEEE 802.16 WiMAX at 3.17 GHz to 4.2 GHz b ands) and the WLAN applications at 2.4 GHz (IEEE 802.11 WLAN a t 2.4 GHZ to 2.5 GHz). Two triangular resonators conn ected with a transmission line are used to form each filter wi th a matching network used to connect the two BPFs with the anten na. The diplexer has less than 2 dB insertion loss and more than 23 dB of isolation. This prototype diplexer is designed for a multiband system operating in the 2.4/3.2GHz respectively. The simulation results are investigated by using ADS from Agilent Technologies . Index Terms

diplexer; Band-pass filter; Triangular loop resonators; isolation; insertion loss. I. NTRODUCTION With the constant development in wireless communica tion systems, compact size, low cost and high performanc e components are increasingly requested. Waveguides are widely used due to their very lo w insertion loss and high isolation however their main disa dvantages are their size, weight and cost. For this reason pl anar technology represents an interesting alternative es pecially microstrip technology, thanks to its advantages of small size, light weight, low cost and easy integration with ot

her front- end circuitry on a single circuit board. Microstrip diplexers represent a key component in m any communication systems which require simultaneous re ception and transmission. Its essential role is to allow to the transmitter and the receiver operating in different frequencies to use the common antenna [1]. The diplexers use band pass filters in the majority of cases. Numerous studies on planar filters have enabled the development of a large number of topologies and des ign methods. Several methods have been reported in the literature such as diplexer based on the cross coupled

stepped impedance resonators [2], a diplexer, employing ban d-stop filters with periodic open-circuited stubs [3], a h igh isolation hairpin line diplexer using stepped impedance coupl ed-line resonators [4], diplexers based on common resonator s sections [5], Parallel coupled lines [6] or square ring reso nators [7]. This paper presents a compact diplexer formed by tw o band pass filters using triangular loop resonators opera ting at 2.4/3.2 GHz, in this work a new approach was used t o design the diplexer which consists in the design of two BP Fs operating at different frequencies then a

coupled-j unction was used to combine these two structures to form the fi nal circuit. II. BAND PASS FILTER USING TRIANGULAR LOOP RESONATORS. Due to their compact size triangular loop resonator s have been widely used to design filters [8-11]. In a previous work [12], two band pass filters were designed and combined us ing triangular loop resonators to form a microstrip dip lexer for the DCS and ISM applications (a)
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2 (b) Figure 1. Structure of the proposed filters for (a) the 2.4 G Hz band (b) the 3.2 GHz band. In order to achieve a compact size with high perfor mances, novel

design of two band pass filters based on tria ngular loop resonators were designed and simulated for the cent er frequency of 2.4/3.2 GHz respectively. Figure 1.a depicts the structure of the designed Rx band pass filter at 2.4 GHz. As we can see, the filter is com posed from two coupled triangular resonators with two cross-co upled feed lines connected to the Input/output ports. Based on the first structure the same method was used to design the Tx band pass filter at 3.2 GHz. Depending on the dimensions of the resonators and t he coupled transmission lines, the two filters can hav e

different operating frequencies. A little change in the dista nce between the resonators and the feed lines can make a signif icant variation in the filter performances especially in the insertion losses values. The Rx and the Tx filters present a compact size of 14 23 mm and 16 30 mm respectively. The substrate used is the FR4 with a thickness of 1.58 mm, a relative electri c constant of 4.4, a loss tangent of 0.01 and a conductor thic kness of 35 um. (a) (b) Figure 2: The simulated results of the proposed f ilters using ADS software (a) Rx Filter (b) Tx Filter. The characteristics of the

two BPFs are investigate d by full wave electromagnetic simulation by using Momentum electromagnetic simulator integrated into ADS. Figu re.2 describes the simulation results obtained for the R x and the Tx filters. The simulated insertion loss is 1.6 dB at 2.4 GHz a nd 1.38 dB at 3.2 GHz, the return loss is better than 25 dB at the two frequencies. The Rx pass band filter has a bandwidt h of about 161 MHz at 3.2 GHz and the Tx band pass filter has bandwidth of 111 MHz at 2.4 GHz. The Rx filter show s a good out-of-band rejection, better than 20 dB while the Tx filter represent an out-of-band

rejection better th an 15 dB which influence the isolation of the diplexer, so a good adjustment of some parameters is primordial to get a circuit with high performances. TABLE I: IMULATION RESULTS OF THE BPF S Parameter Simulation results Tx Rx Frequency GHz 2.4 3.2 Bandwidth 111 MHz 161 MHz Insertion loss [db] 1.6 1.38 Return loss [db] 25 30 Table 1 shows the simulated results of the proposed band pass filters by using ADS Agilent, as we can clearly see good performances are obtained for the transmission and reception channels. III. DIPLEXER DESIGN Having designed the two band pass filters,

and base d on the above discussion the two BPFs are combined to const ruct the microstrip diplexer. Figure.3 shows the structure o f the proposed diplexer and the circuit fits into a 16 47 mm area.
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3 Figure 3: Layout of the designed microstrip triang ular loop diplexer with ADS software In our case the two band pass filters are interconn ected using a coupled-junction which connects the two filters wit h the antenna port. Port1 represents the input port conne cted to the antenna, while the port 2 and 3 represent the outpu t of the receiver filter and the input of the

transmitter fi lter respectively. All ports are designed for 50 Ohm inp ut impedance. Its known that diplexer performances can be distor ted when the two filters are combined and this represent the main challenge in the classical approach. This distortio n can be explained by the presence of weak coupling phenomen a between the two filters after the interconnection. So a careful adjustment of some physical parameters was essentia l to get the desired response. Figure 4: The frequency response of the proposed d iplexer. The diplexer performances were investigated by simu lation. The circuit

was simulated using an EM simulator ADS Agilent and Figure.4 shows the simulated results. As we can observe the isolation between the transmi tter and the receiver is better than 23 dB, the -3 dB bandwi dth is 4.78 % and the minimum insertion loss is 1.38 dB, the re turn loss is better than 30 dB for the Rx filter. The Tx filter has less than 1.7 dB in the insertion loss and better than 30 for the return loss while the bandwidth is about 3.5 %. The out-of -band rejection is better than 20 dB for the Tx and the R x filters respectively. The designed diplexer was simulated with the CST so ftware

to check the electrical performances of the proposed c ircuit. Figure.5 depicts the layout of the designed microst rip triangular loop diplexer with CST microwave softwar e. Figure 5: Layout of the designed microstrip triangu lar loop diplexer with CST microwave software. The simulated results with CST software are found t o be in good agreement with the frequency response of the d iplexer with the ADS Agilent. Figure 6: The simulated results of the proposed dip lexer using CST software. Figure.6 shows the electrical performances of the p roposed diplexer using the 3D simulator CST software.

The d iplexer presents insertion losses of 0.49 and 0.45 dB, and return losses of 16.6 and 12.8 dB, at 2.4 and 3.2 GHz respectivel y, with isolation between transceiver and receiver better t han 19 dB. Each band pass filter presents an out-of-band rejec tion better than 18 dB at the pass band of its counterparts. We can clearly observe an increase of the bandwidth of the two pas s bands, and a deviation of the 70 MHz in the higher channel . This mismatch could be attributed to the use of low mesh ing density in the second simulation with CST microwave software. Acknowledgment We thank Mr.

Mohamed Latrach Professor in ESEO, engineering institute in Angers, France, for allowi ng us to use software and equipment available in his laboratory.
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4 IV. ONCLUSION In this paper, a new and simple low cost microstrip band pass filter using triangular loop resonators operating a t 2.4/3.2 GHz are designed, simulated and connected to form the p roposed diplexer. Hence, the proposed diplexer needs to ope rate for WLAN and WIMAX systems. This work shows that based on triangular loop resonators it is possible to design a diplexer with a compact size and good electrical

performance s. This paper provides also the detailed diplexer geometry and simulated results. The proposed circuit presents go od performances with an insertion loss lower than 1.7 dB in the higher and lower pass bands and a high isolation be tween the two channels greater than 30 dB. EFERENCES [1] D. M. Pozar, Microwave Engineering, John Wiley & So ns 1998. [2] M. Makimoto and S. Yamashita, Band pass filters usi ng parallel coupled stripline stepped impedance resonators, IE EE Trans Microwave Theory Tech., 28 (1980), 14131417. [3] B. Strassner and K. Chang, Wide-band low-loss high

-isolation microstrip periodic-stub diplexer for multiple-freq uency applications, IEEE Trans. Microw. Theory Tech., vol. 49, no. 10, pp. 18181820, Oct. 2001. [4] S. Srisathit, S. Patisang, R. Phromloungsri, S. Bun njaweht, S. Kosulvit, and M. Chongcheawchamnan, High isolation and compa ct size microstrip hairpin line diplexer, IEEE Microw. Wir eless Compon.Lett., vol. 15, no. 2, pp. 101103, Feb. 2005. [5] Chen, C. F., T. Y. Huang, C. P. Chou, and R. B. Wu, Microstrip diplexers design with common resonator sections for compact size, but high isolation, IEEE Trans. Microw. Theory Tech.,

Vol. 54, 1945-1952, 2006. [6] Weng, M. H., C. Y. Hung, and Y. K. Su, A hairpin l ine diplexer for direct sequence ultra-wideband wireless communicati ons, IEEE Microw. Wireless Compon. Lett., Vol. 17, 519-521, 2 007. [7] Ye, C. S., Y. K. Su, M. H. Weng, and C. Y. Hung, A microstrip ring- like diplexer for bluetooth and ultra wide band (UW B) application, Microwave & Opt. Tech. Lett., Vol. 51, 1518-1520, 2 009. [8] Lugo, C. and J. Papapolymerou, Band pass filter des ign using a microstrip triangular loop resonator with dual-mode operation. IEEE Microwave and Wireless Components

Letters, Vol. 15, No. 7, July 2005. [9] R.-B. Wu and S. Amari, New triangular microstrip l oop resonators for bandpass dual-mode filter application, presented i n IEEE MTT-S Int. Microw. Symp. Dig., 2005, pp. 941-944. [10] Gorur, A. and C. Karpuz, Cross-coupled band pass filter using microstrip triangular open-loop resonators, presen ted in IEEE European Microwave Conference 2001, 1-4, London, England, Oc t. 2001. [11] S. Chaimool, S. Kerdsumang, and P. Akkaraekthalin, A novel microstrip band pass filter using triangular open-lo op resonators, Asia-Pac Conf Commun (2003), 788791.

[12] A. Chinig, J. Zbitou, A. Errkik, A.Tribak, H. Benni s, and M. Latrach Microstrip Triangular Loop Resonator Duplexer, I nternational Journal of Computer and Communication Engineering, Vol. 2, No. 4, July 2013.