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Compact dual-band filtering-response power divider with high in-band frequency selectivity
Microelectronics Journal ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Compact dual-band filtering-response power divider with high in-band frequency selectivity Kaijun Song n, Shunyong Hu, Fan Zhang, Yu Zhu, Yong Fan PEHF Key Laboratory of Science, School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
art ic l e i nf o
a b s t r a c t
Article history: Received 16 September 2015 Accepted 3 March 2016
A novel compact dual-passband filtering-response power divider using modified stepped impedance resonators (SIRs) is presented. The quarter-wavelength transmission lines of conventional Wilkinson power divider are replaced by the dual-band bandpass filters to realize dual-passband bandpass response, and the phase shift of the proposed filters is tuned to be 90°. An isolation resistance R is placed at the center of the symmetric plane to realize good isolation between the two output ports. Two modified SIRs are adopted in the dual-passband filters to improve the return loss in both two passbands and control the resonant frequencies. The characteristic of the modified SIR is also analyzed. Meanwhile, the resonant frequencies can be tuned by changing impedance ratio of SIR. The source–load coupling is utilized to improve the frequency selectivity and achieve a high out-of-band rejection. A prototype of the proposed power divider is designed, fabricated, and measured. Reasonable agreement between the simulated results and measured ones is demonstrated. & 2016 Elsevier Ltd. All rights reserved.
Keywords: Dual-band Filtering-response Power divider Compact High frequency selectivity
1. Introduction The power divider is one of the key passive components in many electronic systems, which can be used in microwave circuit to divide or combine the power of microwave signals [1–8]. Moreover, Bandpass filter (BPF) is another important device in RF systems to reject unwanted signals [15,31–35]. The conventional Wilkinson power divider cannot efficiently reject unwanted frequency signals out of its usable bandwidth. Then, the additional bandpass filter has to be used to reject unwanted frequency signals, which will enlarge greatly the size of the systems. In recent year, several power dividers with filtering response by integrating filter and power divider have been developed. There are several ways to integrate the resonators with the power divider. Stubloaded resonator was added to the λ/4 length transmission lines [9,10] to achieve the filtering response. The stepped impedance resonator (SIR) [11,12], net-type resonator [13], embedded dualmode resonator [14], spiral resonator [16,17] and the half/quarterwavelength resonator [18,19,27] were used to realize the filtering response by replacing the λ/4 length transmission lines of the traditional Wilkinson power divider with these resonators. The coupled microstrip line was introduced to achieve a compact layout size and bandpass response in [20–25]. In [26], an asymmetric spiral defected ground structure (DGS) was used to n
Corresponding author. E-mail addresses: [email protected], [email protected] (K. Song).
suppress the second and third harmonics simultaneously. Moreover, an ultra-wideband power divider with bandpass filtering response [28–30] was also constructed by introducing multilayer microstrip line and slotline coupling structure or adding the impedance matching stubs. Besides, some filters using stepped impedance resonators (SIRs) to realize dual-passband bandpass response have been investigated [31–35]. In this paper, a novel compact power divider with dualpassband filtering-response is presented. Modified SIRs with five slots are employed in the proposed dual-passband filters to achieve dual-passband bandpass response and compact size. The characteristic of the modified SIR is analyzed. The central frequencies of the two passbands can be adjusted by tuning the impedance ratio and the size of slots. Several transmission zeros (TZs) can be generated through the source–load cross coupling to improve the frequency selectivity. To verify its performance, a prototype dual-band power divider is designed, fabricated, and measured. The measured results agree with the simulation one closely. The design results indicate that this structure has several advantages, such as compact size, low insertion loss, and good balance of amplitude and phase at output ports.
2. Design and analysis of the proposed power divider The structure of the proposed dual-passband filtering-response power divider based on modified SIRs is shown in Fig. 1. The power divider consists of two dual-band BPFs and an isolation
http://dx.doi.org/10.1016/j.mejo.2016.03.002 0026-2692/& 2016 Elsevier Ltd. All rights reserved.
Please cite this article as: K. Song, et al., Compact dual-band filtering-response power divider with high in-band frequency selectivity, Microelectron. J (2016), http://dx.doi.org/10.1016/j.mejo.2016.03.002i
K. Song et al. / Microelectronics Journal ∎ (∎∎∎∎) ∎∎∎–∎∎∎
resistor. The dual-band BPF is realized by using a ring-like type modified SIR with five slots (the dashed box in Fig. 1). The modifier SIR was bent to realize the coupling structure. Five slots were all etched on the low impedance transmission line part. The slots are used to adjust the different modes to realize the two passband. The input signal will be divided into two channels, and reach to the output ports through a dual-passband filter, respectively. A resistance R is placed between the two output ports to improve the output isolation. Besides, source–load cross coupling are introduced to generated TZs, then the high out-of-band rejection and good frequency selectivity can be obtained. It can be seen from Fig. 1 that the λ/4 length transmission lines of the traditional Wilkinson power divider was replaced by the dual-passband filters to realize dual-passband bandpass response of the presented power divider. As we know, the λ/4 length transmission lines were used in the traditional Wilkinson power divider to implement the 90° phase shift and improve the output isolation (when the isolation resistor R is located at the end of the λ/4 length transmission lines). The λ/ 4 length transmission lines were replaced by the dual-passband filters with 90° phase shift in the presented dual-passband filtering-response power divider. Then, the dual-passband filters should achieve 90° phase shift at the central frequencies of the dual passbands, simultaneously. Fig. 2 shows the phase shift of the dual-passband filter between the input and output ports in the central frequencies of the dual passbands. It can be seen that the phase shift at the central frequencies of the dual passbands are all 90°, which has shown that the λ/4 transmission lines of Wilkinson power divider can be replaced by this dual-passband filter. That is to say, the phase shift of the dual-passband filters can meet the
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Fig. 3. (a) the layout of three structures of the SIR and (b) the frequency response of the three SIRs in the condition of weak coupling.
Fig. 1. Layout of the proposed dual-passband power divider.
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design of the presented dual-band filtering-response power divider after optimizing the structural sizes of SIRs and coupling lines. Fig. 3(a) shows the layout of three structures of the SIR. Case3 is the traditional structure of SIR, case2 and case1 are both the modified SIR with two 90°-crossed slots in the center and three short slots on the side respectively. Fig. 3(b) shows the frequency response of the three SIRs in the condition of weak coupling. It can be seen that the second passband could be shifted to the first passband greatly in the structure of case2. And in the structure of case1, the second passband also can be shifted to the first passband. Both of the two structures make slight affect to the first passband. Thus, the second passband could be adjusted by introducing the five slots, that is to say, the introducing of the five slots affect the resonant modes of the SIR. Fig. 4 illustrates the frequency response of the proposed power divider with different L6. It can be seen that the central frequency of the second passband can be changed greatly by tuning L6, while that of the first passband changes slightly. Fig. 5(a) shows the frequency response of the proposed power divider with different W2, it can be seen that the bandwidth of the first passband can be adjusted by altering W2, whereas that of the second passband is almost constant. Meanwhile, the bandwidth of the two passband can be adjusted by changing L7 greatly (as shown in Fig. 5(b)). So, the operating frequencies and bandwidths can be tuned by changing W2 and the lengths of slots (L6 and L7). That is to say, the resonant frequencies can be controlled by changing the impedance ratio between the high- and low-impedance transmission lines. It can also be seen that the desired operating frequencies and
Please cite this article as: K. Song, et al., Compact dual-band filtering-response power divider with high in-band frequency selectivity, Microelectron. J (2016), http://dx.doi.org/10.1016/j.mejo.2016.03.002i
K. Song et al. / Microelectronics Journal ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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Fig. 6. Photograph of the fabricated dual-passband power divider.
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Fig. 4. Frequency response of the proposed power divider with varied L6.
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Fig. 5. Frequency response of the proposed power divider with varied (a) W2 (b) L7.
bandwidths can be controlled independently. It can be concluded that the impedance ratio between the high- and low-impedance transmission lines generate the first passband, while the five slots generate the second passband.
3. Experimental results According To verify and demonstrate the proposed circuit, the proposed dual-band filtering-response power divider based on modified SIRs has been designed and implemented. The photograph of the proposed power divider is shown in Fig. 6. A Taconic RF-35 substrate with a relative dielectric constant of 3.5, thickness of 0.508 mm, loss tangent of 0.0018 is used. The commercial software HFSS is used for simulating and optimizing the structure of the
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Fig. 7. Simulated and measured results (a) input return loss and insertion loss, (b) output return loss and isolation and (c) amplitude and phase difference.
proposed power divider. The final sizes and parameters of the dualpassband power divider are: L1¼9 mm, L2¼22.55 mm, L3¼ 17.25 mm, L4¼L5¼10.05 mm, L6¼13 mm, L7¼3.5 mm, W0¼ 1.15 mm, W1¼W7¼ 0.6 mm, W2¼0.2 mm, W3¼ 0.9 mm, W4¼ 0.5 mm, W5¼6.4 mm, W6¼1 mm, S1¼ 0.2 mm, S2¼S3¼ 0.3 mm. The proposed power divider was measured using an Agilent 8757DE8363B network analyzer. Fig. 7 shows the simulation and measurement results. Fig. 7(a) shows the simulated and measured results, which demonstrate a good agreement. The central frequency of the lower passband is 2.45 GHz and the lower passband
Please cite this article as: K. Song, et al., Compact dual-band filtering-response power divider with high in-band frequency selectivity, Microelectron. J (2016), http://dx.doi.org/10.1016/j.mejo.2016.03.002i
K. Song et al. / Microelectronics Journal ∎ (∎∎∎∎) ∎∎∎–∎∎∎
4
has 3-dB fractional bandwidth of 10%. The measured maximum return loss within the lower passband is about 13.6 dB, whereas the measured minimum insertion loss of the lower passband is about 1.4 dB (the 3 dB power division loss is not included), which includes the loss of SMA connectors. The three transmission zeros on the both side of the lower passband are located at 1.3, 1.8 and 2.7 GHz because of the source–load cross coupling. The upper passband is located at 3.72 GHz, with 3-dB fractional bandwidth of 3%. The measured maximum return loss within the upper passband is about 14.6 dB, whereas the measured minimum insertion loss of the upper passband, including the loss of SMA connectors, is about 1.5 dB (the 3 dB power division loss is not included). Another three transmission zeros near the upper passband are located at 3.45, 3.9 and 5.2 GHz. It can be seen that six transmission zeros can be observed on both sides of the two passbands for the fabricated dual-band filtering-response power divider. Then, the frequency selectivity and out-of-band rejection are improved greatly by the six transmission zeros. In addition, the out-of-band rejection level is more than 35 dB at the lower stopband (from 0 to 1.9 GHz), 24 dB at the middle stopband (from 2.65 to 3.53 GHz), and 20 dB at the upper stopbands (from 3.8 to more than 6 GHz). Fig. 7(b) shows that the outputs return loss and the isolation between the two output ports. The output return loss of the two passband is 16.1 dB and 15.4 dB. The isolation of the output ports of the two passband is 14.4 dB and 23 dB respectively. Fig. 7 (c) shows that the output amplitude imbalance is about 7 0.2 dB, and the output phase imbalance is about 70.3°. The amplitude and phase balance between the output ports are very good. The measured results are in good agreement with the full wave simulated ones. The tiny deviation is observed, which may be attributed to the fabrication error in the implementation. The overall size of the dual-band filter is only 0.28 λg 0.45 λg, where λg is the wavelength of central frequency of the lower passband. The design results indicate that this structure has several advantages, such as compact size, low insertion loss, and good balance of amplitude and phase at output ports.
4. Conclusion A compact dual-passband power divider using two SIRs has been developed and designed. The central frequencies of the two passbands can be adjusted by tuning the impedance ratio and the size of slots. The frequency selectivity and the stopband performance have been improved greatly by introducing six transmission zeros. The measurements show good agreement with the simulations, which shows that the proposed power divider has the advantage of compact size, high frequency selectivity, flexible band control, and low cost.
Acknowledgments The work for this grant was supported by National Natural Science Foundation of China (Grant no. 61271026).
References [1] K. Song, Y. Fan, Y. Zhang, Eight-way substrate integrated waveguide power divider with low insertion loss, IEEE Trans. Microw. Theory Tech. 56 (6) (2008) 1473–1477. [2] K. Song, Y. Mo, Q. Xue, Y. Fan, Wideband four-way out-of-phase slotline power dividers, IEEE Trans. Ind. Electron. 61 (7) (2014) 3598–3606. [3] M. Bemani, S. Nikmehr, Nonradiating arbitrary dual-band equal and unequal 1:4 series power dividers based on CRLH-TL structures, IEEE Trans. Ind. Electron. 61 (3) (2014) 1223–1234.
[4] H.L. Zhang, B.J. Hu, X.-Y. Zhang, Compact equal and unequal dual-frequency power dividers based on composite right/left-handed transmission lines, IEEE Trans. Ind. Electron. 59 (9) (2012) 3464–3472. [5] K. Song, Q. Xue, Ultra-Wideband (UWB) ring-cavity multiple-way parallel power divider, IEEE Trans. Ind. Electron. 60 (10) (2013) 4737–4745. [6] J.-L. Li, B.-Z. Wang, Novel design of Wilkinson power dividers with arbitrary power division ratios, IEEE Trans. Ind. Electron. 58 (6) (2011) 2541–2546. [7] J.-C. Kao, Z.-M. Tsai, K.-Y. Lin, H. Wang, A Modified Wilkinson power divider with isolation bandwidth improvement, IEEE Trans. Microw. Theory Tech. 60 (9) (2012) 2768–2780. [8] L. Chiu, Q. Xue, A parallel-strip ring power divider with high isolation and arbitrary power-dividing ratio, IEEE Trans. Microw. Theory Tech. 55 (11) (2007) 2419–2426. [9] S.-F. Chao, W.-Cheng Lin, Filtering power divider with good isolation performance, Electron. Lett. 50 (11) (2014) 815–817. [10] S.-F. Chao, Y.-R. Li, Miniature filtering power divider with increased isolation bandwidth, Electron. Lett. 50 (8) (2014) 608–610. [11] Yuxia Mo, Kaijun Song, Pan Tao, Yong Fan, Miniaturized dual-band bandpass filter using modified SIR, Electron. Lett. 49 (14) (2013) 873–875. [12] Kaijun Song, Shunyong Hu, Y. Mo, Y. Fan, Cuilin Zhong, Novel bandpassresponse power divider with high frequency selectivity using centrally stubloaded resonators, Microw. Opt. Technol. Lett. 55 (7) (2013) 1560–1562. [13] C.-F. Chen, C.-Y. Lin, Compact microstrip filtering power dividers with good in-band isolation performance, IEEE Microw. Wirel. Compon. Lett. 24 (1) (2014) 17–19. [14] K. Song, Compact filtering power divider with high frequency selectivity and wide stopband using embedded dual-mode resonator, Electron. Lett. 51 (6) (2015) 495–497. [15] Tao Pan, Kaijun Song, Yong Fan, Compact dual-bandstop filter based on composite right left handed transmission line, Microw. Opt. Technol. Lett. 55 (5) (2013) 958–962. [16] K. Song, F. Zhang, C.L. Zhuge, Yong Fan, Compact dual-band bandpass filter using spiral resonators and shorted-circuit stub-loaded resonator, Microw. Opt. Technol. Lett. 55 (6) (2013) 1393–1398. [17] K. Song, X. Ren, F. Chen, Y. Fan, Compact in-phase power divider integrated filtering response using spiral resonator, IET Microw. Antennas Propag. 8 (4) (2014) 228–234. [18] W.-M. Chau, K.-W. Hsu, W.-H. Tu, Filter-based Wilkinson power divider, IEEE Microw. Wirel. Compon. Lett. 24 (4) (2014) 239–241. [19] Y.C. Li, Q. Xue, X.Y. Zhang, Single- and dual-band power dividers integrated with bandpass filters, IEEE Trans. Microw. Theory Tech. 61 (1) (2013) 69–76. [20] J.-Y. Shao, S.-C. Huang, Y.-H. Pang, Wilkinson power divider incorporating quasi-elliptic filters for improved out-of-band rejection, Electron. Lett. 47 (23) (2011) 1288–1289. [21] L.-S. Wu, Y.-X. Guo, J.-F. Mao, Balanced-to-balanced Gysel power divider with bandpass filtering response, IEEE Trans. Microw. Theory Tech. 61 (12) (2013) 4052–4061. [22] K.-X. Wang, X.-Y. Zhang, B.-J. Hu, Gysel power divider with arbitrary power ratios and filtering responses using coupling structure, IEEE Trans. Microw. Theory Tech. 62 (3) (2014) 431–440. [23] K. Song, Y. Mo, Y. Fan, Wideband four-way filtering-response power divider with improved output isolation based on coupled lines, IEEE Microw. Wirel. Compon. Lett. 24 (10) (2014) 674–676. [24] P.H. Deng, L.C. Dai, Unequal Wilkinson power dividers with favorable selectivity and high-isolation using coupled-line filter transformers, IEEE Trans. Microw. Theory Tech. 60 (6) (2012) 1520–1529. [25] P.K. Singh, S. Basu, Y.-H. Wang, Coupled line power divider with compact size and bandpass response, Electron. Lett. 45 (17) (2009) 892–894. [26] D.J. Woo, T.K. Lee, Suppression of harmonics in Wilkinson power divider using dual-band rejection by asymmetric DGS, IEEE Trans. Microw. Theory Tech. 53 (6) (2005) 2139–2144. [27] X.Y. Zhang, K.-X. Wang, B.-J. Hu, compact filtering power divider with enhanced second-harmonic suppression, IEEE Microw. Wirel. Compon. Lett. 23 (9) (2013) 483–485. [28] Kaijun Song, Yuxia Mo, Chunlin Zhuge, Yong Fan, Ultra-Wideband (UWB) power divider with filtering response using shorted-end coupled lines and open/short-circuit slotlines, Int. J. Electron. Commun. 67 (2013) 536–539. [29] K. Song, Q. Xue, Novel Ultra-Wideband (UWB) multilayer slotline power divider with bandpass response, IEEE Microw. Wirel. Compon. Lett. 20 (1) (2010) 13–15. [30] S.W. Wong, L. Zhu, Ultra-wideband power divider with good in-band splitting and isolation performances, IEEE Microw. Wirel. Compon. Lett. 18 (8) (2008) 518–520. [31] J. Shi, Q. Xue, Novel balanced dual-band bandpass filter using coupled stepped-impedance resonators, IEEE Microw. Wirel. Compon. Lett. 20 (1) (2010) 19–21. [32] K.-S. Chin, J.-H. Yeh, Dual-wideband bandpass filter using short-circuited stepped-impedance resonators on the theory of an antenna with an infinite corner reflector, IEEE Microw. Wirel. Compon. Lett. 19 (3) (2009) 155–157. [33] Y.P. Zhang, M. Sun, Dual-band microstrip bandpass filter using steppedimpedance resonators with new coupling schemes, IEEE Trans. Microw. Theory Tech. 54 (10) (2006) 3779–3785. [34] A.S.S. Mohra, Compact dual band Wilkinson power divider, Microw. Opt. Technol. Lett. 50 (6) (2008) 1678–1682. [35] C.-M. Cheng, C.-F. Yang, Develop Quad-Band (1.57/2.45/3.5/5.2 GHz) bandpass filters on the ceramic substrate, IEEE Trans. Microw. Theory Tech. 20 (5) (2010) 268–270.
Please cite this article as: K. Song, et al., Compact dual-band filtering-response power divider with high in-band frequency selectivity, Microelectron. J (2016), http://dx.doi.org/10.1016/j.mejo.2016.03.002i
Contents lists available at ScienceDirect
Microelectronics Journal journal homepage: www.elsevier.com/locate/mejo
Compact dual-band filtering-response power divider with high in-band frequency selectivity Kaijun Song n, Shunyong Hu, Fan Zhang, Yu Zhu, Yong Fan PEHF Key Laboratory of Science, School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
art ic l e i nf o
a b s t r a c t
Article history: Received 16 September 2015 Accepted 3 March 2016
A novel compact dual-passband filtering-response power divider using modified stepped impedance resonators (SIRs) is presented. The quarter-wavelength transmission lines of conventional Wilkinson power divider are replaced by the dual-band bandpass filters to realize dual-passband bandpass response, and the phase shift of the proposed filters is tuned to be 90°. An isolation resistance R is placed at the center of the symmetric plane to realize good isolation between the two output ports. Two modified SIRs are adopted in the dual-passband filters to improve the return loss in both two passbands and control the resonant frequencies. The characteristic of the modified SIR is also analyzed. Meanwhile, the resonant frequencies can be tuned by changing impedance ratio of SIR. The source–load coupling is utilized to improve the frequency selectivity and achieve a high out-of-band rejection. A prototype of the proposed power divider is designed, fabricated, and measured. Reasonable agreement between the simulated results and measured ones is demonstrated. & 2016 Elsevier Ltd. All rights reserved.
Keywords: Dual-band Filtering-response Power divider Compact High frequency selectivity
1. Introduction The power divider is one of the key passive components in many electronic systems, which can be used in microwave circuit to divide or combine the power of microwave signals [1–8]. Moreover, Bandpass filter (BPF) is another important device in RF systems to reject unwanted signals [15,31–35]. The conventional Wilkinson power divider cannot efficiently reject unwanted frequency signals out of its usable bandwidth. Then, the additional bandpass filter has to be used to reject unwanted frequency signals, which will enlarge greatly the size of the systems. In recent year, several power dividers with filtering response by integrating filter and power divider have been developed. There are several ways to integrate the resonators with the power divider. Stubloaded resonator was added to the λ/4 length transmission lines [9,10] to achieve the filtering response. The stepped impedance resonator (SIR) [11,12], net-type resonator [13], embedded dualmode resonator [14], spiral resonator [16,17] and the half/quarterwavelength resonator [18,19,27] were used to realize the filtering response by replacing the λ/4 length transmission lines of the traditional Wilkinson power divider with these resonators. The coupled microstrip line was introduced to achieve a compact layout size and bandpass response in [20–25]. In [26], an asymmetric spiral defected ground structure (DGS) was used to n
Corresponding author. E-mail addresses: [email protected], [email protected] (K. Song).
suppress the second and third harmonics simultaneously. Moreover, an ultra-wideband power divider with bandpass filtering response [28–30] was also constructed by introducing multilayer microstrip line and slotline coupling structure or adding the impedance matching stubs. Besides, some filters using stepped impedance resonators (SIRs) to realize dual-passband bandpass response have been investigated [31–35]. In this paper, a novel compact power divider with dualpassband filtering-response is presented. Modified SIRs with five slots are employed in the proposed dual-passband filters to achieve dual-passband bandpass response and compact size. The characteristic of the modified SIR is analyzed. The central frequencies of the two passbands can be adjusted by tuning the impedance ratio and the size of slots. Several transmission zeros (TZs) can be generated through the source–load cross coupling to improve the frequency selectivity. To verify its performance, a prototype dual-band power divider is designed, fabricated, and measured. The measured results agree with the simulation one closely. The design results indicate that this structure has several advantages, such as compact size, low insertion loss, and good balance of amplitude and phase at output ports.
2. Design and analysis of the proposed power divider The structure of the proposed dual-passband filtering-response power divider based on modified SIRs is shown in Fig. 1. The power divider consists of two dual-band BPFs and an isolation
http://dx.doi.org/10.1016/j.mejo.2016.03.002 0026-2692/& 2016 Elsevier Ltd. All rights reserved.
Please cite this article as: K. Song, et al., Compact dual-band filtering-response power divider with high in-band frequency selectivity, Microelectron. J (2016), http://dx.doi.org/10.1016/j.mejo.2016.03.002i
K. Song et al. / Microelectronics Journal ∎ (∎∎∎∎) ∎∎∎–∎∎∎
resistor. The dual-band BPF is realized by using a ring-like type modified SIR with five slots (the dashed box in Fig. 1). The modifier SIR was bent to realize the coupling structure. Five slots were all etched on the low impedance transmission line part. The slots are used to adjust the different modes to realize the two passband. The input signal will be divided into two channels, and reach to the output ports through a dual-passband filter, respectively. A resistance R is placed between the two output ports to improve the output isolation. Besides, source–load cross coupling are introduced to generated TZs, then the high out-of-band rejection and good frequency selectivity can be obtained. It can be seen from Fig. 1 that the λ/4 length transmission lines of the traditional Wilkinson power divider was replaced by the dual-passband filters to realize dual-passband bandpass response of the presented power divider. As we know, the λ/4 length transmission lines were used in the traditional Wilkinson power divider to implement the 90° phase shift and improve the output isolation (when the isolation resistor R is located at the end of the λ/4 length transmission lines). The λ/ 4 length transmission lines were replaced by the dual-passband filters with 90° phase shift in the presented dual-passband filtering-response power divider. Then, the dual-passband filters should achieve 90° phase shift at the central frequencies of the dual passbands, simultaneously. Fig. 2 shows the phase shift of the dual-passband filter between the input and output ports in the central frequencies of the dual passbands. It can be seen that the phase shift at the central frequencies of the dual passbands are all 90°, which has shown that the λ/4 transmission lines of Wilkinson power divider can be replaced by this dual-passband filter. That is to say, the phase shift of the dual-passband filters can meet the
Case 1
Case 2
Case 3
0 -20
S21(dB)
2
-40
Case 1 Case 2 Case 3
-60 2
4
6 8 Frequency(GHz)
10
12
Fig. 3. (a) the layout of three structures of the SIR and (b) the frequency response of the three SIRs in the condition of weak coupling.
Fig. 1. Layout of the proposed dual-passband power divider.
Phase (deg)
180 150 120 90
A
B
60 30 0 -30 -60 -90 -120 -150 -180 2.0
2.4
2.8
3.2
3.6
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design of the presented dual-band filtering-response power divider after optimizing the structural sizes of SIRs and coupling lines. Fig. 3(a) shows the layout of three structures of the SIR. Case3 is the traditional structure of SIR, case2 and case1 are both the modified SIR with two 90°-crossed slots in the center and three short slots on the side respectively. Fig. 3(b) shows the frequency response of the three SIRs in the condition of weak coupling. It can be seen that the second passband could be shifted to the first passband greatly in the structure of case2. And in the structure of case1, the second passband also can be shifted to the first passband. Both of the two structures make slight affect to the first passband. Thus, the second passband could be adjusted by introducing the five slots, that is to say, the introducing of the five slots affect the resonant modes of the SIR. Fig. 4 illustrates the frequency response of the proposed power divider with different L6. It can be seen that the central frequency of the second passband can be changed greatly by tuning L6, while that of the first passband changes slightly. Fig. 5(a) shows the frequency response of the proposed power divider with different W2, it can be seen that the bandwidth of the first passband can be adjusted by altering W2, whereas that of the second passband is almost constant. Meanwhile, the bandwidth of the two passband can be adjusted by changing L7 greatly (as shown in Fig. 5(b)). So, the operating frequencies and bandwidths can be tuned by changing W2 and the lengths of slots (L6 and L7). That is to say, the resonant frequencies can be controlled by changing the impedance ratio between the high- and low-impedance transmission lines. It can also be seen that the desired operating frequencies and
Please cite this article as: K. Song, et al., Compact dual-band filtering-response power divider with high in-band frequency selectivity, Microelectron. J (2016), http://dx.doi.org/10.1016/j.mejo.2016.03.002i
K. Song et al. / Microelectronics Journal ∎ (∎∎∎∎) ∎∎∎–∎∎∎
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bandwidths can be controlled independently. It can be concluded that the impedance ratio between the high- and low-impedance transmission lines generate the first passband, while the five slots generate the second passband.
3. Experimental results According To verify and demonstrate the proposed circuit, the proposed dual-band filtering-response power divider based on modified SIRs has been designed and implemented. The photograph of the proposed power divider is shown in Fig. 6. A Taconic RF-35 substrate with a relative dielectric constant of 3.5, thickness of 0.508 mm, loss tangent of 0.0018 is used. The commercial software HFSS is used for simulating and optimizing the structure of the
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proposed power divider. The final sizes and parameters of the dualpassband power divider are: L1¼9 mm, L2¼22.55 mm, L3¼ 17.25 mm, L4¼L5¼10.05 mm, L6¼13 mm, L7¼3.5 mm, W0¼ 1.15 mm, W1¼W7¼ 0.6 mm, W2¼0.2 mm, W3¼ 0.9 mm, W4¼ 0.5 mm, W5¼6.4 mm, W6¼1 mm, S1¼ 0.2 mm, S2¼S3¼ 0.3 mm. The proposed power divider was measured using an Agilent 8757DE8363B network analyzer. Fig. 7 shows the simulation and measurement results. Fig. 7(a) shows the simulated and measured results, which demonstrate a good agreement. The central frequency of the lower passband is 2.45 GHz and the lower passband
Please cite this article as: K. Song, et al., Compact dual-band filtering-response power divider with high in-band frequency selectivity, Microelectron. J (2016), http://dx.doi.org/10.1016/j.mejo.2016.03.002i
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has 3-dB fractional bandwidth of 10%. The measured maximum return loss within the lower passband is about 13.6 dB, whereas the measured minimum insertion loss of the lower passband is about 1.4 dB (the 3 dB power division loss is not included), which includes the loss of SMA connectors. The three transmission zeros on the both side of the lower passband are located at 1.3, 1.8 and 2.7 GHz because of the source–load cross coupling. The upper passband is located at 3.72 GHz, with 3-dB fractional bandwidth of 3%. The measured maximum return loss within the upper passband is about 14.6 dB, whereas the measured minimum insertion loss of the upper passband, including the loss of SMA connectors, is about 1.5 dB (the 3 dB power division loss is not included). Another three transmission zeros near the upper passband are located at 3.45, 3.9 and 5.2 GHz. It can be seen that six transmission zeros can be observed on both sides of the two passbands for the fabricated dual-band filtering-response power divider. Then, the frequency selectivity and out-of-band rejection are improved greatly by the six transmission zeros. In addition, the out-of-band rejection level is more than 35 dB at the lower stopband (from 0 to 1.9 GHz), 24 dB at the middle stopband (from 2.65 to 3.53 GHz), and 20 dB at the upper stopbands (from 3.8 to more than 6 GHz). Fig. 7(b) shows that the outputs return loss and the isolation between the two output ports. The output return loss of the two passband is 16.1 dB and 15.4 dB. The isolation of the output ports of the two passband is 14.4 dB and 23 dB respectively. Fig. 7 (c) shows that the output amplitude imbalance is about 7 0.2 dB, and the output phase imbalance is about 70.3°. The amplitude and phase balance between the output ports are very good. The measured results are in good agreement with the full wave simulated ones. The tiny deviation is observed, which may be attributed to the fabrication error in the implementation. The overall size of the dual-band filter is only 0.28 λg 0.45 λg, where λg is the wavelength of central frequency of the lower passband. The design results indicate that this structure has several advantages, such as compact size, low insertion loss, and good balance of amplitude and phase at output ports.
4. Conclusion A compact dual-passband power divider using two SIRs has been developed and designed. The central frequencies of the two passbands can be adjusted by tuning the impedance ratio and the size of slots. The frequency selectivity and the stopband performance have been improved greatly by introducing six transmission zeros. The measurements show good agreement with the simulations, which shows that the proposed power divider has the advantage of compact size, high frequency selectivity, flexible band control, and low cost.
Acknowledgments The work for this grant was supported by National Natural Science Foundation of China (Grant no. 61271026).
References [1] K. Song, Y. Fan, Y. Zhang, Eight-way substrate integrated waveguide power divider with low insertion loss, IEEE Trans. Microw. Theory Tech. 56 (6) (2008) 1473–1477. [2] K. Song, Y. Mo, Q. Xue, Y. Fan, Wideband four-way out-of-phase slotline power dividers, IEEE Trans. Ind. Electron. 61 (7) (2014) 3598–3606. [3] M. Bemani, S. Nikmehr, Nonradiating arbitrary dual-band equal and unequal 1:4 series power dividers based on CRLH-TL structures, IEEE Trans. Ind. Electron. 61 (3) (2014) 1223–1234.
[4] H.L. Zhang, B.J. Hu, X.-Y. Zhang, Compact equal and unequal dual-frequency power dividers based on composite right/left-handed transmission lines, IEEE Trans. Ind. Electron. 59 (9) (2012) 3464–3472. [5] K. Song, Q. Xue, Ultra-Wideband (UWB) ring-cavity multiple-way parallel power divider, IEEE Trans. Ind. Electron. 60 (10) (2013) 4737–4745. [6] J.-L. Li, B.-Z. Wang, Novel design of Wilkinson power dividers with arbitrary power division ratios, IEEE Trans. Ind. Electron. 58 (6) (2011) 2541–2546. [7] J.-C. Kao, Z.-M. Tsai, K.-Y. Lin, H. Wang, A Modified Wilkinson power divider with isolation bandwidth improvement, IEEE Trans. Microw. Theory Tech. 60 (9) (2012) 2768–2780. [8] L. Chiu, Q. Xue, A parallel-strip ring power divider with high isolation and arbitrary power-dividing ratio, IEEE Trans. Microw. Theory Tech. 55 (11) (2007) 2419–2426. [9] S.-F. Chao, W.-Cheng Lin, Filtering power divider with good isolation performance, Electron. Lett. 50 (11) (2014) 815–817. [10] S.-F. Chao, Y.-R. Li, Miniature filtering power divider with increased isolation bandwidth, Electron. Lett. 50 (8) (2014) 608–610. [11] Yuxia Mo, Kaijun Song, Pan Tao, Yong Fan, Miniaturized dual-band bandpass filter using modified SIR, Electron. Lett. 49 (14) (2013) 873–875. [12] Kaijun Song, Shunyong Hu, Y. Mo, Y. Fan, Cuilin Zhong, Novel bandpassresponse power divider with high frequency selectivity using centrally stubloaded resonators, Microw. Opt. Technol. Lett. 55 (7) (2013) 1560–1562. [13] C.-F. Chen, C.-Y. Lin, Compact microstrip filtering power dividers with good in-band isolation performance, IEEE Microw. Wirel. Compon. Lett. 24 (1) (2014) 17–19. [14] K. Song, Compact filtering power divider with high frequency selectivity and wide stopband using embedded dual-mode resonator, Electron. Lett. 51 (6) (2015) 495–497. [15] Tao Pan, Kaijun Song, Yong Fan, Compact dual-bandstop filter based on composite right left handed transmission line, Microw. Opt. Technol. Lett. 55 (5) (2013) 958–962. [16] K. Song, F. Zhang, C.L. Zhuge, Yong Fan, Compact dual-band bandpass filter using spiral resonators and shorted-circuit stub-loaded resonator, Microw. Opt. Technol. Lett. 55 (6) (2013) 1393–1398. [17] K. Song, X. Ren, F. Chen, Y. Fan, Compact in-phase power divider integrated filtering response using spiral resonator, IET Microw. Antennas Propag. 8 (4) (2014) 228–234. [18] W.-M. Chau, K.-W. Hsu, W.-H. Tu, Filter-based Wilkinson power divider, IEEE Microw. Wirel. Compon. Lett. 24 (4) (2014) 239–241. [19] Y.C. Li, Q. Xue, X.Y. Zhang, Single- and dual-band power dividers integrated with bandpass filters, IEEE Trans. Microw. Theory Tech. 61 (1) (2013) 69–76. [20] J.-Y. Shao, S.-C. Huang, Y.-H. Pang, Wilkinson power divider incorporating quasi-elliptic filters for improved out-of-band rejection, Electron. Lett. 47 (23) (2011) 1288–1289. [21] L.-S. Wu, Y.-X. Guo, J.-F. Mao, Balanced-to-balanced Gysel power divider with bandpass filtering response, IEEE Trans. Microw. Theory Tech. 61 (12) (2013) 4052–4061. [22] K.-X. Wang, X.-Y. Zhang, B.-J. Hu, Gysel power divider with arbitrary power ratios and filtering responses using coupling structure, IEEE Trans. Microw. Theory Tech. 62 (3) (2014) 431–440. [23] K. Song, Y. Mo, Y. Fan, Wideband four-way filtering-response power divider with improved output isolation based on coupled lines, IEEE Microw. Wirel. Compon. Lett. 24 (10) (2014) 674–676. [24] P.H. Deng, L.C. Dai, Unequal Wilkinson power dividers with favorable selectivity and high-isolation using coupled-line filter transformers, IEEE Trans. Microw. Theory Tech. 60 (6) (2012) 1520–1529. [25] P.K. Singh, S. Basu, Y.-H. Wang, Coupled line power divider with compact size and bandpass response, Electron. Lett. 45 (17) (2009) 892–894. [26] D.J. Woo, T.K. Lee, Suppression of harmonics in Wilkinson power divider using dual-band rejection by asymmetric DGS, IEEE Trans. Microw. Theory Tech. 53 (6) (2005) 2139–2144. [27] X.Y. Zhang, K.-X. Wang, B.-J. Hu, compact filtering power divider with enhanced second-harmonic suppression, IEEE Microw. Wirel. Compon. Lett. 23 (9) (2013) 483–485. [28] Kaijun Song, Yuxia Mo, Chunlin Zhuge, Yong Fan, Ultra-Wideband (UWB) power divider with filtering response using shorted-end coupled lines and open/short-circuit slotlines, Int. J. Electron. Commun. 67 (2013) 536–539. [29] K. Song, Q. Xue, Novel Ultra-Wideband (UWB) multilayer slotline power divider with bandpass response, IEEE Microw. Wirel. Compon. Lett. 20 (1) (2010) 13–15. [30] S.W. Wong, L. Zhu, Ultra-wideband power divider with good in-band splitting and isolation performances, IEEE Microw. Wirel. Compon. Lett. 18 (8) (2008) 518–520. [31] J. Shi, Q. Xue, Novel balanced dual-band bandpass filter using coupled stepped-impedance resonators, IEEE Microw. Wirel. Compon. Lett. 20 (1) (2010) 19–21. [32] K.-S. Chin, J.-H. Yeh, Dual-wideband bandpass filter using short-circuited stepped-impedance resonators on the theory of an antenna with an infinite corner reflector, IEEE Microw. Wirel. Compon. Lett. 19 (3) (2009) 155–157. [33] Y.P. Zhang, M. Sun, Dual-band microstrip bandpass filter using steppedimpedance resonators with new coupling schemes, IEEE Trans. Microw. Theory Tech. 54 (10) (2006) 3779–3785. [34] A.S.S. Mohra, Compact dual band Wilkinson power divider, Microw. Opt. Technol. Lett. 50 (6) (2008) 1678–1682. [35] C.-M. Cheng, C.-F. Yang, Develop Quad-Band (1.57/2.45/3.5/5.2 GHz) bandpass filters on the ceramic substrate, IEEE Trans. Microw. Theory Tech. 20 (5) (2010) 268–270.
Please cite this article as: K. Song, et al., Compact dual-band filtering-response power divider with high in-band frequency selectivity, Microelectron. J (2016), http://dx.doi.org/10.1016/j.mejo.2016.03.002i