Abstract
A novel compact ultra wideband (UWB) bandpass filter (BPF) based on composite right/left handed transmission line (CRLH TL) is reported in this paper. The proposed UWB BPF is designed and developed by coupling of two unitcells of vialess CRLH TL, excited by asymmetrical coplanar waveguide (CPW) feedline. The unit cell of CRLH TL is designed using series interdigital capacitor (IDC) in shunt with the shorted inductive stub. Because of the CPWfed, no via is required to get the shunt inductance for the realization of CRLH TL, which minimizes the fabrication steps. The filter is compact in size 11. 9 × 6 mm^{2}. The proposed filter exhibits the returnloss (S_{11}) more than 11. 2 dB and insertionloss (S_{21}) less than 0. 5 dB and low and flat group delay response throughout the passband, 3. 3 GHz to 13. 0 GHz. The proposed UWB BPF also shows the good stopband rejection (S_{21} > 20 dB and S_{11} < 0. 8 dB) from 13. 6 GHz to 15 GHz and steep rolloff from passband to stopband. The fractional bandwidth (FBW) of the filter is found to be 119 %. The equivalent lumped circuit model of the filter is obtained through Ansoft Designer. All simulated results are extracted through method of moment based simulator, IE3D. Agilent vector network analyzer (VNA) is used to get the measured results. All measured results are found in close similarity with the simulated results.
Index Terms
Composite right/left handed transmission line; Interdigital capacitor; Ultra wideband bandpass filter
I. INTRODUCTION
The left handed metamaterials can be realized mainly by two methods, firstly, using periodic arrangement of split ring resonators and thin metallic wires and, secondly by dual of conventional right handed transmission line, i. e. by periodic arrangement of series interdigital capacitors in shunt with the shorted stubs to ground. The first and second methods are respectively known as resonant and nonresonant approach of realization of left handed metamaterials. Due to large in size and lossy in nature, the resonant approach is not well suited for the realization of left handed metamaterials [^{1}[1] A. Lai, C. Caloz, and T. Itoh, “Composite right/lefthanded transmission line metamaterials, ”IEEE Microwave Mag. 5, vol. 5, pp. 3450, 2004.]. Since 2002 the U. S. Federal Communications Commission (FCC) [^{2}[2] Revision of Part 15 of the commission's rules regarding ultra wideband transmission system, "ETDocket 98153, First note and order, Federal Communication Commission,” Feb 2002.] has regularized the unlicensed use of UWB frequency band 31. GHz to 10. 6 GHz, the research in the field of UWB bandpass filter has gained much attention and challenges. The design of ultra wideband components need much efforts and attentions as it requires the good selectivity, low insertionloss and low and constant group delay throughout the passband.
The UWB BPF reported in [^{3}[3] K. U. Ahmed and B. S. Virdee, “Ultrawideband bandpass filter based on composite right/left handed transmissionline unitcell,” IEEE Trans Microwave Theory Tech, vol. 61, pp. 782788, 2013.] is based on conventional CRLH TL designed by using via. The reported UWB BPF in [^{3}[3] K. U. Ahmed and B. S. Virdee, “Ultrawideband bandpass filter based on composite right/left handed transmissionline unitcell,” IEEE Trans Microwave Theory Tech, vol. 61, pp. 782788, 2013.] has good Sparameters characteristics and compact in size (16. 4 × 4. 8 mm^{2}). Moreover because of the use of via it requires the extra fabrication processing steps for drilling and soldering as compared to the proposed UWB BPF. The UWB bandpass filter presented in [^{4}[4] A. Alburaikan, M. Aqeeli, X. Huang, and Z. Hu, ‘Miniaturized ultrawideband bandpass filter based on CRLHTL unit cell, " In: Microwave Conference (EuMC), Rome, Italy, pp. 540543, 2014.] is based on defected ground structure (DGS) as split ring resonator and conventional CRLH TL with via. The reported filter [^{4}[4] A. Alburaikan, M. Aqeeli, X. Huang, and Z. Hu, ‘Miniaturized ultrawideband bandpass filter based on CRLHTL unit cell, " In: Microwave Conference (EuMC), Rome, Italy, pp. 540543, 2014.] is compact in size, 13 × 8. 5 mm^{2}, however because of the split ring resonator structure in ground plane and the presence on via, it requires the more extra efforts in ground plane processing and for creation of via. A single CRLH TL cell based UWB band pass filter [^{5}[5] Fitri Yuli Zulkifli, Andik Atmaja and Eko Tjipto Rahardjo, “Implementation of single cell composite rightleft handed transmission line for ultra wideband bandpass filter, ”International Journal of Technology (IJTech), vol. 2, pp. 121128, 2012.] operating over the frequency band of 4 GHz to 9. 5 GHz is of relatively large in size, 30 × 8. 5 mm^{2} and also requires the via for the realization of CRLH TL. The reported filter [^{5}[5] Fitri Yuli Zulkifli, Andik Atmaja and Eko Tjipto Rahardjo, “Implementation of single cell composite rightleft handed transmission line for ultra wideband bandpass filter, ”International Journal of Technology (IJTech), vol. 2, pp. 121128, 2012.] also suffers with the poor Sparameters performance in passband (S_{21} = 1. 5 dB) as well as in stopband. A compact UWB band pass filter (18. 4 × 4. 5 mm^{2}) reported in [^{6}[6] Nilotpal and Dileep Kumar Upadhyay, “A compact UWB bandpass filter based on CRLH vialess CPWfed, ”Microwave and Optical Technology Lett, vol. 58, pp. 276279, 2016.] has good Sparameters performance (S_{21} < 0. 3 dB and S_{11} > 10 dB) is designed on vialess CRLH TL. Moreover the reported UWB BPF [^{6}[6] Nilotpal and Dileep Kumar Upadhyay, “A compact UWB bandpass filter based on CRLH vialess CPWfed, ”Microwave and Optical Technology Lett, vol. 58, pp. 276279, 2016.] operated over relatively low frequency band 3. 1 GHz to 10. 6 GHz and relatively large in size as compared to the proposed UWB BPF (frequency band, 3. 3 GHz to 13. 0 GHz and size, 11. 9 × 6 mm^{2}). An ultra wideband band pass filter designed using interdigitated coupled lines CRLHTL structure [^{7}[7] B. Qian, D. Jun, and G. Chen Jiang, “New design of ultra wideband filter using interdigitated coupled lines CRLHTL structure, ”In: 2012 10th International Symposium on Antennas, Propagation & EM Theory (ISAPE), Xian, China, pp. 486189, 2012] operated over 3. 9 GHz to 10. 3 GHz is relatively large in size (30 × 15 mm^{2}), requires the generation of via and suffers with relatively poor insertion loss (S_{21} = 1. 5 dB).
Many researchers and scientists worldwide have investigated, designed and developed various UWB BPFs based on different techniques such as; by use of fractal geometry, defected ground plane, coupled line structure and multimode resonator etc. References [^{8}[8] Xu, H. X., Wang, G. M., and Zhang, C. X., “Fractalshaped UWB bandpass filter based on composite right/left handed transmission line, ”Elect. Lett., vol. 46, no. 4, pp. 285287, 2010.
[9] A. M. Abbosh, “Ultra wideband balanced bandpass filter, ”IEEE Microwave Wireless Components Lett., vol. 21, 480482, 2011
[10] B. Xia, L. S. Wu, and J. F. Mao, “An ultrawideband balanced bandpass filter based on defected ground structures, ”Progress In Electromag. Research C, vol. 25, 133144, 2012
[11] Huang, J. Q. and Q. X. Chu, “Compact UWB bandpass filter utilizing modified composite right/lefthanded structure with cross coupling, " Progress In Electromag. Research, vol. 107, pp. 179186, 2010.
[12] Tang, C. W., and Chen, M. G., “A microstrip ultrawideband bandpass filter with cascaded broadband bandpass and bandstop filters, ”IEEE Trans Microwave Theory Tech, vol. 55, pp. 24122418, 2007^{13}[13] Zhang, Z., and Xiao, F., “An UWB bandpass filter based on a novel type of multimode resonator, ”IEEE Microwave Wireless Compon Lett, vol. 22, 506508, 2012] report the various UWB BPFs based on different techniques such as a CRLH TL and fractal geometry based UWB BPF [^{8}[8] Xu, H. X., Wang, G. M., and Zhang, C. X., “Fractalshaped UWB bandpass filter based on composite right/left handed transmission line, ”Elect. Lett., vol. 46, no. 4, pp. 285287, 2010.], the coupled structure based ultra wideband bandpass filter [^{9}[9] A. M. Abbosh, “Ultra wideband balanced bandpass filter, ”IEEE Microwave Wireless Components Lett., vol. 21, 480482, 2011], defected ground structure [^{10}[10] B. Xia, L. S. Wu, and J. F. Mao, “An ultrawideband balanced bandpass filter based on defected ground structures, ”Progress In Electromag. Research C, vol. 25, 133144, 2012], modified CRLH TL with cross coupling [^{11}[11] Huang, J. Q. and Q. X. Chu, “Compact UWB bandpass filter utilizing modified composite right/lefthanded structure with cross coupling, " Progress In Electromag. Research, vol. 107, pp. 179186, 2010.], cascading bandpass and bandstop filters [^{12}[12] Tang, C. W., and Chen, M. G., “A microstrip ultrawideband bandpass filter with cascaded broadband bandpass and bandstop filters, ”IEEE Trans Microwave Theory Tech, vol. 55, pp. 24122418, 2007] and multi mode resonator based UWB BPF [^{13}[13] Zhang, Z., and Xiao, F., “An UWB bandpass filter based on a novel type of multimode resonator, ”IEEE Microwave Wireless Compon Lett, vol. 22, 506508, 2012]. The UWB BPFs [^{8}[8] Xu, H. X., Wang, G. M., and Zhang, C. X., “Fractalshaped UWB bandpass filter based on composite right/left handed transmission line, ”Elect. Lett., vol. 46, no. 4, pp. 285287, 2010.
[9] A. M. Abbosh, “Ultra wideband balanced bandpass filter, ”IEEE Microwave Wireless Components Lett., vol. 21, 480482, 2011
[10] B. Xia, L. S. Wu, and J. F. Mao, “An ultrawideband balanced bandpass filter based on defected ground structures, ”Progress In Electromag. Research C, vol. 25, 133144, 2012
[11] Huang, J. Q. and Q. X. Chu, “Compact UWB bandpass filter utilizing modified composite right/lefthanded structure with cross coupling, " Progress In Electromag. Research, vol. 107, pp. 179186, 2010.
[12] Tang, C. W., and Chen, M. G., “A microstrip ultrawideband bandpass filter with cascaded broadband bandpass and bandstop filters, ”IEEE Trans Microwave Theory Tech, vol. 55, pp. 24122418, 2007^{13}[13] Zhang, Z., and Xiao, F., “An UWB bandpass filter based on a novel type of multimode resonator, ”IEEE Microwave Wireless Compon Lett, vol. 22, 506508, 2012] designed using different techniques are considered in this paper for comparison of various parameters with the proposed UWB BPF.
In this paper design and development of a compact (11. 9 × 6 mm^{2}) ultra wideband bandpass filter based on vialess CRLH TL is reported. Since in CPWfed, the signal plate and ground plate both reside on the top plane of the dielectric substrate, hence no via is required for the realization of proposed CRLH TL, in contrast to conventional design of CRLH TL, where, via is required to short circuit the shunt inductive stub to ground. The absence of via reduces the fabrication steps, saves the valuable time wastage and minimizes the overall bulk production cost. The proposed UWB BPF is designed by coupling between two similar unitcells of CRLH TL. The unitcell of CRLH TL is designed by series five fingers based interdigital capacitor in shunt with the inductive stub shorted to the one of the ground plane of CPW feedline. The filter exhibits the returnloss greater than 11. 2 dB and insertionloss less than 0. 5 dB to whole passband frequency range, 3. 3 GHz to 13 GHz, with steep rolloff during the transition from stopband to passband and stopband rejection level greater than 20 dB for frequency range of 13. 3 GHz to 15 GHz. The filter shows the low (maximum variation of 0. 8 ns) and constant group delay throughout the passband. The proposed UWB BPF is designed and developed on RT/duroid dielectric substrate with relative permittivity of 2. 2, thickness of 1. 57 mm and losstangent of 0. 0009. The equivalent lumped circuit model of the proposed filter is obtained using circuit model tool of Ansoft Designer. The simulation and measured results are obtained from electromagnetic (EM) simulator, IE3D and vector network analyzer respectively. All measured results are found in close similarity with the simulated results.
II. THEORY AND DESIGN OF PROPOSED UWB BANDPASS FILTER
The composite right/left handed transmission line can be realized by dual of conventional right handed transmission line (RH TL), known as nonresonant approach. The pure right handed transmission line (PRH TL) consists of series inductor in shunt with the capacitor, whereas pure left handed transmission line (PLH TL) is realized by series capacitor in shunt with the inductor. Unfortunately, either PRH TL or PLH TL cannot be physically realized because of the unavoidable parasitic effects of microstrip transmission lines. Hence because of the unavoidable parasitic effects, the CRLH TL is realized rather than the PRH TL. The CRLH TL shows the virtue of both, the nature of left handed transmission line (LH TL) at low frequencies and the nature of RH TL at high frequencies [^{1}[1] A. Lai, C. Caloz, and T. Itoh, “Composite right/lefthanded transmission line metamaterials, ”IEEE Microwave Mag. 5, vol. 5, pp. 3450, 2004.].
The unitcell of CRLH TL consists of perunit series LH capacitance (C_{LH}) and perunit right handed inductance (L_{RH}) and perunit shunt LH inductance (L_{LH}) and perunit RH capacitance (C_{RH}). The combination of series RH inductance (L_{RH}) and shunt RH capacitance (C_{RH}) in CRLH TL works as a lowpass filter whose cutoff frequency is given as . The combination of series LH capacitance (C_{LH}) and shunt LH inductance (L_{LH}) in CRLH TL works as a lowpass filter whose cutoff frequency is given as . So, when f_{CR} < f_{CL}, the CRLH TL works as a wideband bandpass filter.
The series, f_{SE} and shunt, f_{SH} resonance frequencies of the CRLH TL are given as follows
For balanced CRLH TL,
Where, f_{C} is known as centre frequency. The lower end, f_{L} and upper end, f_{U} frequencies of CRLH TL are given as follows
The design layout of proposed ultra wideband bandpass filter with the notation of all physical dimensions is depicted in Fig. 1. The filter is excited by asymmetrical CPWfed, which consists of two ground planes. As shown in Fig. 1, UWB BPF is designed using coupling of two symmetrical series interdigital capacitors (IDC). The IDC consists of five fingers of finger length L_{3}, finger width S_{2} and finger spacing S_{1}. The coupling gap between the two IDCs is S_{6}. The two stubs each of length L_{9}, is connected to each IDC and ground plane 2 to get the shunt inductance. Since signal plane and ground plane both are in same planes, hence no via is required to short circuit the stubs to ground plane 2, in contrast to the conventional method of design of CRLH TL with via. The absence of via minimizes the fabrication steps, saves the fabrication time and reduces the overall bulk production cost. The filter is compact in size, 11. 9×6 mm^{2}.
III. EFFECTS OF VARIATION OF VARIOUS PHYSICAL PARAMETERS ON UWB BPF
All optimized physical dimensions of the proposed UWB BPF are obtained by parametric study of the geometry shown in Fig. 1. The nature of variation of Sparameters characteristics of filter is investigated and analyzed for variation on one physical parameter keeping other parameters constant, to get the best optimized physical dimensions of the geometry, which can meet the low insertionloss and returnloss better than 10 dB throughout the passband.
The effects of variation of physical parameter W_{6} is shown in Fig. 2. The optimum value of W_{6} is taken to be 0. 9 mm. It can be seen from Fig. 2 that as the value of W_{6} is increased from 0. 9 mm to 1. 5 mm, the Sparameters improve in frequency band 6. 0 GHz to 8. 0 GHz and deteriorate in the frequency band of 4 GHz to 4. 8 GHz and 11. 7 GHz to 12. 4 GHz for the constant bandwidth 3. 3 GHz to 13. 0 GHz. As the value of W_{6} is decreased from 0. 9 mm to 0. 5 mm, the value of Sparameters deteriorate in frequency band 6. 0 GHz to 8. 0 GHz and improve in 4 GHz to 4. 8 GHz and 11. 7 GHz to 12. 4 GHz. So the value of W_{6} is considered as 0. 9 mm by compromising the performance in passband. The sensitivity for the variation of physical parameter, W_{5} on Sparameters versus frequency plot is shown in Fig. 3. As the value of W_{5} increases from 1. 0 mm to 1. 3 mm, the Sparameters performance deteriorate in frequency band 6. 0 GHz to 8. 0 GHz and improve in the frequency band 4 GHz to 4. 8 GHz. The viceversa effects can be seen for the value of W_{5} less than 1. 0 mm. Hence the optimized value of W_{5} is chosen to be 1. 0 mm, by considering the performance of Sparameters in both bands. For the variation of W_{5}, the overall bandwidth remains almost constant, i. e. from 3. 3 GHz to 13. 0 GHz. The effects of variation of physical parameters L_{2} on Sparameters versus frequency plot is depicted in Fig. 4. Considering the response of Sparameters in the band 4. 0 GHz to 8. 0 GHz and 11. 7 GHz to 12. 4 GHz, the optimum value of L_{2} is considered as 2. 7 mm.
The sensitivity for the variation of physical parameter L_{9} on Sparameters response is shown in Fig. 5. The optimized value of L_{9} is considered to be 1. 6 mm. As the value of L_{9} increases from 1. 6 mm to 2. 2 mm, the Sparameters performance deteriorate in the frequency bands 6. 0 GHz to 8. 0 GHz and 4. 0 GHz to 4. 8 GHz and improve in the frequency bands 9. 0 GHz to 11. 0 GHz and 11. 7 GHz to 12. 4 GHz. For the value of L_{9} less than 1. 6 mm, the viceversa effects are observed in all considered bands. The Sparameters versus frequency plot for the variation of physical parameter L_{5} is shown in Fig. 6. Considering the performance of Sparameter throughout the passband, the value of L_{5} is chosen to be 1. 65 mm. As the value of L_{5} increases 1. 65 mm to 2. 25 mm, the high end frequency shifted from 13. 0 GHz to 12. 5 GHz and Sparameters deteriorate in the frequency band 11. 7 GHz to 12. 4 GHz. For the lower values of L_{5}, the high end frequency shifted from 13. 0 GHz to 13. 5 GHz, but Sparameters response slightly deteriorate in frequency bands 6. 0 GHz to 8. 0 GHz and 4. 0 GHz to 4. 8 GHz.
The effects on Sparameters response for the change of width of ground plane 2, W_{8} is illustrated in Fig. 7. The optimum value of W_{8} is considered as 0. 25 mm. From the Fig. 7, it can be observed that by increasing the value of W_{8} from 0. 25 mm to 0. 85 mm, the Sparameters improve in passband but at the same time the high end frequency decreases from 13 GHz for the case of W_{8} = 0. 25 mm to 12. 4 GHz for the case of W_{8} = 0. 85 mm. The shift in high end frequency to the lower end, decreases the overall bandwidth, which is not desirable. Decreasing the value of W_{8} from 0. 25 mm to 0. 1 mm the overall bandwidth increases, but the passband Sparameters performance become poor. The effect on Sparameters response for the variation of physical parameter S_{4}, is depicted in Fig. 8. Changing the value of S_{4}, the overall bandwidth remains almost unchanged. By increasing the value of S_{4} from 0. 2 mm to 0. 8 mm, the Sparameters performance of the filter deteriorates in passband. Hence, the optimum value of S_{4} is chosen to be 0. 2 mm. The effects of variation of the coupling gap S_{6}, between the two interdigital capacitors on Sparameters performance is illustrated in Fig. 9. Increasing the value of S_{6} from 0. 2 mm to 0. 8 mm, the Sparameters performance and overall bandwidth of the filter remain almost invariant. For zero gap between the two interdigital capacitors (S_{6} = 0. 0 mm), the returnloss and insertionloss deteriorate by considerable amount. Hence, an optimum value of S_{6} is considered as S_{6} = 0. 2 mm. For others value of physical parameters, similar parametric studies discussed for Fig. 2 to Fig. 9 are performed and their optimum values are found. Similar to parametric studies performed and depicted from Fig. 2 to Fig. 9. The various optimized physical dimensions of the proposed UWB BPF is listed in Table I.
IV. EQUIVALENT LUMPED CIRCUIT MODEL ANALYSIS
The equivalent lumped circuit mode of the proposed UWB BPF shown in Fig. 1 is depicted in Fig. 10. The equivalent lumped circuit model results are obtained using circuit model tool of the Ansoft Designer. Considering the layout of the proposed UWB BPF, an equivalent circuit diagram is designed. The lumped element values are manually optimized by changing the each element value so that it can have the good agreement with the simulated results obtained from the full wave simulator. In the lumped equivalent circuit diagram, the mutual coupling between the individual elements is not taken in to consideration. The inductive components, L_{1} and L_{2} are generated because of the input and output CPWfed transmission lines. The left handed capacitors, C_{LH1} and C_{LH2} are introduced because of the input and output interdigital capacitors. The right handed inductances, L_{RH1} and L_{RH2} are included because of the parasitic effects in input and output IDCs. The shunt left handed inductances L_{LH11}, L_{LH12}, L_{LH21} and L_{LH22} are generated because of the input and output stubs shorted to the ground plane 2. The shunt right handed capacitances C_{RH11}, C_{RH12}, C_{RH21} and C_{RH22} are introduced due to the parasitic effects of shorted stubs to ground plane 2 and the gap (W_{5}  W_{4}) between topmost additional finger of IDC to the ground plane 1. The various components values of the equivalent lumped circuit model shown in Fig. 10 are listed in Table II.
The comparative Sparameters versus frequency response of EM simulation and circuit model are illustrated in Fig. 11. The EM simulation results are taken corresponding to the optimized physical parameters listed in Table I. The close similarity between the EM simulation and circuit model results are observed, however a slight deviation between the two may be seen which may arise because of the ignorance of mutual coupling between the individual circuit elements. The −3. 0 dB insertionloss frequency bands for EM simulation and circuit model are found to be 3. 3 GHz to 13. 0 GHz and 3. 2 GHz to 13. 1 GHz respectively. The passband insertionloss is less than 0. 5 dB and 0. 25 dB respectively and reflectionloss greater than 11. 2 dB and 10. 9 dB respectively for EM simulation and circuit model. The EM simulation results show the good stopband rejection (S_{21} > 20 dB and S_{11} < 0. 8 dB) from 13. 6 GHz to 15 GHz and steep rolloff from passband to stopband. The fractional bandwidth of the filter is found to be 119%.
V. MEASUREMENT RESULTS AND DISCUSSION
Based on the optimized physical parameters listed in Table I, the proposed UWB BPF shown in Fig. 1 is fabricated and its performance parameters are measured using Agilent vector network analyzer. Fig. 12 shows the photograph of fabricated prototype of proposed UWB BPF. The comparative simulated and measured Sparameters versus frequency response are shown in Fig. 13. From the Fig. 13, a close similarity between the simulated and measured results can be observed. Moreover a little deviation between the simulated and measured results can be seen, which mainly arise because of the finite ground plane, improper soldering and fabrication tolerances. The measured −3. 0 dB insertionloss frequency band of the proposed UWB BPF is found to be 3.12 GHz to 12. 43 GHz, whereas the simulated −3. 0 dB insertionloss frequency band is found to be 3. 3 GHz to 13. 0 GHz. In throughout the passband, the measured and simulated insertionlosses are less than 0. 6 dB and 0. 5 dB respectively, whereas returnlosses are more than 10. 4 dB and 11. 2 dB respectively. The mesured fractional bandwidth of the filter is found to be 120 %.
The simulated and measured group delay versus frequency response of the proposed ultra wideband bandpass filter is depicted in Fig. 14. The low and constant group delay response can be observed throughout the passband of UWB BPF. The simulation and measured group delay vary between the 0. 7 ns to 1. 5 ns and 0. 76 ns to 1. 74 ns respectively, hence the maximum variation of simulated and measured group delays are 0. 80 ns and 0. 98 ns respectively. However, relatively large variation of group delays in both, simulation and measured results may be observed at both ends of the passband, which arises because of the sharp transition of insertionloss curve from passband to stopband. The large difference between the simulated and experimental results at frequency 2. 6 GHz may be seen because of the fabrication tolerances and improper soldering during the development of the UWB BPF. The low and flat group delay response throughout the operating passband frequency band shows the good time domain response of the filter. Comparative EM simulated, equivalent lumped circuit model and measured performance of the proposed UWB BPF are listed in Table III. The physical parameters, fabrication complexities and performance of the proposed UWB BPF are compared in Table IV with the ealrier reported UWB BPFs.
VI. CONCLUSION
Design and development of a compact CRLH TL based UWB BPF is presented in this paper. The CRLH TL is designed on coupling of two unitcells of vialess CRLH TL. The filter is compact in size 11.9 × 6 mm^{2} and excited by the CPWfed. Due of the absence of via the filter ease the fabrication process and saves the time taken to build the vias. The developed UWB BPF shows the measured insertionloss less than 0. 6 dB and returnloss more than 10. 4 dB throughout the passband 3.12 GHz – 12. 43 GHz with fraction bandwidth of 120 %. Moreover, filter also shows the low (maximum deviation of 0. 98 ns) and flat group delay response throughout the passband. Because of the compact in size and good in performance the proposed UWB BPF may find the potential applications in modem small sized wireless communication systems.
REFERENCES

^{[1]}A. Lai, C. Caloz, and T. Itoh, “Composite right/lefthanded transmission line metamaterials, ”IEEE Microwave Mag. 5, vol. 5, pp. 3450, 2004.

^{[2]}Revision of Part 15 of the commission's rules regarding ultra wideband transmission system, "ETDocket 98153, First note and order, Federal Communication Commission,” Feb 2002.

^{[3]}K. U. Ahmed and B. S. Virdee, “Ultrawideband bandpass filter based on composite right/left handed transmissionline unitcell,” IEEE Trans Microwave Theory Tech, vol. 61, pp. 782788, 2013.

^{[4]}A. Alburaikan, M. Aqeeli, X. Huang, and Z. Hu, ‘Miniaturized ultrawideband bandpass filter based on CRLHTL unit cell, " In: Microwave Conference (EuMC), Rome, Italy, pp. 540543, 2014.

^{[5]}Fitri Yuli Zulkifli, Andik Atmaja and Eko Tjipto Rahardjo, “Implementation of single cell composite rightleft handed transmission line for ultra wideband bandpass filter, ”International Journal of Technology (IJTech), vol. 2, pp. 121128, 2012.

^{[6]}Nilotpal and Dileep Kumar Upadhyay, “A compact UWB bandpass filter based on CRLH vialess CPWfed, ”Microwave and Optical Technology Lett, vol. 58, pp. 276279, 2016.

^{[7]}B. Qian, D. Jun, and G. Chen Jiang, “New design of ultra wideband filter using interdigitated coupled lines CRLHTL structure, ”In: 2012 10th International Symposium on Antennas, Propagation & EM Theory (ISAPE), Xian, China, pp. 486189, 2012

^{[8]}Xu, H. X., Wang, G. M., and Zhang, C. X., “Fractalshaped UWB bandpass filter based on composite right/left handed transmission line, ”Elect. Lett., vol. 46, no. 4, pp. 285287, 2010.

^{[9]}A. M. Abbosh, “Ultra wideband balanced bandpass filter, ”IEEE Microwave Wireless Components Lett., vol. 21, 480482, 2011

^{[10]}B. Xia, L. S. Wu, and J. F. Mao, “An ultrawideband balanced bandpass filter based on defected ground structures, ”Progress In Electromag. Research C, vol. 25, 133144, 2012

^{[11]}Huang, J. Q. and Q. X. Chu, “Compact UWB bandpass filter utilizing modified composite right/lefthanded structure with cross coupling, " Progress In Electromag. Research, vol. 107, pp. 179186, 2010.

^{[12]}Tang, C. W., and Chen, M. G., “A microstrip ultrawideband bandpass filter with cascaded broadband bandpass and bandstop filters, ”IEEE Trans Microwave Theory Tech, vol. 55, pp. 24122418, 2007

^{[13]}Zhang, Z., and Xiao, F., “An UWB bandpass filter based on a novel type of multimode resonator, ”IEEE Microwave Wireless Compon Lett, vol. 22, 506508, 2012
Publication Dates

Publication in this collection
June 2017
History

Received
08 Sept 2016 
Reviewed
08 Sept 2016 
Accepted
12 Jan 2017