диафрагмированные волноводные фильтры / 8ff378e7-0d36-4712-9a2c-42868698d526

bandwidth, symmetry, and out-of-band performance can be simultaneously optimized because of a high-degree of flexibility in the design parameters. Such behavior makes the proposed approach very attractive for the design of compact planar filters for high-frequency space applications.

ACKNOWLEDGMENTS

The authors acknowledge the financial support of MEC (Spain), EGIDE (France) through an ‘‘Accio´n Integrada—Picasso’’ bilateral project. This work has been developed in the framework of a CNES contract (France) and of project GV/2007/215 Generalitat Valenciana (Spain). Also, the authors would like to thank Dr. J. Bonache and Prof. F. Martin from UAB (Spain) for their very helpful comments.

REFERENCES

1.F. Martı´n, F. Falcone, J. Bonache, R. Marque´s, and M. Sorolla, A new split-ring resonator based left-handed coplanar waveguide, Appl Phys Lett 83 (2003), 4652–4654.

2.J. Bonache, F. Martin, F. Falcone, J. Garcia, I. Gil, T. Lopetegi, M.A.G. Laso, R. Marques, F. Medina, and M. Sorolla, Super compact split ring resonators CPW band pass filters, IEEE MTT-S Dig 3 (2004), 1483–1486.

3.F. Falcone, T. Lopetegi, M.A.G. Laso, J.D. Baena, J. Bonache, R. Marque´s, F. Martı´n, and M. Sorolla, Babinet principle applied to the design of metasurfaces and metamaterials, Phys Rev Lett 93 (2004), 197401.

4.J. Bonache, F. Martı´n, F. Falcone, J.D. Baena, T. Lopetegi, J. Garcı´a-Garcı´a, M.A.G. Laso, I. Gil, A. Marcotegui, R. Marque´s, and M. Sorolla, Application of complementary split-ring resonators to the design of compact narrow band-pass structures in microstrip technology, Microwave Opt Technol Lett 46 (2005), 508–512.

5.J. Bonache, F. Martı´n, F. Falcone, J. Garcı´a, I. Gil, T. Lopetegi, M.A.G. Laso, R. Marque´s, F. Medina, and M. Sorolla, Compact coplanar waveguide band-pass filter at the S-band, Microwave Opt Technol Lett 46 (2005), 33–35.

6.J. Bonache, I. Gil, J. Garcia-Garcia, and F. Martin, Novel microstrip bandpass filters based on complementary split ring resonators, IEEE Trans Theory Tech 54 (2006), 265.

7.A.L. Borja, J. Carbonell, V.E. Boria, and D. Lippens, Symmetrical frequency response in a split ring resonator based transmission line, Appl Phys Lett 93 (2008), 203505.

8.J. Carbonell, A.L. Borja, V.E. Boria, and D. Lippens, Duality and superposition in split ring resonator loaded planar transmission lines, IEEE Antennas Wireless Propag Lett 8 (2009), 886–889.

9.A.L. Borja, et al. Highly selective left-handed transmission line loaded with split ring resonators and wires, Appl Phys Lett 14 (2009), 143503.

10.S. Hirsch, Q. Chen, K. Duwe, and R. Judaschke, Design and characterization of coplanar waveguides and filters on thin dielectric membranes at D-band frequencies, SMW’2001 Symposium Proceedings, Kharkov, Ukraine, June 4–9, 2001.

11.O. Dupuis, J. Carbonell, P. Mounaix, O. Vanbe´sien, and D. Lippens, Micromachined coplanar transmission lines in a GaAs technology, Microwave Opt Technol Lett 20 (1999), 106–110.

12.S.V. Robertson, L.P.B. Katehi, and G.M. Rebeiz, Micromachined W-band filters, IEEE Trans Theory Tech 44 (1996), 598–606.

13.G. Prigent, E. Rius, F. Le Pennec, S. Le Maguer, C. Quendo, G. Six, and H. Happy, Design of narrow-band DBR planar pilters in Si-BCB technology for millimeter-wave applications, IEEE Trans Theory Tech 52 (2004), 1045–1051.

14.J.S. Hong and M.J. Lancasterm, Microstrip filters for RF/microwave applications, John Wiley, New York, 2001.

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A NOVEL FOLDED SLOT ANTENNA FOR UWB APPLICATIONS

Chien-Wen Chiu, Chia-Shan Li, and Chih-Hsiang Yang

Department of Electronic Engineering, National I-Lan University, #1, Sec.1, Shen-Lung Rd, I-Lan, Taiwan-260, Republic of China; Corresponding author: alexchiu@niu.edu.tw

Received 1 November 2009

ABSTRACT: This letter presents a compact and novel folded antenna with curved slots for ultra-wideband (UWB) applications. The proposed antenna originates from an antenna, which consists of a pair of symmetrically curved radiating slots fed by a CPW transmission line. This pair of planar curved slots is symmetrically folded in relation to the central feeding lines so that the size is shrunk to one half of the original geometric size. Using the HFSS software, the simulated results shows that the folded type antenna still preserves the UWB transmission characteristics. The impedance bandwidth, radiation pattern, and radiation gains of this shrunken UWB antenna are investigated and further measurement are performed to verify its UWB characteristics.

VC 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1872– 1877, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25299

Key words: UWB antenna; folded slot antenna; curved radiating-slot; printed antenna; coplanar waveguide

1. INTRODUCTION

Ultra-wideband (UWB) is a radio technology that was initially proposed by the US Department of Defense. Its original applications were mostly in military radar systems. Until 2004, UWB radios were collocated into the frequency bandwidth from 3.1 to 10.6 GHz for unlicensed use [1]. UWB transmission has recently received significant attention in both academia and industry for its application in wireless communications. Because of its UWB features, the UWB system has many benefits, such as high-data rate, availability of low-cost CMOS transceivers, low-transmitting power, multipath immunity, and lower interference [2]. Despite the fact that many papers have been published on the UWB antenna, extensive research remains ongoing to develop an effective UWB technology and UWB antenna.

Generally speaking, a UWB system is applied and embedded into a laptop or portable digital device for high-speed video-data transmission. However, in the early developmental stages of the laptop, neither the engineers nor the industrial designers took an antenna into consideration. As a result, the space allocated to design an antenna is quite small. Consequently, a UWB antenna must have a low profile, be planar and of low cost. Numerous planar antennas have been proposed for UWB system applications, including the planar wideband monopole [3–5], and planar slot antenna [6–9]. The planar slot antenna is probably the most promising candidate for UWB applications. The advantages of a slot antenna include wide bandwidth, low cost, and it is planar in the PCB process. However, the size of the present antenna is not small enough to be embedded into a wireless communication device. Thus, size reduction remains an important issue for practical application.

This article proposes a compact folded planar antenna with curved slots fed by a folded transmission line. The proposed antenna originates from a pair of tapered, curved slots fed by a CPW [10]. The slot antenna is folded symmetrically along its central line for size reduction. The performance of this folded UWB antenna is investigated in detail to make sure the UWB features exist. Using HFSS to analyze and design the folded

Figure 1 UWB antenna with a pair of symmetrically curved slots fed by a CPW

antenna, the impedance bandwidth, reflection coefficient, radiation pattern, and antenna gain of the shrunken UWB antenna were investigated. Measurements were also performed to verify that the proposed antenna can reach the UWB system requirements for industrial applications.

2. ANTENNA DESIGN

‘‘Size reduction’’ is an important issue for a UWB system but it is hard to realize. To shrink the geometric size of a slot antenna

Figure 2 Geometry of the proposed folded UWB antenna, (a) top layer view and (b) cross-sectional view. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com]

Figure 3 Characteristic impedance insertion loss of the folded coplanar waveguide. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com]

fed by a CPW, ‘‘folded type’’ is a possible approach. Figure 1 shows an original planar antenna that consists of a pair of symmetrically curved radiating slots fed by a coplanar waveguide to achieve the UWB requirement. The antenna was originally proposed by Sun et al. of NTUT, Taiwan [10]. This original antenna is designed on a rectangular FR4 substrate with a thickness of 1.6 mm and a relative permittivity of 4.4. The loss tangent of the substrate is 0.02 and the size of ground plane has an area measuring 63.53 mm 40 mm. Their research demonstrated that the UWB operation of the antenna, before folding successfully meets the system requirements. This size is shrunken to one half the original geometric sizes if the pair of planar curved slots is symmetrically folded relative to the two center lines (the line A and the line B as shown in Fig. 1). Figure 2 shows the geometry of the proposed folded-slot UWB antenna. This antenna is also fabricated on a rectangular FR4 substrate where its outer-ground size measures only 30.3 40 mm.

Although the slot antenna is symmetrically folded along the two center lines (line A and line B), the feeding CPW

Figure 4 Simulation results for the originally unfolded antenna and the folded antenna. [Color figure can be viewed in the online issue, which is available at www.interscience.wiley.com]

transmission line also has to be folded. Figure 2(b) shows the cross section view of the folded CPW. This folded transmission line is fed from the edge by an SMA connector. In essence, a traditional coplanar waveguide needs an adequate ground plane on both the left and the right side of the center feeding line to work normally. However, the large ground planes for the folded CPW are placed on the top and bottom of the printed circuit board. The center feed line is printed on the right side of the substrate. In this work, the folded transmission line, which is fed from the edge, is used as the feeding structure for the folded antenna. Symmetrical folding of the CPW transmission line is necessary to match the input coaxial cable for launching the signal source.

The folded CPW must be a 50-X transmission line. The electrical parameters of the folded transmission line are designed and calculated using HFSS software. The final parameters for

the transmission lines shown in Figure 2(b) are er ¼ 4.3, the sidewall conductor width is 1.6 mm, conductor conductivity is 5.88 107 S/m, and the metal thickness is 0.036 mm. Considering the capability to fabricate a gap width g by using a circuit board plotter, the gap width is selected to be 0.3 mm. The ground plane width is W ¼ 30.3 mm. Thus, the simulated characteristic impedance is about 49.27 X. Figure 3 shows the transmission performance of a section of folded CPW transmission line with a length L ¼ 40 mm. Because the loss tangent of the FR4 substrate is large, the simulated insertion loss is 1.7 dB at 8.5 GHz and the measured loss is 2.9 dB at 8.5 GHz. As only 10 mm of the edge-fed transmission line was included in the proposed folded antenna, its power loss will be small. Our findings show that it has a good transmission performance.

To verify the impedance matching between the feeding coaxial cable and the folded transmission line, the characteristic

impedance Zo of the folded line is obtained experimentally by

p

using Johnson’s formula Zo ¼ Zopen Zshort where Zopen indicates the input impedance of an open circuit, and Zshort indicates the input impedance of a short circuit [11]. This work measured the return loss of a 40 mm long folded transmission line terminating at an open-end and a short-end discontinuity. Then, Zopen and Zshort are obtained from the measured input impedance in the case of terminating at the open and short discontinuities. This measurement was performed by an Agilent E5071B Network Analyzer in our laboratory. To measure the return loss of the 40-mm folded transmission line terminating at the open and short conditions, the open and short terminators were connected with the SMA connectors on one end of the transmission line. Figure 3 also shows that the measured characteristic impedance of the folded transmission line is nearly 50 X. The maximum and minimum of the impedance are about 52.9 and 47.3 X, respectively. The variation is only about 50 6 2.8 X.

Figure 4 shows the simulation results of the reflection coefficient for Sun’s original structure before folding. The UWB operation demonstrates that it satisfies the system requirements before folding. Figure 4 also shows the simulation results for the folded slot antenna where this pair of planar-curved slot

Figure 7 Measured peak gain of the folded UWB antenna. [Color figure can be viewed in the online issue, which is available at www. interscience.wiley.com]

antennas is symmetrically folded along the center lines (line A and line B). It is worth noting that it also has an ultrawide impedance bandwidth but it has a frequency shift.

Although the folded antenna has an ultrawide bandwidth, the lowest cut-off frequency in Figure 4 is higher than 3.1 GHz, and as such it does not meet the specification requirements for UWB system applications. Some parameters, such as the position,

aperture widths, and the degree of the curvature of the slots shown in Figure 2 are selected to adjust its performance. To lower the lowest cut-off frequency but still preserve the broadband performance, design parameters r1, r2, R1, and R2 are optimized by means of the HFSS simulation tool. Here, fixing r2 and R2, the aperture length R1, and radius r1 are the most important parameters affecting the antenna performance, and they

need to be further investigated. Finally, when the aperture length R1 is adjusted to 26 mm and r1 is 13 mm, a good impedance matching for the ultrawide bandwidth was achieved in this study. Figure 5 shows the simulated field distributions on the slot region at different resonating frequencies. The current distribution demonstrates that the proposed antenna can generate multiple resonating modes to achieve an UWB.

3. MEASURED AND NUMERICAL RESULTS

In this study the proposed antenna shown in Figure 2 was constructed and tested. Figure 6(a) shows the photograph of the actual folded transmission line and the proposed antenna. The folded antenna was printed on two sides of a 1.6 mm thick FR4 substrate with a ground size of 30.3 mm 40 mm. The geometric sizes for the tapered-curved slot antenna folded with two half-ellipse-shaped planes were R1 r1 (26 mm 13 mm) and R2 r2 (15 mm 8.25 mm), respectively. The folded transmission line fed from the edge was 10 mm long with a sidewall strip width of 1.6 mm, the same as the substrate’s thickness, and the gap distance g of the folded CPW was 0.3 mm.

The experiments were performed using an Agilent HP8363PNA network analyzer. The simulation was performed using HFSS software. The SMA connector was also included in the simulation model. Figure 6(b) shows the measured and simulated reflection coefficient of the folded UWB antenna. When comparing the measured and simulated results, our findings show that the measured bandwidth of the folded slot antenna ranges from 2.87 GHz to 11 GHz. The measured bandwidth is more than 8.13 GHz with a reflection coefficient of less than10 dB. The peak resonant points are at 3.11, 4.43, 7.10, 8.92, and 10.31 GHz, respectively. The simulated results show an 8 GHz bandwidth, which ranges from 3 GHz to 11 GHz, and the peak resonant points are at 3.23, 3.98, 6.35, 8.68, and 10.13 GHz, respectively. The difficulties of manufacturing this antenna result in some unavoidable errors at the resonating frequencies and some shift in frequencies, however, the behavior of the simulated and measured results are similar.

Figure 7 shows the peak gains of the measured folded slot antenna. The antenna gain was measured in the anechoic chamber of NTUST, Taiwan, using a standard double-ridge horn antenna (EMCO 3115). Our findings indicate that the gain of the UWB antenna increases in an approximately linear fashion, but there is some variation over the entire bandwidth from 3 GHz to 10 GHz, reaching the maximum at 10 GHz. The maximum gain is about 9 dBi and the minimum gain is about 3 dBi.

The radiation patterns for the novel folded slot antenna were also investigated. The antenna was measured at both vertical and horizontal polarization on the E-plane (XZ-plane) and H- plane (YZ-plane). Figure 8(a) shows the measured E-plane (XZplane) radiation patterns for the proposed folded slot antenna at 3 and 7 GHz, respectively. Figure 8(b) shows the measured H- plane (YZ-plane) radiation patterns at 3 and 7 GHz, respectively. The measured radiation patterns on the E-plane and H-plane are nearly omni-directional at 3 and 7 GHz, respectively, and the nulls appear at higher frequency bands. The patterns seem to be slightly asymmetrical because of the folding.

4. CONCLUSIONS

This article presented a novel planar folded type antenna with curved radiating slots fed by a folded CPW transmission line for UWB system applications. The measured results confirm that the folded transmission line remains a 50-X transmission line. The performance of the proposed folded antenna was theoreti-

cally investigated using HFSS software. To validate the proposed design, this study performed some parameter measurements. The experimental results compared with the simulation results demonstrated that the folded slot antenna preserves the UWB characteristics.

ACKNOWLEDGMENTS

The authors are grateful to the National Center for High-perform- ance Computing for the computer time and the use of the facilities.

REFERENCES

1.Federal Communications Commission, Authorization of ultra-wide- band technology, First Note and Order (FCC 02-48), Washington, DC, Feb. 14, 2002.

2.S. Roy, J.R. Foerster, V.S. Somayazulu, and D.G. Leeper, Ultrawideband radio design: the promise of high-speed, short-range wireless connectivity, Proc IEEE 92 (2004), 295–311.

3.W.S. Lee, D.Z. Kim, K.J. Kim, and J.W. Yu, Wideband planar monopole antennas with dual band-notched characteristics, IEEE Trans antennas Propag 54 (2006), 2800–2802.

4.X.L. Liang, S.S. Zhong, W. Wang, and F.W. Yao, Printed annular monopole antenna for ultra-wideband applications, Electron Lett 42 (2006), 71–72.

5.C.H. Luo, C.M. Lee, W.S. Chen, C.H. Tu, and Y.Z. Juang, Dual band-notched ultra-wideband monopole antenna with an annular CPW-feeding structure, Microwave Optical Technol Lett 49 (2007), 2376–2378.

6.J.Y. Sze and K. L. Wong, Bandwidth enhancement of a microstrip- line-fed printed wide-slot antenna, IEEE Trans Antennas Propag 49 (2001), 1020–1024.

7.J.Y. Chiou, J.Y. Sze, and K.L. Wong, A broad-band CPW-fed strip-loaded square slot antenna, IEEE Trans Antennas Propag 51 (2003), 719–721.

8.R. Chair, A.A. Kishk, and K.F. Lee, Ultrawide-band coplanar waveguide-fed rectangular slot antenna, IEEE Antennas Wireless Propag Lett 3 (2004), 227–229.

9.C.W. Chiu and C.S. Li, A CPW-Fed band-notched slot antenna for UWB applications, Microwave Opt Technol Lett 51 (2009), 1587–1591.

10.J.S. Sun, Y.C. Lee, and S.C. Lin, New design of a CPW-fed ultrawideband slot antenna, Microwave Opt Technol Lett 49 (2007), 561–564.

11.W.C. Johnson, Transmission Lines and Networks, McGraw-Hill, New York, NY, 1963, p 155.

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AN EMBEDDED MULTILAYER LTCC BAND-PASS FILTER USING U-TYPE STEPPED IMPEDANCE RESONATOR

Zhigang Wang, Peng Wu, Bo Yan, Yunchuan Guo, Ruimin Xu, and Weigan Lin

School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu 610054, People’s Republic of China; Corresponding author: zgwang@ee.uestc.edu.cn or wangzhigang19791@163.com

Received 5 November 2009

ABSTRACT: This article proposes a compact multilayer band-pass filter based on low-temperature co-fired ceramic (LTCC) technology. The filter is constructed using U-type stepped impedance resonators (SIR) with microstrip input and output ports. To validate the proposed filter, a three-order X-band Chebyshev band-pass filter is developed and verified by full-wave simulation. The proposed filter is fabricated using multilayer LTCC technology and measured using vector network analyzer (VNA). Covering area of the fabricated band-pass filter is only