A Novel LTCC Bandpass Filter for UWB Applications

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					                                                             (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                            Vol. 8, No. 8, November 2010

                A Novel LTCC Bandpass Filter for UWB
                           Applications
                                              Thirumalaivasan K and Nakkeeran R
                                   Department of Electronics and Communication Engineering
                                   Pondicherry Engineering College, Puducherry-605014, India
                                      thirumalaivasank@pec.edu and rnakeeran@pec.edu



Abstract— Bandpass filter based on parallel coupled line                  gap size are required. Obviously, shrinking the gap size is not
microstrip structure is designed in low-temperature co-fired              only the way to increase the coupling of coupled lines [10].
ceramic technology (LTCC) suitable for short range Ultra-                     The proposed bandpass filter in this paper is based on
Wideband (UWB) applications. Fifth order Chebyshev filter of              LTCC using parallel coupling at center and broad side
0.05 dB passband ripple with fractional bandwidth of 62.17% is            coupling at ends of the proposed filter structure. The filter is
proposed using insertion loss method. The filter demonstrates
                                                                          designed to cover the entire UWB range. The main advantage
-10 dB bandwidth and linear phase response over the frequency
range 3.8 GHz - 7.4 GHz. With the above functional features, the          of the multi-layered structure is to shrink the circuit size. The
overall dimension of the filter is 33.5 mm (height) × 1.6 mm              obtained scattering parameters of UWB bandpass filter convey
(length) × 1.6 mm (breadth). It is not only compact but also              an optimal performance in terms of insertion and return loss.
delivers excellent scattering parameters with the magnitude of            It is distinctive in its structure and it has simple design with
insertion loss, |S21| lower than -0.09 dB and return loss better          less number of design parameters compared to the existing
than -49 dB. In the passband, the computed group delay is well            filter designs in the literature [11]-[13].
within the tolerable variation of 0.1 ns.                                     The rest of the paper is organized as follows: In Section II,
                                                                          the UWB bandpass filter design using LTCC is presented.
Keywords- Ultra-wideband; bandpass filter; parallel coupled               Simulation results and analysis are presented in Section III.
line; low-temperature co-fired ceramic; group delay
                                                                          Section IV concludes the paper.

                         I. INTRODUCTION
                                                                                             II. BANDPASS FILTER DESIGN

    UWB technology has brought out tremendously increasing
research interests since the Federal Communications                           Figure 1 shows one possible circuit arrangement for
Commission (FCC) in USA released its unlicensed use for                   bandpass filter using parallel coupled line microstrip structure
indoor and hand-held systems in 2002 [1]. Efforts have been               at center and broad side coupling at end of the geometry
made in the past eight years towards exploring various UWB                designed in LTCC for UWB range. It consists of transmission
components and devices. As one of the essential component                 line sections having the length of half wavelength at the
blocks, the researchers are attempting to design the UWB                  corresponding center frequency. Half wavelength line
bandpass filter (BPF) with 120% fractional bandwidth                      resonators are positioned so that adjacent resonators are
centered at 6.85 GHz. In the recent years, the market pays                parallel to each other along half of their length. This parallel
much attention towards miniaturization of receiver systems.               arrangement gives relatively large coupling for the given
Hence, researchers are working for the development of small               spacing between the resonators, and thus, this filter structure is
size and cost effective filters [2]-[5].                                  particularly convenient for constructing filters having larger
    Parallel coupled-line microstrip filters are found to be one          bandwidth as compared to the other structures [14]-[17].
of the most commonly used microwave filters in many
practical wireless systems for several decades [6]-[8]. In
addition to the planar structure and relatively wide bandwidth,
the major advantage of this kind of filter is that its design
procedure is quite simple. Based on insertion loss method [9],
filter functions of maximally flat and Chebyshev type can be
easily synthesized. Moreover, the filter performance can be
improved in a straightforward manner by increasing the order
of the filter. When these filters are to be realized by parallel
coupled microstrip lines, one of the main limitations is the
small gap size of first and last coupling stages. To increase the
coupling efficiency, more fractional bandwidth and smaller                        Figure 1. Geometry of the proposed UWB bandpass filter




                                                                    138                                http://sites.google.com/site/ijcsis/
                                                                                                       ISSN 1947-5500
                                                               (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                              Vol. 8, No. 8, November 2010
    The gap between the resonators is introducing a capacitive
coupling, which can be represented by a series capacitance.
The broad side coupling and existence of the substrate result
tight coupling, which provides wide bandpass operation. The
physical parameters of the proposed bandpass filter are
optimized to the following values, l1=5.89 mm; l2=5.86 mm;
d=0.2 mm; g0 = 0.08 mm; g1 = 0.1 mm; a0 = 1.06 mm;
a1 = 1.2 mm; a2 = 1.02; w0 = 1.6 mm; b = 1.6 and h = 33.5 mm
to cover the entire UWB range between 2 GHz and 9 GHz.
Using this configuration, higher coupling is obtained and
therefore wider bandwidth is achieved. This structure is used
to generate a wide passband and expected to achieve a tight
coupling, and lower insertion by reducing both strip and slot
width. 3D view of a LTCC UWB bandpass filter with parallel
and broadside coupling is shown in Figure 2, which consists of
two layers, resonators and substrate with frames.


                                                                                            Figure 3. Simulation S- parameters




         Figure 2. 3D view of proposed LTCC filter structure

                   III. RESULTS AND DISCUSSION
   The proposed filter is designed to provide a wide passband,
low insertion loss and return loss, linear phase over the
passband, flat group delay and high fractional bandwidth.
The simulation S parameters of the proposed UWB bandpass
filter using LTCC are shown in Figure 3. It is clear from the
                                                                                          Figure 4. Simulation group delay
response that the proposed filter has better insertion loss of -
0.09 dB and the low return loss of about -49 dB. The -10 dB
fractional bandwidth computed from the response is about
62.17 %.
   For wideband applications, the examination of the flat group
delay is essential and required. The simulation group delay for
the proposed filter is shown in Figure 4, which exhibits a flat
group delay response below 0.1 ns over the whole passband. It
implies that this proposed UWB filter has a very good linearity
of signal transfer and would ensure the minimum distortion to
the input pulse when it is implemented in the UWB system.
The response of the Figure 5 shows that the phase of S21
throughout the -10 dB passband between 3.8 GHz and
7.4 GHz of designed filter is acceptably linear.
   In order to evaluate the performance of the proposed UWB
bandpass filter, the filter is simulated through the simulation
tool, IE3D [18]. The filter is designed        based on LTCC
substrate with two upper sheet layers, thickness of 1.6 mm and
1.93 mm with dielectric constant of 7.8 and a loss tangent of                            Figure 5.Simulation of phase of S21
0.002.



                                                                   139                               http://sites.google.com/site/ijcsis/
                                                                                                     ISSN 1947-5500
                                                                       (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                                                      Vol. 8, No. 8, November 2010
                            CONCLUSION                                                   [12] Thirumalaivasan K and Nakkeeran R, ―Wired Ring Resonator
                                                                                              Based Compact Ultra-Wideband Bandpass Filters Using Dual-line
                                                                                              Coupling Structure‖, in the Proc. of ACEEE International
     In this letter, a bandpass filter for UWB applications                                   Conference on Control, Communication and Power Engineering
based on LTCC structure is presented. The proposed filter                                     CCPE 2010, July 28-29, 2010, India. DOI: 02.CCPE.2010.1.182.
                                                                                         [13] J.-T. Kuo, ―Accurate quasi-TEM spectral domain analysis of single
demonstrated an excellent ultra-wide bandwidth from 3.8 GHz                                   and multiple coupled microstrip lines of arbitrary metallization
to 7.4 GHz. Total size of the UWB filter is 33.5 mm (height) ×                                thickness,‖ IEEE Trans. Microwave Theory Tech., MTT-43, no.8,
1.6 mm (length) × 1.6 mm (breadth) and the fractional                                         pp. 1881-1888, Aug. 1995.
bandwidth is about 62.17 %. Simulation of bandpass filter                                [14] Thirumalaivasan K, Nakkeeran R, and Oudayacoumar S, ―Circular
                                                                                              Resonator Based Compact Ultra-Wideband Bandpass and Notched
delivers excellent scattering parameters with magnitude of                                    Filters with rejection of 5-6 GHz band‖, in the Proc. of ACEEE
insertion loss, |S21| lower than -0.09 dB and return loss better                              International Conference on Control, Communication and Power
than -49 dB. The obtained group delay for this filter is below                                Engineering CCPE 2010, July 28. DOI: 02.CCPE.2010.1.212.
0.1 ns.                                                                                  [15] Yue Ping Zhang and Mei Sun, ―Dual Band Microstrip Bandpass
                                                                                              Filter Using Stepped Impedance Resonators With New Coupling
                                                                                              Schemes,‖ IEEE Trans. on Microwave Theory and Tech., vol.54,
                                                                                              no.10, Oct 2006.
                            REFERENCES                                                   [16] Thirumalaivasan K, Nakkeeran R, and Oudayacoumar S,
                                                                                              ―Effective Notch Ultra-Wideband Filter Using Ring Resonator for
                                                                                              the Rejection of IEEE 802.11a‖, in the Proc. of IEEE International
    [1]  FCC NEWS (FCC 02-48), Feb. 14, 2002. FCC News release.
                                                                                              Conference on Computing, Communication and Networking
    [2]  Hong, J. S. and M. J. Lancaster, Microstrip Filters for
                                                                                              ICCCNT 2010, July 29. DOI:10.1109/ICCCNT.2010.5592565.
         RF/Microwave Application, Wiley, New York, 2001.
                                                                                         [17] Ravee Phromloungsri, Mitchai Chongcheawchamnan and Ian D.
    [3] C.Q.Scrantom and J.C.Lawson, ―LTCC Technology where we are
                                                                                              Robertson,” Inductively Compensated Parallel Coupled Microstrip
         and where we’re going-II‖, In IEEE MTT Int. Microwave. Symp.
                                                                                              Lines and Their Applications,‖ IEEE Trans. on Microwave Theory
         Dig. 1999.,pp.193-200
                                                                                              and Tech., vol.54, no.9, Sep 2006.
    [4] C.W.Tang,‖Harmonic Suppression LTCC Filter with the Step
                                                                                         [18] IE3D 14, Zeland Software, Ins., Fremont, USA
         Impedance Quarter Wavelength Open stub‖, IEEE Trans. Microw.
         Theory Tech., vol. 51, no. 10, pp. 2112–2118, Oct. 2003.
    [5] Jorge A. Ruiz Cruz, Yunchi Chang, Kawthar A. Zaki, Andrew
         J.Piloto and Joseph Tallo,‖Ultra-Wideband LTCC Ridge                                                  AUTHORS PROFILE
         Waveguide Filters,‖ ," IEEE Microw. Wireless Compon. Lett., vol.
         17, no. 2, pp. 111-117, Feb. 2007.                                         Mr.K.Thirumalaivasan was born in India. He received the B.Tech. degree in
    [6] Jen-Tsai Kuo, Wei-Hsiu Hsu, and Wei-Ting Huang,‖ Parallel                   Electronics and Communication Engineering from Pondicherry University,
         Coupled Microstrip Filters with Suppression of Harmonic                    Puducherry, India, and the M.E. degree in Communication Systems from
         Response,‖ IEEE Microw. Wireless Compon. Lett., vol. 12, no.10,            College of Engineering Guindy, Anna University, Chennai, India, in 2004 and
         Oct. 2002.                                                                 2007 respectively. He is currently working towards the Ph.D. degree at
    [7] L. Zhu, S. Sun, and W. Menzel, "Ultra-wideband (UWB) bandpass               Pondicherry Engineering College, Pondicherry. His current research interest is
         filters using multiple-mode resonator," IEEE Microw. Wireless              in the area of UWB filters and narrowband interference issues with UWB
         Compon. Lett., vol. 15, no. 11, pp. 796-798, Nov. 2005.                    systems.
    [8] Hussein Shaman, Jia-Sheng Hong,‖ Asymmetric Parallel-Coupled
         Lines for Notch Implementation in UWB Filters,‖ IEEE Microw.
         Wireless Compon. Lett., vol. 17, no.7, July 2007.                          Dr. R. Nakkeeran Received BSc. Degree in Science and B.E degree in
    [9] Pozar, D. M., Microwave Engineering, Wiley, New York, 1998.                 Electronics and Communication Engineering from the Madras University in
    [10] T.-N. Kuo, S.-C. Lin, and C. H. Chen, ―Compact ultra-wideband              1987 and 1991 respectively and M.E degree in Electronics and
         bandpass filters using composite microstrip-coplanar-waveguide             Communication Engineering (diversification in Optical Communication) from
         structure,‖ IEEE Trans. Microw. Theory Tech., vol. 54, no. 10, pp.         the Anna University in 1995. He received Ph.D degree from Pondicherry
         3772–3777, Oct. 2006.                                                      University in 2004. Since 1991, he has been working in the teaching
    [11] Oudayacoumar S, Nakkeeran R and Thirumalaivasan K,                         profession. Presently, he is Associate Professor in Pondicherry Engineering
         ―Resonator Based Compact Ultra-Wideband and Notched                        College. He is life member of IETE, ISTE, OSI and IE (I). Also he is member
         Wideband Filters”, in Proceedings of the IEEE National                     of OSA, SPIE and IEEE. He has published seventy five papers in National and
         Conference on Communication (NCC 2010), at IIT Chennai,                    International Conference Proceedings and Journals. He has co-authored a
         January 29-30, 2010. DOI:10.1109/NCC.2010.5430168.                         book, published PHI. His areas of interest are Optical Communication,
                                                                                    Networks, Antennas, Electromagnetic Fields and Wireless Communication.




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