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IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 20, NO. 3, MARCH 2010 145
Compact UWB Bandpass Filter WithUltra Narrow Notched Band
Xun Luo , Student Member, IEEE , Jian-Guo Ma , Senior Member, IEEE , Kaixue Ma , Senior Member, IEEE , andKiat Seng Yeo
Abstract—A compact ultra-wideband (UWB) bandpass filterwith an ultra narrow notched band is proposed using a hybridmicrostrip and coplanar waveguide (CPW) structure. The CPWdetached-mode resonator (DMR) composed of a quarter-wave-length ( 4 ) nonuniform CPW resonator with a short-stub anda 4 single-mode CPW resonator (SMCR) can allocate threesplit frequencies at the lower end, middle, higher end of the UWBpassband. The conventional broadside-coupled microstrip/CPWstructure is introduced to improve the bandwidth enhancementaround the split frequencies, which leads to good UWB operation.To avoid the interferences such as WLAN signals, the 4 me-ander slot-line structure embedded in the DMR is employed toobtain the notched band inside the UWB passband. The designis then verified by experiment. Good passband and stopbandperformances are achieved. Specifically, the fabricated filter hasa 10 dB notched fractional bandwidth (FBW) of 2.06% at thenotched center frequency of 5.80 GHz.
Index Terms—Bandpass filter (BPF), coplanar waveguide(CPW), detached-mode resonator (DMR), microstrip, notchedband, ultra-wideband (UWB).
I. INTRODUCTION
ULTRA-WIDEBAND (UWB) technology has risen dra-matically, since the Federal Communication Commission
(FCC) authorized UWB (range of 3.1–10.6 GHz) for the unli-
censed use of short-distance communication in early 2002 [1].
As one of the key components in the UWB systems, the UWB
bandpass filters (BPFs) are developed with variant structures
[2]–[6]. However, existing undesired narrow band radio sig-
nals, such as wireless local-area network (WLAN), may inter-
fere with the UWB range defined by the FCC. In order to avoid
the interferences from the WLAN signals, UWB BPFs with
notched band using different structures are proposed [7]–[10].
However, the narrowest 10 dB notched fractional bandwidth
Manuscript received October 13, 2009; revised November 09, 2009. Firstpublished January 26, 2010; current version published March 10, 2010. Thiswork was supported by the National Science Foundation of China (NSFC:60688101) and National 111 program.
X. Luo is with the School of Electronic Engineering, University of Elec-tronic Science and Technology of China, Chengdu 610054, China (e-mail:[email protected]).
J.-G. Ma was with the School of Electronic Engineering, University of Electronic Science and Technology of China, Chengdu 610054, China. He isnow with the School of Electronic Information Engineering, Tianjin University,Tianjin 300072, China.
K. Ma is with the ST Electronics, Singapore.K. S. Yeo is with the Center for Integrated Circuits and systems, Nanyang
Technological University, Singapore 639798.
Digital Object Identifier 10.1109/LMWC.2010.2040212
(FBW) reported in the literature is around 4.6%. Much narrower
FBW is required [10].
In this letter, a compact UWB BPF with an ultra narrow
notched band is proposed using a hybrid microstrip and
coplanar waveguide (CPW) structure. Following our early
research in [5], the implemented filter is composed of the CPW
detached-mode resonator (DMR) and conventional broad-
side-coupled microstrip/CPW structure to achieve the UWB
frequency response. Furthermore, with the meander slot-line
structure embedded in the DMR, a desirable notched band
to cancel the WLAN signals in standard UWB passband isachieved. The proposed filter is constructed on the RT/5880
with and . Both simulated and
measured results demonstrate good passband and stopband
performances of the implemented filter.
II. UWB BPF WITH NOTCHED BAND:
SCHEMATIC AND PRINCIPLE
The configuration and transmission line model of the pro-
posed UWB BPF with notched band using the hybrid struc-
ture of microstrip and CPW are shown in Fig. 1. As depicted in
Fig. 1(a), the microstrip structure on the top is used as the input/ output (I/O) feed lines through the broadside-coupled transition
to the CPW resonant structure on the bottom. The microstrip
layer and CPW layer share the same substrate and signal ground.
As shown in Fig. 1(b), the DMR on the CPW layer is composed
of three parts: a nonuniform CPW resonator with characteristic
impedance and electric length , a shunt-stub of ,
and a single-mode CPW resonator (SMCR) of . Inside
the DMR, two symmetrically embedded meander slot-lines with
length and width (i.e., ) are implemented.
A. Detached-Mode Resonator
The DMR is employed to occur three split frequencies at thelower end , middle , and higher end to meet the
concern of the UWB operation. First, the nonuniform CPW res-
onator with quarter-wavelength is introduced to resonate
at the center frequency , where is the microstrip guided
wavelength at . Secondly, for a resonance at , a SMCR
is inserted and separates the nonuniform CPW resonator into
two identical parts. Meanwhile, a higher unwanted harmonic
introduced by this SMCR that could dominate the stopband
bandwidth of the proposed filter. Thirdly, a short-stub connected
to the nonuniform CPW resonator is employed to allocate the
and compose the whole DMR. This lower resonance can be de-
termined when shown in Fig. 1(b) is about 90 at .
1531-1309/$26.00 © 2010 IEEE
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146 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 20, NO. 3, MARCH 2010
Fig. 1. (a) Configuration of the proposed filter. (b) Transmission line model.
B. Broadside-Coupled Microstrip/CPW Structure
The conventional broadside-coupled microstrip/CPW struc-
ture is introduced to provide strong enough capacitive coupling
for bandwidth enhancement [4],[5]. It is found that by extending
the microstrip electric length to90 (i.e., ) atthe center
frequency of , the insertion loss around the split frequencies isreduced and becomes smooth to meet the UWB passband limit.
C. Embedded Meander Slot-Line Structure
To cancel the interferences such as the WLAN signals, the
meander slot-line structure embedded in the DMR is employed.
This novel structure could easily achieve a desirable notched
band inside the UWB operation. It is found that the center fre-
quency of the notched band can be finely adjusted when the
meander slot-line length is about at . Besides, the
bandwidth of the notched band can be controlled by tuning the
width of the meander slot-line structure.
D. Filter Design
To demonstrate the operation of the proposed structure
above, the full-wave EM simulator [11] is used. Three cases
are compared and studied as follow. Case (a) is the structure of
the DMR. The nonuniform CPW resonator with characteristic
impedance of and electric length of 91.8 and the
short-stub with of and of 32.2 at 6.85 GHz are
chosen, respectively. The SMCR has characteristic impedance
of and electric length of 90.4 at 9.34 GHz. Case
(b) is the DMR with conventional hybrid broadside-coupled
microstrip/CPW structure, where the microstrip characteristic
impedance and electric length are chosen to be
and 90.2 at 6.85 GHz, respectively. Case (c) is the structure of case (b) with the meander slot-line structure embedded in the
Fig. 2. Frequency responses of the configuration of the proposed filter.
Fig. 3. Effects of embedded meander slot-line structure on notched band.(a) Curve to relate the center frequency of notched band to slot-line length L .(b) Curve to relate the bandwidth of notched band to slot-line width W .
DMR. These meander slot-lines shown in Fig. 1 have width of
0.2 mm and electric length of 91.1 at 5.80 GHz. The results
of three cases are compared in Fig. 2, respectively. Curve (a)
in Fig. 2 shows that three split resonant frequencies could be
allocated by the DMR at the lower end, middle, and higher end
of the UWB band, i.e., 3.79, 6.81, and 9.34 GHz. Besides, due
to the use of the SMCR which makes the spurious passband
about the triple of the center frequency at 6.85 GHz, higherunwanted harmonic resonance appears around 17.2 GHz.
Curve (b) depicts that good UWB response can be achieved by
the broadside-coupled microstrip/CPW structure. In addition,
with the advantages of the microstrip feed-line structure, two
transmission zeros close to the passband are formed, which lead
to good selectivity. Curve (c) illustrates that the UWB operation
is still obtained and a notched band with center frequency
of 5.80 GHz is achieved.
Fig. 3(a) and (b) show the simulated frequency response of
the proposed filter with tuning and of the embedded
meander slot-line structure, respectively. It is clearly observed
that with increasing length , the notched band is shifted to
lower frequency and with decreasing width , the bandwidthof the notched band slightly decreases. After choosing of
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LUO et al.: COMPACT UWB BANDPASS FILTER 147
Fig. 4. Layout of the fabricated filter. (L = 9 : 6 , L = 1 : 3 , L = 0 : 8 ,L = 6 : 2 , L = 6 : 0 5 , L = 1 : 3 , L = 4 : 1 5 , L = 6 : 1 , L = 0 : 8 ,L = 1 0 : 3 , W = 5 : 3 , W = 0 : 6 , W = 0 : 8 , W = 0 : 2 , W = 1 : 6 ,W = 1 : 2 , W = 1 : 0 5 , and W = 0 : 2 .).
Fig. 5. Measured and simulated results of the fabricated UWB BPF with anultra narrow notched band.
10.3 mm and of 0.2 mm, a 10 dB notched FBW of 2.06%
at the notched center frequency of 5.80 GHz can be achieved.
III. FABRICATION AND EXPERIMENTAL RESULTS
The investigation above shows the principle of the proposed
filter. To further improve the passband/stopband performances
and demonstrate this type of filter experimentally, the fabri-
cated filter is slightly modified and displayed in Fig. 4. -pa-
rameters and group delay response measurements are performed
using Agilent 5230A network analyzer over the frequency range
from 10 MHz to 18 GHz. Fig. 5 demonstrates the simulated
and experimental results of the proposed filter, where excel-
lent agreement is obtained. The proposed filter exhibits a good
UWB bandpass performance from 2.96 to 10.72 GHz with a
fractional bandwidth (FBW) of 113.5% at a midband frequency
of 6.84 GHz. The measured results show the emergence of a
notched band at 5.80 GHz with 24.7 dB insertion loss and 10 dB
notched FBW of 2.06%. The measured minimum insertion loss
is found to be 0.5 and 0.9 dB in the lower and upper passbands,
respectively. The measured return loss is better than 14.3 dB
over the lower band and better than 11.6 dB over the upper band.
Two transmission zeros are found at 0.86 and 11.8 GHz, and
the upper stopband is observed from 11.4 to 16.4 GHz. Mean-
while, the implemented filter exhibits a flat group delay response
below 0.48 ns and group delay variation less than 0.28 ns overthe lower and upper passbands. In addition, the proposed filter
has the merit of a compact size ( by , where
is the guided wavelength of microstrip structure at the center
frequency of 6.84 GHz) when compared to the published UWB
BPF with a notched band.
IV. CONCLUSION
In this letter, a compact UWB BPF with an ultra narrow
notched band is proposed based on a hybrid microstrip and
CPW structure. The DMR on the CPW layer and conventional
broadside microstrip/CPW coupled structure are constructed to
meet the UWB limit. To achieve the notched band in the UWBpassband, the meander slot-line structure embedded in the
DMR is employed. As such, the UWB filter with notched band
is designed and implemented. Specifically, the proposed filter
exhibits an ultra narrow notched band at 5.80 GHz with 24.7 dB
insertion loss and 10 dB notched FBW of 2.06%. With good
frequency performance and a compact size, the proposed filter
is attractive to the UWB systems for the purpose of blocking
unwanted radio signals.
REFERENCES
[1] Revision of Part 15 of the Commission’s Rules Regarding Ultra-Wide-band Transmission System, ET-Docket 98–153, First Note and OrderFederal Communication Commission, 2002.
[2] K. Li, D. Kurita, and T. Matsui, “An ultra-wideband bandpass filterusing broadside-coupled microstrip-coplanar waveguide structure,” in
IEEE MTT-S Int. Dig., Jun. 2005, pp. 675–678.[3] C. L. Hsu, F. C. Hsu, and J. T. Kuo, “Microstrip bandpass filter for
ultra-wideband (UWB) wireless communications,” in IEEE MTT-SInt. Dig., Jun. 2005, pp. 679–682.
[4] T. N. Kuo, S. C. Lin, and C. H. Chen, “Compact ultra-wideband band-pass filters using composite microstrip-coplanar-waveguide structure,”
IEEE Trans. Microw. Theory Tech., vol. 54, no. 10, pp. 3772–3778,Oct. 2006.
[5] X. Luo, J.-G. Ma, K. Ma, and K. S. Yeo, “An ultra-wideband band-pass filter using hybrid structure of microstrip and CPW,” Microw. Opt.Technol. Lett., vol. 51, no. 10, pp. 2470–2473, Oct. 2009.
[6] K. Ma, K. C. B. Liang, R. M. Jayasuriya, and K. S. Yeo, “A wideband
and high rejection multimode bandpass filter using stub perturbation,” IEEE Microw. Wireless Compon. Lett., vol. 19, no. 1, pp. 24–26, Jan.2009.
[7] W. Menzel and P. Feil, “Ultra-wideband (UWB) filters with wlannotch,” in Proc. 36th EuMC., Sep. 2006, pp. 595–598.
[8] S. W. Wong and L. Zhu, “Implementation of compact UWB bandpassfilter with a notch-band,” IEEE Microw. Wireless Compon. Lett., vol.18, no. 1, pp. 10–12, Jan. 2008.
[9] G. M. Yang, R. Jin, C. Vittoria, V. G. Harris, and N. X. Sun, “Smallultra-wideband (UWB) bandpass filter with notched band,” IEEE Mi-crow. Wireless Compon. Lett., vol. 18, no. 3, pp. 176–178, Mar. 2008.
[10] H. Shaman and J. S. Hong, “Ultra-wideband (UWB) bandpass filterwith embedded band notch structures,” IEEE Microw. WirelessCompon. Lett., vol. 17, no. 3, pp. 193–195, Mar. 2007.
[11] Zeland Software, Inc. Fremont, CA, 2007.