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Proceedings of the 8th National Conference on

Advances in Electronic Communications (ADELCO’ 12), 24th Feb, 2012,National Engineering College, Kovilpatti, Tamil Nadu.

63

DESIGN OF PLANAR BANDPASS FILTER FOR ULTRAWIDE BAND

COMMUNICATION SYSTEMS

M.SHALU1

H.UMMA HABIBA2

1 M.E Communication Systems, Sri Venkateswara College of Engineering

Chennai, India

[email protected] Assistant Professor, Department of ECE, Sri Venkateswara College Of Engineering

Chennai, India

Abstract— A planar band pass filter topology is built

using broadside coupled structure. The design is

aimed at achieving pass band that covers the

frequency range from 3.1GHz to 10.6 GHz. as

required by modern Ultra Wide Band (UWB) indoor

and outdoor communication systems . Multiple

unlicensed users could share spectrum previously

allocated to the users, including licensed users, on a

non-interference basis .The filter is formed byattaching three pairs of circular impedance-stepped

stubs in shunt to a high impedance microstrip line.

We obtain a filter with upper pass band frequency

(4.7GHz to 9.9GHz) of UWB having a uniform

return loss. Attenuation in lower pass band is -30 db.

The filter is successfully designed using Advanced

Design System (ADS) software and measured results

are presented in this work.

Keywords-component; Bandpass filter (BPF), Ultra

Wide Band (UWB) , planar filter

I. INTRODUCTION

Ultra wideband is a radio technology that can be

used at very low energy levels for short-range high-bandwidth communications by using a large portion of

the radio spectrum. Ultra-Wideband (UWB) is a

technology for transmitting information spread over a

large bandwidth (>500 MHz) that should, in theory and

under the right circumstances, be able to share spectrum

with other users. Regulatory settings of Federal

Communications Commission (FCC) in United States

are intended to provide an efficient use of scarce radio

bandwidth while enabling high data rate personal area

network (PAN) wireless connectivity and longer-range,

low data rate applications as well as radar and imagingsystems. Ultra-Wideband (UWB) may be used to refer

to any radio technology having bandwidth exceeding

the lesser of 500 MHz or 20% of the arithmetic centerfrequency, according FCC authorizes the unlicensed use

of UWB in the range of 3.1 to 10.6 GHz. The FCC

power spectral density emission limit for UWB emitters

operating in the UWB band is -41.3 dBm/MHz. This is

the same limit that applies to unintentional emitters in

the UWB band, the so called Part 15 limit. However, the

emission limit for UWB emitters can be significantly

lower (as low as -75 dBm/MHz) in other segments of

the spectrum. In order to meet the strict emission

regulation, band pass filter (BPF) becomes essential

components in the development of UWB

communication systems

The UWB BPFs that have been reported in the

literature can be classified into two main types; the

parallel or edge- coupled structures [2]-[4], and the

broadside-coupled structures [5]-[l3]. The tolerance of

the microstrip and coplanar waveguide (CPW)

fabrication process imposes an upper limit upon the

coupling levels for the parallel- and edge-coupledstructures. This makes the manufacturing process for

the UWB filters utilizing those structures difficult

as their performance is very sensitive to themanufacturing errors. This difficulty can be

circumvented by the other class of filters that

utilizes broadside-coupled structures to achieve the

required tight coupling for UWB performance.

In another method, a broadside-coupled slotline-

microstrip structure was utilized to build UWB BPF

[7]. However, the proposed device is sensitive to the

alignment errors between the narrow slotline and the

microstrip stubs.The multilayer technology was

employed to achieve the required tight coupling forUWB performance [8]. Elliptical shaped broadside

microstrip-slot couplers [9] are used to construct

UWB bandpass filters. In order to improve the

performance at the high stopband, multiple broadside-

coupled sections were utilized. The drawback of this

approach is an increased size of the device. In a

recent modification to the structure proposed in [8], a

lowpass filter is embedded within the feed line of

the filter to improve its high stopband performance

without significantly increasing the size [10]. In this

paper, a tapered broadside-coupled microstrip/ CPW

structure is utilized as an effective method in the

design of UWB BPFs. The proposed configuration

suits the use of the two-sided printed circuit board

(PCB) and produces desired outputs. Figure 1 shows the

emission mask of Ultra Wide Band (UWB) systems.

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Fig. 1 Emission mask of UWB systems

II. PROPOSED BANDPASS FILTER

Advanced Design System's tuning capability

enables you to change one or more design parameter

values and quickly see its effect on the output without

re-simulating the entire design. Multiple tracesgenerated from various tuning trials can be overlaid inthe Data Display window. This can help you find the

best results and the most sensitive components or

parameters more easily. By Richard transformation and

Kuroda’s identity we get the equivalence circuit.

Fig 2. Equivalent circuit

The design equation is given by

where f is cut off frequency

where RL=1Ω

The UWB filter is realized by attaching three pairs

of circular impedance-stepped stubs in shunt to a high

impedance microstrip line. It is implemented on the

substrate with a relative dielectric constant of 4.6 and a

thickness of 1.6 mm. The distance between two circular

patch is 1.73mm and the coupling length is 3.5mm.The

above structure produces good return loss and the pass

band is narrow i.e 4.7 GHz to 9.9 GHz. This is

explained below.

The circular patch design is implemented using

attaching three pairs of circular impedance-stepped

stubs in shunt to a high impedance microstrip line of

radius 0.6 mm at centre and the common radius as 0.5

mm.

Fig 3. Circular Patch Design

The length of the coupled line for half wavelengthparallel coupled band pass filter is given as

(3)

Where l a is the length of coupled element, θe is the

even mode electrical length, λ e is the even mode

wavelength, δi is the positive integer, θo is the odd

mode electrical length andλ

o is the odd modewavelength. The above length equation is calculated

using MATLAB simulation

The filter is fabricated on a FR4 Substrate with

following details,

Table 1

Relative

dielectric permittivity

εr =4.6

Thickness of the

substrate

h = 1.6 mm

Following the above-mentioned considerations, the

characteristic impedances of the high- and low-impedance lines are chosen as Z 0 L = 100 ohms and Z 0C =

50 ohms. For very thin conductors (i.e., t → 0), the

closed-form expressions that provide accuracy better

than one percent are given as

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Using the above equation A is calculated and we get

the value as 3.8.Substituting the vale in the equation(3)

we get the value as 1.7.From the given specification we

have h as 1.6mm.Therefore we have w as 0.2mm.

III. RESULTS

A bandpass filter with pass band frequency 3.6GHz

to 10.3GHz. This pass band is used for UWB

application. The applications are WPAN used in mobile

device desktop and laptop PCs and CE devices. It is also

used for Positioning, Geolocation , Localization, High

Multipath Environments and Obscured Environments.

The circuit parameters of Fig. 1 have the following

values: C1= C3=0.75 pF, L1= L3=0.92 nH, C2=0.37

pF, and L2=l.83 nH. With these values for the

circuit parameters, ADS shows that the performance is

as depicted in Fig. 5, which clearly indicates an

ultra-wideband performance.

Fig. 4 Schematic

This filter produces an upper pass band filter

forUWB application with frequency 4.7GHz to

9.9GHzhaving a uniform return loss ( >-15db).

Attenuationin lower pass band is about -30 db and

Attenuation in upper pass band is poor( <5db).This band

width is used for high data rate transmission(11 to

55Mbits/sec) for applications which involve imaging

and multimedia .

Fig. 5 Schematic Results

Fig. 6 Layout results

This filter produces an upper pass band filter forUWB application with frequency 4.7GHz to 9.9GHzhaving a uniform return loss ( >-15db). Attenuation inlower pass band is about -30 db and Attenuation in upperpass band is poor( <5db).This band width is used forhigh data rate transmission(11 to 55Mbits/sec) for

applications which involve imaging and multimedia .Amillimeter-wave-based alternative physical layer (PHY)was developed for the existing 802.15.3 WirelessPersonal Area Network (WPAN) Standard 802.15.3-2003. The IEEE 802.15.3 Task Group 3c (TG3c) wasformed in March 2005. This mm Wave WPAN operatesin clear band including 57–64 GHz unlicensed banddefined by FCC 47 CFR 15.255. The millimeter-waveWPAN will allow high coexistence (close physicalspacing) with all other microwave systems in the 802.15family of WPANs. In addition, the millimeter-waveWPAN allows very high data rate over 2 Gbit/sapplications such as high speed internet access,streaming content download (video on demand, HDTV,home theater, etc.), real time streaming and wireless data

bus for cable replacement. Optional data rates in excessof 3 Gbit/s will be provided.

IV. CONCLUSION

In this work, a compact UWB BPF is formed byattaching three circular impedance-stepped stubs in shuntto a high impedance microstrip line. The resultsdepicted in Fig. 4 indicate a pass band that covers therange from 4.7 GHz to 9.9 GHz assuming the 3 dBinsertion loss as a reference. having a uniform returnloss ( >-15db).The harmonic responses are removedentirely from the band of interest. This result provesthe success of the proposed structure to build UWB

BPF.

REFERENCES

[1]. Amin M. Abbosh,(1999)“Design of compact directional

couplers for UWB applications” ,IEEE Trans. Microwavetheory Tech.

[2]. B.Yao, Y. Zhou, Q. Cao, and Y. Chen, "Compact UWBbandpass filter with improved upper-stopbandperformance," IEEE Microw. Wireless Compon. Lett.,vol. 19, no.l, pp.27-29, 2009

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[3]. K. Song, and Y. Fan, "Compact ultra-wideband bandpassfilter using dual-line coupling structure," IEEEMicrolV. Wireless Compon. Lett., vol. 19, no.l, pp.30-32,2009.

[4]. L. Han, K. Wu, and X. Zhang, "Development of packaged ultra-wideband bandpass filters," iEEE TransMicrowave Theory Tech,

[5]. vo1.58, no.l, pp.220-228, 2010

[6].

K. Li, D. Kurita, and 1. Matsui, "An ultrawidebandbandpass filter using broadside-coupled microstrip-coplanar waveguide structure," IEEE In/. MicrowaveSymposium, California, 2005

[7]. H. Hu, X. Huang, and C. Cheng, "Ultra-widebandbandpass filter using CPW-to-microstrip couplingstructure," Electronics Letters, vo1.42, no.10, pp., 2006

[8]. N. Thomson, and 1. Hong, "Compact ultra-widebandmicrostrip/coplanar waveguide bandpass filter," IEEEMicrow.

[9]. Abbosh, "Planar bandpass filters for ultra widebandapplications," IEEE Trans. Microwave Theory Tech.,vol. 55, no. 10, pp. 2262-2269, 2007Wireless Compon.Lett., vol. 17, no.3, pp.184-186, 2007..

[10]. Abbosh, and M. Bialkowski, "Design of compactdirectional couplers for UWB applications," iEEE Trans.Microwave Theory Tech., vol. 55, no.2, pp. 189-

194,2007.[11]. Abbosh, M. Bialkowski, and D. Thiel, "Ultra wideband

bandpass filter using microstrip-slot couplers combinedwith dumbbell slots and H-shaped stubs," Asia-pacificMicrowave Conference, Singapore, 2009.

[12]. W. F. Richards, Y. T. Lo, and D. D. Harrison, “Animproved theory of microstrip antennaswith applications,”IEEE Trans. Antennas and Propagation, vol. AP-29.

[13]. W. F. Richards, Y. T. Lo, and D. D. Harrison, “Animproved theory of microstrip antennaswith applications,”IEEE Trans. Antennas and Propagation, vol. AP-29.

[14]. M. Zweki, R. A. Abd – Alhameed, M. A. Mangoud, P. S.Excell, and J. A. Vaul, “ Broadband Analysis of Finite

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