How To Design A Bandpass Filter At.45 Ghz On Single Layer On A Board

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1 International Journal of Engineering Research and Developent e-issn: X, p-issn: X, Volue 5, Issue (February 03), PP Design and Perforance Analysis of.45 GHz Microwave Bandpass Filter with Reduced Haronics Ibrahi Azad, Md.Aran Hossen Bhuiyan, S. M. ahea Mahbub 3, Dept. Of Coputer Science and Telecounication Engineering Noakhali Science and Technology University, Noakhali-384, Bangladesh. 3 Dept. Of Electronic and Telecounication Engineering Pabna Science and Technology University, Pabna-6600, Bangladesh. Abstract:- Many technologies require installation of different filters with advanced features. Microwave bandpass filter is one of those filters that can be used for wireless LAN and Bluetooth.This paper describes how to design a interdigital icrowave bandpass filter for.45ghz. So, this work focuses on the design of parallel coupled line bandpass filter, two sets of interdigital band-pass filter at.45 GHz on singlelayer structures, copare aong these filters, proposed one suitable for users. Priarily coupled line filter, then asyetrical and syetrical interdigital band pass filter has been designed for single layer structure. To design these filters and to study siulation results, highly efficient, powerful application software Advanced Design Syste and Sonnet EM responses were used frequency transission coefficient Forward S, Forward reflection coefficient S were represented and coparative studies aong designed filters were perfored. Siulated results are very close to the desired response. The results showed that each filter works well at operating frequency. Asyetric filters have excellent return loss at centre frequency, very sharp roll off factor. In contrast, syetrical interdigital band-pass filters have narrow bandwidth and iniized ripple. Keywords:-Bandpass Filter, Chebyshev Filter, Interdigital, Coupled-line, SAI, and SSI I. INTRODUCTION A icrowave filter is a two-port network which provides transission at frequencies within the pass band of the filter and attenuation in the stop band of the filter for controlling the frequency response at a certain point in a icrowave syste. Generally speaking, a filter is any passive or active network with a predeterined frequency response in ters of aplitude and phase. The icrowave filter is used to pass energy at a specified resonant frequency at icrowave range. Filters play iportant roles in uch RF/icrowave applications. Now counication industry needs ore stringent requireents higher perforance, saller size, lighter weight, and lower cost. There are any recent developents in novel aterials and fabrication technologies, such as high-teperature superconductors (HTS), low-teperature cofired ceraics (LTCC), onolithic icrowave integrated circuits (MMIC), icroelectroechanic syste (MEMS), and icroachining technology. To fabricate ore efficient device using these novel aterials, ore functional filters are needed which can be used in wireless LAN and Bluetooth application. In recent electronic counication systes, like Wireless Local Area Network (LAN) and Bluetooth technology, high perforance and sall size bandpass filters are essentially required to enhance the syste perforance and to reduce the fabrication cost. Existing Parallel coupled icrostrip filters have been widely used in the RF front end of icrowave and wireless counication systes for decades. But their large size is incopatible with the systes where size is an iportant consideration. The length of parallel coupled filter is too long and it further increases with the order of filter. To solve this, the copact filter structures are required in deand for space-liited operations. Interdigital filter is one of the available copact configurations. There are any advantages using this structure. This paper focuses on the perforances of Coupled line icrostrip Bandpass filter, asyetrical and syetrical interdigital filter configuration on single layer. II. RELATED WORKS The basic concept of filters was proposed in 95 independently by Capbell and Wagner. Their results were obtained fro earlier work on loaded transission lines and classical theory of vibrating systes. Afterwards, two different filter theories were developed, known as iage paraeter theory and insertion loss theory [], []. The iage paraeter ethod was developed in the 90s by Capbell, obel, and soe others. This ethod involves specification of the passband and stopband characteristics for a cascade of -port networks. 57

2 Design and Perforance Analysis of.45 GHz Microwave The iage viewpoint, used in this ethod is siilar to the wave viewpoint used in the analysis of transission lines. Hence, this ethod provides a link between practical filters and infinite periodic structures [3]. Siple filters can be designed without requiring a coputer. However, soeties ipractical coponent values can be obtained using iage paraeter ethod [4]. This approxiate technique was the only practical filter design ethod until coputers becoe widespread. The insertion loss theory, also known as odern filter theory, is far ore coplex but accurate design technique. It owns its origin to the work of Cauer and Darlington who put forward a theory that involves a set of probles relating to odern network synthesis [5]. This design ethod consists of two basic steps: deterination of a transfer function that approxiates required filter specification and synthesis of electrical circuit using frequency response estiated by the previous transfer function. Although this ethod was very efficient, it had becoe widely used only since high speed coputers, used to ake all necessary coplex calculations, becae widely available. Nowadays, lowpass prototype network with angular cutoff frequency of rad/s terinated by in -Ω ipedances is norally used as a starting point in the design of icrowave filters. The final design of lupedeleent lowpass, bandpass, bandstop and highpass filters can be obtained fro lowpass prototype using frequency and ipedance transforation. Modern filter theory is expanded fro luped eleent (LC) resonators to distributed resonators, such as waveguide, coaxial and icro-strip/strip-line. In the design of any distributed resonator filters values of eleents of lowpass prototype network are used to deterine iportant transission characteristic of filters using forula derived for each type of filters [6]. In wireless counications bandpass filters are the ost widely used filter. For the design of icrostrip bandpass filters, several various techniques exist and ost of proposed novel filters with advanced characteristics are based on these several structures [7]. Interdigital filters consist of parallel coupled quarter-wavelength lines which are short-circuited at one end and open-circuited at another end [8]. Interdigital filters have the first spurious haronic at 3f 0. Coupling between interdigital lines is stronger than between coblines and gap between resonators can be larger, aking interdigital filters sipler to fabricate for high frequency and wide bandwidth applications, when diensions of filters are quite sall [9]. Accurate design of interdigital filters in icro-strip also involves optiization techniques, for exaple aggressive space apping optiization [0] or optiization that uses an accurate coputer aided design ethod which is based on the identification of direct and parasitic coupling of each resonator []. Due to the developent of wireless counications and the appearance of new systes there is high deand in sall size, low cost filters with high perforance. Therefore, iniaturization of bandpass filters with iproveent of their characteristics is a big challenge in odern filters design. This is achieved by iproveent of conventional concepts and approaches, as well as by introduction of new topologies and designs like interdigital filter. III. PARALLEL COUPLED-LINE BANDPASS FILTERS Fig. 3. illustrates a general structure of parallel coupled-line icrostrip bandpass filter that uses half-wavelength line resonators. They are positioned so that adjacent resonators are parallel to each other along half of their length. This parallel arrangeent gives relatively large coupling for a given spacing between resonators, and thus, this filter structure is particularly convenient for constructing filters having a wider bandwidth as copared to the other structures. Fig. 3.: General structure of parallel coupled-line icrostrip bandpass filter The design equations for this type of filter are given by [5] J 0 FWB g g. ()

3 Design and Perforance Analysis of.45 GHz Microwave J j, j FWB j ton.. () gg 0 j j J nn, FWB g g. (3) 0 n n Where, n is a nuber of filter order, and g 0, g,... g n are the eleent of a ladder-type lowpass prototype with a noralized cutoff Ω c =, and FBW is the fractional bandwidth of bandpass filter. J j,j+ are the characteristic adittances of J-inverters and 0 is the characteristic adittance of the terinating lines. This is because of the both types of filter can have the sae lowpass network representation. However, the ipleentation will be different. To realize the J-inverters obtained above, the even- and odd-ode characteristic ipedances of the coupled icrostrip line resonators are deterined by J j, j J j, j ( 0 e) j, j j 0ton J j, j J j, j ( 0 o) j, j j 0ton (4) (5) The use of the design equations and the ipleentation of icrostrip filter of this type will be illustrated after few sections. IV. INTERDIGITAL BAND PASS FILTER The Interdigital configuration is the ost copact filter where the resonators are placed side by side with one end short circuited and other end open circuited alternatively as shown in Fig.4. []. The filter configuration shown, consists of an array of n TEM- ode or quasi-tem- ode transission line resonators, each of which has an electrical length 90º at center frequency, f 0. In general, the physical diensions of the line eleents or the resonators can be the sae or different depending on the designs. Coupling is achieved by the way of the fields fringing between adjacent resonators separated by spacing S i,i+ for i =.. n-. The filter input and output used tapped lines, each with a characteristic adittance, t which ay set to be equal to the source or load characteristic adittance 0. An electrical length is θ t, easured away fro the short circuited end of the input or output resonator, indicates the tapping position, where = n denotes the single icrostrip characteristic ipedance of the input or output resonator. Interdigital band pass filters shown in Fig 4. have several features such as [] Very copact structures. The tolerances required in anufacture are relatively relaxed because of the relatively large spacing between resonator eleents. The second pass band is centered at three ties the center frequency of the first pass band. Besides that, there are no possibility spurious responses in between. Filter can be fabricated in structural fors, which are self-supporting so that dielectric aterial need not be used. Thus, electric loss can be eliinated. Strength of the stop band and rates of cutoff can be enhanced by ultiple order poles of attenuation at dc and even ultiples of the center frequency of the first pass band. 59

4 Design and Perforance Analysis of.45 GHz Microwave Fig. 4.: Interdigital band pass filter structure W 0 = width of characteristic ipedance W = width of resonator K = coupling efficiency S = space between resonator L= length of resonator This type of icrostrip band pass filter is copact, but requires use of grounding icrostrip resonator, which is accoplished with via holes. However, because the resonators are quarter-wavelength long using the grounding, the second pass band filter is centered at about three ties the center frequency of the desired first pass band, and there are no possibilities of any spurious response in between. A. INTERDIGITAL BAND PASS FILTER DESIGN Original theory and design procedure for interdigital band pass filters with coupled-line input or output are described here. Explicit design equations for the type of band pass filter with tapped line are explained in this section []. The electrical length can be obtained fro FBW.(6) Where, FBW is the fractional bandwidth and g i represents the eleent values of a ladder type of low pass prototype filter with noralized cutoff frequency at Ω c =. The adittance is,. (7) tan Inverter adittance of each resonator is expressed by Jii, for i= to n- (8) gg i i sin i, i i, i J for i= to n- (9) Self Capacitance, C i (i = to n) per unit length for the each line eleents can be obtained fro, C v n, n Cn.(0) v i, i i, i Ci fori to n v Mutual Capacitance, C i,i+ (i = to n - ) per unit length for the each line eleents can be obtained fro C ii, ii, for i= to n- () v C t is the capacitance to be loaded to the input and output resonators in order to copensate for resonant frequency shift due to the effect of the tapped input and output. It can be obtained fro 3 costsin t Ct () cos sin t 0t 0 t Where, t, and t sin 60 sin g g FBW (3) It ay also be desirable to use the even and odd ode ipedances for filter designs. The self and utual capacitances per unit length of a pair of parallel coupled lines denoted by a and b ay be related to the line characteristic adittances and ipedances by:

5 Design and Perforance Analysis of.45 GHz Microwave a oe vc a a v( C C ) oo a ab b b oe vcb oo v( Ca Cab) a Ca oe a Cb Cab vf oe vf b Cb b C oo a Cab oe vf vf F C C C ( C C ).... (4) a b ab a b In order to obtain the desired even and odd ode ipedances, the coupled lines in association with adjacent coupled resonators will generally have different line widths, resulting in pairs of syetric coupled lines. The two odes, which are also tered c and π odes, correspond to the even and odd odes in the syetric case have different characteristic ipedances. This ay cause soe difficulty for filter design. To overcoe it, an approxiate design approach is used. The designs equations are: oo,,, oo, oei, i / oei, i i. i i, i oen, n ooi, i / n, n i, i oei, i, oon, n n, n, for i= to n- for i= to n- (5) Where, and oei, i are the even and odd ode ipedances of coupled lines associated with ooi, i resonator i and i +. For a asyetrical coupled lines filter design, each of the even and odd ode ipedances ay be seen as an average of the two c ode ipedances for adjacent coupled lines. Siilarly, each of the odd ode ipedances ay be seen as an average of the two associated odes ipedances. The noralized coupling coefficient of a pair of resonators is given by f f Knn,.. (6) f g g Where, f f f and r=. c 0 / 0 g n, the center frequency, are the low pass prototype eleent values noralized to The single loaded Q for the filter is given by Q L f g f g 0 0 n f f f f The position of the input and output line point s l can be calculated fro. (7) Q L 0 / 0 4sin / L. (8) B. ASMMETRICAL INTERDIGITAL BAND PASS FILTER Asyetrical interdigital band pass filter is interdigital band pass filter with asyetrical coupled lines. This eans that the resonator will not have sae line widths []. Fig. 4. shows an exaple of asyetrical interdigital band pass filter. 6

6 Design and Perforance Analysis of.45 GHz Microwave Fig. 4.: Asyetrical interdigital band pass filter C. SMMETRICAL INTERDIGITAL BAND PASS FILTER In syetrical interdigital band pass filter, all the resonators will have the sae line width []. There are two advantages of this configuration. Firstly, the ore design equations and data on syetric coupled lines are available for the filter design. Secondly, the unloaded quality factor of each resonator will be uch the sae. However, a difficulty arises because it is generally not possible to realize arbitrary even and odd ode ipedances with a fixed line width. Therefore, instead of atching to the desired and 0 ei, i, the spacing S 0 oi, i i,i+ are adjusted for atching to K ii, 0 ei, i 0 oi, i 0 ei, i 0 oi, i.. (9) Fig. 4.3: Syetrical interdigital band pass filter V. DESIGN & SIMULATION In general there are two types of filter, one is coposed of luped eleents and another is of distributed eleents. But, at high frequency (e.g. Microwave frequency) the distributed effect will be doinant, and this is the cause of the degradation of perforance of luped eleent filter. Due to this reason, ost of the icrowave bandpass filters are based on distributed eleents (e. g. waveguides, icrostrip lines, coplanar waveguide lines).the easy integration technique and low cost ake the the ain candidates for icrowave filter designs. To design an efficient filter, use of filter synthesizer technique is very iportant. There are two ain filter synthesizer techniques: paraeter ethod and insertion loss ethod [3]. In this work, insertion loss ethod is used because it gives coplete specification of physically realizable frequency characteristics over the entire pass and the stop bands fro which the icrowave filters are synthesized or designed preferable. A. INSERTION LOSS METHOD Basic design icrowave filters are ade fro a prototype low pass design. In this ethod, a physically realizable network is synthesized that will give the desired insertion loss versus frequency characteristic. This ethod consists of the steps below: Design a prototype low pass filter with the desired pass band characteristic. Transforation of this prototype network to the required band pass filter with the specified centre and band edge frequencies. Realization of the network in the icrowave for by using sections of icrowave transission lines, whose reactance corresponds to those of distributed circuit eleents. B. CHEBSHAPE PROTOTPE FILTER For Chebyshape lowpass filter with an insertion loss L Ar =0.dB at the cutoff Ω c =, the eleent values coputed by (.50).The values for n=3 are given below 6

7 Design and Perforance Analysis of.45 GHz Microwave Table : Eleent values for Chebyshape lowpass prototype filters (n=3,ω c =, L Ar =0.dB) g 0 g g g 3 g C. SIMULATOR USED In this work, Advanced Design Studio 009(ADS) and Sonnet Lite.53 has been used. They could be integrated within theselves and provide a friendly interface for the user. Soe features of the are discussed below. D. DESIGN SPECIFICATION For the first step of designing bandpass filter principle, the nuber of sections fro the specified attenuation characteristics has to deterine. Table () shows the chosen of design specification to use for design bandpass filter response. Table : The Design Specification Filter type Chebyshev Nuber of order,n 3 Center frequency,f 0.45GHz Fractional Bandwidth, f 0. or.4% The board paraeters are as follows: Nae = Rogers TMM0 Dielectric constant = 9.6 Substrates thickness =.7 Metal thickness = ) Parallel Coupled Line Filter Design: Fro Table (), we got the eleent values for a 3 rd order Chebyshape Bandpass filter. Using those values, design specification and equation () to (5), we get the following table: Table 3: The values of even and odd characteristic ipedance for 3rd order coupled line filter n g n 0 J n 0e J n 0o J n Using LineClac of Advanced Design Syste [4], the values for the resonator spacing s, the length and the width of the traces can be obtained. We get the following table: Table 4: The values of Width, Length and Sapcing for 3rd order coupled line filter n Width,w() Spacing,s() Length,l() (90 ) The calculated values are then ipleented using Advanced Design Studio 009. MCFIL blocks are used as coupled lines. The corresponding tuned values are then put on their respective fields of the blocks. Input and output are terinated with 50. line as MLIN blocks. The circuit scheatic view is shown in Fig

8 Design and Perforance Analysis of.45 GHz Microwave Fig. 5.: Scheatic View of 3rd order Coupled Line Filter ) Single Layer Interdigital Filter Design.. Single Layer Asyetrical Interdigital Filters (SAI): Using the values of table for a 3 rd order Chebyshape filter, design specification and equation (6) to (5), we get the following table of even and odd ode ipedances Table 5: The values of Even and Odd ode characteristics ipedance n 0ei,i+ 0oi,i Filter diension of the SAI filter is calculated fro graph of even and odd ode characteristic ipedances for coupled icrostrip lines [4].Fro this graph, we get the width of two coupled lines ( W) and spacing between the (s) are shown in Table (6). W W Table 6: SAI filter design paraeter W L. 76 S S e o re re W t L t. 3 And the tuned paraeter values are Table 7: Tuned paraeter values for SAI filter design W W L S W e o 3 S 3 re W re t Those values are than ipleented using ADS-009. Here we use the following T-line Microstrip, MACLIN3 used as a coupled section MLSC used as short circuited end MLEF used as open circuited end MTEE-ADS used as tapped line connector MLIN used as tapped line Circuit scheatic view is shown in Fig 5.. L t 64

9 Design and Perforance Analysis of.45 GHz Microwave Fig.5.: Scheatic view of SAI Filter circuit.. Single Layer Syetrical Interdigital Filters (SSI): Using the values of table for a 3 rd order Chebyshape filter, design specification and equation (9), we get the following Table of coupling coefficient of SSI filter. Table 8: the values of Coupling Coefficient i K i,i+ 0.0 Taking w/h=0.7, we can calculate the Width. Fro coupling coefficient and Q of interdigital filter (J. S. Wong [8] ), we get spacing between the resonators as suarized below. Fro the sae graph, we get the Physical length easured fro the input or output resonator to tap point. The values are shown in Table 3.9. Table 9: SSI filter design paraeter W() L() S () S 3 () W t () L t () The values are than tuned, to get the desired frequency response. Table 0: Tuned paraeter values for SSI filter design W() L() S () S 3 () W t () L t () Those values are than ipleented using ADS-009. Here we use the following Tline- Microstrip, MACLIN3 used as a coupled section MLSC used as short circuited end MLEF used as open circuited end MTEE-ADS used as tapped line connector MLIN used as tapped line Circuit scheatic view is is shown in Fig 5.3. Fig. 5.3: Scheatic view of SSI Filter circuit VI. RESULT & DISSCUSION Once the designing process has been copleted, the this work oves onto the next step, where the siulations are being done to see the result of this project and to analyze whether the project had attained the objective, target and concept. The siulation process covers the entire coupled line filter, single layer asyetric interdigital and single layer syetric interdigital filter. A. SIMULATION RESULT OF PARALLEL COUPLED LINE BANDPASS FILTER Analysis of the parallel coupled line Bandpass filter has been ade fro the siulation results. The perforance of the Parallel Coupled line Bandpass filter is suarized in Table (). Table : Coupled line filter siulation responses Filter Parallel Coupled line Bandpass filter n S at.45 GHz (db) 65 S at.45ghz (db) Bandwidth at 3dB (GHz)

10 Design and Perforance Analysis of.45 GHz Microwave Fig. 6.: Return Loss and Insertion Loss for Parallel Coupled line filter In the Fig 6., blue and red colored line shows the S() and S() response of a icrostrip coupled line bandpass filter. At -axis, gain in db has plotted and in X-axis, frequency in GHz has been plotted. Here, we have seen that the insertion loss is higher, but the bandwidth at -3dB is at 0.36GHz.It is a little bit higher than the desired bandwidth (0.3GHz) of 0.06GHz. B. SIMULATION RESULT OF SAI & SSI FILTERS Analysis has been ade fro the siulation results. Table () suarized the perforances of the SAI and SSI filters. And Fig. 6. and Fig. 6.3 depicts the graphs of the perforances. Fig. 6.: Return Loss and Insertion Loss for SAI filter Fig. 6.3: Return Loss and Insertion Loss for SSI filter Table : SAI & SSI filter siulation responses Filter n S at.45ghz (db) S at.45ghz (db) Bandwidth at 3dB (GHz) SAI filter SSI filter Here, fro Fig 6., 6. and 6.3, it is evident that the insertion loss in SAI and SSI filter is lower than the icrostrip coupled line bandpass filter, and SSI has lower than the SAI filter of -0.0 db. The bandwidth at - 3dB is at 0.4GHz for SAI filter and 0.5GHz for SSI filter. Here SAI has a bandwidth higher than the desired bandwidth (0.3GHz) of 0.GHz and SSI has a lower bandwidth than desired bandwidth of 0.05GHz. SSI has a sharper slope than SAI filter, but the ripple in SSI is larger copared to SAI filters. Fig. 6.4: S response of Coupled line BPF Another proble is that, in case of coupled line BPF, the passband ripple in first haronic. The passband ripple is at 4.3GHz to 5.3GHz. Fig 6.4 shows passband ripples of coupled line BPF fro GHz to 0 66

11 Design and Perforance Analysis of.45 GHz Microwave GHz range. For SAI and SSI, insertion loss and return loss are good enough copared to coupled line filter. So the haronics that produced in the coupled line filter are significantly reduced by using interdigital filter. VII. CONCLUSION The goal of this work is to design a icrostrip line icrowave single layer interdigital Chebyshev band pass filter of centre frequency.45ghz and fractional bandwidth 0. has been nearly achieved using ADS 009 and sonnet EM software. In this work, 3 rd order Chebyshev icrostrip line filter of coupled line and interdigital filter structures have been copared using Rogers TMM0 aterial as substrate. The optiu structure of the filter has found to be 3 rd order interdigital structure. The designed filters were siulated for its input return loss S and insertion loss S responses. However, the siulated results were close to the desired specification but not exactly atched with the desired specification. One ain reason for this scenario is the software liitations. This could be due to the personal coputer inability to handle large eory siulation files. There were soe software liitations to coplete the siulation in a satisfactory tie frae with accurate results. Although the designed filter did not eet the specification perfectly therefore there are roos for further iproveent. REFERENCES []. Grieg, D. D.; Engelann, H. F. (Dec. 95). "Microstrip-A New Transission Technique for the Kliloegacycle Range". Proceedings of the IRE 40 (): []. Matthaei, George L.; oung, Leo; Jones, E. M. T. (980). Microwave Filters, Ipedance-Matching Networks, and Coupling Structures. Norwood, MA: Artech House. ISBN [3]. Bansal, R., Handbook of Electronic Electroagnetics, CRC Press, 004. [4]. MR. NIKORN SUTTHISANGIAM, A DESIGN OF THE NOVEL COUPLED-LINE BANDPASS FILTER USING DEFECTEDGROUND STRUCTURE WITH WIDE STOPBAND PERFORMANCE FOR UWB APPLICATIONS. [5]. Jia-Sheng Hong and M. J. Lancaster. Microstrip Filters for RF/Microwave Applications. New ork: John Wiley & Sons, Inc., 00. [6]. Wheeler, H., A., Transission-line properties of a strip on a dielectric sheet on a plane, IEEE Tran. Microwave theory tech., vol. MTT-5, pp , Aug [7]. I.A. Glover, S. R. Pennock and P. R. Shepherd, Microwave devices, circuits and subsystes for counications engineering, University of Bath, UK. [8]. Arne Brejning Dalby, Interdigital Microstrip Circuit Paraeters Using Epirical Forulas and Siplified Model, IEEE Transaction on Microwave Theory and Techniques, Vol. MTT-7, No.8, August 979, Page(s): [9]. Sina Ahktazad, Thoas R Rowbotha, Peter B Johns, The designed of coupled Microstrip Lines, IEEE Transaction on Microwave Theory and Techniques, Vol. MTT-3, No 6, June 975, Page(s): [0]. [0] G.L Mattaei, Interdigital Band Pass Filters, IRE Transactions on Microwave Theory and Techniques, Noveber 96, Page(s): []. Jia-Shen G. Hong, M. J. Lancaster, Microstrip Filters for RF/ Microwave Applications John Wiley & Sons, Inc, 00. []. G.L Matthaei, L. oung, and E.M.T Jones, Microwave Filters, Ipedance Matching Networks and Related Structures, New ork: McGraw- Hill, 964. [3]. C. W. Tang Haronic-suppression LTCC filters with the Step-Ipedance Quarter-Wavelength Open Stub IEEE Transaction on Microwave Theory and Techniques, vol. 5, no. pp , Feb-004. [4]. ADS anual. [5]. Rashid Ahad Bhatti, Jahangir Khan Kayani, Design and Analysis of a Parallel Coupled Microstrip Band Pass Filter, nd International Bhurban Conference on Applied Science and Technology, June 003, Page(s):