Optimization of Microstrip Ring UWB filter using ANN- PSO

Transcription

1 Internatonal Journal of Scentfc and Research Publcatons, Volume 3, Issue 8, August Optmzaton of Mcrostrp Rng UWB flter usng ANN- PSO Mandpa Nath AIACTR, elh mandpa.deoghar@gmal.com Abstract- Ultra-Wde Band (UWB) s promsng technology for many wreless applcatons due to ts large bandwdth, good rato of transmsson data and low power cost. The man goal of ths work s to desgn an UWB flter sutable for that purpose n the frequency band GHz. In order to acheve that goal, one UWB flter confguraton s nvestgated, desgned and characterzed. Theoretcal analyss s done to compute the flter parameters, such as the return loss, nserton loss and attenuaton characterstc over the full frequency band. The sze of ths flter s also studed because of ts mportant aspect on the frequency behavor. Index Terms- UWB, flter, frequency response, nserton loss, return loss. I. INTROUCTION UWB technology s promsng and attractve for local area networks, poston locaton, trackng and radar systems. The technology has the characterstcs of low cost, hgh data transmsson rate and very low power consumpton. Many UWB devces and crcuts are proposed and nvestgated wdely [1-5]. It s mportant to reduce ther sze and weght n order to ntegrate them wth other components as a compact system. Compact and broadband bandpass flter (BPF) s a key passve component and hghly demanded n a UWB system. A planar BPF based on a mcrostrp structure can provde the advantages of easy desgn, low cost, compact sze. A mcrostrp BPF wdely used n a varety of RF/mcrowave and mllmeterwave systems and compact UWB mcrostrp BPF can be used n a UWB communcaton system. UWB flters should have a fractonal bandwdth of more than 70.0% and t s very dffcult to acheve such a wde passband wth a tradtonal parallel-coupled transmsson lne structures. A practcal requrement exsts for UWB BPF wth a strong couplng structure that can be easly realzed and fabrcated. A rng shaped mcrostrp resonator crcut wth quarter wavelength short crcuted stub s analyzed usng EM theory and resultng dmensons are utlzed to desgn a sngle secton of an UWB flter n the desred frequency range. Consequently fve such crcular rng resonators are desgned and successve stages are coupled usng nterconnected lnes. Here proper tunng stub s used to mplement a strong couplng between the nput/output port and the resonator. Thus an UWB mcrostrp BPF wth low loss s desgned and further optmzed for best achevable frequency response. After the release of UWB bandpass flters wth a passband of the same frequency range (3.1 GHz GHz, a fractonal bandwdth of 110%) were challenges for conventonal flter desgns. Before md 2003 the bandwdth of the passband for a bandpass flters was extended from 40% to 70% [2]. These flters are named as broad bandpass flters.

2 Internatonal Journal of Scentfc and Research Publcatons, Volume 3, Issue 8, August They were not coverng the whole UWB frequency range. In [3] a bandpass flter coverng the whole UWB frequency range wth a fractonal bandwdth of 110% was realzed by fabrcaton sgnal lnes on a lossy composte substrate. A successful transmsson of the UWB pulse sgnal was demonstrated usng the proposed bandpass flter. Ths s one of the early reported flters that possess an ultra-wde passband. However, t has a hgh nserton loss n the passband due to the lossy substrate. Not much research work was reported n 2003 and In 2004, a rng resonator wth a stub was proposed whch shows a bandwdth of 86.6% [4]. A bandpass flter coverng the whole UWB frequency band was a challenge for mcrowave flter desgners and researchers n that perod of tme. There are manly four types of structures that are able to realze an ultra-wde passband. II. UWB FILTER CONFIGURATION UWB was orgnally developed for mltary communcatons and radar. In the feld of UWB technology dfferent methods and structures [2-6] has pushed development of new UWB flters. Lumped-element flter desgn s generally unpopular due to the dffculty of ts use at mcrowave frequences along wth the lmtatons of lumped element values. Hence conventonal mcrostrp flters are often used. The new proposed flter desgn s based on rng resonators havng quarter wavelength short-crcuted stub and realzed n mcrostrp confguraton. The paper focuses on systematc desgn and realzaton of an UWB n prnted crcut confguraton. The flter desgn s done wth rng shaped resonator and realzed n mcrostrp confguraton. The dameter of the rng s desgned accordng to the frequency requrements and stub matchng s used to tune the flter to the desred band of operaton. Stub wdth and rng dameter, nter rng separaton s taken as desgn parameter to optmze ts frequency response performance. It s desgned as per FCC recommended band from GHz. Fgure 1. Rng resonator confguraton as flter III. UWB FILTER ESIGN PROCESS The UWB s desgned usng ANN model of rng resonator and PSO optmzaton technques. Here Artfcal Neural Network (ANN) and Partcle Swarm Optmzaton (PSO) algorthm s used for the synthess of the UWB flter usng rng resonator. The PSO algorthm s used to optmze the flter geometry n order to obtan a wdeband performance of the mcrostrp flter. The confguraton of the rng structure actng as resonator s shown n Fgure 1. whose resonance frequency s controlled by a tunng stub. The stub dmensons are fed as nput to a traned ANN to model the reflectance and transmttance of the sngle rng resonator. In ths work mcro strp substrate s used n order to realze the flter usng rng structure (substrate thckness 10 ml, delectrc constant 9.8). Analyss usng method of

3 Internatonal Journal of Scentfc and Research Publcatons, Volume 3, Issue 8, August moment and further smulaton usng commercal software tools s performed to nvestgate and verfy the performance of the rng flter. The EM smulaton results are n good agreement wth those obtaned usng the ANN algorthm. The objectve of ths work s to use the ANN model coupled wth the partcle swarm optmzaton (PSO) algorthm to synthesze the UWB flter usng multple rngs and optmze ts performance as UWB flter. In ths desgn, successve stages of coupled crcular rng structure wth proper tunng stub s used to mplement strong couplng between the nput/output port and the resonator. Fgure 2. Measured results of reflectance and transmttance of a sngle rng mcrostrp flter Fgure 3. UWB flter confguraton usng rng structure The EM smulaton tools are used to optmze the frequency response performance of ths UWB flter. Smulated results predct performance of the flter as per FCC Standard. It s observed that the desgn dmensons are crtcal n decdng the flter responses. The rng dmenson and stub wdth are requred to be precse for the mcrostrp flter under concern as per optmzed results to meet the specfcaton.fnal pcb desgn s generated based on the optmzed desgn for the multple rng resonator structure wth connectng lnes. The flter hardware based on the optmzed desgn s fabrcated and measured to verfy the UWB performance over the FCC band. The flter under concern s desgned to provde an Inserton Loss 1 db and average roll off 30 db/decade. The measurement results are qute encouragng.

4 Internatonal Journal of Scentfc and Research Publcatons, Volume 3, Issue 8, August Fgure 4. Layout of the UWB rng Fgure 5. 3 model of UWB flter for smulaton The new proposed desgn of rng flter s assocated wth a quarter wavelength short-crcuted stub for frequency tunng. Fve sectons are combned and optmzed usng PSO for ts best achevable flter performance n the UWB frequency range from GHz. A systematc desgn and realzaton of an UWB flter n mcrostrp confguraton s done usng stub tuned rng shaped resonator havng sngle nput and sngle output. The dameter of the rng s desgned accordng to the resonatng frequency requrements and stub matchng s used to tune the flter to the desred band of operaton. Stub wdth, rng dameter, nter rng separaton s taken as desgn parameter for ANN model of each secton of the rng. Fve such sectons are modeled usng ANN to cover the whole UWB range and combned to form the ntegrated rng flter whose S parameters are computed usng theory and verfed by MOM smulaton tools (IE3). The reflectance and transmttance of the whole flter s optmzed usng PSO for FCC recommended band from GHz. III. THEORY OF RING RESONATOR The theoretcal nvestgaton and analyss s done to relate the geometry parameters of the rng wth ts S parameters. Method of moments analyss n the spectral doman n conjuncton wth the Mxed- Potental Integral Equaton (MPIE) approach s used by transformng the expanson and weghtng functons [7-8]. Usng the decomposton of Green s functons, the method of moment matrx entres can be reduced to a sum of two ntegrals. The frst one s expressed n the spatal feld and corresponds to the quas-statc contrbuton. It s analytcally evaluated wth the exponental terms n the functon to be ntegrated. The ntegrals expressed n the spectral feld and correspondng to the dynamc part have the advantage of beng calculated on a fnte range and ths s ndependent of the

5 Internatonal Journal of Scentfc and Research Publcatons, Volume 3, Issue 8, August choce of the bass and test functons. The ntegrals expressed n the spectral feld are performed by usng numercal ntegraton [9-12]. The formulaton begns wth the development of an ntegral expresson whch defnes the electrc feld resultng from an arbtrary current dstrbuton. Ths ntegral expresson employes a Green s functon whch relates the electrc feld at an arbtrary observaton pont to the current at an arbtrary source pont. The MOM apples orthogonal expansons to translate the ntegral equaton nto a system of crcut-lke smultaneous lnear equatons. Approprate bass functons are used to expand the current dstrbuton. Testng functons are used to nvoke the electrc feld boundary condtons. Matrx methods are then used to solve for the expanson coeffcents assocated wth the bass functons. The current dstrbuton soluton s then constructed from the expanson coeffcents. The MOM smulaton tools (IE3) are used to verfy the performance of ths flter n terms of S 11 and S 12 of ths optmzed wdeband rng flter. It s observed that the desgn dmensons are crtcal n decdng the flter responses. The rng dmenson and stub wdth are optmzed to meet the specfcaton and accordngly fnal PCB desgn s generated. The UWB flter s desgned to provde an nserton loss 1 db and average roll off of 30 db / decade. Smulated results predct performances of the flter as per FCC Standards are shown n Fgure 2. The flter based on the optmzed desgn s fabrcated and tested. The measurement results are qute encouragng. IV. ESIGN OF RING FILTER An exact analyss of the structure s very tedous. Hence a synthess procedure s followed whch nvolves a number of smplfyng approxmatons that permt straghtforward, easy to-use desgn calculatons [13-16]. However these approxmate desgn equatons are found to be suffcently accurate for most practcal applcatons. The flter desgn s based on rng structure wth quarter wavelength short-crcuted stubs [17-22]. Here fve short crcuted stubs are desgned for a dstrbuted mcrostrp rng band pass flter whose connectng lnes are non-redundant. In order to reduce the flter sze the length of the connectng lne are optmzed. The characterstc mpedances of these short-crcuted stubs and the characterstc mpedances of the connectng lnes are chosen at 3.1 GHz. The dmenson of the ndvdual rng and ts stub lne mpedance s computed usng MOM consderng fundamental resonance [23-30]. V. ANN MOEL OF RING FILTER A tranng set of 670 randomly dstrbuted ponts of the parameters n the range gven n table I. The backpropagaton tranng algorthm along wth the sgmod functon as the actvaton functon s used for the feedforward network of the ANN n order to tran t. Fve sectons of the rng resonators wth controllng stubs are used to develop the full UWB rng flter. A three layer ANN wth a hdden layer havng 16 neurons s used to successfully model the geometry parameters of the rng such as dameter of the rng, characterstc mpedance of the rng structure, nter rng separaton and stub dmensons of ndvdual rng to decde dfferent resonance frequences coverng the UWB band. The tranng and testng data set s generated from the results of the analyss of the rng structure usng method of moments. The accuracy of the traned network wth ths archtecture s gven n table II n terms of average error and standard devaton. Therefore, for a gven set of nput parameters, the geometry parameters of the rng can be accurately computed n the frequency range of nterest n neglgble tme usng the developed ANN.

6 Smulated S parameter(db) Internatonal Journal of Scentfc and Research Publcatons, Volume 3, Issue 8, August VI. EVELOPMENT OF UWB FILTER The ndvdual rng structure wth mcrostrp lne stub havng extended ground plane s desgned and smulated usng IE3 for verfcaton of the frequency response. The sngle rng flter structure s fabrcated and mpedance bandwdth s measured as shown n Fgure 2(consderng fundamental and harmonc frequences). The measured result shows a frequency bandwdth of 1.3 GHz (8.0 GHz - 9.3GHz) wth an nserton loss of 2.7 db (average). Fve such sectons coverng the whole UWB band s desgned and ntegrated to form the UWB flter as shown n Fgure 3 and 4. It s observed that the ntegrated fve secton rng flter can be used for FCC regulated UWB operatons where bandwdth enhancement of 150.0% or more s possble. Smulaton model of the rng flter s shown n fgure 5 and the frequency response of the fve secton rng flter s verfed usng MOM smulator for UWB operaton as shown n fgure 6. 0 Smulated flter response ( S parameter) of mcrostrp UWB structure S21 S Frequency n GHz. Fgure 6. Smulated reflecton & transmsson characterstcs of the UWB flter havng fve ntegrated rng n mcrostrp confguraton. VII. PSO FITNESS FUNCTION The reflectance and transmttance of the whole flter s optmzed usng PSO for FCC recommended UWB band from GHz. The reflectance and transmttance of the ntegrated rng flter havng fve sectons wth dfferent stub wdth and length are fed to PSO for bandwdth optmzaton of the same. A sutable ftness functon for PSO s used consderng maxmum bandwdth and mnmum return loss of the mcro strp rng flter and s shown below. Ftness = N 1 N T R 1 T =max S, S ) ( S=mn S, S ) ( 11 11

7 Internatonal Journal of Scentfc and Research Publcatons, Volume 3, Issue 8, August T = S 21 S21 S21 & S21 S21 mn( S, S21 ) otherwse 21 R = S 11 S11 S11 - S - S K S 11 otherwse Where the subscrpt ndcates dfferent n frequency ponts. N ndcates the total number of smulated frequency ponts. S 11 (n db), S 21 (n db) are the desgn requrements for S11 and S21 respectvely. The sgn ndcates that ths operaton s taken as soon as ths condton s satsfed at all frequences. K s set to 1 for all test cases n order to reach an equally weghted sum of reflecton coeffcent and transmsson coeffcent. The possble maxmum sum of all R s - S 11 *N. It can be acheved f all S11 are smaller than S 11. The PSO algorthm s converged wthn 50 teratons wth suffcent accuracy (Fgure 7.). The optmzed dmensons of the stubs controllng the resonance frequency of ndvdual rngs are used to fabrcate the UWB flter and the frequency response of the same s also verfed from MOM smulator. The optmzed dmensons of geometrcal parameters of the fve secton rng flter are tabulated n table III. The fabrcated rng flter s shown n Fgure 8. The MOM smulaton tools (IE3) are used to verfy the performance of ths flter n terms of S11 and S 21 of ths optmzed wdeband rng flter. It s observed that the desgn dmensons are crtcal n decdng the flter responses. The rng dmenson and stub wdth are optmzed to meet the specfcaton and accordngly fnal PCB desgn s generated. VIII. MEASUREMENT The fnal flter layout s generated and fabrcated usng CER-10 usng optmzed dmenson of the geometry parameters wth best possble fabrcaton precesson avalable. The fnal crcut after ntegraton and packagng undergone for testng. The fabrcated flter s measured for transmsson and reflecton performance wth the help of Network Analyzer (E8363B). The measured attenuaton and VSWR plot of the flter s shown n Fgure (9.a-b). Measurement results shows good flter characterstc over the whole UWB band. The measured nserton loss over the band s 3.0 db (average) and a 7.3 GHz flter passband from GHz. wth -10 db return loss, and VSWR band wdth of 6.5 GHz s obtaned. Measured results are compared wth that of the smulated performance as shown n table IV. These results have ndcated a very good agreement between smulaton and measurements. Ths nserton loss can be further reduced usng low loss substrate and SMA connectors. The fabrcaton process s requred to be precse to mprove ths loss fgure and to realze the full bandwdth for UWB operatons. The mountng of the flters s requred be rgd and full flatness of the substrate should be ensured to avod surface wave loss. The other performance s seen to be satsfactory.

8 Internatonal Journal of Scentfc and Research Publcatons, Volume 3, Issue 8, August Fgure 7. PSO convergence plot Fgure 8. Fabrcated rng flter n mcrostrp confguraton. (a) Reflecton measurement

9 Internatonal Journal of Scentfc and Research Publcatons, Volume 3, Issue 8, August (b) Transmsson measurement Fgure 9. Measured results of reflecton and transmsson characterstcs of the UWB rng flter (a) Reflecton measurement (b) Transmsson measurement. Table I Selecton of Range of Input Parameters of Rng flter for ANN model Rng Characte Inter stub stub damet rstc rng length wdth er mpedan separat ce of on) rng ohm Table II The accuracy of developed ANN model ANN Input/out put parameter Rng da (mm) Charact erstc mpedan ce of Inter rng separat on Stub length (mm) Stub wdth (mm) s rng () (mm) Tranng Average

10 Internatonal Journal of Scentfc and Research Publcatons, Volume 3, Issue 8, August error Testng Average error Table III Optmzed dmensons of the rng flter (ANN-PSO model) Rng Charact Inter rng stub stub dam erstc separato length wdth eter) mpeda n n nce of rng n ohm S1 8.5 S2 8.1 S3 8.0 S S5 7.8 S1 2.0 S S S S5 8.2 Table IV Comparson table of the smulated and measured performance of the UWB rng flter Flter Parameter Smulated Measured VSWR Bandwdth 5..8 GHz 5.88 GHz Inserton loss 4 db 3.0 db(avg.) CONCLUSIONS

11 Internatonal Journal of Scentfc and Research Publcatons, Volume 3, Issue 8, August In ths chapter an UWB mcrostrp BPF wth low nserton loss s desgned and optmzed for ts frequency response performance usng PSO. Each ndvdual rng resonator s assocated wth a quarter wavelength short-crcuted stub for frequency tunng. A systematc desgn and realzaton of an UWB flter n prnted crcut confguraton s done usng stub tuned rng shaped mcrostrp structure havng sngle nput and sngle output. The dameter of the rng s chosen accordng to the resonatng frequency requrements and stub matchng s used to tune the flter to the desred band of operaton. Stub wdth, rng dameter, nter rng separaton s taken as nput desgn parameter for the ANN model. Fve dfferent rng resonators are ntegrated to form UWB flter where the geometrcal parameters of the ndvdual rng resonators are obtaned from output of respectve ANN model. Fve sectons are combned and optmzed usng PSO where reflectance and transmttance of the ntegrated mcrostrp rng flter s optmzed for UWB frequency range from GHz. In ths process of optmzaton the physcal dmensons of ndvdual rngs are altered and the flter as a whole becomes capable of effcent transmsson for UWB band. Fnally the fnal flter layout s generated and fabrcated usng optmzed dmensons of the rng structure wth best possble fabrcaton precesson avalable. The S parameters of the fabrcated flter s measured to verfy the transmsson and reflecton performance of the same wth the help of VNA and compared wth that of the smulated performance as shown n table IV. These results have ndcated a very good agreement between smulaton and measurements. So t can be concluded that ANN-PSO technque s effcently utlzed for desgn and development of one UWB flter havng optmum frequency response. The nserton loss and measured bandwdth are near to that of the desred value and can be mproved further wth some precautons. REFERENCES 1. A. Sato, H. Harada, and A. Nshkata, evelopment of Band Pass Flter for Ultra Wdeband (UWB) Communcaton Systems, Internatonal Mcrowave Symposum, Phladelpha, Pennsylvana, USA, June H. Ishda and K. Arak, A esgn of tunable UWB Flters Internatonal Mcrowave Symposum, Fort Worth, Texas, USA, June L. Zhu, S. Sun, and W. Menzel "Ultra-wdeband (UWB) Bandpass Flters Usng Multple-Mode Resonator", IEEE Mcrowave and Wreless Components Letters, Vol. 15, No.11, November 2005, pp H. Wang and L. Zhu, "Ultra-wdeband Bandpass Flter Usng Back-to-back Mcrostrp-to-CPW Transton Structure", Electronc Letters, Vol. 41, No.24, November K. L,. Kurta, and T. Matsu, An Ultra- Wdeband Bandpass Flter Usng Broadsde-Coupled Mcrostrp-Coplanar Wavegude Structure, Internatonal Mcrowave Symposum, Long Beach, CA, USA, June C. Hsu, F. Hsu, and J. Kuo, Mcrostrp Bandpass Flters for Ultra-Wdeband (UWB) Wreless Communcatons, Internatonal Mcrowave Symposum, Long Beach, CA, USA, June C. Tang, C. Tseng, H. Lang, and S. You, evelopment of Ultra-wdeband LTCC Flter, IEEE Internatonal Conference on Ultra-Wdeband, Zurch, Swtzerland, September, S. Sun, and L. Zhu, "Capactve-Ended Interdgtal Coupled Lnes for UWB Bandpass Flters wth Improved Out-of- Band Performances", IEEE Mcrowave and Wreless Components Letters, Vol. 16, No.8, August 2006, pp

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13 Internatonal Journal of Scentfc and Research Publcatons, Volume 3, Issue 8, August Hong, J. S. and H. Shaman, A compact ulrtrawdeband (UWB) bandpass flter wth trans- msson zer7," EuMA, , Spt Hong, J. S. and M. J. Lancaster, Mcrostrp Flters for RF/Mcrowave Applcatons, Wley, New York, 2001.