A Scalar Interpolator for the Improvement of an ADC Output Linearity Nikos Petrellis

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1 ISS: ISO 900:008 Cerified Inernaional Journal of Engineering Science and Innovaive Technology IJESIT) olume, Iue, May 0 A Scalar Inerpolaor for he Improvemen of an ADC Oupu Lineariy io Perelli Abrac The archiecure of an inerpolaor ha can be ued for lineariy improvemen and daa compreion a he oupu of an Analog Digial Converer ADC) i preened in hi paper. The developed inerpolaor can correc ADC lineariy error, increae i dynamic reoluion or reconruc ignal from fewer ample in non-uniform diance. I oupu i available boh in compreed or uncompreed form. Muliple inerpolaor can be conneced in erie uing he uncompreed oupu for furher lineariy improvemen. A -age inerpolaor wih 9-bi inpu and -bi oupu ypical reoluion i implemened uing 7% of he Logic Elemen of a low co Alera Cyclone II EPC5F56C8 Field Programmable Gae Array FPGA) and i eed uing he ADC and he ouch pad preure enor of a commercial microconroller developmen board. A Signal o oie Raio SR) improvemen by more han 7dB %) wa meaured uing he microconroller ADC oupu. A.5 ime lower Mean Square Error MSE) wa achieved a he microconroller ouch pad enor oupu and a 6.5 ime lower MSE wa meaured when an image wih degraded reoluion wa proceed by he propoed inerpolaor. Index Term Inerpolaion, AnalogDigial Converion, Lineariy, Po Proceing, Compreion I. ITRODUCTIO The ampling frequency and he reoluion of an ADC have o be increaed in order o achieve lower error in he digiizaion proce of a ignal. The lineariy error of an ADC can dramaically change beween differen inpu ignal frequencie. Alhough a low frequencie an ADC behave according o i ypical pecificaion, i behavior may be poor when operaing a high inpu ignal frequencie. Cuomized calibraion mehod can be incorporaed in he ame chip wih he ADC, correcing he lineariy error of he ADC core. Inead of employing ADC wih ever increaing hroughpu and reoluion a well a cuomized calibraion mehod, a differen oluion can be adoped by employing generic po-proceing module ha can be ued for he correcion of he lineariy error of differen ADC module. The Differenial or Incremenal on-lineariy DLIL) error ha are correced by po-proceing module are aic and can be eimaed by applying DC level a he ADC inpu or more ofen uing echnique lie Hiogram [] or be fi curve []. The hiogram approach include he exciaion of an n-bi ADC wih a ramp ignal in order o ge he iniial n oupu. Then, he ramp ignal i hifed up and he procedure i repeaed by recording anoher e of n oupu. The Lea Square mehod i hen ued a he difference of he correponding oupu o eimae a number of parameer ha characerize he inpu non-lineariy []. Dynamic lineariy error are meaured by Signal o oie and Diorion Raio SDR), Spuriou Free Dynamic Range SFDR) and Toal Harmonic Diorion THD) and hee parameer depend on he operaing frequency of he ADC. A Buil-in Self Te BIST) module i ofen embedded wih he ADC under e providing a real ime ADC characerizaion concerning i dynamic feaure []. I i obviou in hi cae ha he SR of he BIST module hould be much higher han he SR of he ADC under e. DL lineariy error can be correced by adding appropriae igned error correcing facor ha are ored in large loo up able. Thee facor require calibraion baed on he meauremen of he ILDL [5]. An accurae aw ooh ignal generaor i ued in [6] o eimae he IL and exrac error compenaion coefficien of pipeline ADC. A digial correcion performed in a ime inerleaved ADC archiecure i examined in [7]. Each ub channel ADC i implemened a a dynamically configured pair of ADC wih lower reoluion. The problem of error ource removal i formed a a marix problem in [7] and i implemened in hardware. The po proceing module preened in hi paper for he enhancemen of he lineariy of an ADC oupu i baed 59

2 ISS: ISO 900:008 Cerified Inernaional Journal of Engineering Science and Innovaive Technology IJESIT) olume, Iue, May 0 on Inerpolaion. The converion of he ADC oupu o an analog ignal hrough an ideal Digial o Analog Converer DAC) i acually a zero-order inerpolaion. Fir order inerpolaion i more efficien auming ha wo ucceive ADC value are conneced linearly. Alhough fir-order i more accurae han zero-order inerpolaion, i canno model he curvaure and lope of he original ADC inpu ignal. Cubic pline inerpolaion [8] can give more accurae approximaion when a curve hould fi o more han wo poin bu ill i i no guaraneed ha he reuling cubic funcion will fi o all ADC inpu ignal. Moreover, he complexiy for implemening a cubic pline inerpolaion in hardware i much higher han fir order inerpolaion. In [9] a barycenric inerpolaion i decribed derived eiher by he repeaed ue of Bernein inequaliy and Taylor heorem, or by runcaing a Lagrange-ype erie. The inerpolaor derivaive are alo eimaed. I applicaion on uniform or non-uniform and long inerval i examined. The auhor of [9] how how he complexiy of he calculaion can be efficienly decreaed alhough muliplicaion and diviion are ill required. In [0] he inerpolaion i alo performed by a weighed ummaion of a number of preceding and ucceeding available ample in order o eimae he curren ignal value. The Lea Mean Laice LSL) inerpolaion algorihm i compared o a QR Decompoiion LSL algorihm QRD-LSL) developed by he auhor of [0] ha how a db lower quared error. A fir order inerpolaion in ime i ued in hi paper aemping o achieve a very low co hardware implemenaion ha doe no require complicaed operaion lie muliplicaion, diviion, Fourier ranform, ec. Alhough, hi ype of inerpolaion doe no ae ino conideraion he lope and curvaure of he iniial ignal i can ignificanly improve low reoluion ignal highly diored by he digiizaion proce. More pecifically, he SR of a inuoidal ignal i improved by 7dB %) uing he propoed po proceing module. I ue wih differen ype of ignal lie enor oupu or ignal repreening image i alo eed. Excep from he SR improvemen, he decribed archiecure can alo perform real ime compreion in he cae of pare or lowly changing ignal. The calabiliy of he propoed archiecure i anoher criical feaure allowing he achievemen of higher lineariy if muliple inerpolaor are conneced in erie or if an inerpolaor i ued recurively. The low complexiy of he propoed inerpolaor i proven by he fac ha hree inerpolaor wih 9, 0 and bi inpu reoluion and heir correponding decompreion uni a heir oupu fi in a mall Alera Cyclone II EPC5F56C8 FPGA uing only 7% of i Logic Elemen LE). The modeling of he inerpolaion mehod ued i decribed in Secion. The archiecure and implemenaion iue of he inerpolaor are dicued in Secion. The imulaion and experimenal reul are preened in Secion. II. THE PROPOSED ITERPOLATIO METHOD In he zero-order inerpolaion or zero-order hold) he inermediae poin of a ignal beween wo ucceive nown ample ae he value of he fir ample. Thi i acually he oupu of a DAC if i inpu i conneced o he ADC and no filering i ued. The fir-order inerpolaion or fir-order hold) approximae he inermediae poin uing a piece of line connecing hem and i i more accurae han zero-order hold if he diance beween he wo ucceive ample i mall enough. In pracical applicaion a fir-order or a differen ype of inerpolaor i implemened hrough filering. The eimaion of he inermediae poin beween wo ucceive ADC oupu no necearily in uniform inerval) wih fir order hold i hown in Fig.. The employed inerpolaion mehod doe no ue he ADC ampling rae ince he digial circui ha implemen hi inerpolaor ue a local higher frequency cloc. The original ADC oupu coni of he value,, ec. The olid line in Fig. i he zero-order inerpolaion beween hee value. The value appear for inerpolaor cloc period. Then he value appear for, ec. 59

3 ISS: ISO 900:008 Cerified Inernaional Journal of Engineering Science and Innovaive Technology IJESIT) idenical ample olume, Iue, May 0 ample wih value +) ample wih ample value +) idenical ample ample wih value ample wih value +) +) Fig.. The inerpolaion mehod ued. The propoed inerpolaion cheme i baed on replacing half of he occurrence of he la ample value by he average value of he wo ucceive ample. For example, he value in he la inerpolaor cloc period are replaced by + ). The dahed line in Fig. how he reuling inerpolaed ignal. Addiional inermediae poin could have been eimaed if he aforemenioned procedure i applied recurively. Thi inerpolaion procedure i ucceful if he original ignal i monoonically increaing or decreaing beween each pair of ucceive nown ample value. Thi can be viewed graphically in Fig. a where he dahed line inerpolaed ignal) i obviouly cloer o he original curve. In Fig. b inead, where he inpu ignal doe no change monoonically beween ucceive ample value, he propoed inerpolaion cheme doe no guaranee a lower approximaion error. The cae of Fig. b may appear when he ucceive ADC oupu are rerieved uing oo long ampling inerval, compared o he inpu ignal frequency. More formally, if for example he inpu ignal ) i monoonically decreaing beween he ucceive ample 0 )= and - )= > >0) and he inerpolaor cloc ample ime he value before he appear, hen he error ε beween he original ignal and he iniial digiized one can be expreed a: 0 0 )) )) )) ) The inerpolaed ignal will replace he la ample wih he value + ) and he correponding error ε will be: )) )) )) ) 0 0 From ) and ) above i i obviou ha ε <ε ince: ) ) for < ) In a imilar way, i can be proved ha he error of he propoed inerpolaion i lower if he inpu ignal i monoonically increaing inead of decreaing. If a econd inerpolaion i ued a he oupu of he fir inerpolaor, a econd pair of value will be produced. The fir i + ) and appear beween and + ) afer he -h ample) and he econd i + ) and appear beween + ) and afer he -h ample). The approximaion error i furher decreaed in hi way ince he error ε beween he oupu 59

4 ISS: ISO 900:008 Cerified Inernaional Journal of Engineering Science and Innovaive Technology IJESIT) olume, Iue, May 0 59 of he econd inerpolaor and he original ignal i: f) T T, + ) a) b) Fig.. The inerpolaion mehod ued in monoonic a) and non-monoonic b) inerval. 0 )) )) )) )) ) The error ε i lower han ε ince he relaion beween he econd and fourh erm of equaion ) and he correponding erm of equaion ) i: ) ) 5) and ) ) 6 6 6) everhele, i ha o be noed ha he ample ) i no necearily equal o + ), hu he econd inerpolaion i performed beween a real and an eimaed ignal value. If addiional inerpolaion are recurively performed, he improvemen will gradually decreae ince hey will be applied on eimaed inermediae value and no real one. A rade off ha o be made beween he deired improvemen and he ue of addiional inerpolaor conneced in erie. III. THE ARCHITECTURE OF THE ITERPOLATOR The archiecure of he digial inerpolaor ha implemen he mehod decribed in he previou ecion i hown in Fig.. The M-bi ADC oupu which i acually he inerpolaor inpu i conneced o a pair of lache. One of he lache i conneced o he inerpolaor cloc CLK enabling each ADC oupu value o appear a he lach oupu wih one CLK period delay. The inpu and he oupu of hi lach are digially compared by CMP ha generae a pule a i oupu EQ) when i deec ha he ADC oupu ha changed. The pule a he EQ ignal i appropriaely delayed ignal EQ_DEL) and combined wih he inerpolaor cloc CLK in order o generae a pair of pule a he ignal BUF_E when he ADC oupu change. Moreover, he ignal SEL i generaed by

5 ISS: ISO 900:008 Cerified Inernaional Journal of Engineering Science and Innovaive Technology IJESIT) olume, Iue, May 0 combining he oupu of he delay elemen a he CMP oupu o ha i i high a he fir and low a he econd CLK pule during he ime inerval where he ignal BUF_E i acive. The inerpolaor cloc CLK ha a much higher frequency han he frequency of he ADC inpu ignal, hu he ame ADC oupu value may la everal inerpolaor cloc period. The cloc or load inpu) ued a he econd lach i he ignal EQ_DEL ha allow a new ADC oupu value o appear a i oupu wih wo CLK period delay. During hee wo cloc period, he ADDER generae he um of he wo ucceive value of he ADC Oupu or in oher word heir average muliplied by. Since he ADDER inpu are repreened wih M-bi, i oupu ha a reoluion of M+ bi. When he EQ_DEL ignal ge acive, he K-bi couner a he boom-righ of Fig. i ree and ar couning he number of he inerpolaor cloc period ha he new ADC oupu value will la. During he wo inerpolaor cloc period beween he acivaion of EQ and EQ_DEL he alernaing value of he SEL ignal elec eiher he previou value of he ADC oupu from he boom lach) or he ADDER oupu + ) o pa hrough he muliplexor MUX. The ADDER oupu i M+ bi while i repreened wih M bi. Thi ADC oupu ) i acually hifed lef muliplied by ) a he inpu of he MUX by padding i wih a 0 a i lea ignifican bi. The wo MUX oupu decribed in he previou paragraph and + ) are ored a he end of a FIFO buffer ince he BUF_E ignal allow hee value o be ored in wo ucceive inerpolaor cloc period. During hee period, he K-bi Couner oupu denoe he number of inerpolaor cloc period ha he value appeared a he ADC oupu. The K- mo ignifican bi of he K-bi Couner are ored in a econd FIFO buffer along wih he value and + forming pair of ype: AL, CT). The value AL appear for CT inerpolaor cloc period. The AL, CT) pair are he main inerpolaor oupu and implemen he mehod decribed in he previou ecion. Moreover, he informaion provided by he AL, CT) pair i compreed following he echnique ued in lole compreion andard lie LZ7778 employed by PG, GIF ec. The higher he pare level i, or he lower he frequency of he ADC inpu ignal i, he higher compreion raio can be achieved. The decompreion of he inerpolaor oupu pair AL, CT) may be ueful eiher a he ide of he module ha receive he inerpolaor oupu or if muliple inerpolaor need o be conneced in erie in order o achieve higher lineariy an inerpolaor require uncompreed inpu value). I can be merely implemened by a new pair of FIFO buffer, a down couner wih parallel inpu and a decompreion lach a he oupu of he inerpolaor FIFO buffer. Each ime a new pair AL, CT) appear a he beginning of he inerpolaor FIFO buffer, i i ranferred a he FIFO buffer of he decompreion uni. The value AL from he fir pair of he decompreion uni FIFO buffer i ranferred o he decompreion lach and he correponding CT value i loaded o he down couner. When he value of he couner i equal o zero, he nex pair of AL, CT) value i popped from he decompreion uni FIFO. In hi way, he oupu of he decompreion lach repreen he uncompreed value of he ADC oupu ha are correced by he inerpolaor. The FIFO are ued for he compenaion of he rae ha he value change a he ADC oupu and he proceing peed of he inerpolaor and he decompreion uni. Boh he inerpolaor and he decompreion uni archiecure decribed in hi ecion, where decribed in HDL and implemened on an Alera Cyclone II EPC5F56C8 FPGA uing he low co FTDI Morph-IC-II evaluaion board. The ize of he couner i eleced o be K=6 while he oal FIFO deph i 6. An inerpolaor wih 9-bi inpu and 0-bi oupu required 59 LE % of he FPGA LE) while a decompreion uni for he oupu of hi inerpolaor required 78 LE 6% of he FPGA LE). The hree age of inerpolaion ued in he e eup of he nex ecion and heir correponding decompreion uni occupied 7%, LE) of he FPGA LE. 595

6 ISS: ISO 900:008 Cerified Inernaional Journal of Engineering Science and Innovaive Technology IJESIT) olume, Iue, May 0 BUF_E CLK EQ CLK M-bi ADC Lach EQ_DEL CMP D D EQ_DEL Lach SEL M+ bi padded wih 0 a he LSB) ADDER M+ bi oupu) M+ bi MUX M+ bi BUF_E EQ_DEL K-bi Couner Ree Cl Oupu K- MSB BUF_E CLK I EABLE I PAIR OF FIFO BUFFERS OUT OUT AL CT Fig.. The archiecure of he inerpolaor. I. EXPERIMETAL RESULTS Ho Compuer Reul USB Morph-IC-II Alera EPC5F56C8) Funcion Generaor ADC Touch Senor Freecale TWR Κ70F0Μ Fig.. The experimenal eup. 596

7 ISS: ISO 900:008 Cerified Inernaional Journal of Engineering Science and Innovaive Technology IJESIT) olume, Iue, May 0 a) b) c) Fig. 5. The ADC oupu a), he inerpolaor oupu b) and he rd inerpolaor oupu c). The efficiency of he inerpolaor decribed in he previou paragraph i evaluaed uing hree ype of inpu: a) he value a he ADC oupu of he MK70FM0MJ microconroller from a Freecale Kinei TWR K70F0M developmen board, b) he indicaion of a ouch pad of a TWR K70F0M board which i acually a preure enor and c) a pixel grey image. The experimenal eup ued in hi paper i hown in Fig.. An 8-bi reoluion wa eleced for he Segmenaion and Reaembly ADC of he Freecale TWR K70F0M developmen board. I inpu i conneced o a funcion generaor ha i ued o produce a inuoidal ignal. Two period of he inuoidal ignal are iolaed and he correponding ADC oupu value are iniially ored a he RAM of he MK70FM0MJ microconroller and hen ranferred o a Ho compuer. In a imilar manner, he Touch Sene Inpu TSI) module of he TWR K70F0M board microconroller i ued o ample a ouch pad preure enor. The ho compuer conrolling he TWR K70F0M board i alo conneced o an FTDI Morph IC II wih 50 MHz ocillaor) evaluaion board wih an Alera Cyclone II EPC5F56C8 maximum operaing frequency 0MHz) FPGA where he inerpolaion mehod decribed in Secion i implemened. More pecifically, inerpolaor wih 9, 0 and bi inpu reoluion are conneced in erie hrough decompreion uni. The reul are en bac o he Ho for proceing and meauremen uing MATLAB. Excep from he ADC and TSI indicaion, he ho may end o he FPGA oher ype of daa lie image or virual enor indicaion for he evaluaion of he inerpolaion algorihm. 597

8 ISS: ISO 900:008 Cerified Inernaional Journal of Engineering Science and Innovaive Technology IJESIT) olume, Iue, May 0 Fig. 6. Uing he inerpolaor wih he indicaion of a preure enor. A far a he ADC daa are concerned, he funcion generaor produce a inuoidal ignal of 0 Hz. The period of he inuoidal ignal i high enough compared o he ampling period of he ADC which i.5 uec, in order o have hor enough ampling inerval where he ignal change monoonically Fig. 5a). The reconruced inuoidal ignal from he and he rd Inerpolaor oupu i hown in Fig. 5b and Fig. 5c repecively. The SR of he ADC oupu i.7 db while he SR of he, he nd and he rd age inerpolaor oupu are 7.9 db, 0.9 db and. db. Thu, an improvemen of 7. db or.%) i achieved in he SR. The efficiency of he inerpolaor when he ouch pad preure enor i ued i hown in Fig. 6. The TSI inerface ha a reoluion of 6-bi bu he examined par of he curve can be conidered o have a 9-bi reoluion which i furher degraded by -bi o avoid flucuaion wih monoonic error. The value of he degraded ignal are he inpu of he inerpolaor. The degraded ignal and he oupu of he and nd inerpolaor are be fied in he original enor ignal and he Mean Square Error MSE) a well a he ormalized MSE MSE) i meaured. The MSEMSE of he degraded ignal i while he MSEMSE of he and he nd inerpolaor oupu are and repecively. The rd inerpolaor oupu wa no ued ince i wa difficul o achieve a be fiing wih he re of he curve. The propoed inerpolaion cheme i no argeed for image proceing applicaion ince he value of adjacen pixel do no alway change moohly. everhele, he propoed inerpolaor may be ueful for proceing infrared image, nigh viion camera ignal, medical image lie MRI, PET ec, where he color or grey level change moohly. The grey image of Fig. 7a wa ued a an inpu o he age of he inerpolaor oupu afer degrading o 8 grey level only -bi reoluion) a hown in Fig. 7b. The oupu of he age of he inerpolaor i hown in Fig. 7c. The MSEMSE of he degraded image Fig. 7b) compared o he original one of Fig. 7a i 750. while he MSEMSE of he age inerpolaor oupu i reduced o Alhough he error in he correced pixel i ignificanly reduced compared o he -bi grey level image, he qualiy i no improved ince he picure appear o be dragged from lef o righ. An opical improvemen can alo be achieved by uing addiional rule o he inerpolaor ha are cuomized for image proceing applicaion. For example, he inerpolaion can only be applied o grey level value ha do no differ much, if hee level appear a a comparable number of adjacen pixel. Thi rule wa incorporaed in he inerpolaor ha ued a inpu he image ha wa degraded o a 5-bi reoluion. The reuling oupu i hown in Fig. 7d and i MSEMSE compared o he iniial image i The furher udy of cuomized inerpolaor verion for image proceing applicaion i ou of he cope of hi paper. Table I ummarize he feaure of he referenced approache. Alhough ome auhor may achieve a higher improvemen eiher in he IL error of an ADC or i dynamic behavior, eiher no informaion i provided on heir 598

9 ISS: ISO 900:008 Cerified Inernaional Journal of Engineering Science and Innovaive Technology IJESIT) olume, Iue, May 0 hardware implemenaion or hey require complicaed hardware large loo up able, muliplicaiondiviion, ec). The propoed inerpolaor inead, i baed only on adder, couner and mall buffer. a) b) c) Fig. 7. Originial image a), he image degraded o -bi reoluion b), he image correced by he inerpolaor c) and he correced by he cuomized inerpolaor oupu image d). TABLE I. Reference Improvemen oe [] Upgrade o bi reoluion from 0 bi [5] [6] [7] [0] Thi wor SFDR improved from o 7dB, SDR improved from o 6dB IL improved by LSB 0 bi ADC).dB uncorreced oupu), 9.9dB wih error correcion) db improvemen in quare error wih QRD-LSL SR increaed from.7db o.db FEATURES OF THE REFERECED APPROACHES IL improvemen by uing 56 correcion code exraced from he 7 MSB of he ADC. Teed in imulaion level only The -bi AD665 i ued, Bayeian calibraion of he loo up able wa perfromed a a imulaion level in MATLAB Calibraion circui implemened in a Xilinx XCS00 Sparan FPGA Pair of ubchannel ADC wih: 6b reoluion, ±LSB IL, ±0.5LSB DL error. The error correcion circui excluding he addiional area of he ADC pair) occupie 0.5m in 0.5um proce. Achieved wih 8-bi preciion. QRD-LSL require fewer ieraion han LSL inerpolaor 7% of LE of an Alera Cyclone II EPC5F56 FPGA ued, LZ77 compreion performed ACKOWLEDGMET The wor preened in hi paper i proeced by he proviional paen wih appl. no Gree paen office) REFERECES [] F. Sefani, D. Macii, A. Mochia, P. Carbone and D. Peri, Simple and Time-Effecive Procedure for ADC IL Eimaion, IEEE Tran. on Inrumenaion and Mea. ol. 55, o., pp. 8-89, Aug [] I. Kollár, and J. Blair, Improved Deerminaion of he Be Fiing Sine Wave in ADC Teing, IEEE Tranacion on Inrumenaion and Meauremen, ol. 5, o. 5, pp , Oc d) 599

10 ISS: ISO 900:008 Cerified Inernaional Journal of Engineering Science and Innovaive Technology IJESIT) olume, Iue, May 0 [] L. Jin, D. Chen and R. Geiger, A digial elf-calibraion algorihm for ADC baed on hiogram e uing low-lineariy inpu ignal, Proceeding of he IEEE ISCAS 05, pp [] H. C. Hong, F. Y. Su & S. F. Hung, A Fully Inegraed Buil-In Self-Te Σ Δ ADC Baed on he Modified Conrolled Sine-Wave Fiing Procedure, IEEE Tranacion on Inrumenaion and Meauremen, ol. 59, o. 9, pp., Sep. 00. [5] L. De io, H. Lundin and S. Rapuano, Bayeian Calibraion of a Looup Table for ADC Error Correcion, IEEE Tran. on Inrumenaion and Mea. ol. 56, o., pp , June 007. [6] B. Provo and E. Sánchez-Sinencio, A Pracical Self-Calibraion Scheme Implemenaion for Pipeline ADC, IEEE Tran. on Inrumenaion and Mea., ol. 5, o., pp. 8 56, Apr. 00. [7] J.A. Mceill, C. David, M. Coln, R. Croughwell, Spli ADC Calibraion for All-Digial Correcion of Time-Inerleaved ADC Error, IEEE Tranacion on Syem and Circui II, Expre Brief, ol. 56, o. 5, pp. -8, 009. [8] S. A. Dyer and J. S. Dyer, Cubic Spline Inerpolaion, IEEE Inrumenaion and Meauremen Magazine, ol., o., pp. -6, 00. [9] J. Selva, Deign of Barycenric Inerpolaor for Uniform and onuniform Sampling Grid, IEEE Tranacion on Signal Proceing, ol. 58, o. ), pp , 00. [0] Z. Sun and L. Guo, An Improved LSL Inerpolaor o Suppre arrow-band Inerference for Direc-Sequence Spread-Specrum Syem, Proceeding of he IEEE ChinaCom 06, pp. -5, 006 AUTHOR BIOGRAPHY io Perelli i an aian profeor a he Compuer Science and Engineering Dep., TEI of Thealy, Greece from 00. He received hi diploma from Compuer Engineering and Informaic Dep. and hi PhD in Elecrical and Compuer Engineering Dep. in 99 and 999 repecively boh from Univeriy of Para, Greece. He ha wored wih everal companie lie GiGA Hella SA Inel Corp.) and Amel Hella SA. He ha been an adjunc profeor for 8 year a Univeriy of Para eaching Microcompuer and Microproceor coure. He ha publihed more han 60 paper in inernaional journal, conference proceeding and boo chaper. He i a member of IEEE and Technical Chamber of Greece. Hi reearch inere include Embedded Syem deign, LSI, mixed analogdigial yem deign. 600