Các thành phần chính trong hệ thống RFID(2)

Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)

Cc thnh phn ca mt h thng RFIDCc thnh phn chnh trong h thng RFID l th, reader v c s d liu. Mt h thng RFID ton din bao gm bn thnh phn: 1. Th RFID (RFID Tag, Transponder - b pht p) c lp trnh in t vi thng tin duy nht. 2. Cc reader (u c) hoc sensor (ci cm bin) truy vn cc th. 3. Antenna thu, pht sng v tuyn. 4. Host computer - server, ni m my ch v h thng phn mm giao din vi h thng c ti. N cng c th phn phi phn mm trong cc reader v cm bin. C s h tng truyn thng: l thnh phn bt buc, n l mt tp gm c hai mng c dy v khng dy v cc b phn kt ni tun t kt ni cc thnh phn lit k trn vi nhau chng truyn vi nhau hiu qu. Hnh 1: Cc thnh phn trong h thng RFID

Nhm n 2 |Cng ngh RFID (Radio Frequency Identification) v cc ng 1 dng


Nguyn l lm vic ca RFID.B c pht ra sng in t, th cha ng mt h thng tip sng vi mt chip nh k thut s lu gi mt m sn phm in t duy nht v anten ca th c ng gi vi mt thit b truyn tip, v thit b gii m pht ra mt tn hiu kch hot th RFID. V vy n c th c v vit d liu ln n. Khi mt th RFID i xuyn qua mt vng in t, n tm ra cc tn hiu kch hot ca b c; cc th RFID th ng hp th nng lng t trng in t do b c to nn v s dng nng lng nui cc mch vi chp, vi chp sau iu ch sng th pht li v pha b c v b c bin i cc sng thnh tn hiu s v t nhn dng mn c gn th RFID.

Chc nng, cu to v phn loi ca cc thnh phn trong h thng RFID Th RFID (RFID Tag, Transponder - b pht p).

I.

a. Chc nng: L thit b lu tr d liu thc t ca mt h thng RFID, thng bao gm mt phn t kt ni (Coupling element) v mt vi chp in t. b. Cu to: Th gm c 2 phn chnh: - Chip: lu tr mt s th t duy nht hoc thng tin khc da trn loi th: readonly, read-write, hoc write-once-read-many. - Antenna: c gn vi vi mch truyn thng tin t chip n reader. Antenna cng ln cho bit phm vi c cng xa. c. Phn loi: Cc th RFID c phn loi da trn vic th c cha mt cung cp ngun gn bn trong hay l c cung cp bi thit b chuyn dng: - Th ng (Passive) - Tch cc (Active) - Bn tch cc (Semi-active, cn gi bn th ng - semi-passive)

Th th ng:Loi th ny khng c ngun bn trong (on-board), s dng ngun nhn c t reader t tip sinh lc hot ng v truyn d liu


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)c lu tr trong n cho reader. Th th ng c cu trc n gin v khng c cc thnh phn ng. Th nh th c mt thi gian sng di v thng c sc chu ng vi iu kin mi trng khc nghit. i vi loi th ny, khi th v reader truyn thng vi nhau th reader lun truyn trc ri mi n th. Cho nn bt buc phi c reader th c th truyn d liu ca n. Th th ng c c khong cch t 11cm trng gn (ISO 14443), n 10m trng xa (ISO 18000-6), v c th ln n 183m khi kt hp vi ma trn. Th th ng nh hn v cng r hn th tch cc hoc bn tch cc. Cc th th ng c th thc thi tn s low, high, ultrahigh, hoc microwave Th th ng bao gm nhng thnh phn chnh sau: - Vi mch (microchip). - Antenna.

Vi mchVi mch thng thng gm c: - B chnh lu (power control/rectifier): chuyn ngun AC t tn hiu antenna ca reader thnh ngun DC. N cung cp ngun n cc thnh phn khc ca vi mch. - My tch xung (Clock extractor): rt tn hiu xung t tn hiu antenna ca reader. - B iu ch (Modulator): iu chnh tn hiu nhn c t reader. p ng ca th c gn trong tn hiu iu ch, sau n c truyn tr li reader. - n v lun l (Logic unit): chu trch nhim cung cp giao thc truyn gia th v reader. - B nh vi mch (memory): c dng lu tr d liu. B nh ny thng c phn on (gm vi block hoc field). Addressability c ngha l c kh nng phn tch (c hoc ghi) vo b nh ring ca mt vi mch ca th. Mt block nh ca th c th gi nhiu loi d liu khc nhau, v d nh mt phn ca d liu nhn dng i tng c gn th, cc bit checksum (chng hn kim tra li CRC) kim tra chnh xc ca d liu c truyn v.v S tin b ca k thut cho php kch thc ca vi mch nh n mc nh hn ht ct. Tuy nhin, kch c ca th khng c xc nh bi kch thc vi mch ca n m bi chiu di antenna ca n.

AntennaAntenna ca th c dng ly nng lng t tn hiu ca reader lm tng sinh lc cho th hot ng, gi hoc nhn d liu t reader. Antenna ny c gn vo vi mch, antenna l trung tm i


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)vi hot ng ca th. C th c nhiu dng antenna, nht l UHF, chiu di antenna tng ng vi bc sng hot ng ca th. Mt antenna lng cc bao gm mt dy dn in (chng hn ng) m n b ngt trung tm. Chiu di tng cng ca mt antenna lng cc bng na bc sng tn s c dng nhm ti u nng lng truyn t tn hiu antenna ca reader n th. Reader c th c th ny nhiu hng khc nhau. Chiu di antenna ca th thng ln hn nhiu so vi vi mch ca th v vy n quyt nh kch c vt l ca th. Mt antenna c th c thit k da trn mt s nhn t sau y: - Khong cch c ca th vi reader. - Hng c nh ca th i vi reader. - Hng ty ca th i vi reader. - Loi sn phm ring bit. - Vn tc ca i tng c gn th. - phn cc antenna ca reader. Nhng im kt ni gia vi mch ca th v antenna l nhng kt ni yu nht ca th. Nu c bt k im kt ni no b hng th xem nh th khng lm vic c hoc c th hiu sut lm vic gim ng k. Hin ti, antenna ca th c xy dng bng mt mnh kim loi mng (chng hn ng, bc hoc nhm). Tuy nhin, trong tng lai c th s in trc tip antenna ln nhn th, hp v sn phm ng gi bng cch s dng mt loi mc dn c cha ng, cacbon v niken.

Th tch cc:Th tch cc c mt ngun nng lng bn trong (chng hn mt b pin, hoc c th l nhng ngun nng lng khc nh s dng ngun nng lng mt tri) v in t hc thc thi nhng nhim v chuyn dng. Th tch cc s dng ngun nng lng bn trong truyn d liu cho reader. N khng cn ngun nng lng t reader truyn d liu. in t hc bn trong gm b vi mch, cm bin v cc cng vo/ra c cp ngun bi ngun nng lng bn trong n. i vi loi th ny, trong qu trnh truyn gia th v reader, th lun truyn trc, ri mi n reader. V s hin din ca reader khng cn thit cho vic truyn d liu nn th tch cc c th pht d liu ca n cho nhng vng ln cn n thm ch trong c trng hp reader khng c ni . Khong cch c ca th tch cc l 100 feet (xp x 30,5 m) hoc hn na khi my pht tch cc ca loi th ny c dng n. Th tch cc bao gm 4 thnh phn chnh sau: - Vi mch: Kch c v kh nng lm vic vi mch thng ln hn vi mch trong th th ng.


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)- Antenna: c th truyn tn hiu ca th v nhn tn hiu reader. i vi th bn tch cc, gm mt hoc nhiu mnh kim loi nh ng, tng t nh th th ng. - Cung cp ngun bn trong. Ngun nng lng bn trong Tt c cc th tch cc u mang mt ngun nng lng bn trong cung cp ngun cho in t hc bn trong v truyn d liu. Nu s dng b pin th th tch cc thng ko di tui th t 2 n 7 nm ty thuc vo thi gian sng ca b pin. Mt trong nhng nhn t quyt nh thi gian sng ca b pin l tc truyn d liu ca th. Nu khong cch cng rng th b pin cng tn ti lu v v th thi gian sng ca th cng di hn. - in t hc bn trong. in t hc bn trong cho php th hot ng nh mt my pht v cho php n thc thi nhng nhim v chuyn dng nh tnh ton, hin th gi tr cc tham s ng no , hoc hot ng nh mt cm bin v.v Thnh phn ny cng c th cho php chn la kt ni vi cc cm bin bn ngoi. V vy th c th thc thi nhiu nhim v thng minh, ty thuc vo loi cm bin c gn vo. (Hai thnh phn u tin (vi mch, antenna) c m t trong phn trc)

Th bn tch cc (bn th ng):Th bn tch cc c mt ngun nng lng bn trong (chng hn l b pin) v in t hc bn trong thc thi nhng nhim v chuyn dng. Ngun bn trong cung cp sinh lc cho th hot ng. Tuy nhin trong qu trnh truyn d liu, th bn tch cc s dng ngun t reader. Th bn tch cc c gi l th c h tr pin (battery-assisted tag). i vi loi th ny, trong qu trnh truyn gia th v reader th reader lun truyn trc ri n th. Ti sao s dng th bn tch cc m khng s dng th th ng? Bi v th bn tch cc khng s dng tn hiu ca reader nh th th ng, n t kch ng, n c th c khong cch xa hn th th ng. Bi v khng cn thi gian tip sinh lc cho th bn tch cc, th c th nm trong phm vi c ca reader t hn thi gian c quy nh (khng ging nh th th ng). V vy nu i tng c gn th ang di chuyn tc cao, d liu th c th vn c c nu s dng th bn tch cc. Th bn tch cc cng cho php c tt hn ngay c khi gn th bng nhng vt liu chn tn s v tuyn (RF-opaque v RF-absorbent). S c mt ca nhng vt liu ny c th ngn khng cho th th ng hot ng ng dn n vic truyn d liu khng thnh cng. Tuy nhin, y khng phi l vn kh khn i vi th bn tch cc. Phm vi c ca th bn tch cc c th ln n 100 feet (xp x 30,5m) vi


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)iu kin l tng. Vic phn loi tip theo da trn kh nng h tr ghi chp d liu: - Ch c (RO) - Ghi mt ln, c nhiu ln (WORM) - c - Ghi (RW) Th read only (RO) Th RO c th c lp trnh (tc l ghi d liu ln th RO) ch mt ln. D liu c th c lu vo th ti x nghip trong lc sn xut. Vic ny c thc hin nh sau: cc fuse ring l trn vi mch ca th c lu c nh bng cch s dng chm tia laser. Sau khi thc hin xong, khng th ghi d liu ln th c na. Th ny c gi l factory programmed. Nh sn xut loi th ny s a d liu ln th v ngi s dng th khng th iu chnh c. Loi th ny ch tt i vi nhng ng dng nh m khng thc t i vi quy m sn xut ln hoc khi d liu ca th cn c lm theo yu cu ca khch hng da trn ng dng. Loi th ny c s dng trong cc ng dng kinh doanh v hng khng nh. Th write once, read many (WORM) Th WORM c th c ghi d liu mt ln, m thng th khng phi c ghi bi nh sn xut m bi ngi s dng th ngay lc th cn c ghi. Tuy nhin trong thc t th c th ghi c mt s ln (khong 100 ln). Nu ghi qu s ln cho php, th c th b ph hng vnh vin. Th WORM c gi l field programmable. Loi th ny c gi c v hiu sut tt, c chc nng an ton d liu v l loi th ph bin nht trong lnh vc kinh doanh ngy nay. Th read write (RW) Th RW c th ghi d liu c nhiu ln, khong t 10.000 n 100.000 ln hoc c th hn na. Vic ny em li li ch rt ln v d liu c th c ghi bi reader hoc bi th (nu l th tch cc). Th RW gm thit b nh Flash v FRAM lu d liu. Th RW c gi l field programmable hoc reprogrammable. S an ton d liu l mt thch thc i vi th RW. Thm vo na l loi th ny thng t nht. Th RW khng c s dng rng ri trong cc ng dng ngy nay, trong tng lai c th cng ngh th pht trin th chi ph th s gim xung.

II.

Reader (u c)a. Chc nng: Reader l h thn kinh trung ng ca ton h thng, phn cng RFID thit lp vic truyn vi thnh phn ny v iu khin n, l thao tc quan trng nht ca bt k thc th no mun lin kt vi thc th phn cng ny.


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)b. Cu to: Mt reader in hnh cha mt module tn s v tuyn (my pht v my thu) l mt n v iu khin v l phn t kt ni n b pht p. Ngoi ra cc reader cn c gn vi mt giao din b sung (RS232, RS485) chng c th chuyn tip d liu c c n mt h thng khc (PC, h thng iu khin robot). Reader RFID c gi l vt tra hi (interrogator), l mt thit b c v ghi d liu cc th RFID tng thch. Hot ng ghi d liu ln th bng reader c gi l to th. Qu trnh to th v kt hp th vi mt i tng c gi l a th vo hot ng (commissioning the tag).

Cc thnh phn chnh ca reader bao gm:- My pht (Transmitter) - My thu (Receiver) - Vi mch (Microprocessor) - B nh - Knh vo/ra i vi cc cm bin, c cu truyn ng u t, bng tn hiu in bo bn ngoi (mc d ni ng ra y l nhng thnh phn khng bt buc, chng hu nh lun c cung cp vi mt reader thng mi). - Mch iu khin (c th n c t bn ngoi) - Mch truyn thng - Ngun nng lng

My phtMy pht ca reader truyn ngun AC v chu k xung ng h qua antenna ca n n th trong phm vi c cho php, n chu trch nhim gi tn hiu ca reader n mi trng xung quanh v nhn li p ng ca th qua antenna ca reader.

My thuMy thu nhn tn hiu tng t t th qua antenna ca reader. Sau n gi nhng tn hiu ny cho vi mch ca reader, ti ni ny n c chuyn thnh tn hiu s tng ng (c ngha l d liu m th truyn cho reader c biu din dng s).

Vi mchThnh phn ny chu trch nhim cung cp giao thc cho reader n truyn thng vi th tng thch vi n. N thc hin vic gii m v kim tra li tn hiu tng t nhn t my thu.

B nhB nh dng lu tr d liu nh cc tham s cu hnh reader v mt bn


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)k khai cc ln c th. V vy nu vic kt ni gia reader v h thng mch iu khin/phn mm b hng th tt c d liu th c c khng b mt.

Cc knh nhp/xut ca cc cm bin, c cu truyn ng u tv bng tn hiu in bo bn ngoi. Cc reader khng cn bt sut. Cc th c th ch xut hin lc no v ri khi reader mi cho nn vic bt reader sut s gy lng ph nng lng. Thm na l gii hn va cp trn cng nh hng n chu k lm vic ca reader. Thnh phn ny cung cp mt c ch bt v tt reader ty thuc vo cc s kin bn ngoi. C mt s loi cm bin nh cm bin v nh sng hoc s chuyn ng pht hin cc i tng c gn th trong phm vi c ca reader. Cm bin ny cho php reader bt ln c th. Thnh phn ny cng cho php reader cung cp xut cc b ty thuc vo mt s iu kin qua mt bng tn hiu in bo (chng hn, bo bng m thanh) hoc c cu truyn ng u t (chng hn, m hoc ng van an ton, di chuyn mt cnh tay robot, v.v).

Mch iu khinMch iu khin l mt thc th cho php thc th bn ngoi l con ngi hoc chng trnh my tnh giao tip, iu khin cc chc nng ca reader, iu khin bng tn hiu in bo v c cu truyn ng u t kt hp vi reader ny. Thng th cc nh sn xut hp nht thnh phn ny vo reader (nh phn mm h thng (firmware) chng hn).

Giao din truyn thngThnh phn giao din truyn thng cung cp cc lnh truyn n reader, n cho php tng tc vi cc thc th bn ngoi qua mch iu khin, truyn d liu ca n, nhn lnh v gi li p ng. Thnh phn giao din ny cng c th xem l mt phn ca mch iu khin hoc l phng tin truyn gia mch iu khin v cc thc th bn ngoi. Thc th ny c nhng c im quan trng cn xem n nh mt thnh phn c lp. Reader c th c mt giao din tun t. Giao din tun t l loi giao din ph bin nht nhng cc reader th h sau s c pht trin giao din mng thnh mt tnh nng chun. Cc reader phc tp c cc tnh nng nh t pht hin bng chng trnh ng dng, c gn cc Web server cho php reader nhn lnh v trnh by kt qu dng mt trnh duyt Web chun.

Ngun nng lngThnh phn ny cung cp ngun nng lng cho cc thnh phn ca reader. Ngun nng lng c cung cp cho cc thnh phn ny qua mt dy dn in c kt ni vi mt ng ra bn ngoi thch hp.


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)c. Phn loi: Reader c phn loi ch yu theo tiu chun l giao din m reader cung cp cho vic truyn thng. Trong tiu chun ny, reader c th c phn loi ra nh sau: - Serial. - Network.

Serial readerSerial reader s dng lin kt serial truyn vi mt ng dng. Reader kt ni n cng serial ca my tnh dng kt ni tun t RS232 hoc RS485. C hai loi kt ni ny u c gii hn trn v chiu di cp s dng kt ni reader vi my tnh. Chun RS485 cho php cp di hn chun RS232. u im ca serial reader l c tin cy cao hn network reader. V vy s dng reader loi ny c khuyn khch nhm lm ti thiu s ph thuc vo mt knh truyn. Nhc im ca serial reader l ph thuc vo chiu di ti a ca cp s dng kt ni mt reader vi mt my tnh. Thm na, thng th trn mt my ch th s cng serial b hn ch. Tc truyn d liu serial thng thp hn tc truyn d liu mng. Nhng nhn t ny dn n chi ph bo dng cao hn v thi gian cht ng k.

Network readerNetwork reader kt ni vi my tnh s dng c mng dy v khng dy. Thc t, reader hot ng nh thit b mng. u im ca network reader l khng ph thuc vo chiu di ti a ca cp kt ni reader vi my tnh. S dng t my ch hn so vi serial reader. Thm na l phn mm h thng ca reader c th c cp nht t xa qua mng. Nhc im ca network reader l vic truyn khng ng tin cy bng serial reader.

III.

AntenAnten c chc nng pht sng kch hoat cc the RFID v nhn cc thng tin t cc the RFID ny. Anten c nhim vu truyn tn hiu nhn c ti cc thit bi oc the. Trong cc thit bi oc the, anten c th c tch hp bn trong hoc tch ri.

S chung ca h thng v tuyn in cng vi thit b anten nh sau:



Cc yu cu i vi anten ca h RFID vi cc chip vi x l chotrc c th c tng hp li nh sau: o Phi hp tr khng ti u khi nhn cc tn hiu ln nht t u c cp ngun cho chip vix l. nh c th gn vo bt k i tng cn nhn dng no. Khng b nh hng bi cht liu ca i tng cn nhn dng nhm bo ton hiu sut. C biu bc x theo yu cu (ng hng, nh hng hay hnh bn cu). C cu trc c hc chc chn v bn Chi ph v cht liu cng nh sn xut thp

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o

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Di cc iu kin khc nhau cho cc ng dng RFID khc nhau, mt s cc kha cnh sau y cn phi xem xt khi thit k anten tag cho RFID:

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Bng tn: Loi anten s dng th ph thuc hon ton vo tn s hot

ng. Trong cc ngdng RFID LF v HF, cc anten cun xon c s dng ph bin nht thu nhn tn hiu t uc bng cch ghp cm ng. cc


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)tn s UHF v MWF, cc anten dipole, anten khe v cc anten mch di c s dng rng ri.

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Kch thc: Yu cu v kch thc ca th phi nh sao cho chng c th

gn c vo btk mt i tng cn nhn dng no (hp cc tng, th hnh l hng khng, th ID hay nhn in).Yu cu v kch thc l mt trong nhng thch thc khi thit k anten th cho RFID. Kch thcnh th s gii hn kh nng ghp cm ng ca anten vng c bit ti cc tn s LF v HF, v k chiu sut ca anten ti cc tn s UHF v MWF cng thp. V nh vy th ng nhin khong cca RFID cng s gim i ng k.

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Biu bc x: Mt s ng dng yu cu anten tag c nhng biu

bc x xc nh nh lng hng, nh hng hay hnh bn cu nhy vi i tng: Hot ng ca th s b thay i khi n c gn

trn mt i tngcn nhn dng (hp cc-tng) m trong li cha cc cht liu gy tn hao ln nh l chai nhacha nc hoc du hay cc thng kim loi. Do anten s phi c iu chnh ti hot ng tiu trn tng i tng c th hoc s phi c thit k sao cho n t b nh hng i vi cc loii tng k trn nht khi n c nh km vo

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Chi ph: Th RFID cn phi c chi ph cng thp cng tt i vi cc ng

dng cn nhiuth. iu ny cng c ngha l cu trc cng nh cht liu la chn lm anten s b hn ch, k c chip vi x l. Cc cht liu c s dng lm anten l di dn in v cht in mi. Cht in mi bao gm poliexte do, mm i vi LF v HF v cc bo mch in cng nh l FR4 cho cc ng dng UHF v MWF

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tin cy: Th RFID phi l mt thit b tin cy, c kh nng thch nghi

vi cc iu kinca mi trng nh nhit , m, p sut, v cc tc ng khc nhau khi gn nhn, in v dt mng


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)i vi cc h thng RFID trng xa, thit k anten th ng mt vai tr v cng quan trngtrong ton b h thng v c hiu sut v tin cy do th RFID th ng hot ng da vo trngin t m chng thu nhn c t cc u c.

Hnh: Nguyn l hot gia u c v th trong mt h thng RFID th ng trng xa.

ng Radio Trong h thng RFID, khong c b gii hn bi khong cch ln nht m ti th vn c th nhn c nng lng hot ng v phn hi tr li cho u c, v khong cch ln nht m ti u c vn c th thu c tn hiu ny ca th. Khong c ca


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)mt h thng RFID th nh hn so vi c hai khong cch ny. V c bn, nhy ca u c l cao, do khong c c xc nh bng khong cch t th ti u c. u c s pht i mt tn hiu RF lin tc cha ngun dng xoay chiu v tn hiu ng h ti th tn s sng mang m u c ang s dng. in p RF cm ng trn anten th c bin i thnh dng trc tip v cp ngun cho vi x l. Vi x l thng cn khong 1.2V t tn hiu ca u c. Sau vi x l s gi li thng tin cho u c bng cch bin i tr khng u vo RF phc. Tr khng thng c thay i gia hai trng thi khc nhau (phi hp v khng phi hp) iu ch tn hiu tn x tr li. Khi nhn c tn hiu iu ch ny, u c s gii m v nhn thng tin ca th. Xem xt h thng RFID di y:

Hnh:C ch hot ng truyn nng lng v thng tin cho cc h thng truyn nng lng trng xa. 2 Anten ch yu trong h thng l: 1. Anten ca Tag.


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)Anten ca tag c dng ly nng lng t tn hiu ca reader lm tng sinh lc cho tag hot ng, gi hoc nhn d liu t reader. Anten ny c gn vo vi mch. Anten l trung tm i vi hot ng ca tag. C th c nhiu dng anten, nht l vi tn s UHF v thit k mt anten cho mt tag ph hp vi nhiu ng dng cn phi c nh gn, thm m v tinh t. Chiu di anten tng ng vi bc sng hot ng ca tag. Mt anten lng cc bao gm mt dy dn in (chng hn ng) m n b ngt trung tm. Chiu di tng cng ca mt anten lng cc bng na bc sng tn s c dng nhm ti u nng lng truyn t tn hiu anten ca reader n tag. Mt anten lng cc bao gm hai cc, c th gim c nhy chun trc ca tag (tags alignment sensitivity). Reader c th c tag ny nhiu hng khc nhau. Folded dipole

Bao gm hai hoc nhiu dy dn in c ni song song nhau v mi dy bng na chiu di bc sng ca tn s c dng. Khi hai dy dn c cun vo nhau th folded dipole c gi l 2-wire folded dipole. Loi3-wirefolded dipole bao gm ba dy dn in c ni sng song nhau.



Chiu di anten ca tag thng ln hn nhiu so vi vi mch ca tag v vy n quyt nh kch c vt l ca tag. Mt anten c th c thit k da trn mt s nhn t sau y: Khong cch c ca tag vi reader. Hng c nh ca tag i vi reader. Hng ty ca tag i vi reader. Loi sn phm ring bit. Vn tc ca i tng c gn tag. phn cc anten ca reader. Nhng im kt ni gia vi mch ca tag v anten l nhng kt ni yu nht ca tag. Nu c bt k im kt ni no b hng th xem nh tag khng lm vic c hoc c th hiu sut lm vic gim ng k. Anten c thit k cho mt nhim v ring bit (nh gn tag vo mt hp) c th hot ng km hn khi thc hin nhim v khc (nh gn tag vo mt item ring l trong hp). Vic thay i hnh dng anten mt cch t ng (chng hn gim hoc gp n li) khng phi l mt tng hay v iu ny c th lm mt iu hng tag, a n hiu sut cng gim theo. Tuy nhin, mt s ngi bit h s phi lm g c th gim anten ca tag mt iu hng n (chng hn nh khoan mt l tag) v tht s lm tng kh nng c ca tag. Hin ti, anten ca tag c xy dng bng mt mnh kim loi mng (chng hn ng, bc hoc nhm). Tuy nhin, trong tng lai c th s in trc tip anten ln nhn tag, hp v sn phm ng gi bng cch s dng mt loi mc dn c cha ng, cacbon v niken.Hin nay vi mch cng ang c nghin cu xem n c th c in vi loi mc hay khng. Ci tin tng lai ny cho php in mt tag RFID nh m vcn n chi ph cho mt tag RFID c th gim di mc 0.5$ mt tag. Nu khngc kh nng in mt vi mch, th anten c in cng c th c gn vo mt vi mch to mt tag RFID hon chnh nhanh hn nhiu vic gn mt anten kim loi.

2. Anten ca reader



Reader truyn thng vi Tag thng qua anten ca reader, l mt thit b ring m n c gn vo reader ti mt trong nhng cng anten ca n bng cp. Chiu di cp thng gii hn trong khong 6-25 feet. Tuy nhin, gii hn ny c th khc nhau. Nh cp trn, mt reader c th h tr n 4 anten ngha l c 4 cng anten. Anten ca reader cng c gi l phn t kt ni ca reader v n to mt trng in t kt ni vi tag. Anten pht tn tn hiu RF ca my pht reader xung quanh v nhn p ng ca tag. V vy v tr ca anten ch yu l lm sao cho vic c chnh xc (mc d reader phi c t hi gn anten v chiu di cp ca anten b hn ch). Thm na l mt s reader c nh c th c anten bn trong. V vy trong trng hp ny v tr ca anten i vi reader bng 0. Ni chung anten ca RFID reader c hnh dng hp vung hoc ch nht. Anten phn cc Linear UHF ca Alien Technology Du vt ca anten(Antenna Footprint) Du vt anten ca reader xc nh phm vi c (c gi l read window) ca mt reader. Ni chung, du vt anten cng c gi l m hnh anten, c 3 min kch thc c hnh dng gn ging hnh elip hoc hnh cu nh ra trc anten. Trong min ny, nng lng ca anten tn ti, v vy reader c th c tag t trong min ny d dng. Hnh di y trnh by m hnh anten n gin nh th.


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)M hnh anten n gin Trn thc t th do c tnh ca anten, du vt ca anten khng c hnh dng n nh nh mt hnh elip m lun mo m, c ch nh ra. Mi ch nh ra b bao quanh bi min cht, min cht ny c gi l null.

Hnh sau trnh by minh ha m hnh anten nh th.

M hnh anten mo, nh S phn x tn hiu anten ca reader trn i tng chn sng RF gy ra multipath.Trong trng hp ny, sng RF b phn x ri rc c th ti anten ca reader khng ng thi theo nhng hng khc nhau. Mt s sng n c th cng pha (ngha l hp vi m hnh sng ca tn hiu anten gc). Trong trng hp ny, tn hiu anten gc tng khi cc sng ny p t vi cc sng gc lm tng mo dng. Hin tng ny c gi l nhiu c xy dng. Mt s sng c th n ngc pha nhau (ngha l ngc li vi m hnh sng anten gc). Trong trng hp ny tn hiu anten gc b hy khi hai dng sng ny p t vo nhau. Hin tng ny c gi l nhiu tiu cc. Kt qu l null. Hnh sau trnh by minh ha multipath



M hnh multipath

Tag c t ti mt trong nhng min nh ra s c c cn nu tag di chuyn sao cho n nm trong min cht bao quanh th khng th c tag c na. Chng hn t tag xa reader th khng th c tag nhng khi di chuyn (cng hng) li reader th c th c c tag, tuy nhin nu tag ny di chuyn hng khc th khng c c n. V vy vic c tag gn min nh ra khng ng tin cy. Khi t anten quanh phm vi c, lm sao khng ph thuc vo min nh ra tng ti a khong cch c l iu quan trng.Chin lc ti u nht l t bn trong min c hnh elip d c ngha l b qua mt vi feet phm vi c, nhng an ton vn hn. iu quan trng l xc nh du vt ca anten, du vt anten xc nh nhng ni m c th hoc khng th c tag. Nh sn xut c th quy nh du vt anten nh mt c im k thut ca anten. Tuy nhin, nn s dng thng tin nh mt nguyn tc ch o, v trn thc t du vt s khc ty mi trng hot ng. C th s dng k thut hon ton chnh xc nh phn tch tn hiu vch ra du vt anten. Phn tch tn hiu l o tn hiu t tag, s dng thit b nh my phn tch ph hoc my phn tch mng li truyn thanh nhng iu kin khc nhau (chng hn trong khng gian khng c rng buc, nhng hng tag khc nhau v trn nhng vt liu dn hoc vt liu ht thu). Nh vo vic phn tch cng tn hiu c th xc nh chnh xc du vt anten.

IV.

My ch Server - H thng phn mm

My chu l my vi tnh c dung chay cc phn mm trung gian v phn mm ng dung. My chu c nhim vu thu nhn, lu tr v x l cc d liu nhn c t cc thit bi oc the.


Cc thnh phn chnh trong h thng RFID (Tag Reader Anten My ch server)a. Phn mm trung gian (Middleware)Middleware phn mm ni h thng RFID vi mt h thng IT (Information Technology) qun l lung d liu. Phn mm trung gian l cc phn mm c s dng nhn v x l cc d liu th nhn c t cc my c chuyn ti cc phn mm qun tr th vin. y l mt thnh phn khng th thiu trong h thng RFID. Phn mm ny thng c xy dng v cung cp bi cc nh cung cp thit b RFID.

Phn mm ng dng (Application software)L cc phn mm c s dng x l v t ng ha cc cng vic ca mt c quan, t chc. Trong lnh vc th vin, phn mm ng dng chnh l cc phn mm th vin in t tch hp trong c lu thng tin v cc ti liu, bn c, qu trnh mn/tr, h thng kho m th vin qun l. Phn mm ny s nhn d liu c x l t phn mm trung gian phn tch. giao tip gia h thng qun tr th vin tch hp vi cc ng dng ca RFID ngi ta s dng chun SIP2 (Standard Interface Protocol, version 2) do 3M xy dng hoc NCIP (ANSI/NISO Z39.83 2002 Circulation Interchange), trong SIP 2 c s dng ph bin hn. Mi nh cung cp ng dng RFID s dng cc chun khc nhau cho ng dng ca mnh v d cng ty 3M s dng chun SIP 2.


Các thành phần chính trong hệ thống RFID(2)

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