Nghiên cứu nâng cao tỷ số s n của tín hiệu nhỏ từ cảm biến

» * BAO CAO TOM TAT Dcks ftii the measuring equipment, test of operation of the manufactured equipment in praxis such as determination of the deformalion of bridge, ihennal expansion and conUiiclion of specified materials Results - 01 research paper "On Several Correlation huegrnh of the DI.TS' published on the journal Condensed Matter 2003, cond-mat/0008207, Cornell University F-Prini 2003 - 01 research paper " PN sensor and appiicatiori" published on ihe Science and Technology Journal of the Thai Nguyen University, No (26), 2003 - 01 report on the 4"'-Vietnam Solid State Conference, Nui Coc 11/2003 '''Application of mechanico-magneto-eiectric sensor for measuremenl of the small movement.*f\ - Train 01 MSc thesis of MSc student Nguyen Huu Cuong, 2003 - Sample product "Small movement defection equipmenr presented at the P'Vielnam TECHMART Fair 10/2003 (Giang Vo, Ha Noi) MUC LUC MdDAU Chuangl-THUTfNHlgUNHO 1.1 Tin hifiu nho 1.1.1 Dac trung cua tin hi6u 1.1.2 Dac trimg cua nhifiu 1.1.3 Dac trung cua lap nOi 1.2 Tfnh chat vk dac trimg co ban cila tap n6i 1.2.1 Susinhtapn6i chuyen d6i khftng dien sang dien 1.2.2 Phan loai m6t stf tapn6i cac linh kien cam bien 1.2.3 M6l stfdi^m luu y viSc danh gia tap nOi 1.2.4 Tap am b6 khud'ch dai nhi6u iSng 1.3 NhiSu phep thirc nghiSm Chuong - M O T SO PHUONG PHAP LAM TANG T Y SO S/N 2.1 Ty s6 tin hieu iren tap S/N 2.1.1 -Mdd^u 2.1.2 - H6 s6' tap am F 2.2 MOl s6' phuong phap nang cao ly s6 S/N 2.2.1 -Trung philng tin hifiu, loai trOrnhieu 2.2.2 - Phuong phap khufich dai vi sai (KDVS) 2.2.3 - Phuong phap bien dieu I 2 3 11 11 II 11 12 12 13 16 2.2.4 - Lpc xin sd'nang cao ly sO' ' ^ 20 2.2.5 - Chon Ipc ihofi gian (Boxcar) 2.2.6 - Chon pha (Lock-in) 21 26 : Chuong - CAM BIEN DICH CHUYEN NIIO DUNG NGUYEN LY VI SAI 3.1 Dinh ngliTa va dac trung chung cua cam biC'n 3.2 M6 hinh ca'u tao mOt tliiC't bi pliat hiCn dich chuyOn nho 3.3 B6titfpnhan dich chuyCn 3.4 BO bie'n thtfvi sai 3.4.LBi6'n the'vi sai lOi kh6ng khf 32 32 33 VI 34 34 3.4.2 Bie'n the'vi sai loi Fcrilc 3.^ 3.4.3 Bien the vi sai khung dong 37 3.5 BO dao dong diCn tij 3.6 BO xirly tin hicu 3S 42 3.6.1.Mach chinh luu ntjra song 3.6.2 Mach chinh luu loan song 3.6.3 Tai ciia bo chinh luu 3.6.4 Khau Ipc b6 chinh luu 3.7 BO khu&h dai va chi thi 3.7.1 BO khu^fch dai 3.7.2 B6 hi^n ihi 42 43 44 45 46 46 48 Chuong - KfiT QUA THUC NGHTEM vA BIEN LUAN 4.1 Xijr 1^ s6li6u thuc nghifim bang phuong ph^ph6i quy tuyen tmh 4.2 Cac phep thuc nghidm 4.2.1 Xac dinh dac trung E =E(x)ciia thi^'t bi 4.2.2 xac dinh sirphu thuOccualm hieu E theo vi tri ciia vat 4.2.3 SiJr dung Ihi^t bi nhu mOl can dien tu 4.2.4 Sijr dung ihie'l bi dO vong ciia mOt m6 hlnh cay c^u 4.2.5 Ki^m nghifim sugian nd vl nhiei ciia cac ihanh vat lieu 4.3 Bien luan 51 51 52 52 58 62 64 66 68 IC^LUAN TAI LI6UTHAMKHAO 71 72 CHU'dNG THUTfNHI$UNH6 1.1 Tin hi^u n h o Trong can ph6ng yen iTnh ta c6 Ihd nghe ro am phai tir mot cliiec may quay bang c6 cOng sua'l loa chi vao cd 0,1W Neu dem may d6 nghe tren mOt chuye'n tau hoi ihl am ihanh c5n nghe hdu nhu bi Iftn vao tie'ng gi6 n't, tieng xlnh xich ciia banh tku tren duorng ray Khi xem v6 tuye'n Iruyen hinh, ne'u anten chinh lot thi hinh va tieng ro neu anten khOng lO't thi hinh anh bi lan dam nhieu, am re kho nghe nhiJng viing sau vung xa, c6 khue'ch dai tin hicu tu anlen len nhiOu Ian ma ngu5i la v5n khOng thd nhin ro dupe hinh iinh tren man huih vo luyen Cau hoi dat day la: nao Ihl tin hieu dupe xem la dii Ion? Khi nao tm hieu dupe xem la nho? Khai niem \6u nho cua tin hieu la tuyet doi hay urong dO'i? Xet mOt he thu tin hiCu ba't ky: + Tin hieu nho la tin hieu mk cudng dO ciia no tuoiig duong nhu cuong d6 cua nhiSu \k tap + DO lofn hay nho ciia tin hieu chi la tuong doi Nhu vay, nhifiu tin hieu chi c6 bien dO co vai ciuic micro vOn cung dupe xem la Idn, co tin hieu co hang vOn cung bi xem la niio Van de la a cho so sanh luong quan giGa tin hieu va tap nhieu sao? VI the', ta cung co the noi: + Tin hieu dupe gpi la nho cOng sua'l ti'n hieu liron;^ duong vol cong suat cua nhieu, tap + Thu tin hieu nho co dat chA't lupng cao hay khOng plui iluipc \ao cong suat tO'i Ihidu ma ta thu dupe, khOng bi lan v6i lap nhieu Luu y : Cdn phan biel cac khai niem: tin hieu - nhiSu - lap nOi T/n hicu: dai lupng ciin Ihu Nbidu: thiing giang tir ben ngoai anh liirong vao he tini Tap noi: nhung ihang giang xual liiOn ironi! noi lai he nuiv llui /././ Dfc tnmgda dahi^u Thudng thi ta bi^t trudc m6t s6' ihOng tin chii dOng vd lin hieu nhu: + ThOng tin v6 tea dO khOng gian: MOt tin hieu co ih^ dupe phal lir mOt diem nao d6 khOng gian Ta c6 th^ di; dodn mOl s6 ihOng sO' ciia didm loa ciu nhu khoang cdch (r), cdcgdc (^,^) + ThOng tin v^ mi^n idn s^ ciia tin hieu (f) + ThOng tin v6 Ihdi gian xay tin hieu (t) Vi du: MOt dai phal ihanh co tSn sO' song mang f^, nao Dai chi phal song tir 6h sang de'n niia dem, nghi tieng Gpi tin hieu cin thu tir dai phal la So, la co the bieu dien tin hieu ihu dupe tai mdy thu S dang: S = So.A(t).B(f) ^ fO Trong do: ^ B A=^ I t6 Oh + 6h IG 6h -^ 24h f^f„ f = f (May chi thu dupe ifn hieu chinh f = fo) Nhu vay, nh6 bi^t tru6c mOt s6 thOng lin v^ iin hieu ma la thu dupe ti'n hieu ro rang dim lap am 1.1.2 Die tnmg da nhiSu Khdc v6i tin hieu, dac trung ciia nhieu phan 16n khong biet truoc vl chung la nhOng thang giang, bie'n cO' ngau nhien tir ben ngoai dua vao he thu ciia ta (chfing han nhu: nhieu cac dai phal song, cac thiel bi dijng cong nghicp va sinh boat, nhi^u chdp set quy^n va cac bijfc xa tir vu iru ) VI the', ne'u nhidu c6 dac trung giO'ng tm hieu thi la khong bict dupe la nhieu Nhieu Irudng hpp khong phan bict dupe nen iiguoi phai chap nliAn nhieu la tin hieu Chi nao ta bie't dupe si; khac giua tin hicu va nhieu ihi mofi CO the tlm each lach nhieu khoi tin hieu Vl du: May canh bao Irpm dOl nhap sir dung nguycn ly llui hue xa lion