Ob lub teeb liab thiab suab nrov hauv kev sib txuas lus tuaj yeem suav tias yog cov txheej txheem random uas hloov nrog lub sijhawm.
Cov txheej txheem random muaj cov yam ntxwv ntawm qhov sib txawv ntawm qhov sib txawv thiab lub sijhawm ua haujlwm, uas tuaj yeem piav qhia los ntawm ob qhov sib txawv tab sis zoo sib xws: (1) Cov txheej txheem random yog cov txheej txheem ua haujlwm tsis kawg; (2) Cov txheej txheem random yog cov txheej txheem random variables.
Cov khoom txheeb cais ntawm cov txheej txheem random tau piav qhia los ntawm lawv qhov kev faib ua haujlwm lossis qhov ua tau qhov ntom ntom ntom ntom. Yog tias cov khoom txheeb cais ntawm cov txheej txheem random yog ywj siab ntawm lub sijhawm pib, nws yog hu ua cov txheej txheem nruj nruj.
Numerical nta yog lwm txoj hauv kev zoo los piav txog cov txheej txheem random. Yog hais tias lub ntsiab lus ntawm tus txheej txheem yog tas mus li thiab autocorrelation muaj nuj nqi R (t1, t1 + τ) = R (T), cov txheej txheem yog hais tias yuav generalized nyob ruaj ruaj.
Yog hais tias tus txheej txheem yog nruj me ntsis nyob ruaj ruaj, ces nws yuav tsum broad nyob ruaj ruaj, thiab vice versa tsis tas yuav muaj tseeb.
Tus txheej txheem yog ergodic yog tias nws lub sij hawm nruab nrab yog sib npaug rau qhov sib npaug ntawm qhov nruab nrab.
Yog hais tias tus txheej txheem yog ergodic, ces nws tseem nyob ruaj ruaj, thiab vice versa tsis tas muaj tseeb.
Lub autocorrelation muaj nuj nqi R (T) ntawm ib tug generalized nyob ruaj ruaj txheej txheem yog ib tug txawm muaj nuj nqi ntawm lub sij hawm sib txawv r, thiab R (0) yog sib npaug zos rau tag nrho cov nruab nrab hwj chim thiab yog tus nqi siab tshaj ntawm R (τ). Lub zog spectral ntom ntom Pξ (f) yog Fourier hloov pauv ntawm autocorrelation muaj nuj nqi R (ξ) (Wiener - Sinchin theorem). Qhov khub ntawm kev hloov pauv no txiav txim siab qhov hloov pauv kev sib raug zoo ntawm lub sijhawm sau npe thiab zaus sau npe. Qhov tshwm sim ntawm kev faib tawm ntawm Gaussian txheej txheem ua raws li kev faib tawm ib txwm muaj, thiab nws cov lus piav qhia ua tiav tsuas yog yuav tsum muaj nws tus lej xwb. Qhov kev faib tawm ib-dimensional probability tsuas yog nyob ntawm qhov nruab nrab thiab qhov sib txawv, thaum qhov kev faib tawm ob-dimensional probability nyob ntawm qhov kev sib raug zoo. Cov txheej txheem Gaussian tseem yog txheej txheem Gaussian tom qab kev hloov pauv. Kev sib raug zoo ntawm qhov kev faib tawm ib txwm muaj thiab Q(x) lossis erf(x) muaj nuj nqi yog qhov tseem ceeb hauv kev tshuaj xyuas cov suab nrov ntawm kev sib txuas lus digital. Tom qab cov txheej txheem random nyob ruaj ruaj ξi(t) dhau los ntawm txoj kab nruab nrab, nws cov txheej txheem tso zis ξ0(t) kuj ruaj khov.
Cov yam ntxwv ntawm cov txheej txheem nqaim-band random thiab sine-yoj ntxiv rau nqaim-band Gaussian suab nrov yog tsim nyog rau kev soj ntsuam ntawm fading multipath channel hauv kev hloov kho / bandpass system / wireless kev sib txuas lus. Rayleigh distribution, Rice tis thiab ib txwm faib yog peb qhov kev faib tawm hauv kev sib txuas lus: lub hnab ntawv ntawm sinusoidal carrier signal ntxiv rau nqaim-band Gaussian suab nrov yog feem ntau Rice faib. Thaum lub teeb liab amplitude loj, nws nyhav rau ib txwm faib. Thaum lub amplitude me me, nws yog kwv yees li Rayleigh faib.
Gaussian dawb suab nrov yog cov qauv zoo tshaj plaws los soj ntsuam cov suab nrov ntxiv ntawm cov channel, thiab lub suab nrov tseem ceeb hauv kev sib txuas lus, suab nrov thermal, belongs rau hom suab nrov. Nws cov txiaj ntsig ntawm ob lub sijhawm sib txawv tsis sib xws thiab tsis muaj kev txheeb cais. Tom qab lub suab nrov dawb dhau los ntawm lub kaw lus tsis txwv, qhov tshwm sim yog suab nrov band-limited. Low-pass dawb suab nrov thiab band-pass dawb suab nrov yog muaj nyob rau hauv theoretical tsom xam.
Cov saum toj no yog "random txheej txheem ntawm kev sib txuas lus" tsab xov xwm coj los rau koj los ntawm Shenzhen HDV Phoelectron Technology LTD., thiab HDV yog lub tuam txhab tshwj xeeb hauv kev sib txuas lus kho qhov muag raws li cov khoom siv tseem ceeb, lub tuam txhab tus kheej tsim: ONU series, optical module series,OLT series, transceiver series yog kub series ntawm cov khoom.
