Uma isekethe ye-analog (RF) kanye nesekhethi yedijithali (microcontroller) zisebenza kahle ngazinye, kodwa uma usubeke kokubili ebhodini lesifunda elifanayo futhi usebenzisa ukunikezwa kwamandla okufanayo ukuze kusebenze ndawonye, lonke uhlelo lungase lungazinzi.Lokhu kungenxa yokuthi isignali yedijithali ivamise ukushwiba phakathi komhlaba kanye namandla akhona (usayizi 3 V), futhi isikhathi sifushane kakhulu, ngokuvamile izinga le-ns.Ngenxa ye-amplitude enkulu kanye nesikhathi esincane sokushintsha, lezi zimpawu zedijithali ziqukethe inani elikhulu lezingxenye ze-high-frequency ezizimele ngaphandle kwemvamisa yokushintsha.Engxenyeni ye-analogi, isignali esuka ku-antenna tuning loop iye engxenyeni eyamukelayo yedivayisi engenantambo ngokuvamile ingaphansi kuka-1μV.
Ukuhlukaniswa okunganele kwemigqa ebucayi kanye nemigqa yesignali enomsindo kuyinkinga evamile.Njengoba kushiwo ngenhla, amasignali edijithali ane-swing ephezulu futhi aqukethe inani elikhulu lama-harmonics aphezulu-frequency.Uma izintambo zesiginali yedijithali ku-PCB iseduze namasiginali e-analog azwelayo, ama-harmonics emvamisa ephezulu angase ahlanganiswe adlule.Ama-node azwelayo wamadivayisi e-RF imvamisa iyisekhethi yesihlungi se-loop ye-phase-locked loop (PLL), i-voltage yangaphandle elawulwa yi-oscillator (VCO) inductor, isignali yereferensi yekristalu kanye nesiphetho se-antenna, futhi lezi zingxenye zesekhethi kufanele zelashwe. ngokunakekelwa okukhethekile.
Njengoba isignali yokufaka/yokukhiphayo inokujikajika kwe-V embalwa, amasekhethi edijithali ngokuvamile ayamukeleka kumsindo wokuphakelwa kwamandla (ngaphansi kuka-50 mV).Amasekhethi e-analog ayazwela emsindweni wokunikezwa kwamandla, ikakhulukazi kuma-voltage e-burr namanye ama-harmonics aphezulu.Ngakho-ke, umzila kagesi ebhodini le-PCB eliqukethe amasekhethi e-RF (noma amanye ama-analog) kufanele acophelele kakhulu kunezintambo ezisebhodini lesekhethi yedijithali evamile, futhi umzila ozenzakalelayo kufanele ugwenywe.Kufanele futhi kuqashelwe ukuthi i-microcontroller (noma enye isekethe yedijithali) izomunca ngokuzumayo iningi lamanje isikhathi esifushane phakathi nomjikelezo wewashi wangaphakathi ngamunye, ngenxa yomklamo wenqubo ye-CMOS yezilawuli ezincane zesimanje.
Ibhodi lesekhethi ye-RF kufanele lihlale linesendlalelo somugqa ophansi oxhunywe ku-electrode eyinegethivu yokuphakelwa kukagesi, okungase kukhiqize izenzakalo ezingavamile uma zingaphathwa kahle.Lokhu kungase kube nzima kumklami wesifunda sedijithali ukuthi akuqonde, ngoba amasekhethi amaningi edijithali asebenza kahle ngisho nangaphandle kongqimba oluyisisekelo.Ku-RF band, ngisho nocingo olufushane lusebenza njenge-inductor.Uma kubalwa, i-inductance per mm ubude icishe ibe ngu-1 nH, futhi ukusabela kwe-inductive komugqa we-PCB ongu-10 mm ku-434 MHz cishe ku-27 Ω.Uma ungqimba olungaphansi lungasetshenziswa, imigqa eminingi yomhlabathi izoba yinde futhi isifunda ngeke siqinisekise izici zokuklama.
Lokhu kuvame ukunganakwa kumasekhethi aqukethe amaza omsakazo nezinye izingxenye.Ngaphezu kwengxenye ye-RF, kuvame ukuba namanye amasekethe e-analog ebhodini.Isibonelo, izilawuli ezincane eziningi zineziguquli ze-analog-to-digital (ADCs) ezakhelwe ngaphakathi ukuze zilinganise okokufaka kwe-analog kanye nogesi webhethri noma amanye amapharamitha.Uma uthi lwe-RF transmitter luseduze (noma luvuliwe) le PCB, isignali ephumayo yamaza aphezulu ingase ifinyelele okokufaka kwe-analog kwe-ADC.Ungakhohlwa ukuthi noma yimuphi ulayini wesekethe ungathumela noma wamukele amasiginali e-RF njengothi.Uma okokufaka kwe-ADC kungacutshungulwanga kahle, isignali ye-RF ingase izijabulise ngokokufaka kwe-ESD diode ku-ADC, kubangele ukuchezuka kwe-ADC.
Konke ukuxhumeka kungqimba lomhlabathi kufanele kube kufushane ngangokunokwenzeka, futhi imbobo yomhlabathi kufanele ibekwe (noma isondele kakhulu) iphedi yengxenye.Ungalokothi uvumele amasiginali amabili aphansi ukuthi abelane ngembobo yomhlabathi, engabangela ukungqubuzana phakathi kwamaphedi amabili ngenxa yokuphazamiseka kokuxhuma kwembobo.I-decoupling capacitor kufanele ibekwe eduze kwephinikhodi ngangokunokwenzeka, futhi i-capacitor decoupling kufanele isetshenziswe kuphini ngalinye elidinga ukuhlukaniswa.Ukusebenzisa ama-capacitor e-ceramic asezingeni eliphezulu, uhlobo lwe-dielectric luyi-"NPO", "X7R" futhi lusebenza kahle ezinhlelweni eziningi.Inani elifanele le-capacitance ekhethiwe kufanele libe ngendlela yokuthi uchungechunge lwayo lwe-resonance lulingane nobuningi besignali.
Isibonelo, ku-434 MHz, i-SMD-mounted 100 pF capacitor izosebenza kahle, kule mvamisa, ukusabela kwe-capacitive kwe-capacitor cishe ku-4 Ω, futhi ukusabela kwe-inductive kwembobo kusebangeni elifanayo.I-capacitor kanye nembobo kuchungechunge kwenza isihlungi senotshi semvamisa yesignali, esivumela ukuthi sinqanyulwe ngempumelelo.Ku-868 MHz, ama-capacitor angu-33 p F ayinketho ekahle.Ngokungeziwe ku-RF ehlukanisiwe yenani elincane le-capacitor, i-capacitor yenani elikhulu kufanele futhi ibekwe entanjeni yamandla ukuze kufinyezwe imvamisa ephansi, ingakhetha i-ceramic engu-2.2 μF noma i-tantalum capacitor engu-10μF.
I-Star wiring iyindlela eyaziwayo ekwakhiweni kwesekethe ye-analog.Izintambo zenkanyezi - Imojula ngayinye ebhodini inolayini wayo wamandla osuka endaweni yamandla kagesi evamile.Kulokhu, izintambo zenkanyezi zisho ukuthi izingxenye zesekhethi zedijithali neze-RF kufanele zibe nezintambo zazo zamandla, futhi lezi zintambo zikagesi kufanele zihlukaniswe ngokuhlukana eduze ne-IC.Lokhu ukuhlukaniswa kwezinombolo
Indlela esebenzayo yomsindo wengxenye kanye nogesi ophuma engxenyeni ye-RF.Uma amamojula anomsindo omkhulu abekwe ebhodini elifanayo, i-inductor (ubuhlalu obuzibuthe) noma ukumelana okuncane (10 Ω) kungaxhunywa ochungechungeni phakathi kolayini wamandla kanye nemojula, kanye ne-tantalum capacitor okungenani engu-10 μF. kufanele isetshenziswe njengokunqanyulwa kokuphakelwa kwamandla kulawa mamojula.Amamojula anjalo angabashayeli be-RS 232 noma izilawuli zokuhambisa amandla ezishintshayo.
Ukuze unciphise ukuphazamiseka okuvela kumojula yomsindo kanye nengxenye ye-analog ezungezile, ukuhlelwa kwemodyuli ngayinye yesifunda ebhodini kubalulekile.Amamojula azwelayo (izingxenye ze-RF nezinti) kufanele ngaso sonke isikhathi agcinwe kude namamojula anomsindo (ama-microcontrollers kanye namashayeli e-RS 232) ukuze kugwenywe ukuphazamiseka.Njengoba kushiwo ngenhla, amasignali e-RF angabangela ukuphazamiseka kwamanye amamojula esekethe e-analog abucayi njengama-ADC uma ethunyelwa.Izinkinga eziningi zenzeka kumabhendi okusebenza aphansi (afana no-27 MHz) kanye namazinga aphezulu okukhipha amandla.Kuwumkhuba omuhle wokuklama ukuqaqa amaphuzu azwelayo nge-RF decoupling capacitor (100p F) exhunywe phansi.
Uma usebenzisa izintambo ukuxhuma ibhodi le-RF kusekethe yedijithali yangaphandle, sebenzisa izintambo ezisontekile.Ikhebula lesignali ngayinye kufanele ihlanganiswe nentambo ye-GND (DIN/ GND, DOUT/ GND, CS/GND, PWR _ UP/ GND).Khumbula ukuxhuma ibhodi lesekhethi ye-RF kanye nebhodi lesifunda lesicelo sedijithali ngekhebula ye-GND yekhebula elisontekile, futhi ubude bekhebula kufanele bube bufushane ngangokunokwenzeka.Izintambo ezinikeza amandla ibhodi le-RF kumele futhi zisontelwe nge-GND (VDD/ GND).
