Matsayin Antenna & Daidaita

Matsayin sanya antenna shine abu na #1 a cikin aikin tsarin RFID. ya fi mahimmanci fiye da ƙwarewar tag ko ƙarfin mai karatu. Mai karatu na $5,000 da antennas da ba su da kyau zai yi ƙasa da mai karatu na $500 da antennas da aka sanya da kyau. Manufar ita ce ƙirƙirar yankin karatu da aka fayyace sosai (sararin 3D inda ake karanta tag ɗin da tabbatacce) yayin rage karatun da ba a so daga wajen yankin da ake nufi.

Misalin ainihi: motsa antenna na ƙofar dock daga tsayin 2.5m zuwa 2.0m da karkasa shi ƙasa da digiri 15° ya inganta ƙimar karatu daga 87% zuwa 99.2% a babban aikin logistik. Ƙananan canje-canje a matsayi suna haifar da manyan bambance-bambancen aiki saboda ƙarfin siginar RF yana bin dokar ƙa'idar murabba'in ƙasa. ninka nisan yana nufin ƙarfin sigina ya ragu zuwa ¼.

Polarisation na antena yana ƙayyade ƙudurin igiyoyin lantarki. Wannan ɗaya ne daga cikin muhimman shawara a cikin ƙirar tsarin saboda yana sarrafa kai tsaye ko alamomin a cikin ƙuduri daban‑daban za su iya karantawa.

Yankin karatu shine ƙimar 3D inda za a iya karanta tag ɗin da tabbatacce. Yana da siffar kibiya ko lobe da ke faɗa daga fuskar antenna, tare da girma da aka ƙayyade ta hanyar haɓakar antenna, ƙarfin TX na mai karatu, da ƙwarewar tag. Antenna mai 9 dBic a ƙarfin 30 dBm tare da tag na NXP UCODE 9 (-22.1 dBm ƙwarewa) yana ƙirƙirar yankin karatu kusan mita 8–10 zurfi da mita 3–4 faɗi a ƙarshen nesa.

Near-field vs Far-field: Antennan UHF RFID suna aiki a yankuna biyu. Near-field (cikin kusan 35cm a 920 MHz) yana amfani da haɗin maganadisu don karatu ƙanana, masu sarrafawa. Ya dace da tashoshin POS inda kake son karanta kawai abubuwan da ke kan tebur. Far-field (beyond 35cm) yana amfani da yaduwar electromagnetic don mafi yawan aikace-aikacen RFID. Antennan near-field an ƙera su musamman da yankunan karatu da aka iyakance don ƙirƙirar matakin abu da point-of-sale.

Jagororin ƙarfin: 33 dBm don iyakar nisa (~10m, ƙofofin dock). 30 dBm don nisa na al'ada (~6–8m, amfani gaba ɗaya). 25 dBm don nisa matsakaici (~3–5m, belun conveyor). 20 dBm don nisa ƙanƙanta (~1–2m, point-of-sale). 15 dBm don near-field (~0.5m, masu karanta shelf). Kullum a fara da ƙarfin ƙasa sannan a ƙara har sai an cimma ƙimar karatu da ake nufi. Ƙarfin da ya wuce yana haifar da karatun da ba a so.

33 dBm → ~10m   dock doors, max range
30 dBm → ~6-8m  general warehouse
25 dBm → ~3-5m  conveyor belts
20 dBm → ~1-2m  point-of-sale
15 dBm → ~0.5m  shelf / near-field

VSWR (Voltage Standing Wave Ratio) yana auna yadda ƙarfin wuta ke watsawa daga mai karatu zuwa antena. Daidaito cikakke shine 1:1 (duk ƙarfin wuta ya fita). Duk abin da ya fi 2:1 yana nufin ƙarfin wuta mai yawa yana komawa ga mai karatu, yana rage aiki kuma zai iya lalata PA amplifier a tsawon lokaci. Mafi yawan antena na RFID na kasuwanci suna samun 1.2–1.5:1 VSWR a duk faɗin band ɗin aiki.

Matsalolin VSWR gama gari: Kebul ɗin RF da aka lalata ko ya lankwasa (maye gurbin idan VSWR ya wuce 2:1). Nau'in haɗin da ba daidai ba (yi amfani da RP-TNC ko SMA kamar yadda aka ƙayyade). Antenna da aka ɗora kai tsaye a kan ƙarfe ba tare da spacer ba (yi amfani da standoffs 15mm+). Shigar ruwa a haɗin waje (yi amfani da RP-TNC mai kariya da takalmin ruwa). Tsawon kebul da ya wuce mita 10 ba tare da kebul mai ƙarancin asara ba (yi amfani da LMR-400 ko daidai da shi don gudu sama da mita 5).

Kullum a tabbatar da VSWR a duk faɗin band ɗin aiki (920–925 MHz don Vietnam). Antenna na iya nuna VSWR mai kyau 1.2:1 a 920 MHz amma ya sauka zuwa 2.5:1 a 925 MHz, wanda ke nufin ƙarancin aiki a rabi na tashoshin FHSS ɗinku.

Yawancin aiwatar da samarwa suna amfani da antena da yawa ga kowane mai karatu. Mai karatun Nextwaves yana tallafawa har zuwa tashoshin antena 32. Muhimman abubuwa: Tazara. yawanci 1–2 mita tsakanin ƙofofin doka, tare da overlap na 15–20% don cikakken rufe. Kusan ɗora. 15–45° karkatarwa zuwa ciki don aikace‑aikacen portal don mayar da hankali kan yankin karatu a ƙofar. Tsarin antena. mai karatun yana canza tsakanin antena ta atomatik don hana watsawa a lokaci guda daga yankuna masu overlap.

Misalin daidaita portal (ƙofar doka): Sanya antena 4. 2 a kowanne gefe na ƙofar a tsayin 1.5m da 2.5m, karkatar da 30° zuwa ciki. Yi amfani da polarisation linear da aka nufi fuskar pallet. Saita mai karatu zuwa Session S2 tare da Q=6 don manyan motar forklift masu sauri. Wannan yana ba da ƙimar karatu sama da 99% akan lodin pallet na al'ada na 48–100 akwatunan da aka yi alama.

Misalin ramin conveyor: Sanya antena 4 masu polarisation circular a tsari murabba'i a kewaye da belti. sama, ƙasa, hagu, dama. Saita Session S1 don karatun wucewa guda. Ƙarfi a 25 dBm don iyakance yankin karatu zuwa ramin. Wannan yana hana karanta alama a kan conveyors na makwabta.

CONFIGURE_ANTENNA_ENABLE payload (4 bytes):

Ports 1-4:    0x0F 0x00 0x00 0x00  (0b00001111)
Ports 1,3:    0x05 0x00 0x00 0x00  (0b00000101)
Port 1 only:  0x01 0x00 0x00 0x00  (0b00000001)

Bit 0=ANT1  Bit 1=ANT2  ...  Bit 31=ANT32

Fuskar ƙarfe ita ce tushen tsangwama na #1 a manyan wuraren ajiya. Suna madauki siginar RF, suna haifar da yankunan matattu da tsangwama mai hanyoyi da yawa. Magani: saka antena a kan ƙafafun da ba su da ƙarfe ko amfani da tazara na 50mm+ daga ƙayyadaddun ƙarfe. Daidaita antena don babban ƙaho ya guje wa bango ko rukunin ƙarfe kai tsaye.

Ruwa da sauran ruwa suna shanye igiyoyin rediyon UHF sosai. Kwandon kwalaben ruwa tsakanin antena da pallet da aka yi alama na iya toshe karatu gaba ɗaya. Magani: sanya antena don hanyar RF ta guje wa kwantena na ruwa, ko ƙara ƙarfin wuta da 3–6 dB don daidaita asarar shanyewar.

Sauran masu karatu da ke aiki a kusa na iya haifar da tsangwama. Yanayin Mai Karatu Mai Cunkoso (DRM) da FHSS na taimakawa, amma ƙarin matakai sun haɗa da: saita maskin tashoshi da ba su overlap ba tsakanin masu karatu masu makwabta, amfani da antena masu shugabanci don rage yaduwa, da aiwatar da jadawalin TDMA idan middleware ɗinku yana goyan bayan sa.

Riƙe antena aƙalla 1m daga fitilun fluorescent (tushen hayaniyar RF) da aƙalla 2m daga wuraren samun Wi‑Fi. Duk da cewa Wi‑Fi yana aiki a 2.4/5 GHz (dabam da UHF 920 MHz), kayan da ba su da kariya sosai na iya haifar da harmonics na broadband.