Zitsanzo za Mafunso Okhudza Kukambirana za Mafunde a Radio
Mafunde a wailesi ndi mtundu wa ma radiation amagetsi omwe amagwira ntchito mu mauthenga opanda zingwe. Ndi ma frequency kuyambira pa kilohertz (kHz) ochepa mpaka gigahertz (GHz) angapo, mafunde a wailesi amagwiritsidwa ntchito m'njira zosiyanasiyana—kuyambira pa wailesi ndi wailesi yakanema mpaka machitidwe olumikizirana a m'manja. M'nkhaniyi, tikambirana zitsanzo za mafunde a wailesi ndi mafotokozedwe awo kuti timvetse mfundo ndi momwe mafundewa amagwiritsidwira ntchito pa moyo watsiku ndi tsiku.
Chitsanzo Funso 1: Kuchuluka kwa Mafunde ndi Kutalika kwa Mafunde
Funso:
Siteshoni ya wailesi imatumiza mafunde a wailesi pa liwiro la 100 MHz. Werengani kutalika kwa mafunde. (Liwiro la kuwala ndi 3 x 10^8 m/s.)
Kukambirana:
Mafupipafupi (f) ndi kutalika kwa mafunde (λ) a mafunde a electromagnetic amagwirizana ndi liwiro la kuwala (c) kudzera mu equation:
\[ c = f \times \lambda \]
Kumene:
– \( c \) = liwiro la kuwala (3 x 10^8 m/s)
– \( f \) = pafupipafupi (100 MHz kapena 100 x 10^6 Hz)
– \( \lambda \) = kutalika kwa nthawi (kupezeka)
Kuchokera pa equation yomwe ili pamwambapa, kutalika kwa mafunde kumatha kuwerengedwa ndi:
\[ \lambda = \frac{c}{f} \]
Kotero:
\[ \lambda = \frac{3 \times 10^8}{100 \times 10^6} = 3 \ \text{meter} \]
Chifukwa chake, kutalika kwa mafunde a pafupipafupi ya 100 MHz ndi mamita atatu.
Chitsanzo Funso 2: Mphamvu Yotumizira ndi Mphamvu
Funso:
Chotumizira wailesi cha ma watt 50 chimatulutsa mafunde a wailesi mozungulira (mofanana mbali zonse). Werengani mphamvu ya mafunde a wailesi pamtunda wa mamita 10 kuchokera pa chotumizira.
Kukambirana:
Mphamvu (I) ya mafunde otulutsidwa ndi isotropically ikhoza kuwerengedwa ndi:
\[ I = \frac{P}{A} \]
Kumene:
– \( P \) = mphamvu yotumizira (50 watts)
– \( A \) = malo ozungulira mlengalenga (4πr^2)
Pa mtunda (r) = mamita 10, malo ozungulira mpira ndi awa:
\[ A = 4\pi (10)^2 = 400\pi \]
Kotero:
\[ I = \frac{50}{400\pi} = \frac{1}{8\pi} \ \text{watt/m}^2 \]
Kotero, mphamvu ya mafunde a wailesi pamtunda wa mamita 10 kuchokera pa chotumizira ndi \( \frac{1}{8\pi} \) watt/m².
Chitsanzo Funso 3: Bandwidth ndi Channel Capacity
Funso:
Njira yolumikizirana imakhala ndi bandwidth ya 20 MHz. Ngati mukugwiritsa ntchito modulation ya QPSK (Quadrature Phase Shift Keying), kodi mphamvu yayikulu ya njirayo ndi yotani?
Kukambirana:
Kusintha kwa QPSK kuli ndi magawo anayi osiyanasiyana, kotero kumatha kutumiza ma bits awiri pa chizindikiro chilichonse panthawi imodzi.
Chiwerengero cha zizindikiro pa sekondi iliyonse chomwe bandwidth ya 20 MHz imatha kuthana nacho ndi:
\[ \malemba{Chizindikiro} = 20 \nthawi 10^6 \ \malemba{chizindikiro/sekondi} \]
Popeza QPSK imatumiza ma bits awiri pa chizindikiro chilichonse, mphamvu kapena chiwerengero cha ma bits pa sekondi iliyonse (bitrate) ndi:
\[ \text{Bitrate} = 20 \times 10^6 \times 2 = 40 \ \text{Mbps} \]
Chifukwa chake, mphamvu yayikulu ya njira ndi 40 Mbps.
Chitsanzo Funso 4: Kusokoneza ndi Kusokoneza
Funso:
Chotumiza wailesi pa ma frequency a 101.1 MHz chimakumana ndi kusokonezedwa ndi chotumiza china pa ma frequency a 101.3 MHz. Werengani ma frequency otsatirawa.
Kukambirana:
Mafupipafupi a beat \( f_{beat} \) amapezeka chifukwa cha kusiyana pakati pa ma close frequency awiri ndipo amatha kuwerengedwa ndi:
\[ f_{beat} = |f_1 – f_2| \]
Kumene:
– \( f_1 \) = 101.1 MHz
– \( f_2 \) = 101.3 MHz
Kotero:
\[ f_{beat} = |101.1 – 101.3| = | -0.2 | = 0.2 \ \malemba{MHz} \]
Chifukwa chake, ma frequency otsatirawa ndi 0.2 MHz.
Chitsanzo Funso 5: Doppler Effect mu Mafunde a Radio
Funso:
Siteshoni ya wailesi imatumiza mauthenga pa liwiro la 95 MHz. Ndege imayandikira siteshoni ya wailesi pa liwiro la 340 m/s. Werengani ma frequency omwe ndegeyo imalandira ngati liwiro la mafunde a wailesi ndi lofanana ndi liwiro la kuwala (3 x 10^8 m/s).
Kukambirana:
Mphamvu ya Doppler pa mafunde a wailesi ikhoza kufotokozedwa motere:
\[ f_{accept} = f_{0} \left(\frac{c + v}{c}\right) \]
Kumene:
– \( f_0 \) = mafupipafupi oyambirira (95 MHz)
– \( v \) = liwiro la ndege (340 m/s)
– \( c \) = liwiro la mafunde (3 x 10^8 m/s)
Kotero:
\[ f_{accept} = 95 \times 10^6 \left(\frac{3 \times 10^8 + 340}{3 \times 10^8}\right) \]
\[ f_{accept} = 95 \nthawi 10^6 \kumanzere(\frac{3 \nthawi 10^8 + 3.4 \nthawi 10^2}{3 \nthawi 10^8}\kumanja) \]
\[ f_{accept} \pafupifupi 95 \nthawi 10^6 \kumanzere(1 + \frac{3.4 \nthawi 10^2}{3 \nthawi 10^8}\kumanja) \]
\[ f_{accept} \pafupifupi 95 \nthawi 10^6 \kumanzere(1 + 1.1333 \nthawi 10^{-6}\kumanja) \]
\[ f_{accept} \pafupifupi 95 \nthawi 10^6 \nthawi 1.0000011333 \]
\[ f_{accept} \pafupifupi 95.000107 \ \text{MHz} \]
Kotero, ma frequency omwe ndege yomwe ikubwera imalandira ndi pafupifupi 95.000107 MHz.
Kutseka
Kumvetsetsa mfundo zoyambira ndi machitidwe owerengera mafunde a wailesi ndikofunikira m'magawo osiyanasiyana aukadaulo ndi sayansi. Mavuto omwe ali pamwambapa akupereka zitsanzo za momwe sayansi ya mafunde a wailesi ingagwiritsidwire ntchito m'malo osiyanasiyana ogwira ntchito. Njira yopezera kumvetsetsa kozama ndi kudzera mu kuchita nthawi zonse ndi kufufuza momwe mafunde a wailesi amagwiritsidwira ntchito m'dziko lenileni muukadaulo wolumikizirana womwe timagwiritsa ntchito tsiku lililonse.
