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This lesson talks about the principle of sending and receiving in the 2G frequency band,

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that is, the principle of the sending and receiving channel of the frequency band

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Look at the received signal first

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The antenna converts the electromagnetic wave signal into an electrical signal,

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and conducts it to the filter through the coaxial switch

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After the filter filters out the clutter, it is given to the antenna switch

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The antenna switch depends on the card you insert in this phone

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If it is a China Mobile card, the antenna switch will use the receiving channel of B8

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If it is a China Unicom card, it will go through the receiving channel of B3,

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if it is a China telecom card, it will go through the receiving channel of B26

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This received signal is passed to the receiving amplifier

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The receiving amplifier amplifies the power of the signal, and the frequency does not change after amplification

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The signal is then passed to the RF transceiver

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The RF transceiver internally performs down-conversion,

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that is, removes the high-frequency carrier, demodulates the basic voice signal,

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and sends the IQ bus to the baseband CPU

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The baseband CPU performs demodulation, and the demodulated voice signal is sent to the CPU

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This is the channel it receives

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No matter which operator it is,

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the signal must pass through such components and finally reach the baseband CPU

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Let's see its launch process

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The baseband CPU modulates the sound signal transmitted by the large CPU,

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and sends it to the RF transceiver through the IQ signal

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The RF transceiver carries this low-frequency signal

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onto a high-frequency carrier to form a high-frequency transmitted electrical signal, such as the mobile GSM 900

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The signal is sent to the power amplifier

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The power amplifier amplifies the power of the transmitted signal, and then passes it to the antenna switch

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The antenna switch transmits this signal to the antenna end under the control of the baseband

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or the control of the radio frequency

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The filter filters out the clutter, and then it is handed over to the coaxial switch,

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and the switch is turned on to the antenna

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The antenna turns the signal into a high-frequency electromagnetic wave and transmits it to the base station

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This completes the reception and transmission of 2G signals

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This is the component that the 2G channel passes through

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If any component is abnormal, it will cause a signal failure

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All 2 g bands need to go through these main components

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That's all for this lesson