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This lesson continues to look at the receiving and transmitting channels of the GSM 900 of Huawei mobile phones

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Open the drawings made by Xinzhi and find the drawings of the Mate 305G version

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In the last lesson, it was mentioned that the antenna signal reaches pin 31 of U4901

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This received signal to continue

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What is the antenna switch doing here

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It connects the internal switch to pin 31

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When other frequency bands need to work, its switch connects other frequency bands to pin 31

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This is a many-to-one antenna switch

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The reception of GSM 900 and the reception of B8 take the same channel

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RX is receiving, the 7th pin of U4901 is the receiving of B8, the receiving of B8 is also the receiving of GSM 900

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Double click on it to see where it goes

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It reaches a matching circuit

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The received signal reaches the receiving amplifier chip U5501 after passing through the inductor L4928

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The chip U5501 has no particularly obvious logo, but the signals leading to this chip all have LNA

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First, this is the received signal

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Second, all received signals come with LNA a

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Then this chip is the receiver amplifier chip

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The receiving amplifier chip is also called the receiving power amplifier

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IN is input, OUT is output

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After the output it reaches the H5 pin of another receiving chip

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After being amplified again it reaches the RF chip

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After the output of the F5 pin, we double-click it to see where it leads

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It leads to the receiving power amplifier U6301 and goes out from the B7 pin

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Double click on it and it goes to the chip called U4401

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The model of the chip is Hi 6365, which is the radio frequency transceiver chip

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When the signal comes in, the RF IC will play its role, remove the carrier of this high-frequency signal, and send it to the baseband CPU through the qlink bus

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The process from the mobile phone to the base station is called uplink,

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and the downlink is the base station sending signals to the mobile phone

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This is the receiving channel of GSM 900 for Huawei mobile phones

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That's all for this lesson