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This lesson goes on to talk about the call channel of Huawei mobile phone GSM 900

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Then the last lesson, the last lesson is about the receiving channel

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The baseband CPU of this mobile phone is contained in the big CPU

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The big CPU transmits the signal of the sound circuit, and sends it from the uplink signal to the RF transceiver

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This is actually part of the baseband CPU.

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The large CPU is given to the radio frequency through this Qlink bus

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We double click it

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It reaches the AA24 and AB25 pins of the RF

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U4401 is the RF transceiver of Hisilicon 6365

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After reaching the radio frequency, the transmitted signal converts the low-frequency Qlink signal containing the voice signal

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The radio frequency itself generates high frequency, and after generating high frequency,

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the voice signal is placed on it

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TX is transmit, LB is low frequency band, GLB is low frequency band of GSM

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The transmitting signal starts from the AC10 pin of the RF IC, and it finally reaches the antenna end

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The transmitted signal reaches the chip U4601 after passing through a frequency selection circuit composed of an inductor and a capacitor

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This chip is a GSM power amplifier, we usually call it a power amplifier

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After being amplified by the power amplifier, it is emitted from pin 7

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It passes through the inductor L4602, and then through a capacitor to form a low-frequency transmission signal, GSM_LB

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We double click it

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It goes to pin 16 of a low-band antenna switch U4901

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In fact, it is also a low frequency amplifier.

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The antenna switch switches the transmit signal to the antenna, and it reaches the antenna end through pin 31

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Here everyone should pay attention, the reception of GSM 900 is the same channel as the reception of B8

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Its launch does not go through the launch channel of B8, it has its own separate channel

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GSM 900 passes through an inductor, passes through a capacitor,

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and then passes through a capacitor to reach the main antenna in the low frequency band

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It goes through the filter Z5701 on the way to the main antenna, enters from pin 1,

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and exits from pin 3

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Its direction is exactly opposite to that of receiving

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The transmitted signal is coupled by the capacitor, reaches the RF 3 pin of the RF switch U5704,

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and finally reaches the low-frequency antenna J5703

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This is the launch channel of Huawei's GSM900

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That's all for this lesson