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This lesson talks about the receiving and transmitting channels of the radio frequency circuit

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of Huawei P40 B3 frequency band

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In this lesson, we mainly talk about the launch channel

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The circuit we want to run and launch can start directly from the CPU position,

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and directly find the USR UL signal at the CPU position

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This UL refers to uplink data, which is actually transmitting data.

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All radio frequency bands in our mobile phones are transmitted through UL and received through DL.

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Everyone here should pay attention, we open the drawing, and then go to the position of the previous class

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Of course start here at CPU position U300

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The CPU is in this position

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The baseband CPU in the CPU transmits the transmission data through the USRUL bus

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UL is uplink

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The mobile phone is a small individual, and the base station is all the users to deal with,

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so the external transmission of the mobile phone is called uplink

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This UL signal is the transmission signal of our B3 frequency band

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Let's find one of them

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The baseband CPU is for data communication with the radio frequency

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Then let's look at the launch direction

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It is bound to lead to this H I 6365 RF chip

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We select it by finding the next item

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It goes to pin A A24 of this chip and pin A B 25 of this

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This chip is actually the U4401 RF transceiver

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USR UL signal it is a low frequency signal

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Such a low-frequency signal cannot travel long distances and quickly in the air

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Only high-frequency electrical signals can be transformed into electromagnetic waves

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for long-distance and rapid propagation in the air

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This transmit signal is given to the RF

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The radio frequency transceiver generates a high-frequency carrier,

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and it carries the low-frequency signal onto the high-frequency carrier to form the transmission signal

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Of course, the launch we're looking for belongs to B3

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Let's look at the launch, here's the G H B code

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G H B is 1,800 and 1,900 of G S M

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It has high and mid bands for transmission

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The B3 frequency band belongs to the middle frequency band. In fact, this M B includes B1 and B3

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Therefore, the RF transceiver generates a high-frequency carrier, mixes the incoming uplink signal

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and then processes it, finally forming a high-frequency high-frequency signal

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The launch of the B3 we're looking for is here

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T X is transmit; M B is mid-band

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So what does this HB2 represent here?

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Because all radio frequency bands in mobile phones are usually high frequency

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It is referred to here as a high-frequency signal

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All radio frequencies belong to high frequency, the most important thing we look at is the MB behind

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M B refers to the specific mid-band

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The frequency bands B1, B2, B3, B4, B25, B34, and B39 of the mid-band range pass here

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Of course, what we are looking for is B3

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Then let's look at the B3's transmission signal coming out of the radio frequency

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It is already a very high frequency signal, for example B3 is around 1,800M

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It contains the data to be routed to the base station

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We see the next step it leads to

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Generally its next step is usually to power amplifier

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The transmitted signal output by the RF transceiver, no matter it is a mid-band, high-band or low-band,

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it is relatively weak, and it is bound to lead to the power amplifier for power amplification

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We search for the signal

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It leads to pin 12 of the chip U4701

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This chip, we judge its function according to its pin definition

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It is a transmitting power amplifier for low, medium and high frequency bands

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After the B3 frequency band enters the 12-pin of this U4701,

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the internal power amplifier passes through to amplify the electric power

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It forms the transmission signal of its own separate frequency band in various frequency bands

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For example, B3 has been enlarged and reached the 25 feet here

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The output of the power amplifier is B3 or four-band, 3 and 4 go together

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After the power amplifier is amplified, it usually leads to the antenna switch

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That's all for this lesson