Author Topic: Huawei RRU3928 1800MHz radio base station teardown (part 1 and 2)  (Read 4541 times)

Offline Mads Barnkob

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The RRU3928 is an outdoor remote radio unit. It processes baseband and RF signal data. With the Software Defined Radio (SDR)technology, the RRU3928 supports the dual-mode operation of any two modes of GSM, UMTS, and LTE through software configuration modification. RRU3928 has a dual-transmitter and dual-receiver structure, which supports higher output power and carrier capacity.

It can f.ex. do 6x GSM carriers at each 10 Watt and 1x LTE carrier at 2x10 Watt or 4x GSM carrier at each 10 Watt and 2x UMTS carriers at 2x20 Watt.

This is the initial teardown and later on I will release part 2 which is the circuit analysis video.

« Last Edit: January 08, 2019, 08:25:55 AM by Mads Barnkob »
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Offline Mads Barnkob

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Re: Huawei RRU3928 1800MHz radio base station teardown (part 1 of 2)
« Reply #1 on: January 08, 2019, 08:25:08 AM »
/>


Above pictures shows the coaxial cavity band pass filter which in popular speech is called a duplexer or diplexer. Duplexer band pass filter explained: https://www.youtube.com/watch?v=HNaAQ3a7Duc



The power amplifier consists of a series of low noise amplifiers, general purpose amplifiers and power amplifiers. The first amplifier IC is not able to be identified. First identifiable IC is a NXP BLF6G22LS-40P 1.8-2.1 GHz 5-15 Watt dual amplifier that feeds the Infineon PTFB182012FC which is a dual power amplifier rated for 2x 10 Watt dissipation at 1.8 GHz. Anaren Xinger 1P503S, Anaren Xinger II XC1900A-03S and Anaren Xinger III X3C19P1-05S hybrid and direct couplers are used. One output circulator is used for double protection against reflected energy from the duplexer and antenna array.



The system boards 4 ADC/DAC main processors are unknown HI FPGAs that has a generic part number which is not identifiable. A Altera Arria II GX EP2AGX260 FPGA seems to be the heart of the unit and does all system control and communication with other units of the system. It has 16 transceivers that can run up to 550 MHz. 102600 Adaptive Logic Modules and 244188 Logic Elements available.



The digital to analog signal path starts with one of the HI FPGA ICs that sends a single highspeed bitstream to the Analog Devices TxDAC AD9122. It is a dual 16-bit DAC with a capability of 1230 MSPS. Analog Devices ADF4902 PLL and Analog Devices ADL5372 1.5-2.5 GHz Quad Modulators seems to be the next part of the path before the output power adjusting TriQuint TQM879005A which is a 1.4-2.7 GHz Variable Gain Amplifier. It can adjust 0.5 dB amplification at a 6-bit scale input.



The analog to digital signal path starts with 6 NEDITEK NDF9117 1747.5 MHz SAW filters (explained here: https://youtu.be/qO127zY3voE?t=963 ) which feed into a Skyworks SKY64341-11 1.7-2.0 GHz RF frontend. This has by other parts a downconversion mixer (explained here: https://youtu.be/qO127zY3voE?t=865 ) which by the use of a local oscillator can bring down the carrier frequency of the signal to something lower that is easier to work with.

The two separate lines now go through the Analog Devices AD8376 dual Variable Gain Amplifiers that has a bandwidth of 700 MHz at -4dB to 20 dB. The last stage is the Texas Instruments ADS58C20 which is a dual IF multimode receiver capable of working with both GSM / 3G / LTE. If this is the final analog to digital conversion IC or it is one of the HI FPGAs is hard to tell.



Good power supply layout with a lot of transient protection at the input. A single full-bridge of PSMN4R8-100BSE 100V MOSFETs is used for first stage voltage stabilization before the smaller high current planar transformers are driven by D70N1045 MOSFETs.
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Offline Da_Stier

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Re: Huawei RRU3928 1800MHz radio base station teardown (part 1 and 2)
« Reply #2 on: March 01, 2020, 06:22:28 PM »
So after having the amplifier board on my desk for the past year, I decided it was about time to do something with it.

I started as usual to identify all the components on the board.
This is what I came up with.



The first, pretty obvious thing is that the amplifier part of the board is basically symmetrical around the center.
Each of the halves has its own power contacts. The two outer contacts are for GND, the middle one of each side delivers the 27V Drain voltage for the LDMOS devices.

The power supply for the logic portion of the board is not symmetrical and supplies both halves. The big connector on the ground has some more GND pins, as well as one pin for what I call the digital supply.
This pin feeds some kind of LDO regulator.
I was not able to find the actual part that was used, however the drop out voltage is only around .6V and there is no switching component or Coil around, so I guess it must be a LDO.

The output of this LDO is +5V.
The regulator works with input voltages between ~5.6V up to around 9V. If you supply it with more than 9V the output goes away so I guess it has some overvoltage protection.

The 5V rail feeds all the OP484E quad operational amplifiers at the top as well as the AMC7812 devices.

Additional there are two LP2980 LDOs that produce two 3.3V rails.
One of them is used on the AMC7812 ICs. The other one feeds some mystery ICs which I believe are propably some RF amplifiers, since they are in the coupled path from the output.

I also managed to check all the SOT-23 devices for their type.
There are only two types used, some NPN transistors, as well as some P-MOS FETs.

The next step will be to figure out, which circuit was used for the gate biasing of each transistor.
Therefore I guess it would be interesting to find which ADC and DAC channels of the LMC7812 feeds which gate.
Knowing that might enable me to actually communicate with the LMC7812s.

Offline saurabh

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Re: Huawei RRU3928 1800MHz radio base station teardown (part 1 and 2)
« Reply #3 on: April 27, 2021, 01:34:37 PM »
So after having the amplifier board on my desk for the past year, I decided it was about time to do something with it.

I started as usual to identify all the components on the board.
This is what I came up with.



The first, pretty obvious thing is that the amplifier part of the board is basically symmetrical around the center.
Each of the halves has its own power contacts. The two outer contacts are for GND, the middle one of each side delivers the 27V Drain voltage for the LDMOS devices.

The power supply for the logic portion of the board is not symmetrical and supplies both halves. The big connector on the ground has some more GND pins, as well as one pin for what I call the digital supply.
This pin feeds some kind of LDO regulator.
I was not able to find the actual part that was used, however the drop out voltage is only around .6V and there is no switching component or Coil around, so I guess it must be a LDO.

The output of this LDO is +5V.
The regulator works with input voltages between ~5.6V up to around 9V. If you supply it with more than 9V the output goes away so I guess it has some overvoltage protection.

The 5V rail feeds all the OP484E quad operational amplifiers at the top as well as the AMC7812 devices.

Additional there are two LP2980 LDOs that produce two 3.3V rails.
One of them is used on the AMC7812 ICs. The other one feeds some mystery ICs which I believe are propably some RF amplifiers, since they are in the coupled path from the output.

I also managed to check all the SOT-23 devices for their type.
There are only two types used, some NPN transistors, as well as some P-MOS FETs.

The next step will be to figure out, which circuit was used for the gate biasing of each transistor.
Therefore I guess it would be interesting to find which ADC and DAC channels of the LMC7812 feeds which gate.
Knowing that might enable me to actually communicate with the LMC7812s.

Hi Da_Stier,
is the routing of the transmitter section done on a 2 layer board or a 4 layer board. I'm currently working on a design and the amplifiers provided by NxP don't provide enough room for a thicker board. so was curious to know how the stack up of these boards were

Offline Da_Stier

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Re: Huawei RRU3928 1800MHz radio base station teardown (part 1 and 2)
« Reply #4 on: April 27, 2021, 04:28:52 PM »
Hi saurabh and welcome (I think this was your first post, right?)


Most of the amplifiers, especially the simpler ones, like for example:
https://highvoltageforum.net/index.php?topic=1113.0
https://highvoltageforum.net/index.php?topic=765.0
have a double layer rogers PCB.
It is between 0.8 and 1mm thick.
The bottom layer is completly flooded with a GND polygon and soldered to the heatspreader.
Sometimes there are a few single control signal traces on the bottom as well.
The RF layout is done comoletely on the top layer.

Here is a side view of one of the "wet amplifiers":



The more complex boards use a combined PCB stackup most of the times.
They have a top portion of Rogers RF substrate, followed by a GND plane, followed by a few layers of conventional FR4 for all the signalling and stuff.
This is the side view of an Ericsson board.



You can see the white layer on the bottom (this is the top of the PCB with the RF stuff)
and the brown layers on top of that.
The boards of this kind, that I have seen have the double Layer Rogers and between 4 and 6 normal FR4 layers.

The Huawei board from this tread actually has a two layer Rogers board.
(which surprised me to be honest)
However the bottom layer is used for signalling in a few places, where no GND plane is needed.
(mostly underneath the DAC and control ICs in the middle)
Here is a side view of the Huawei board:



Let me know if you need anything else, I'm happy to help.  :)
And out of curiosity, can you share more details on your build, it sounds very interesting.



Greetings,
Michael

Offline saurabh

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Re: Huawei RRU3928 1800MHz radio base station teardown (part 1 and 2)
« Reply #5 on: April 29, 2021, 12:44:57 PM »
Hi,

You mentioned that the Huawei board in this thread uses a two layer Rogers board, and that the routing in certain regions was done below the board. An immediate question that popped up in my mind was, the heat sink is present underneath the entire board, if there is routing as well as ground lines below the board wouldn't they be shorted. or am i missing something here.

Thanks
« Last Edit: April 29, 2021, 12:50:00 PM by saurabh »

Offline Da_Stier

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Re: Huawei RRU3928 1800MHz radio base station teardown (part 1 and 2)
« Reply #6 on: April 29, 2021, 03:12:54 PM »
Hi,

your concerns are right of course.
If some of the bottom layer is used for signal routing, this section has solder mask over it, so it is protected.
In addition, the heatsink plate has pockets milled out in these places to provide another layer of safety.

As an example, you can take a look at this teardown, that Mads Barnkob did:
/>At 4:11 you can see how the typical interface between the heatsink and the PCB looks.  :D

Greetings,
Michael

Offline saurabh

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Re: Huawei RRU3928 1800MHz radio base station teardown (part 1 and 2)
« Reply #7 on: April 29, 2021, 03:44:33 PM »
Ahh that's a nice way to provide room for routing. Thanks.

Offline Da_Stier

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Re: Huawei RRU3928 1800MHz radio base station teardown (part 1 and 2)
« Reply #8 on: April 29, 2021, 08:00:18 PM »
I went ahead and searched the Huawei board (or what is left of it, I did a few experiments with it).
You can see the milled pockets and channels quite clearly.
You can also kind of see the green soldermask on the bottom, where the pockets are.
(not sure how much of it is visible on the picture)











Greetings,
Michael

High Voltage Forum

Re: Huawei RRU3928 1800MHz radio base station teardown (part 1 and 2)
« Reply #8 on: April 29, 2021, 08:00:18 PM »

 


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