Huawei RRU3928 1800MHz radio base station circuit analysis (part 2 of 2)

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 2×10 Watt or 4x GSM carrier at each 10 Watt and 2x UMTS carriers at 2×20 Watt.

If you missed part 1, see it here:

Above pictures shows the coaxial cavity band pass filter which in popular speech is called a duplexer or diplexer. Duplexer band pass filter explained:

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: ) which feed into a Skyworks SKY64341-11 1.7-2.0 GHz RF frontend. This has by other parts a downconversion mixer (explained here: ) 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.

About Mads Barnkob

Electrician, programmer, experimenter and amateur scientist with experience in industry automation, programming and all kinds of high voltage generating electronics. Administrator of and the high voltage community forum
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