Nokia Siemens Networks Flexi WCDMA teardown: Power amplifier (part 2 of 3)

Nokia Siemens Networks Flexi Multiradio BTS is a GSM/EDGE, WCDMA/(I-)HSPA, and LTE base station for use in mobile telecommunication antenna networks. A network that you use daily on your cellphone.

Part 1: System station and Part 3: Antenna

The following 12 minute video shows the teardown step by step with explanations, high resolution pictures of content is further down this post.

In the above pictures we see the tuning cavities of the band pass filter for the transmit and receive channels for the antenna connections. There is a total of three separate band pass filters. Each filter consists of a, from the left, receiving band pass filter, in the middle transmitting band pass filter and at the right another receiving band pass filter.

Most of the enclosure work also includes the small drums for tuning the cavities with the adjustable pins seen in the second picture, but in the transmitting cavities the silvered drums are, very unusually, made of a ferrous metal that is attracted with a magnet. Earlier I have only seen these as silver plated brass, but it does seem that even cheaper metals with enough silver plating can do the same job.

The tuning pins are however of a extraordinary good quality, very smooth surface with gold plating.

In the above pictures we see the three-sector RF amplifier boards, there is a total of three of these boards. The board itself is a Aluminium Silicon Carbide heat sink on which all the components are directly mounted. The input connectors in the bottom of the pictures leads the signals through a coupler to the Freescale / NXP MD7IC2250GN integrated RF LDMOS which is a 2-2.2GHz 5 Watt amplifier. From here the signal is routed via a Aeroflex P131103 output filter to the Anaren X3C21P1-05S Xinger III coupler where it distributes to the three output amplifiers through a additional coupler. The last stage of amplification is handled by three Ampleon / NXP BLF8G22LS-160BV Power LDMOS transistors which are 2-2.2GHz 160 Watt transistors, but in this setup used for a combined 60 Watt output of the module. The output filter is a Aeroflex 5608098 ISO-2100-33CW with a built in PT-100W 50Ω attenuation.

In the above pictures we can see that there is a massive amount of ceramic capacitor filtering on the input DC voltage that could range from 40.5 to 57 VDC.  The input is protected by varistor’s, chokes and diodes.

The digital signal processing board has its own power supply seen down in the right corner and each power amplifier module also has its own power supply which consists of a controller, transistors, planar transformer, output capacitors and choke to regulate the voltage very tight for the amplifier. There is also a massive amount of ceramic capacitors for filtering the voltage right up to where is connects to the modules.

In the above pictures we see the digital signal processing board with the three optical inputs in the bottom of the picture. Digital data is processed by the Freescale / NXP MCP8378 PowerQUICC II CPU and its associated Altera Cyclone IV FPGA (it should have been IV, not II on the picture).

Translation and splitting of the telecommunications protocol data and selection of different drive modes, if the amplifier is used for GSM, EDGE, HSPA, WCDMA or LTE, is done by the Nokia Siemens Networks marked ICs. The NSN 4371734 MURKKU2 and P155718 MERA CPUs are impossible to locate any data on, they do however have great resemblance to the NEC marked CPUs I have seen in GSM/EDGE amplifiers.

The Skyworks SKY65338-21 IC is a GSM 450-470 MHz transmit / receive front end.

The AD9122 TxDAC is a 16-Bit digital analogue converter that translates the telecommunications protocol into a analogue data stream with as much as 1230 MSPS. The analogue signal is amplified by the Skyworks SKY65387-11 IC that is a WCDMA variable gain amplifier.

A part of the receiving signal processing and filtering are the TriQuint 856731 192 MHz SAW filters that form a network to feed into the AZ4246 (ADS4246) which is a dual 14-Bit ADC analogue digital converter that translates the analogue data stream back into the telecommunications protocol with a speed of 160 MSPS. This section is most likely related to the GSM part of the receiving amplifier.

 

Specifications

Frequency bands: 700, 800, 850, 900, 1800, 1900, 1700/2100, 2100, 2300 and 2600 MHz.

Maximum capacity: Up to 6+6+6 GSM or 4+4+4 WCDMA or 1+1+1 LTE at 20 MHz or flexible combination of the above technologies in concurrent mode.

Multi-radio configuration: 1 Flexi 3-sector RF module + 1 system module for GSM/EDGE + 1 system module for WCDMA/HSPA and LTE. Remote Radio Head (RRH) solution also supported.

RF power amplifier technology: Multicarrier power amplifier (multi-standard)

Height x width x depth: 133 x 447 x 560 mm per module, indoors and outdoors. Fits in any 19” rack.

Weight: 25 kg per module

Operating temperature range: -35 °C to +55 °C

Power supply: 40.5 – 57 VDC, 184 – 276 VAC with power module

Typical power consumption: 790W for combined GSM and WCDMA site

Output power: 240 W per RF module or 40 W + 40W per Remote Radio Head (RRH)

Ingress protection class: IP 65

About Mads Barnkob

Electrician, experimenter and amateur scientist with experience in industry automation, programming and all kinds of high voltage generating electronics.
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One Response to Nokia Siemens Networks Flexi WCDMA teardown: Power amplifier (part 2 of 3)

  1. Pingback: Nokia Siemens Networks Flexi WCDMA teardown: System station (part 1 of 3) | Kaizer Power Electronics

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