Nokia Siemens 3G Flexi 2100MHz 50W Amplifier Circuit Analysis (Part 2 of 3)

Introduction

I have here a circuit analysis of a 2100 MHz cellular amplifier from a UMTS basestation setup. The initial teardown video can be found in Nokia Siemens 3G Flexi 2100MHz 50W Amplifier Teardown (Part 1 of 3).

Video

Cellular Basestation Overview

The Nokia Siemens Networks FRGL module consists of two 50 Watt amplifier modules. The module is almost identical enough to have been mirrored down the middle, with a shared main computer board. The transmit sections uses different ICs, most likely for different telecom protocols. The RED CPU board controls everything. GREEN TX is the transmitting DAC and pre-amplifiers. BLUE PA is the power amplifier and YELLOW RX is the receiving ADC and filters.

Cellular Amplifier Computer

The main CPU is a AMCC / IBM PowerPC RISC 32-bit PCC440GX-3NF533C. It is a 533 MHZ CPU, with 32 kB L1 cache and no FPU. It has 4×128 MB DDR SDRAM 9BF42-D9FQV. A optical network interface is driven by a Marvell 88E6061-LAJ1 7-port 100 Mbps switch and has a HALO Quatra TG110-EMX6NX 4-port 10/100BASE Ethernet isolation transformer.

The distributed clock comes from a 153.6 MHz oscillator that is fed into a Texas Instruments CK7005Z 1:5 PLL Clock Synchronizer. From here its distributed through a Texas Instruments CDCLVP110 1:10 differential clock distribution IC.

Each transmitting power amplifier has a Altera Stratix II FPGA. EP2S30F48414N with 180,000 LEs, 96 DSP blocks and 12 PLLs. It can operate at up to 550 MHz. Each Altera Stratix II FPGA has 2×128 MB DDR SDRAM 9BF42-D9FQV. Right side telecom protocol IC is a NEC 4379318 “INSPAP”, Nokia part number, no datasheet. Left side has a Altera Stratix GX FPGA with integrated transceiver capabilities, EP1SGX25FF102016N.

The receiving telecom protocol CPU for encoding is a NEC 4372536 “PIMU-R2”, Nokia part number, no datasheet.

Cellular Amplifier Digital to Analog Circuits

Firstly the digital to analog conversion from CPU is done by a NXP TDA9935 dual DAC with a 14-bit 160 Msps bandwidth. Secondly the signal is fed into a Analog Devices AD8349 700-2700 MHz up-conversion mixer. Further it is amplified by a RF Micro Devices SBA4089Z DC-5GHz amplifier. The variable attenuation is done by a Macom 4VAT2007 Voltage Variable Attenuator 23 dB 1700-2000 MHz. Further it is amplified by a RF Micro Devices SBA4089Z DC-5GHz amplifier. After that a ceramic band pass filter is used before the signal goes to the power amplifier.

The microstrip coupled feedback signal goes into a Maxim 9996E 1700-2200 MHz to 40-350MHz down-conversion mixer. Its analog to digital conversion is done with a NXP TDA9910 ADC with a 12-bit 80 Msps bandwidth.

Cellular Power Amplifier

The power amplifier uses Anaren Xinger JP503S 3dB Hybrid Couplers in all places where phase shift and signal splitting is needed. The first amplifier IC is a RF Micro Devices RF2128, which is a 100mW linear amplifier in the 1900 – 2200 MHz range. The RF2128 works as a preamplifier to the NXP BLF6G22-45 which is a 45 Watt power LDMOS with a working range between 2000 to 2200 MHz. This BLF6G22-45 is the preamplifier of the two large NXP BLF6G22-180PN. The BLF6G22-180PN is a 180 Watt power LDMOS with a working range between 2000 to 2200 MHz. The output signal from the main amplifier chips are combined in a quarter wave strip before going through the TDK CU13N output circulator. The output circulator ensures that the output signal from 1 goes to 2, the antenna. Any reflected energy from the antenna 2, goes to the 50 Ohm termination on 3.

Cellular Amplifier Diplexer Filters

The output diplexer or band pass filter consists of a receive channel and a combined transmit and receive channel. The receive channel is a 5-pole filter and the transmit channel is a 4-pole filter. There is no cross coupling with holes or bridges between champers. Moreover the filter has a small servo gear motor for automatic filter tuning to match the connected antenna panels. The automatic filter tuner uses a Freescale NXP MCF5208 32-bit MCU with 16 kB SRAM and 8 Kb cache. It has integrated DDR SDRAM controller, 16-channel DMA controller and 10/100 Mbps Ethernet controller. The monitor output for the service technician goes through a Anaren Xinger II XC1900E-03S Coupler rated for 1700-2000 MHz at 120 Watt. Anaren Xinger 1P503S Hybrid Couplers 1700-2000 MHz -3dB 90 degree couplers are used to switch phase. Wilkinson power splitter and Wilkinson power combiners are used for individual phase amplification.

Cellular Amplifier Analog to Digital Circuits

The input connectors goes straight to some unknown small amplifiers and goes to some SAW filters. Secondly after that, is a unknown ST microelectronics dual maxier used for down-conversion. It is nicknamed ST “SMURF”. The dual output from each down-conversion mixer is fed into each their Texas Instruments ADS55221 ADC with a 12-bit 105 Msps bandwidth. The telecom protocol encoding CPU is a NEC 4370692 “HEPPU” IC, Nokia part number, no datasheet. The clock for the CPUs and down-conversion mixer from from the ST STW81102 multi-band RF frequency synthesizer. With a working area of 905-3260 MHz for the integrated VCOs voltage controlled Oscillators.

The Texas Instruments LM75A temperature sensors are connected through Texas Instruments PF574 8-bit i2C bus I/O expanders to a ST “Plankton” microcontroller.

Texas Instruments LVC04A Hex Inverters are used in front of the Fairchild FIN1048 LVDS to LVTTL 100mV to 3.3V converter. From here its distributed through a Texas Instruments CDCLVP110 1:10 differential clock distribution IC.

Cellular Amplifier Power Supply

The power supply takes a 48 VDC at a maximum of 18 Ampere. The main controller for all 5+ individual power supplies on the PCB is a Freescale MC908A, which is a 8 MHz MCU with 32 kB flash and 512 B EEPROM. The input section consists of some IR FS52N15D (150V 60A 32mΩ) and IR F2907Z (75V 75A 4.5mΩ) MOSFETs. Therefor it properly chops down the input voltage to 32 VDC, else it is hard to understand why the 28 VDC power amplifier outputs are only using IR FR3709Z (30V 86A 6.5mΩ) MOSFETs. The output choke and capacitors are accompanied by WeEn BYV42EB ulfra-fast diodes (200V 30A).