Rohde & Schwarz M3SR Series 4100, Руководство по обслуживанию

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Motherboard - Function R&S M3SR Series 4100 HF Transceivers
1.27 6124.9007.82.01
1.3.2.9 Motherboard - Function
The Block Diagram of the Motherboard is shown in Fig. 1.12.
The Motherboard consists of the following functional groups:
¾ Control logic essentially consisting of an FPGA to control and monitor the periphery, LEDs on
Front Panel, fan speed, temperature and generated power
¾ FLASH-Memory for configuration of data, module parameters and look-up tables
¾ BOOT CPLD (Complex Programmable Logic Device)
¾ VCXO (Voltage Controlled Crystal Oscillator) with 40 MHz, synchronised with a 100 kHz
reference sine wave signal coming from the Synthesizer
¾ Audio Switch Matrix and Audio Bus
¾ Ethernet hub
The FPGA is commanded by the Radio Controller via a parallel Radio Control Bus which is also
connected to other modules. The FPGA generates a 20 MHz clock for the Ethernet hub.
Configuration
After power-up, the FPGA needs the BOOT CPLD to load the configuration from Flash into the FPGA.
In case of no errors and appropriate supply voltages, the CPLD switches the address and control
signals to high impedance. The FPGA can now control the
FLASH m emory. In this case it is possible to
download a new configuration into the F
LASH m
emory via the Radio Control Bus.
ON/OFF Control
The ON/OFF Control is implemented with an 8 bit microcontroller with internal Oscillator (4 to 20 MHz),
Timer and Watchdog timer, integrated FLASH-ROM for program, RAM and EEPROM for data.
Basically, the last power state (ON or OFF) is stored in an EEPROM for retrieving this state after a
power interruption. Pressing the switch button on the Front Panel toggles the current power state so
that the state recorded in EEPROM matches the new state. After a power interruption, the device will
be turned on when there is an "ON" found in EEPROM. When the microcontroller decides to turn off
the device, it first tells the Radio Controller. It turns off the power immediately as soon as the Radio
Controller responds or 5 s elapse. There is a 2 s delay after power-off, before power can be turned on
again.
Audio
Analog switches connect the sources and sinks with different electrical characteristics to the Audio Bus
as needed. The switches located on Motherboard are collectively named "Audio Switch Matrix". The
Audio Bus on Motherboard consists of 4 Audio Bus lines at a nominal level of -8 dBm at 600
Ω
and a
dynamic range of ±10 dB. Each source has an impedance of 600
Ω
, this makes the bus short-circuit
proof and allows as a side effect the mixing of audio sources. The Audio Bus extends directly to the
Interface Module to be accessible for modules located there (e.g. NMEA). The audio signals to and from
the Radio Controller (LINE_TX and LINE_RX) are fed via an amplifier for impedance and level match-
ing.