Rohde & Schwarz R&S SMU200A, Service Manual

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Instrument Design and Function Description R&S SMU200A
1007.9845.82 3.12 E-6
Fading Simulator (FADER) and Fading Simulator Extension (FADEX)
Depending on the configuration, the Fading Simulator module can be installed with or without Path
Extension.
Fading Simulator module without Fading Simulator Extension :
The module must be installed in the signal flow downstream of the Universal Coder and upstream of
the DAC Interface. If the Fading Simulator is installed, all other baseband modules are moved one slot
towards the front of the instrument.
Fading Simulator module with Fading Simulator Extension :
The Path Extension module is mounted downstream of the Fading Simulator. Both modules are
connected by a fader bridge (1160.2013.02 from connector X50 to X51).
The Fading Simulator module allows propagation conditions to be simulated for moving transmitters or
receivers. For this purpose, the modulation signal is firstly delayed and then multiplied using a rotating
vector whose amplitude and phase are derived from the models for the channel (e.g. Rayleigh) and
from the rate of motion (Doppler shift). Such a combination of delay and complex multiplication is
referred to as a 'path'. Up to 20 such paths can be calculated on the R&S SMU-B14. They are
combined into groups of 5 paths. R&S SMU-B15 increases the computing power to up to 40 paths.
The Fading Simulator module consists of the following blocks:
-
Bus interface and DSP: These are used to control the module. The DSP provides the simulation
data for the respective arithmetic units in the paths. The bus interface is active after power ON which
means that this module is already detected by the BIOS.
-
Four simulation groups: Each group has a delay memory (2 SRAM) and the arithmetic units (for
each FPGA) to calculate the path models. These groups can be configured differently according to
the desired resolution of the path delay and the possible number of paths.
-
LVDS interface: The first group also contains the demultiplexers and multiplexers for receiving and
sending the I-Q data.
The modules R&S SMU-B14 and R&S SMU-B15 do not have a dedicated clock source or alignment
points.