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designers address these linearity
and efficiency requirements, Visual
System Simulator™ (VSS) system
design software supports load
pull based on digitally-modulated
active devices like power transistors
to generate constant contours
for communication performance
metrics such as adjacent channel
power ratio (ACPR), error vector
magnitude (EVM), and bit error rate
(BER) using either measured load-
pull data or a nonlinear behavioral
model based on measured or
simulated circuit/active device data
(Figure 5).
Models and Libraries
System and PA simulation for
communication applications specific
to VSS is further enabled with new
libraries and capabilities introduced
in V13. The VSS software now
provides LTE-Advanced (LTE-A)
support for carrier aggregation
of intra-band and inter-band
component carriers and 5G
candidate modulated waveforms
(Figure 6) such as filter-bank
multicarrier (FBMC), generalized
frequency-division
multiplexing
(GFDM), and filtered orthogonal
frequency-division
multiplexing
(OFDM).
These technologies take advantage
of faster processing speeds to offer
higher data rates and are therefore
being considered to replace OFDM
download (DL) and single-carrier
frequency-division multiple access
(SC-FDMA) upload (UL).
Measurements and
Results
For sharing and re-using results
in subsequent simulations, a new
output file measurement feature in
VSS writes a compatible nonlinear
behavioral model text file that
includes information on fundamental
input,
fundamental
output,
intermodulation (IM3) products (for
two-tone simulations), harmonics
(for one-tone simulations), S11,
S22, characteristic input and output
impedances, and noise figure. In
addition, signal heritage information
obtained from the RF Inspector
(RFI) technology within VSS can be
exported to an .xml file.
Even before a simulation is
Figure 5. VSS supports load pull based on digitally-modulated active devices like power transistors to
generate constant contours for communication performance metrics such as ACPR and EVM.
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