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Figure 1. Three Use Cases for 5G
Figure 2. DPD Algorithm Using 5x Signal Bandwidth
wireless radios cost 20 percent of
today’s prices, next-generation test
equipment must be capable of faster
and more parallel test approaches.
Evolution of the NI Vector
Signal Transceiver
In 2012, NI announced the revolutionary
new PXI Vector Signal Transceiver
(VST). The VST was unique in
that it combined a 6 GHz RF signal
generator, 6 GHz RF signal analyzer,
and a user-programmable FPGA into
a single PXI module. Not only did the
instrument’s excellent RF performance
allow it to serve applications
from R&D to manufacturing test,
but its user-programmable FPGA
enabled applications ranging from
measurement acceleration to channel
emulation. However, the evolution of
wireless technology demands a new
approach to RF design and test. As
a result, NI has introduced a second-
generation VST that offers wider
bandwidth, extended frequency range,
and a larger FPGA in an even smaller
form factor.
Bandwidth
Over the past decade, wireless
standards have evolved to use
significantly wider bandwidth channels
to achieve higher peak data rates. For
example, since 2003, Wi-Fi has evolved
from 20 to 40 to 160 MHz in today’s
802.11ax. Mobile communication
channels have evolved from 200 kHz
in GSM to 100 MHz in today’s LTE-
Advanced technology. In the future,
technologies like LTE-Advanced Pro
and 5G will drive this trend even
further.
Especially when testing semiconductor
devices, the bandwidth requirements
of the instrument often exceed the
bandwidth of the signal. For example,
when testing RF power amplifiers
(PAs) under digital predistortion (DPD)
conditions, the test equipment itself
must extract a PA model, correct for
nonlinear behavior, and then generate
a corrected waveform. Advanced DPD
algorithms often require 3X to 5X
the RF signal bandwidth. As a result,
instrument bandwidth requirements
can be up to 500 MHz for LTE-
Advanced (100 MHz signal) and 800
MHz for 802.11ac/ax (160 MHz signal).
One of the most significant
enhancements of the second-
generation VST is its wider
instantaneous bandwidth: 1 GHz.
Because of this wider bandwidth,
engineers can use the second-
generation VST to solve application
challenges that currently can’t be met
32 l New-Tech Magazine Europe