Evaluation_Engineering_October_2020 - 14

SIGNAL GENERATORS

Rohde &
Schwarz R&S
SMCV100B
vector signal
generator.
Courtesy
of Rohde &
Schwarz.

R&S SMB100B, R&S SMBV100B, R&S
SMC100A, and R&S SMCV100B in a compact form," he said. "The R&S SMCV100B,
for example, offers a formfactor with 2 HU
and one-half 19-in. width, and the instrument includes simple operation for ease
of use, in addition to allowing customers
to create their own user menu. Plus, the
instrument's upgrade concept allows users to add desired functions via software
keycodes and even upgrade features without sending the instrument to a Rohde &
Schwarz service center."
For customers looking for automation,
Wilson said, "R&S signal generators offer a unique SCPI recorder capability that
enables engineers to quickly and easily
create the test code required to control
the generator. Having a range of compact
bench generators enables customers to
select the performance and price point
that meets their requirements, while
saving space and benefitting from the
convenience of a benchtop instrument."
"PXI-based signal generators are ideal
for a wide range of functional test applications where high performance in a
compact package is valued," according
to Semancik at Marvin Test Solutions.
"Many test designers are tasked with
reducing overall test-set footprint, and
PXI-based solutions serve this need," he
said. "Additionally, this format is ideal
when tight coupling with other instrumentation is required, thanks to the triggering functionality incorporated in the
PXI standard."

14

EVALUATION ENGINEERING OCTOBER 2020

Semancik noted that traditional
benchtop and rack-and-stack instruments that incorporate high-speed
communications interfaces such as
Ethernet (LXI) are not constrained by
the size restrictions put forth by the PXI
standard, reducing some of the component selection and placement challenges.
"However, interfaces such as LXI have
inherent latencies that may pose synchronization challenges for certain applications, requiring external triggering
and handshaking implementations not
typically needed with PXI instrumentation," he said.
Lipps at Newark commented that
since most benchtops are geared toward
a specific application, traditional benchtop instruments can provide the greatest performance compared to the other
configurations (handheld, USB, and PXI),
but they can be bulky and space can be
limited. In contrast, handheld instruments with display offer portability.
"However, they generally suffer from
lower performance and functionality
due to constraints on size and weight,"
she said.
Lipps added that USB instruments
provide portability, "...but again, performance is restricted, and a PC is required
to work with the equipment, reducing
flexibility." Finally, she said, "PXI modules are great for mass-production testing, and users are able to customize with
other modules in a single test solution.
However, they require a PXI rack to work

with other PXI modules, which can be a
limiting factor for some engineers who
don't already have these requirements
in place."
Chonko at SIGLENT largely agreed
on the benefits of the various formfactors, adding, "Handheld designs are very
portable and easy-to-use in the field, but
this typically comes at a price premium
for the battery operation and the design expertise required for engineering
battery-powered devices. USB and PXI
modules are ideal for production test
where space for instrumentation is at
a premium, but a computer is required
for operation, and there is no easy way
to simply 'see' what is going on without
working through a computer interface.
The current SSG format is benchtop, but
it easily integrates into a rack-mount for
automated test and is small enough to
be considered portable."
Cassacia, Plorin, and Hsu commented
on several trends that instruments like
the M9384B and M9383B address, including high output power, high signal
integrity, and phase coherence for multiple channels. "Exponential growth in demand for faster data-rate applications has
triggered the need for new technologies
capable of wide signal bandwidth at high
frequencies," they said. "However, wider
bandwidths gather more noise and higher
frequencies cause more path loss. A microwave or millimeter-wave vector signal
generator requires higher output power to
overcome the excessive path loss."
They pointed out that wider bandwidths cause inferior frequency responses and higher frequencies have
higher phase noise. "They both degrade
modulation quality," they said. "When
increasing output power, it also introduces nonlinear distortion to the output
signal and degrades modulation quality."
They continued, "Most of the new wireless technologies are adopting multiantenna techniques such as multi-input
multi-output (MIMO) and beamforming
techniques to improve spectral efficiency
and radio coverage. The timing synchronization and phase coherency between
tested channels must be aligned precisely to accurately assess multichannel
signal performance."
Evaluation_Engineering_October_2020

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