Novel Technologies
Some new technologies require T&M companies to come
up with systems for testing special systems, such as mesh networks and MIMO.
Orthogonal frequency-division multiplexing (OFDM), which is the modulation/
access scheme of choice for most new
wireless systems, presents special problems for both test signal generation and
analysis given the many different formats
used. Another challenge involves testing
systems like WiMAX, with adaptive modulation that adjusts to changing channel
conditions.
Fixed And Mobile TV
A quickly
emerging test challenge concerns wireless digital and high-definition television
(HDTV). While a predominance of video
comes to the TV set by cable, there's still
a need to test over-the-air and satellite TV.
Growing adoption of big-screen digital
and HD sets, as well as Congress' mandate to get rid of analog TV in favor of digital TV in 2009, creates a need for wireless TV testing.
Another forthcoming testing challenge
will be the video capabilities of cell
phones. They're already present in some
designs, but the major push hasn't really
begun. Standard test techniques can be
used to test video delivered over the
existing networks, though some special
measures will be required when separate TV receivers are built into cell phones. As usual, multiple standards will
prevail, like Europe's DVB-H and Qualcomm's MediaFLO.
Software-Defined Radio
How do
you test an SDR anyway? It has an RF section, meaning some basic RF tests will
work. But the real challenge lies in the analog-to-digital converter/digital-to-analog
converter sections, up/down conversion,
and the baseband parts of the system.
Here, software rules and multiple levels of
operation occur, not to mention the use of
multiple protocols in some cases. Obviously, SDR testing is largely software. Like
some standards, testing procedures will
be defined, and T&M companies will participate in creating test procedures.
Speed And Ease Of Use
Speed is
becoming an even greater challenge as
time-to-market gets shorter and margins
fall. Reducing test time will make any
manufacturer more competitive and profitable. With cell-phone handset sales slated to exceed 1 billion this year, how will all
of those units get tested to the strict standards that define them in a timely manner?
On top of that, ease of use is essential. Setup
time must be minimal, and a zero learning curve
is desirable. With standards and testing getting
more complex every day, speed and ease of use
get tougher to achieve. But for customer satisfaction, these features are a must.
Automation
Test automation is common
but becoming more important, particularly to
achieve speed and ease-of-use goals. That
means automated test systems are essential to
achieve those volumes. In most cases, the key is
better software.
Under Pressure
To reach the goals set for
wireless test equipment, vendors have begun to
adopt a more modular approach to testing. PXIbased modular test solutions are smaller and
lower in cost. They also offer the flexibility to be
quickly set up, changed, and expanded thanks
to the hundreds of modules available from multiple manufacturers.
Test time has become more critical in most
wireless test systems. When analyzing test time,
it becomes clear that it breaks out into four primary segments: device-under-test (DUT) setup,
test-equipment setup, signal-acquisition time,
and data-processing and analysis time. Instrument setup and signal-processing times tend to
dominate, so any optimization of the equipment
focuses on reducing those times.
One promising approach is to adopt an SDR
architecture for building test systems, which can
be done in a modular fashion. For signal analysis, an SDR receiver is a front end with downconversion and a fast IF digitizer. Software modules then demodulate and further analyze the
resulting digitized signal. Analysis may be on a
Pentium PC, a fast RISC processor, a DSP, an
ASIC or FPGA, or some combination as the test
situation requires.
For signal generation, an SDR architecture
would use arbitrary waveform generators
(AWGs), direct digital synthesizers (DDSs), and
fast DACs. Again, modularity is the key, giving
the instrument flexibility to be configured and
reconfigured to the job.
Finally, overall performance means any new
instrument must have ever-faster signal processing and analysis to speed test throughput,
wide modulation and demodulation bandwidth,
wide dynamic range, and low noise. While all
test instruments manifest themselves as an
expensive piece of hardware, the sophisticated
software inside does the analysis and automates the process.