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APPLICATION NOTEInterference Hunting
Introduction
Over the past decade there has been a dramatic increase in
the population of wireless transmitters found in the world,
with the inevitable result being a dramatic increase in radio-
frequency noise pollution. Every significant electronic device
leaks radiation at some level and the number of cellular phones
in circulation now outnumbers people. The growth of the
Internet of Things (IoT) is only going to make things worse.
Much worse in fact as billions of wireless-enabled devices
populate everything from shop floors to living rooms.
At the same time, wireless technology has become critical to
our daily lives. Drive down any residential neighborhood or
business center with even a basic RF sniffer and you’ll see
Wi-Fi transmitters in literally every location, all powered up and
enabling a steady flow of vital communications. Smartphones
– often with Bluetooth radios in action – keep the wheels
of commerce turning and keep us connected to family and
friends. Maintaining these wireless links in the face of abundant
potential for interference is important work.
In today’s crowded spectrum, just about every frequency is
being shared by some other device. Even if you might think
you don’t have interference, chances are it’s because you
haven’t bothered to look. Hunting down sources of interference
can be extremely challenging and nearly impossible in some
cases – for instance short duration intermodulation products
– without the right tools and knowledge about such factors as
antenna types and signal characteristics.
In this application note, we’ll provide an overview of
interference finding techniques and offer examples to help your
next interference hunting efforts to be more successful. We’ll
also look at why real-time spectrum analyzers (RTSAs) have
emerged as the go-to tool for tracking down elusive signals in
a crowded spectrum. Once expensive and desk-bound, a new
class of affordable, battery-powered, USB-based RTSAs such
as the Tektronix RSA500 make an RTSA a powerful tool for
interference-hunting applications.
The Interference of Things
One of the drawbacks of having so many electronic devices in
our world is that they all emit electronic signals which causes
the disruption of radio and wireless signals. The “noise”
created by these signals creates interference with other nearby
signals which disrupts transmissions. Noise can be created by
a microwave oven, cell phones, poorly shielded power lines,
fluorescent and neon lights or dimmer switches. With more and
more electronic devices being developed and sold, there’s no
doubt that noise and interference will continue to be a major
issue for engineers and spectrum managers alike.
The problem is only going to get worse as the Internet of
Technology (IoT) technology expands, increasing the number
of signals fighting over spectrum space. It’s not a stretch
to rename IoT the “interference of things.” While this is the
reality of having a shared unlicensed spectrum, the challenges
that the IoT are bringing are a major issue. The IoT adds very
complex RF-control chips to a vast number of electronic
devices such as light switches, cars and many types of
appliances. Each device is a potential generator of more noise
and interference. While it’s possible for design engineers to
reduce the amount of noise by adding additional shielding and
other noise-reducing features to products, it raises the cost to
the consumer and there’s no getting around the fact that there
are relatively few channels available for millions of devices.
Another challenge to tackling these issues is that there is no
perfect system for detecting noise. Trying to locate problems
in a city is especially difficult, compared to the suburbs or
countryside, since there are so many electronic devices in
use. Adding yet another layer of complexity, noise can change
over time based on a wide variety of issues such as location or
weather. The interference of things is already a challenge and
is certain to get worse over time.