It's been said that most assumptions have outlived their
uselessness, but I assume a few things nonetheless. First, I assume you
have an interest in the wireless industry and filter technologies. If
so, this article will be of interest for you! Next, I assume you're a
design engineer, manager, salesperson, customer, supplier, investor, or
just someone who needs to know more about filter technologies. As such,
here are ten important things you probably should know about RF filter technologies.
- Filters remove unwanted frequency
components from a signal while preserving desired frequency
- The quality factor (Q factor) is
one of the main determiners of filter loss. Lower Q leads to higher
loss and rounding of the filter corners. This rounding of the
corners can be problematic for narrowband modulations.
- The wider the bandwidth and the
greater the required selectivity, the more the insertion loss
parameter must be sacrificed. The design engineer must balance
these characteristics in order to eliminate increasing the power
amplifier (PA) output and potential increased current and matching
- The most common filter
configuration for mobile devices is an acoustic filter — surface acoustic
wave (SAW) and bulk acoustic wave (BAW).
- The most common acoustic filter
architecture is a ladder configuration, where multiple resonators
are connected in a series and shunt arrangement.
- A duplexer with a high isolation
between the transmit and receive frequencies is optimal when trying
to achieve high sensitivity in a user's wireless system
- SAW devices work best at lower
frequencies below 1.5 GHz, while BAW technology works best for
filter designs above 1.5 GHz.
- In today's mobile environment, the amount of bands required in
one device is staggering — and the trend will only increase.
Supporting all these bands causes coexistence issues requiring
filters to reject bands, such as public safety, global navigation
satellite system (GNSS), Wi-Fi, and others. Filters have an
important role in allowing coexistence between bands.
- Spectrum allocation for new
frequencies requires filters to have much tighter temperature
drift. Qorvo's LowDrift™
and NoDrift™ filter technology best addresses these
temperature drift requirements. NoDrift technologies can produce an
essentially zero parts per million per degree Celsius (ppm/°C)
- Advanced packaging technologies
developed by Qorvo, such as CuFlip (pronounced "copper flip") and
wafer level packaging (WLP), enable high
performance and high levels of integration. These
characteristics will be increasingly necessary as the band
count and complexity level of radio frequency (RF) front ends
continue to increase.
To learn more about RF filter technology, download our e-book,
RF Filter Technologies For Dummies®. You'll
learn the basics of RF filters, temperature drift, acoustic filters and
filter packaging technologies.
– Excerpted with permission from John Wiley & Sons, Inc.,
from RF Filter Technologies For Dummies.