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FCC Narrowbanding Deadline
Calls for High-Performance Filters
There’s now less than a year left before the FCC’s narrowbanding edict goes
into effect when all public safety and business land mobile radio systems
operating in the 150 to 174 and 421 to 512 MHz bands must switch from 25 kHz
to 12.5 kHz channels. The FCC’s mandate covers public safety systems, public
utilities, schools, transportation departments, and mass transit. Services
that don’t comply by January 1, 2013 will be subject to FCC enforcement
action that can include fines or loss of license. It translates into one
voice path in a 12.5 kHz channel, two voice paths in a 25 kHz channel, or
data channels with data rates greater than 4.8 Kb/s per 6.25 kHz channel.
Modulation can be either analog or digital as long as they have “12.5-kHz
efficiency”.
Designers of receiver multicouplers and transmit/receive distribution networks
(among other subsystems) need more stringent receive filtering--and crystal
filters are the obvious choice for achieving it. Anatech has been designing
standard and custom filters for just this application for more than 20 years.
They’re used in receivers that operate in every channel of type of affected
system and exhibit the exceptional performance that narrowbanding will
require.
Based on our vast library of designs, we can manufacture crystal filters for
any frequency band covered by the mandate that meet the requirements for
highly-selective filtering. For more information, please call us at (973)
772-4242 or send us an e-mail to sales@anatechelectronics.com.
Microwaves to Speed Drug Development?
English company Uniqsis and Sweden's WaveCraft are jointly developing
microwave-based flow chemistry systems to improve the ability to scale up
compound synthesis during drug development. The team will integrate Uniqsis’
microwave applicator technology and WaveCraft reactors. WaveCraft’s
technology uses an applicator and proprietary microwave generator based on
mobile phone technology to apply microwave energy and accelerate chemical
reactions. Combining flow chemistry with microwave heating could enable
researchers to continuously change power and frequency to optimize synthesis
reactions. Scale-up could then be carried out without the need to re-optimize
conditions.
Help Us Out…
Get a Spectrum Chart!
We’re interested in your opinion and we know how valuable your time is. So if
you would please take a few minutes to answer our short questionnaire, we’ll
send you a copy of the complete U.S. frequency spectrum chart in full color
spectrum chart…always a handy reference.
Please click here
to take the survey….and thanks in advance!
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Greetings {FIRST_NAME},
The Filter Answer Man
The first of our new series of tutorials on filter and other product
characteristics is provided this month by Chung Au, our international sales
manager, who answers some questions he recently received.
If you have any questions you’d like us to answer, please send them to us at filters@anatechelectronics.com.
We’ll answer them in the next issue!
These two terms are often used interchangeably when in fact they are two
different types of devices. A diplexer is a three-port network that separates
incoming signals from one port into two paths. The input signals must be
different enough in frequency to allow filters to provide unhindered
rejection. Conversely, a duplexer is also a three port network but it instead
allows a transmitter and receiver to use the same antenna at the same
frequency. In both cases a high degree of rejection is required to ensure
that the signals do not interfere with each other.
 
Diplexer
Duplexer
Notch Filter Passbands
When specifying a notch filter, we have been asked to provide a design with
the same passband frequencies and notch frequencies.The conflict is obvious
when shown graphically:
SAW Filter Bandwidth Limitations
We have often been asked to provide SAW filters with very wide bandwidths, in
the latest case 91 MHz with a center frequency of 870 MHz. However, such a
bandwidth is too wide for a SAW filter with this bandwidth as the maximum can
10% or less of the center frequency.
Testing for the “Real World”
A seemingly obvious yet often overlooked requirement for system designers is
subjecting the finished product to signals and a signal environment in which
it will actually operate. This was once just “desirable” but thanks to close
channel spacing and an overcrowded spectrum, designers who fail to evaluate
their products under worst-case can conditions do so at their peril.
Fortunately, modern test equipment makes it possible to create simulated
signal environments with relative ease. In addition, there are system-level
software tools that allow a circuit design to be evaluated and modified by
subjecting them to real-world signals. Such efforts may take more time, but
are well worth the effort.
The Importance of Rejection
The rejection of out-of-band signals is obviously the primary goal of every
filter but the specification has taken on new meaning in today's congested
spectrum. As a result, in order to effectively attenuate a signal 3 MHz from
the desired signal the filter must have rejection of at least 40 dB outside
its passband. Less rejection can be tolerated in some circumstances but these
are fewer and fewer every day. Duplexers must have especially sharp cutoff
characteristics as well as high isolation and the lowest possible insertion loss
so that that neither the receive or transmit
frequencies will interfere with each other.
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A Message from Sam Benzacar
Every day we get requests from current and prospective customers for
filters and other products with specifications that simply cannot be achieved
-- by anyone. We also get questions such as the first one in this issue about
diplexers and duplexers, which are often considered the same thing but
aren't.
With that in mind, beginning this month we are dedicating the center column
of the Anatech Electronics newsletter to answering common questions posed by
our customers. Some may seem simple and others will be notoriously complex,
but we’re hoping novices and veterans alike will benefit from a little
“refresher”. We hope you find this information useful.
New Functionality for AMCrf.com!
We have just added several new features to our Web store, www.AMCrf.com, that make it more informative
and easier to use. We have categorized products by specific applications,
added more relevant content to the banner area at the top of the home page,
and several other features we hope will make specifying our products easier
than ever before.
WHAT'S NEW...
When Politics Mix With Technology
LightSquared has charged the government with rigging the latest tests to
evaluate its compatibility with GPS systems so its system would fail (which
it did). And members of Congress have alleged that the Obama administration
and the President himself played major roles in promoting the proposal.
Not Everyone Thinks Smart Meters Are Brilliant
Residents of Chicago suburb of Naperville are fighting the city’s $22 million
program to install utility smart meters, gathering more than 4,200 signatures
and primarily citing health as the biggest concern, as the meters emit (low
intensity) microwave signals.
Taiwan Stays with WiMAX
As the world moves to LTE, WiMAX subscribers are growing fast in Taiwan. The
government says it will push development of WiMAX applications to help the
countries six WiMAX operators expand their networks.
Did you know...
1. The Internet was originally called ARPANet (Advanced
Research Projects Agency Network) designed by the US Department of Defense.
2. In 1878 the first telephone book ever made contained
only 50 names.
3. Originally in 1886 Coca Cola was introduced as an
'intellectual beverage' to boost brain power.
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