The Opportunities and Challenges of LTE Unlicensed in 5 GHz
David Witkowski, Executive Director, Wireless Communications Initiative
In 1998, the Federal Communications Commission established the Unlicensed National Information Infrastructure or U-NII 5 GHz bands. These are used primarily for Wi-Fi networks in homes, offices, hotels, airports, and other public spaces and also consumer devices. U-NII is also used by wireless Internet Service Providers, linking public safety radio sites, and for monitoring and critical infrastructure such as gas/oil pipelines.

MMD March 2014

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Band Reject Filter Series
Higher frequency band reject (notch) filters are designed to operate over the frequency range of .01 to 28 GHz. These filters are characterized by having the reverse properties of band pass filters and are offered in multiple topologies. Available in compact sizes.
RLC Electronics

SP6T RF Switch
JSW6-33DR+ is a medium power reflective SP6T RF switch, with reflective short on output ports in the off condition. Made using Silicon-on-Insulator process, it has very high IP3, a built-in CMOS driver and negative voltage generator.

Group Delay Equalized Bandpass Filter
Part number 2903 is a group delayed equalized elliptic type bandpass filter that has a typical 1 dB bandwidth of 94 MHz and a typical 60 dB bandwidth of 171 MHz. Insertion loss is <2 dB and group delay variation from 110 to 170 MHz is <3nsec.
KR Electronics

Absorptive Low Pass Filter
Model AF9350 is a UHF, low pass filter that covers the 10 to 500 MHz band and has an average power rating of 400W CW. It incurs a rejection of 45 dB minimum at the 750 to 3000 MHz band, and power rating of 25W CW from 501 to 5000 MHz.

LTE Band 14 Ceramic Duplexer
This high performance LTE ceramic duplexer was designed and built for use in public safety communication and commercial cellular applications. It operates in Band 14 and offers low insertion loss and high isolation to enable clear communications in the LTE network.
Networks International

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July 2013

Toward Mapping RF Activity on Earth

By Jim Taber, Director of Marketing & Sales
X-COM Systems

Fred Ortiz, President, dB Control

I f the electromagnetic spectrum was traded as a commodity, its spot price would make gold prices look cheap in comparison. Like gold and other natural resources, some spectrum is of a “higher grade“ in terms of its usefulness but unlike other resources, it is found everywhere, we know where it is – and that when it’s fully utilized in a given area, there’s no more to be found. With this in mind, you’d think accurate knowledge of spectrum utilization in key (that is, the most financially lucrative) geographical areas would be well known. In reality it’s not, thanks to the sheer enormity of the task of acquiring it.

Even armed with the best mapping, drive-by testing, modeling, and other tools, the broadcasting and wireless industries as well as government, aviation, defense, and other entities know surprisingly little about what activity is actually taking place at key frequencies over time. Propagation models that are routinely employed when deploying or upgrading a communication site are very accurate but cannot account for seasonal and other changes in foliage, new construction, and a host of other variables. Drive-by systems and their accompanying software provide accurate coverage maps but only where the measurements are taken, which omits some areas of the coverage footprint that invariably contain low signal strength.

Achieving situational awareness applies not only to the battlefield but to any location where knowing “what’s out there” is important. With the aforementioned finite spectrum and its extremely high value as a backdrop, making the best use of it can translate into increased revenue for a surprisingly diverse group of parties. The federal government would be far better equipped to make decisions about spectrum usage, allocations, and auctions if it knew more about actual activity. Municipalities could more accurately determine places where revenue-generating wireless base stations could be placed. Wireless carriers, which spend huge sums every year claiming they have the best and most broad-based, hole-free “4G” coverage, would be better able substantiate their claims, while reducing churn as well. And these are just a few.

This situation has not been lost on DARPA, and about a year ago the agency issued a broad agency announcement for its Advanced RF Mapping (RadioMaps) program that in partnership with industry will create real-time awareness of spectrum usage over frequency, geography, and time. The program’s goal is to provide a dynamic map that accurately portrays spectrum use so spectrum managers can be more effective in reducing spectrum congestion and reducing interference. DARPA likens it to cameras that show vehicle traffic flow at various times of day. Think of it as a Google Earth for RF (Google isn’t listed as an interested participant – yet).

RadioMaps and other similar industry efforts are clearly not trivial (thus DARPA’s interest) but are potentially achievable. One of the most daunting challenges will be ingesting large swaths of spectrum in a single gulp not once but repeatedly, which will require the talents of increasingly-proficient ADCs and DACs. The result will be massive amounts of data, as even narrowband spectrum capture files can be many terabytes deep. The next step will be to process all of this information to provide meaningful results.

Fortunately, thanks to broadband high-resolution converters, digital signal processing, FPGAs, high-speed mass storage and communications buses, spectrum recording systems and analysis software (all of which are available), accurate information about spectrum utilization may become available that is currently well beyond what commercial and government interests have today.

X-COM Systems
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Uncertain Times for DefenseOpen’s Systems and Changes in DoD Procurement: This Time It’s Real
By Barry Manz

The U.S. Department of Defense has a well-earned reputation for inertia. Many proposals for change are made – but nothing happens. The COTS initiative, which promised cost savings through the use of off-the-shelf commercial parts, sounded terrific at the time. It heralded a major departure from standard DoD procurement that more or less guaranteed that every system would be different in part because it used parts that were developed from scratch, leading to “one-off” systems that were very expensive. Read More...

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