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 2014

Interference: The Creeping Menace
By Sam Benzacar President, Anatech Electronics

Liam Devlin, CEO, Plextek RF Integration

Interference has been the bane of communication system designers since the earliest days of radio. At least back then, there were fewer sources to contend with but also far fewer remedies at their disposal. Today, every type of communications system faces interference challenges that are unprecedented and getting worse. The reason is simple but the solutions can be complex.

For a graphic representation of just how many emitters are out there, simply hook up an antenna to a spectrum analyzer or RF recording system and examine the results. One vendor of the latter type of system noted that when connecting a length of wire to it inside their building in the urban area where there facility was located and recording the results at 2400 MHz, the result was more than 10,000 signals (including periodically the company’s microwave oven) over a period of only 15 minutes.

Consider the sheer number of services competing for spectrum between HF and about 6 GHz. At the low end there are the dozens of traditional services that have found a way to coexist even though they have to accommodate not just interference among themselves but atmospheric disturbances, continually varying propagation conditions, and spurious and harmonic content coming from sources covering the entire globe. As we move into the VHF region, atmospheric interference sources are less an issue, although propagation anomalies such as atmospheric ducting can still play havoc with avionics and public safety systems, among others. Above this frequency and up to about 1 GHz, the spectrum is essentially filled with licensed services ranging from FM radio and TV to wireless carriers, public safety and land mobile radio, as well as a broad array of government and defense systems, and even more.

Moving up higher in frequency adds radar, satellite communications, and unlicensed ISM systems, all of which are increasingly more densely packed than ever, giving wireless carriers even more heartburn. In fact, there is so little spectrum left that the Obama administration has mandated that government agencies must either share the spectrum they have – or lose it. As no one likes to share, least of all the Department of Defense, the speed of “creating” additional spectrum for wireless data services through sharing has been less than an unbridled success.

One of the alternatives is to begin using spectrum higher in the microwave and even millimeter-wave regions, which are far less populated but have their own problems, the most formidable of which is that thanks to their shorter propagation distances, it requires far more base stations, repeaters, and small cells to cover a given area than are required at lower frequencies. This trend is already in its early stages and it is very likely that “5G” wireless services will need to resort to these frequencies, even those well into the millimeter-wave region where propagation over even moderate distances is difficult.

To all of these sources we must now add small cells and Distributed Antenna Systems that are appearing in increasing numbers, and analysts project that the vast majority of such systems have not yet even been deployed. Finally, there is the extraordinary expansion of Wi-Fi, which bears as much resemblance to its origins as a Model T Ford does to a Mustang Shelby. Cable companies have already deployed hundreds of thousands of Wi-Fi hotspots throughout the more populated areas of the country, and thanks to Hotspot 2.0 and its roaming capabilities, hundreds of thousands more are likely to appear in the near future. Not only can they interfere with each other they can also interfere with all the other services operating at these frequencies.

So what’s the answer? Incredibly strict tolerances on adjacent-channel interference (and their impact on the design of communications components and systems) and greater spectral efficiency in general will play key roles. And of course, as they have done time immemorial, RF and microwave filters will continue to be the most widely-used hardware solutions.

Contrary to what many people believe, filter technology is not static and filter manufacturers such as Anatech Electronics are working to squeeze every last decibel of attenuation from every type of design from tiny SAW filters to huge cavity filters and everything in between. The most advanced designs can provide extraordinary amounts of rejection, a metric that will continue to be in great demand for obvious reasons.

So in short, interference is here to stay and filters as well as digital techniques of various types will have to stay ahead of (or at least keep up with) the advancing interference menace.

Anatech Electronics
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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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