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.

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...


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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Obama to Government: It’s Time to Share
By Barry Manz

The President decreed in a memorandum on June 14 that more spectrum must be “found” to satisfy wireless carriers’ need for more bandwidth. As most every slice of spectrum of practical use to the wireless industry is currently allocated to a specific service, this means something will have to give.

That something will be the federal government, as it “owns” more spectrum than everyone else. The allocations of DoD in particular make up the greatest share of what the government owns, even though it uses only about 10% of them. As spectrum has become the world’s most precious commodity, and as DoD has historically clung to its allocations like a drowning man to a lifejacket, this task is likely to be Herculean at best. This will be further complicated by the fact the FCC will have to work together with the Department of Commerce to achieve the end result. The FCC has authority over commercial and all government entities except the federal government, which is the domain of the commerce department.

The message, as the memorandum repeatedly points out, is that the time for band sharing has come. Government agencies must either share their allocations with commercial services or lose them. No more playing the “national security” card for DoD, unless it can prove that moving whatever it’s doing at a specific band will have a major negative impact on its operations and the nation’s safety. DoD isn’t alone in its loathing for sharing electromagnetic resources: Wireless carriers fear that sharing spectrum with anyone, least of all the federal government, is likely to cause interference problems and is a lot more uncertain than gaining it exclusively through auctions. Nevertheless, sharing will soon become a fact that no one likes but everyone will have to live with. That is, unless the White House and the FCC can defy the laws of physics and truly “find” more spectrum.

This situation wouldn’t have risen to its current state if services that rely on the ether all appeared at once and were simultaneously allocated places to operate. Rather, when new services appeared, beginning with radiotelegraphy in the early 20th Century, they were plopped into the spectrum for which equipment could be made. As technology evolved and it was possible to communicate on higher and higher frequencies, a new service could be allocated spectrum best suited to its needs (assuming again that it was technically possible). The result is today’s spectrum map, which looks like a hard drive in need of defragmenting.

All frequencies have propagation characteristics that are well suited for some application or applications, but for wireless carriers the region between VHF and the low microwave frequencies is by far the “best”, falling off rapidly in usefulness beyond this point. Higher frequencies are technically viable but economically nightmarish, requiring huge numbers of small cells to cover a specific area.

Practically speaking, what this means is that any spectrum that can be wrested away from its current owners will be at those VHF-to-low microwave frequencies that carriers can use. The federal government owns quite a bit of it. If the challenges just mentioned were the only ones, then perhaps government/private industry band-sharing would be less onerous. However, sharing a band may mean that the current occupant will have to move at least some of its service elsewhere, at potentially massive cost, which “someone”, probably taxpayers, will wind up funding at least in part. The new band may also not be as suitable for that application as the previous one, so band-sharing combinations will have to be carefully sculpted. Multiply this by the number of band-sharing plans and other refarming efforts that the government will have to orchestrate to gain the 1 GHz it thinks is available, and the enormity of the tasks ahead become clear.

The good news for the RF and microwave industry is that in its entirely the plan will requires substantial amounts of new hardware, essentially creating a new market where there was none before. Who could argue with that?

Barry Manz is a contributing editor to Microwave Product Digesting can be reached at



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MMD March 2014

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The Design of Ultra Narrowband Amplifiers Using Small-Signal Varactor Upconverters
This paper presents a method of realizing tunable microwave amplifiers with ultra narrow bandwidths that can be less than 0.5% by the use of a varactor up-converter (UC).
Planar Monolithics

Directivity and VSWR Measurements
Return loss and VSWR measurements are complicated by the finite performance of the directional device used to measure the reflected power. The only accurate and convenient way to make return loss measurements is with a well matched high directivity directional coupler or bridge.
Marki Microwave

Switch Solutions for Systems with Low PIM Requirements
Dow-Key Microwave has invested in R&D for new RF switch products designed specifically to reduce intermodulation (IM) in coaxial switches.
Dow-Key Microwave

How to Specify RF and Microwave Filters
Covers cavity, ceramic, LC, crystal and helical filters.
Anatech Electronics

Mounting Considerations for Medium Power Surface-Mount RF Devices
Covers all factors that must be considered when mounting SMT devices.
TriQuint Semiconductor

Biasing MMIC Amplifiers
How to bias MMICs along with theory and techniques.

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