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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November 2013

The New Face of Hardware in the Loop
By Justin Panzer, Business Development Manager, Tektronix

Liam Devlin, CEO, Plextek RF Integration

The extraordinary complexity of smartphones, tablets, and other wireless-enabled products coupled with new product “sell-by” dates measured in months can make design, testing, and verification a formidable challenge at best. This assumes that prototype hardware is even available to test throughout the process, which there often is not. In short, it is no longer economically feasible to wait for systems to be built before evaluating their constituent functional blocks using real-world stimuli. It’s not surprising then that testing of RF and microwave subsystems and systems with hardware-in-the-loop (HIL) has evolved from rudimentary to revolutionary in less than a decade.

HIL itself is hardly new, and has been used in developing automotive, industrial, aerospace, automation systems (among others) for many years. Even in the RF and microwave domain, HIL has been employed for decades --- using noise sources to stimulate mobile phones and satellite communications terminals for example. However, the difference today is the versatility of the test equipment used to realize HIL and how it can reduce development time, cost, and angst. The real-time spectrum analyzer and arbitrary waveform generator can play important roles in obtaining these benefits.

It was once common practice to produce a working system or major subsystem prototype before subjecting it to the signal environments it would experience in service. Using the wireless industry as an example, in the mid 1990s when CDMA one was first deployed as part of the IS-95 standard, Additive White Gaussian Noise (AWGN) was the stimulus employed to test CMDA system performance. This provided a fair approximation of a signal environment--and there was no better option. However, when placed into service, base station transceivers often performed poorly in the real world to which they had never been exposed.

As digital transmission schemes evolved and began to use higher-order modulation schemes, simulation with such a simplistic stimulus was no longer acceptable. Test equipment manufacturers, whose requirement is always to be a step ahead of what their customers need, quickly harnessed the most advanced digital signal processing available to produce arbitrary waveform generators and dedicated test systems capable of producing representative stimulus signals at baseband and RF frequencies. This allowed the subsystem under test to be exposed to exact replicas of signals contained in the latest standard, legacy standards, or basically any waveform the designer required.

Today not only can these test systems produce these signals, they can produce entire signal environments, including impairments such as multipath and fading, multiple signals of various types, as well as interference, singly or together. Without this ability, the development of wireless-enabled devices would require significant redesign and testing, resulting in development cycles that would well exceed the time available.

The need for accurate stimulus signals is made even more important as the FCC attempts to cram as many services as possible in a given amount of spectrum and reduces guard bands between them. This places an enormous burden on RF power amplifiers as they must be squeaky clean (no spurs, no spectral regrowth) and on receivers that must be highly resistant to interference. Only by subjecting the transmit and receive signal paths to realistic signal environments at one or more stages of development can a reasonable margin of safety be ensured.

The consumer market offers a good example of the power of HIL testing, but it is far from the only one. Defense systems, whether battlefield radios, satcom terminals and transponders, electronic attack and protection systems, or radars, must perform in extraordinarily dense signal environments created by emitters they cannot control. Dropped calls are minor annoyances compared to soldiers in-theater whose radios don’t work or fighter pilots whose radar warning receiver miss a threat.

An EW, SIGINT, or ELINT system captures signals at RF, digitizes them, processes them, reconverts them to RF, and in the case of a jammer, retransmits them in a form designed to “fool” the threat. A real-time spectrum analyzer can be used to capture these signals, which can then be used at baseband or RF to which the system-under-development can be subjected. An arbitrary waveform generator can be inserted in this “loop” to help create the waveforms and waveform sequences that form the stimulus signal.

In many locations throughout the world, even a relatively short-term recording of RF activity at frequencies in the most densely-populated areas of the spectrum and within a relatively narrow bandwidth can be quite long. In fact, surveillance systems often remain in place for days to find random, intermittent, or other signals of interest. Storage for such capture files requires terabytes of storage, which is far beyond what a bench-top instrument can store, as mass storage is obviously not required in its primary roles.

For this purpose, spectrum analyzers can be supported by long-duration RF signal capture, record them as baseband I&Q signals, and played back either at baseband or quadrature modulated to the original or any other frequency. In between, software tools can be used to find “signals of interest” in this spectral haystack along with where and when they were recorded. Instances of their occurrence can be extracted from the main spectrum capture file and passed to RF editing software that allows a new, much smaller file to be created that includes only the signals of interest. This file can be used as a stimulus for the system under development – and a variety of other purposes as well.

These are just a few of the many examples of how real-time spectrum analyzers and arbitrary waveform generators can provide significant benefits in an HIL environment. In each one, their unique capabilities can make the difference between creating a product that works as intended and gets to the marketplace on time.

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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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