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Fachzeitschrift für Hochfrequenz- und Mikrowellentechnik

Products Clock

Products Clock Oscillators Offering Tight Stability Euroquartz has launched a new range of clock oscillators from Statek offering tight frequency stability of ±20ppm over the military temperature range and ±10ppm for industrial applications. Available in frequencies from 10 to 55 MHz, the new STXO range also offers low RMS jitter and low phase noise. Stateof-the-art design, process, manufacturing and test capabilities have made the development of this ultra-miniature 3.2 x 2.5 mm STXO oscillator possible. Key performance capabilities include low RMS jitter typically less than 300 fs, typical noise floor less than -161 dBc/Hz, high shock survival options (>20,000 g) and ultra-low Allan Deviation and period jitter (1.4 ps RMS). Supply voltage options are 2.5 and 3.3 V ±10% with current consumption of 3 mA (no load across temperature range). Offering 15 pF CMOS output load with enable/disable and tristate functions, the new Statek STXO range delivers fundamental frequency output with no PLL artefacts and is housed in a hermetically-sealed ceramic four-pad surface mount package. Offered in versions for industrial applications over -10 to +85 °C and military applications over -55 to +125 °C, the new STXO clock oscillators are available with full military testing per MIL PRF 55310 on request. Tighter frequency stability performance can also be provided to special order. Additional specifications include start-up time of 5 ms maximum, rise/fall time of 5 ns maximum, duty cycle of 45% minimum/55% maximum and low ageing of 2ppm in first year. Defence and aerospace applications include smart munitions, communications, guidance and navigation. Euroquartz Ltd./Frequency Products Ltd. www.euroquartz.co.uk Antennas Directional Patch Antennas for Body-Worn Tactical Applications RFMW Ltd. announced design and sales support for body-worn antennas from Southwest Antennas. Model 1065-031 is a right-hand, circularly polarized (RHCP) antenna while model 1065-032 offers lefthand polarization (LHCP). Developed to offer high performance, rugged antenna options, the antenna radome housing is resistant to damage from drops, being stepped or jumped on, and other potential abuse. Both 1065-031 and 1065-032 antennas are designed for use with handheld or body-worn MIMO/MANET radio systems operating from 1350 to 1390 MHz. Circular polarization offers performance enhancements in multi-antenna radio configurations, crowded RF/non line-of-sight scenarios, and improved performance in adverse weather conditions providing greater radio range for law enforcement, military or civilian applications. Freespace gain is specified at 4.2 dBic. Measuring only 3.75 x 3.75 x 0.51 inches and weighing 3.4 ounces, the 1065-031 and 1065-032 feature a high performance stainless steel SMA(f) RF connector and waterproof, UV stable radome that can withstand immersion in 20 m of salt water for two hours if the RF connector is mated or sealed with a protective end cap. Southwest Antennas body worn products are easily secured into pouches, vests and MOLLE gear. ■ RFMW, Ltd. info@rfmw.com www.rfmw.com 58 hf-praxis 2/2017

RF & Wireless Test & Measurement Noise - Friend and Foe of Engineers Thermal noise is “white” and has a Gaussian amplitude distribution. The term “white” specifies constant output power over a linear frequency spectrum, as opposed to “pink” noise that provides constant power over a logarithmic frequency spectrum. Because of this evenly distri buted power, certain frequency segments of equal bandwidth provide the same power level with white noise, which can be very helpful when analyzing filters, amplifiers, and system responses. Overall output power of white noise sources is dependent on the specified bandwidth. Output characteristics can be described in different ways: Power: dBm, dBm/Hz, dBm/frequency band Voltage: V/Hz Figure 1 shows two white noise sources. Spectrum A has a large variance in power distribution, and thus provides a low crest factor. Spectrum B has a high crest factor, so unwanted signal levels are less frequent By Wolfgang Damm, Product Management Director, Wireless Telecom Group Foe - agreed, but friend? How can noise be appreciated by engineers who labor at the edge of technology when trying to move signals and information as fast as possible from A to B? Isn’t noise something we all want to avoid and eliminate? This column addresses engineers who are interested in exploring the concept of utilizing noise for test and measurement purposes. It discusses how white Gaussian noise can be employed as a versatile signal source. A short introduction discusses causes, sources, and quantities relevant to noise, followed by two application examples that utilize noise: noise as a broadband reference and noise load to determine optimal system operation levels. What Is Noise? Noise is omnipresent in the universe. With the exception of absolute zero temperature point at 0 Kelvin (0 K), all materials produce noise with a power level proportional to the physical temperature of the material. Noise is generated by random vibrations of conducting electrons and holes in the material. It is often referred to as thermal noise. A variety of other effects generate noise as well, but it would exceed the scope of this document to discuss them all. Noise energy emitted by one single element is rather minuscule, but the almost infinite count of vibrating elements sum up to a significant power level - large enough to challenge us when developing sensitive receivers, or operating with ADCs and DACs that have a high bit resolution, just to name two applications. White Noise Ratios: ENR (excess noise ratio), noise temperature (K) The fact that power spectral density is constant over frequency implies that noise power is proportional to bandwidth. If the measurement bandwidth is doubled, the detected noise power is doubled as well and increases by 3 dB. Total power (P) in dBm and spectral power (PS) in dBm/Hz of white noise sources are related by the following equation: P = PS + 10log(BW) BW is the measured bandwidth, and PS is a characteristic quantity of a particular noise source, usually provided on datasheets. Specific noise sources are built for optimal flatness over the frequency band. Gaussian Distribution And Crest Factor Statistical evaluations of related occurring events present always certain kinds of distribution hf-praxis 2/2017 59

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