Interconnection
Ruggedised micro miniature coax connectors deliver SWaT based RF data
Electronic circuits featuring high density, low weight and rugged signal integrity are demanded in nearly every portable electronic system today. Today’s EMS (electromagnetic spectrum) is covering our earth from use in electronic warfare to civilian communication services. Bluetooth and button coax are both used within small portable systems, but both systems are severely limited in supporting higher signal speeds, longer distances and do not withstand the rigors of high shock and vibration. Bob Stanton, director of Technology, Omnetics Connector Corp. tells us how to solve these issues
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ano-coax connectors are available with threaded metal coupling systems to ensure constant RF service up to 20 gigahertz with a quarter the size of older SMA connectors and pass extreme shock and vibration specifications. Miniature coax cabling also adds shielding and cyber protection that enhances the rapid transfer quality and rate of data and images from light-weight man-portable products to mounted surveillance cameras in airports. Coax also enables equipment inside the box by offering increased signal transfer speeds from electronic module to module without fear of noise, signal loss or distortion.
Unmanned aerial vehicles (UAVs) and satellites collect high resolution images and transfer them to earth. As our electronic modules densify and shrink, they are also expected to handle much more data per second. Since nano- coax connectors require only a quarter the size of older designs, and use miniature coax cable, the whole electronic system is reduced in size and weight. The challenge is to offer complete performance at full RF signal wavelengths at these reduced sizes. Omnetics nano-coax interconnects maintain that level of “military-quality” ruggedness while continuing to offer performance up to 20 gigahertz speeds. Key advantages include long term performance, lower power demand and full RF quality transmission signalling for circuitry used in more extreme environmental applications. The aeronautics industry is
redesigning much of their control, storage and data processing systems from inside the cockpit to portable remote pilot control systems. Military aeronautics groups are extending their requirements to include interaction processing from pilot-worn helmets to heads
As our individual
mobility and use of remote equipment increases, so does the demand for very fast high-quality data transmission. Signals are being captured, processed and transmitted with low power nano-coax from mobile antennas on backpacks and often sent afar from field radio. Soldiers and field engineers depend upon GPS sensing and can overlay data and future positions on computer maps and navigation systems.
14 December 2018/January 2019
up displays. Interconnection systems that support upgrading signal processing, with higher speeds, and more data are needed. Across the aircraft, increased signal capacity and reduction of size and weight of the electronics is significantly increasing flight times. UAVs, for example, are have extended distance capability from home control systems. Standard coax connector and cable systems are being reviewed where cable size and flexibility are needed
Components in Electronics
in the newer compact systems. By using more compact electronics, portable tarmac test and instrument maintenance equipment can be moved quickly and applied in unique environments.
Nano-coax is coming of age in space, with the increased use of cube satellites and micro-satellites operating on positioning technologies and/or offering radio systems that often operate on frequencies of four to 20 gigahertz. NASA and the ESA (European Space Agency) have recognised the use of micro- miniature and nano-coax connectors. Because great performance and use of high speed interconnection systems demand a thorough understanding of both connector and cable, we must detail the design of both elements of the nano- interconnections. The connectors are designed using the same materials as larger connectors specified in SMAs and other screw-lock type coax connectors. Designers vary in the metal used for shells and select either brass or 6061 aluminium. The Nano-coax uses copper alloy contacts specified in MIL-DTL-83513 that are nickel and gold plated to pass high shock and vibration specifications. Some applications are plugged and unplugged frequently and it is key to design with pin to socket mating systems capable of exceeding over 2000 mates and de-mates. This feature also assures constant signal integrity during high shock and vibration. Materials used within nano-coax connectors have been selected to have passed NASA and other agency chemical out-gassing requirements to protect other circuitry within the same satellite. Connector designers work carefully with coax cable suppliers to retain the highest signal speeds while also reducing diameter. Cable jacket and insulation are selected to assure dependable impedance and flexibility. Omnetics typically uses a supplier patented, low loss 29 AWG coax cable measuring .047” in diameter that is designed to match 50 ohms impedance circuits. Signal speeds are often specified in
relation to how fast a signal can pass down the cable compared to how fast it would travel in free space. That relationship is stated as a ratio or percentage of one over the other. For example, the coax transmission lines to our houses are often stated as vF of 66 per cent. The small coax cable used in micro miniature systems are selected to be at least 70 per cent velocity of propagation and are set at about 29 Pico farads (one trillionth of a farad). This capacitance
specification is also critical because it is the measure of the capacity of a circuit component to store charge and we do not want to store any of the signal on the cable or slow the signal down with unwanted capacitance. Cable jacket materials are Teflon FEP (Fluorinated Ethylene Propylene) because it offers a combination of great electrical properties as well as good physical and chemical resistance. In addition, the jacket protects the cable in service temperatures up to 200°C and is flame resistant. The great thing about nano-coax technology is that it is well defined, ready and available for designers. This will help reduce size and weight simultaneously in their efforts to design RF circuitry up to and above 20 gigahertz for rugged and extreme environmental applications. A wide variety of individual formats are available from cable to cable, cable to board and even board to board. To reduce weight and size, multiple nano-coax sets can be set inside a standard micro-d connector. To further reduce total circuit size and weight, hybrid coax and signal systems are readily available in the industry. With combinations of nano-coax and standard signal pin and socket systems, the system designer can request a special insulator housing that directly matches his circuit requirements. Combinations of power, signal and RF interconnections can be modelled quickly on solid image systems by the connector supplier within as little as one day. The system designer can link directly to the new model and talk on the phone with the connector company to refine details and ensure fit. Miniature coax and nano-interconnect systems are on the rise and assisting in offering compact designs for portable and rugged high speed transmission designs. Dream small, and dream fast for the capability is here.
www.omnetics.com
www.cieonline.co.uk
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