FEATURE MILITARY & DEFENCE SUPPLEMENT RUGGED HIGH-SPEED DATA CONNECTORS
The need for high-speed connections has expanded from office environments to more difficult implementations, including those for the military. Here, Nick Harper MD at ODU UK, looks at rugged high-speed data connector requirements and how they are currently being met
here has been many new market developments and changes in the military and security sectors around the world in recent years, but the requirements have remained constant: The end-users demand technologies and equipment that are increasingly powerful but smaller, faster, lighter, as well as more reliable in extreme conditions – so the OEM’s want connectors of reduced weight, increased robustness and simpler handling, all in a smaller
space-envelope.To this has to be added never- ending increases in high-speed data levels. We’re all familiar with the types of
T
connectors that transfer high-speed data in our everyday lives - whether we take notice of them or not - there are also high-speed connectors found in commercial and industrial applications such as data storage, servers, switches, and routers. These products offer superior high-speed electrical signal performance, required for the ever- increasing amounts of data processing that our lives demand. Unfortunately, although these familiar connector designs are perfectly adequate for relatively benign home or office use, they do not offer the ruggedness needed for the more demanding military environment. The transfer of commercial technologies into the military domain has increased the need for USB, Firewire and RJ45 connectivity. The rapidity of this change has resulted in a lack of suitable connectors that are able to support data-transfer whilst achieving military ruggedness standards. The current response has been to re- package the standard commercial connector inside a MIL-STD approved housing. However, this solution, whilst functional, does not allow for OEM’s to reduce the size and weight of their equipment, the prime demand from the end-user.
THE SOLUTION Push-pull connectors do not require the additional ‘finger-space’ between connectors needed by traditional MIL-STD screw or bayonet connectors, so the overall space- envelope can usually be reduced by about one-third. So, apart from the space-saving, what turns a connector into a first-class, high-speed connection? Above all, it’s in the detail. Weight is a prime factor for most field-use
S8 JULY/AUGUST 2015 | ELECTRONICS
frequency parameters such as a stable dielectric constant and a low dielectric dissipation factor.
DATA RATES Skilled contact arrangement and design with the precise addition of compensation regions can optimise a connection to the point that it is possible to transmit data rates of up to 10Gb/s. Achieving this entails optimisation of the characteristic impedance, so as to achieve an acceptable return loss. When deciding the contact arrangement, it is also essential to make sure that crosstalk among the differential pairs is minimised by the use of targeted field control. This allows CAT 6A quality to be achieved without the necessity of adding an expensive internal shield plate. Field use calls for a lot of technology in a
Figure 1: Figure1:
Disconnect space needed between connectors
Figure 2:
ODU AMC Push-Pull or Break-Away
equipment. So, if the end device must be lightweight, the weight reduction starts with the connector. For example, using aluminium reduces the weight of the housing. When combined with a special, low-reflection surface, the connector is ideally suited for field use. The choice of the insulation body material also demands special attention. The plastic must withstand the hard environmental conditions and cope with sensitive high-
compact package, which makes it all the more important to have 360˚ EMC shielding, even for miniaturised connectors. This shielding blocks the penetration of interference (both external and among the various systems) that could impair the signal and data transmission. For example, radio and GPS equipment are often located close together, but neither system can interfere with the other. In a system solution, an especially critical factor is the continuous flawless contact of the cable on the connector housing, so as to guarantee the 360˚ shield.
ROBUSTNESS Connectors used in military and security systems face extreme conditions such as water, dirt, salt, temperature, and mechanical stress. No matter how small they are, connectors must withstand all these environments. Connector solutions must be tested in accordance with MIL standards and offer an IP68 rating to ensure that they are tightly sealed and resistant to salt-water spray. Specially designed ‘easy-clean’ versions are also available for field use. Mating reliability is also a critical criterion
for miniature and subminiature connectors. The use of both mechanical and colour coding guarantees reliable and simple handling. Also, the ‘scoop-proof’ design offers additional reliability as the connector pin contacts are not damaged if the connector shells are misaligned during mating. Where needed, connectors to the same specification are also available with a break-away or ‘snatch’ function. With a diameter of 10mm to 18.5mm and up to 40 contacts - a neat solution to an awkward problem.
ODU UK
www.odu-uk.co.uk 01509 266433
/ ELECTRONICS
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