Unmanned Systems Technology 024 | Wingcopter 178 l 5G focus l UUVs insight l CES report l Stromkind KAT l Intelligent Energy fuel cell l Earthsense TerraSentia l Connectors focus l Advanced Engineering report

86 such as Lidar or phased-array radar. These sensors rely on a high number and range of transmissions for their imaging capabilities, which in turn requires high pin counts from their circuit boards in very tight spaces, increasingly exceeding those which micro-D can provide. As a rule of thumb, a typical micro-D connector is four times smaller than a typical D-sub. The nano-D, in turn, tends to be around four times smaller than the micro-D. Much like the micro-D, the nano-D can be ‘stretched’ by suppliers to provide more contacts. As many as 65 contacts can now be held by a single nano-D, potentially to replace multiple shorter nano-Ds and save on fastener space. The smaller standard nano-D also uses two screws either side of the connection for a relatively costly but secure locking mechanism. Alternatively, latching nano-Ds are offered by some suppliers, if saving space is important. The quicker, tool- free mate that this enables can also reduce a vehicle’s manufacturing and maintenance times. Further, both micro-D and nano-D connectors are increasingly being customised with hybridised configurations for carrying power and multiple signals at once. Advances in solid-modelling software to generate these new and complex designs saves a lot of space and weight inside unmanned vehicles because multiple subsystems can be run through a single cable harness to the autopilot. For example, two power pins might carry the higher currents for power supply, with multiple small-wire contacts to carry the 1-3 A currents for the data signals. The space and weight being saved through this increasing customisation of micro-D and nano-D connectors is far greater than what is achievable using other high-reliability Mil-Spec designs, such as MIL-DTL-38999 circular connectors. It also allows designers and engineers to trade-off length and height of connectors to their PCBs. They can go from single-row D connectors to dual, triple or quadruple rows (retaining the same number of contacts) if too much space is being taken up along the length of the circuit board, or to reduce the number of rows if vertical space is at a premium. That may not matter so much for very large maritime surveillance MALE UAVs or large UGVs or USVs, in which size and weight constraints are not a critical factor. In these cases, the nano-D will not be considered, and reducing manufacturing and integration costs by using the larger D-sub or non- customised micro-Ds may be preferable. However, micro-D and nano-D can have a slight disadvantage versus other connectors owing to their interconnection. The high pin densities of the standards mean they forgo any mechanical retention features to hold the February/March 2019 | Unmanned Systems Technology Focus | Connectors PCB connectors for small unmanned systems often come with a pre-crimped length of wire (Courtesy of Harwin) Unmanned networking technologies such as swarming and 4G LTE links will depend on advances in RF coax connectors to make them capable of higher speeds (Courtesy of LEMO)