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35 Improvements in silicon chip technology are also allowing the production of less costly transceivers, which integrate much of the signal processing and some of the tracking capabilities of previous radar systems. That is opening up the ability to use radar as a digital altimeter in UAVs to track the terrain underneath at a constant height – especially helpful for applications such as surveying. Reducing the size of the radar system on an unmanned vehicle can be achieved in a number of ways. New ‘metamaterials’ open up opportunities to reduce the size and weight of the antenna system, and offer ways to reduce the power consumption of the chips handling the signal processing. Reducing the power consumption also reduces the amount and weight of the thermal cooling subsystem. Networking topologies can also help reduce the processing requirements on a vehicle. For example, a mesh network of low-cost radar systems on the ground can provide unmanned aircraft with additional data about objects in the sky, reducing the scanning and detection requirements of the onboard radar system and therefore reducing the weight and power requirements, boosting the flight time. These size and weight reductions rely on clear design specifications. Knowing how many objects have to be detected and at which distances allows the radar system to be optimised. These requirements are clearly defined in the automotive area: detecting objects such as pedestrians at a range of 100-200 m within a lateral angular spread of 120 º and a vertical spread of ±40 º . For unmanned aircraft though, the requirements are a lot less clear. They can range from detecting another aircraft the size of a four-seat light aircraft at 3 km, to detecting several 1 kg remotely piloted UAVs at a range of 100-200 m – all with 360 º monitoring. These are very different requirements. Optimisation Optimising the signal chain for a more complex radar system can be handled by an FPGA. For example, a multi- channel frequency modulated continuous wave (FMCW) radar for detecting non- cooperative objects and measuring their relative position vectors and radial velocities can be built from the chipsets developed for FMCW radars in the Radar systems | Focus Improvements in silicon chip technology are opening up the ability to use radar as a digital altimeter in UAVs to track terrain Unmanned Systems Technology | October/November 2018 The first stage of a radar collision detection system developed by the University of Kansas using COTS components (Courtesy of University of Kansas)