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17 microwave, radar and UAVs, and if you combine all these elements together you can see dramatic things happening, where you can use the embedded systems technology to put radar and sensing technology into UAVs,” he says. “This combination could generate something magical. “I firmly believe that the MPU-FPGA combination will be the future of all UAV processors. The market is being misled by the commercial UAV companies. Flight controllers for consumer drones run everything on one chip to reduce the cost of the technology so that it can be used by everyone, and this is cool, but I still think the future of the UAV relies on some serious processing and some serious sensors with reliable and secure processing, and almost zero chance of failure. “From that perspective you need real- time processing to simplify the whole design,” he says. Radar-autopilot combo The first step towards this future is a low- cost, light radar system combined with a UAV’s autopilot for sense-and-avoid and collision-detection applications. “Now we have the knowhow to miniaturise a radar system that previously needed a lot of power and electronics,” says Dr Wang. The key to this is the FPGA – large arrays of programmable logic, called a fabric, that are particularly good for handling signal processing. That means elements of the autopilot and the radar processing can be implemented in the fabric. Instead of using thousands of processor cycles to handle the signals, it can be performed in a few hundred cycles by the logic on the fabric. That saves power and provides more performance so that signals from a radar sensor can be analysed quickly. Unlike a microcontroller programmed in a language such as C, the logic for an FPGA is designed in a high-level language such as VHDL or Verilog. This logic is then synthesised into a bit stream that is stored on an external memory chip and then downloaded to the FPGA to configure it. “We focus on two technologies. One is sensing, and we are focused expressly on microwave sensing, as we believe this could be something useful for UAVs,” says Dr Wang. “We can compensate for the disadvantages of other sensors and provide something unique – it can’t be blocked as an optical sensor and is not as easy to interfere with as ultrasound. “The second area is the processing technology, and we are especially interested in the combination of FPGA and MPU. That’s a big challenge, as we need to do the signal processing to retrieve the signals returning from the obstacles and the targets. “It’s not about the sensor but the combination of the sensor and the processing algorithms. That makes things a bit challenging to engineers as you need a clear understanding of the whole signal chain.” One way to get the FPGA technology small enough for use in UAVs is to optimise the signal chain and reduce the range of the sensor. “For most commercial UAVs you don’t need kilometres of range so you don’t need as much power – a couple of hundred metres of range is pretty good, and that’s why we were able to shrink the size and make the radar system smaller with less power consumption in a relatively small FPGA,” he says. “We design the sensing and processing systems ourselves, so everything can be tuned for UAVs. It’s not a case of, ‘Let’s make a small radar that can be used for UAVs’ as you need to tune the antenna pattern, the power budget, the link budget, the processing and interaction with flight controllers.” Frequency spectrum Aerotenna is working with a range of chip makers on the radar transmitter and receiver chain for various frequency ranges. “We use a very wide spectrum – we are not fixed though; we have a bunch of products with different ranges,” he says. Each of these uses a separate logic design that is downloaded to the most suitable type of FPGA. However, it is the ‘system on chip’ (SoC) combination of both FPGA and ARM processor cores on a Xilinx Zynq SoC that opens up the opportunities for UAV control systems. “This combination is spot-on for our solution, using the ARM cores for the flight control core Dr Zongbo Wang | In conversation Unmanned Systems Technology | June/July 2016 Dr Zongbo Wang has more than 15 years of experience in sensor and electronics development. He honed his expertise by leading numerous engineering and technology research projects at universities and research institutes in China, Spain, the Netherlands, Singapore and the US. He received his BSc and PhD in Electronic Engineering from the Beijing Institute of Technology in 2004 and 2009 respectively, and founded Aerotenna in 2015. Dr Zongbo Wang