Our major strength is the ability to bring together specialist expertise across many disciplines to engineer something very special. Plextek’s current micro-radar project is an excellent example of this. The project was funded through Autonomous Systems Underpinning Research (ASUR), with the aim of investigating how radar might be applied to the problem of collision avoidance in small-sized UAVs. In just a few months, our engineers have taken the initial concept through detailed system performance and design calculations, to an integrated, highly manufacturable single-board radar sensor head, suitable for use in airborne trials.
Given the application, it was apparent from the outset that size, weight and power would all need to be ruthlessly minimised. In order to facilitate navigation through closely spaced obstacles, the sensor must achieve high angular resolution – to only a few degrees. To achieve this from an antenna only centimetres across dictated the use of millimetre-wave frequencies. Initial systems engineering calculations concentrated on selecting a waveform that would maximise the detection performance achievable with only milliwatts of transmitted power, aiming for compatibility with an emerging generation of highly integrated commercial millimetre-wave ICs.
Having identified candidate active devices, the next problem to solve was that of the antenna. Although radar antenna gain requirements may be similar to those of demanding communications applications, radar applications typically also mandate that very narrow beamwidths and ultra-low sidelobe levels are achieved across very wide bandwidths. In this particular case, size and weight must also be kept to a minimum. Plextek’s antenna engineers evolved a novel printed design, which was verified and refined using advanced EM simulation software tools.
Through the creative use of state-of-the-art PCB design and manufacturing techniques, it proved possible to integrate the transceiver circuitry and antenna onto the same PCB, not only minimising size and weight, but also eliminating the need for bulky waveguide or lossy coaxial cable interconnects. 3D printing was employed to realise supporting mechanical components. Throughout the design process, input from Plextek’s manufacturing engineers ensured that this advanced design would be readily manufacturable.
Plextek’s signal processing expertise was brought to bear in providing real-time display of the sensor output, along with raw data logging to facilitate refinement of detection algorithms off-line. Code has been designed to be compatible with a variety of platforms, with a view to enabling the efficient use of pre-existing processing resource, if required.
Trials of the complete radar have demonstrated the ability to detect relevant obstacles at up to 100 metres with an update rate of several Hertz, in a lightweight low-SWaP package. The successful outcome of the micro radar development highlights the benefits of bringing together systems design, millimetre-wave engineering, antenna design and EM simulation, mechanical design and digital signal processing skills in the realisation of a uniquely capable low-SWaP sensor. Future work will concentrate on further development of algorithms for UAV collision avoidance as well as for ground vehicle and static applications, and also the analysis of target micro-Doppler.
Demonstrations have strayed beyond the originally intended application, with one particular favourite being a real-time, high update rate display of a game of catch with a golf ball!