New-Tech Europe Magazine | March 2018

of the radar front-end to eliminate deterministic phase variations between the receive channels. 24 GHz Multi-Channel Radar A 24 GHz radar is widely used in commercial and industrial applications, offering high accuracy, low power consumption and small size. These characteristics also make a 24 GHz radar a good fit for commercial and consumer UAV manufacturers, particularly considering the desire to reduce payload and power requirements. One such system developed by Analog Devices is shown in Figure 2. A common misconception is the radar can operate at 77 GHz rather than 24 GHz. Current regulations dedicate the 77 GHz band to automotive vehicles and do not allow use with UAVs. While 77 GHz offers higher bandwidth for improved resolution, today’s regulations prohibit a 77 GHz radar being used for UAV applications. When building a radar sensor, every dB improvement in receiver sensitivity extends the detection range. Most sensors available today focus on cost reduction, trading off phase noise and the number of channels. This trade-off degrades the receiver signal-to-noise (SNR) ratio, which limits the detection of smaller targets in the presence of larger objects. In real-world radar applications, busy or cluttered target scenarios cumulatively increase system phase noise and desensitize the radar receiver. The higher system noise masks or hides small targets and prevents object detection—detecting a narrow tree branch masked by the façade of a building—which can compromise UAV safety. Most single-channel, single chip, low-cost sensors do not provide the needed performance to make this distinction. Using a 24 GHz multi-channel

platform with higher performance, UAV manufacturers can: Use the FMCW radar mode to detect the range and velocity of objects up to 200 m with a resolution of approximately 60 cm; the resolution can be improved to 15 cm using an antenna design developed for the specific application. Achieve a field of view of approximately 120 degrees in azimuth and 15 degrees in elevation, depending on the antenna array design; using DBF, the field of view can be extended. Reduce power consumption while improving sensitivity 2x and extending the detection range 1.5x compared to traditional low-cost, single-channel radar sensors. Summary The UAV/UAS market is growing quickly and offers tremendous potential for many new commercial applications. The landscape of sensor technologies is also changing rapidly, with newer sensor technologies such as light detection and ranging (LiDAR), time of flight (ToF) and ultrasonic being developed and adopted. UAV manufacturers should be aware of these newer options and incorporate the latest technologies as they mature. However, radar remains the most compelling sensor technology, offering performance and versatility. To help the widespread commercial adoption of UAVs, UAV manufacturers need to lead the industry by embracing RF, microwave and mmWave radar, considering more than just the cost of the hardware, to demonstrate that UAVs can be safely operated autonomously. Reference 1. www.marketsandmarkets.com/ Market-Reports/commercial-drones- market-195137996.html.

the resolution. Angular resolution depends on the carrier frequency; the higher the carrier frequency, the better the resolution. Compared to laser detection, which measures a single spot, or camera detection, which only captures a 2D image within the camera’s field of view, FMCW radars provide a continuous, inherent average of the information from the target’s reflection. This provides a wide, 3D field of view by measuring the distance, speed and angle, from as close as a few centimeters to several hundred meters between the sensor and the targets. Range-Doppler - In range-Doppler mode, the range and speed of the target are analyzed. Range-Doppler is one of the most powerful modes because it processes multiple transmit ramps or chirps simultaneously using a 2D Fourier transform. The processed range-Doppler data is displayed in a 2D map that enables targets with different velocities to be separated, even if they are the same distance from the sensor. This is important to distinguish multiple targets moving at high speed in different directions, e.g., resolving complicated air traffic scenarios with targets traveling in opposite directions or during overtaking maneuvers. DBF - With digital beamforming (DBF), the distance and the angle to the target are displayed. The receive signals from the four receive channels are used to estimate the angle of the target, and the data contains the spatial distribution of the targets in the xy-plane. In the DBF mode, the system is configured the same as FMCW; however, the down-converted IF signals are processed differently. After calculating range, the angle information of the target is calculated by evaluating the phase differences between the four receive channels. The DBF mode requires a calibration

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