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For autonomous driving to move forward at predicted levels, technological improvements in advanced driver-assistance systems (ADAS) are needed to power advances in sensors such as radar. Fortunately, a look around the industry shows that the necessary advances are happening.
Radar works by measuring the time it takes for radio waves to leave the antenna, hit the target, and return to the antenna. A processor then can calculate the position and movement of the object or objects. Radar systems enable autonomous vehicles to make informed decisions and take appropriate actions, thereby reducing the risk of accidents.
Automobiles have an increasing number of radar sensors with short-, medium- and long-range versions supporting autonomous driving. Short-range radar covers distances of 15 to 50 meters and a field of view (FOV, the angular coverage it has in both the horizontal and vertical planes) of 80 to 90 degrees. Medium-range radar is for a range of 50 to 150 meters with an FOV of 50 to 60 degrees. And long-range radar (LRR) maintains a range of 150 to 250 meters or more and a field of view (FOV) of 20 to 25 degrees.
In a cost-sensitive market, designers now face the challenge of advancing automotive automation at lower cost. At the same time, new generations of high-performance radars provide an image of the scene that's closer to cameras and LiDARs (light detection and ranging) than traditional radars.
Enhanced Radar with Ethernet PHY Transceivers
Achieving autonomous operation requires the real-time collection and processing of a large amount of sensor data. If the sensors are synchronized, software can use the sensor data to build a virtual image of the world around the vehicle. With this virtual image, the ADAS microcontroller (MCU) can then compute the correct path or avoid obstacles.
Synchronization in both the time and frequency domains enables the central ADAS MCU to use the data extracted from the sensors with little post-processing. Ethernet PHY transceivers with hardware synchronization increase the accuracy, efficiency, and range of automotive radar systems by simplifying ADAS architectures and reducing software stack processing.
TI’s DP83TC817S-Q1 Ethernet PHY transceiver not only reduces processing at the ADAS MCU, but also shrinks development cycles and increases the performance capabilities of a full radar system, allowing for architectures previously limited by cost. The TI Ethernet PHY transceiver can synchronize radar frames at the hardware level in both the time and frequency domains within nanoseconds across two or more radars.
The device provides all of the physical-layer functions needed to transmit and receive data, can work with unshielded twisted-pair cable, and has xMII interface flexibility with support for standard MII, RMII, and RGMII MAC interfaces. The media-independent interface (MII) was originally defined as a standard interface to connect a Fast Ethernet (i.e., 100 Mbits/s) medium-access-control (MAC) block to a PHY chip. The MII is standardized by IEEE 802.3u and connects different types of PHYs to MACs.
The DP83TC817-Q1 also provides a high-quality, time-synchronized clock signal for ADAS sensor data synchronization. It features an integrated time-sensitive-networking (TSN) engine, supporting the IEEE 802.1AS standard. The transceiver reduces development cycles and increases the performance capabilities of a full radar system, opening the door to architectures previously limited by cost.
Satellite Architectures
Modern radar modules mainly operate in the 76- to 81-GHz E-band. LRRs use the 76- to 77-GHz band because regulations allow for higher equivalent isotropic radiated power (EIRP, a measurement of a transmitter's output power in one direction). More power means more range.
The typical architecture today is edge, consisting of radar sensors streaming processed data through a Controller Area Network (CAN) or 100-Mb Ethernet interface to an ADAS electronic control unit (ECU).
These sensors are designed for high performance and consist of a processor and, often, a specialized accelerator to perform range, Doppler, and fast Fourier transform (FFT) calculations, along with subsequent high-level algorithms for object detection, classification, and tracking. The final object data from each edge radar sensor is then sent to the ADAS ECU.
Edge architecture is evolving and giving way to satellite architectures, where the sensor heads placed around the car stream pre-processed range FFT data to a central ECU through a high-speed 1-Gb Ethernet interface (see figure).
Satellite architecture adds value through a sensor-fusion algorithm. The larger computing capability in the central ECU gives automakers the option to use over-the-air software updates to improve system performance.
TI’s AWR2544 77-GHz millimeter-wave (mmWave) radar sensor chip (the 76- to 81-GHz band is often called the mmWave band in automotive contexts) is the industry's first for satellite radar architectures. It enables higher levels of autonomy by improving sensor fusion and decision-making in ADAS.
The AWR2544 radar-on-chip sensor is designed specifically for satellite architectures. It features an integrated 77-GHz transceiver with four transmitters and four receivers, providing increased range detection and superior performance.
The sensor also includes a cost-optimized radar-processing accelerator and a throughput-enhanced 1-Gb/s Ethernet interface to generate and stream range FFT-compressed data. It’s Automotive Safety Integrity Level (ASIL) B-capable and provides a secure execution environment through a hardware security module.
In addition, TI said the AWR2544 is the industry's first with launch-on-package (LOP) technology. LOP technology helps reduce the size of the sensor by as much as 30% by mounting a 3D waveguide antenna on the opposite side of the printed circuit board.
By leveraging LOP technology, sensor ranges can extend beyond 200 meters with a single chip. In satellite architectures, these features enable automakers to increase ADAS intelligence for higher vehicle autonomy levels to make smarter decisions from farther away.
With ADAS applications evolving to keep pace with rising safety requirements, are you ready for the emerging automotive radar satellite architecture?
Conclusion
TI’s extensive portfolio of radar components includes automotive-qualified Ethernet PHYs. Its IEEE-compliant devices provide integrated protection, high immunity, and low latency in small-form factors for reliable performance in harsh environments, enabling higher levels of autonomy by improving sensor fusion and decision-making in ADAS.
