March 6, 2018
|By: Kishore Racherla, and Matt Waight
Principal Member of Technical Staff, Automotive Business Unit, Maxim Integrated
AM radio still has an important role in our digital age, but it's challenging to offer this band in electric vehicles (EVs). So, many electric and hybrid vehicles simply don't have AM radio. This is largely due to the pesky electromagnetic interference (EMI) problem. If not addressed, EMI can hamper performance of advanced driver assistance systems (ADAS), infotainment systems, and other vehicle subsystems. EMI from electric drivetrains interfere with the reception of the AM signal.
In electric vehicles, the source of interference is the frequency converter, which changes electrical energy into mechanical energy to control the electric motor’s speed and rotational direction. These converters turn the current and voltage on and off in quick succession, producing EMI. EV manufacturers have turned to filters and to insulating the cables in order to provide radio reception in their cars. But there are still challenges around cost, weight, and performance to consider while mitigating EMI, not to mention the need to transport voluminous amounts of data through the vehicle.
EMI in a vehicle can interfere with various sub-systems, including the AM radio.
Considering systems like ADAS and infotainment, today’s vehicles are like computers on wheels, packed with lots of electronic components. An Ethernet backbone is commonly found in cars to transport all of the data for these subsystems. Ethernet can transport data over a link 100x faster than a CAN bus. However, as we advance toward Level 5 fully autonomous vehicles, the volume of video, audio, and communications data will continue to rise. High-definition (HD) video displays are paving the way to ultra HD (UHD) displays, the number of cameras is proliferating, and Internet connectivity is fueling a multitude of in-vehicle applications. Serial links with higher speed and increasing levels of bandwidth, performance, and reliability, as well as low latency, will be essential to deliver the real-time responses that many applications require.
For electric and hybrid vehicle manufacturers, a key design challenge involves managing the interaction between electronic systems, EMI, and high-speed serial links. Copper wire has long been the choice to support a vehicle’s electrical needs. A vehicle's wiring harness, consisting of many copper wires, has become one of the costliest and heaviest components. Fortunately, IEEE® standards have emerged to provide for higher bandwidth operation over single twisted-pair copper cable.
But, considering the types of applications that cars are already expected to support and knowing what the future might bring, even Ethernet may not be enough. A next-generation serial link solution is needed, and that can be found in Gigabit Multimedia Serial Link (GMSL) serializer/deserializer (SerDes) technology. GMSL SerDes technology simultaneously transports HD video, audio, control information, aggregated sensor data, and Gigabit Ethernet over 15m of a single coaxial cable or 10m to 15m of shielded-twisted pair cabling. These high-speed links meet stringent automotive electromagnetic compatibility (EMC) specifications. Coaxial and shielded-twisted pair cables simplify what would otherwise be a complex interconnect backbone, while also supporting video multi-streaming at lower system cost. The technology is compression free, and the current generation delivers video for automotive applications at a 10x faster data rate than Ethernet and with 50% lower cabling costs, also compared to Ethernet. With a built-in spread-spectrum capability, GMSL SerDes ICs offer enhanced the EMI performance.
To learn more about how GMSL SerDes technology can let you include AM radio in your EV design and support fast, simultaneous transport of multiple data types in the vehicle, read our article, "Addressing EMI in Electric Cars with Radio Tuner Architecture," on the IEEE Xplore Digital Library.