Akita, H., Matsudaira, N., Chen, C., Ito, T. et al., "A Novel Distortion Cancelling Technique Enabling 50-Mbps High Speed Data Transmission for Bus Connected ECUs," SAE Int. J. Passeng. Cars – Electron. Electr. Syst. 8(1):130-136, 2015, doi:10.4271/2015-01-0198.
With the evolution of automotive features, larger flash program size has been required even at the local electronic control units (ECUs). As the flash programming data rate increases, Ethernet is adopted as a global data port from the external source. However, it can not be applied to the bus type network topology between the domain control unit (DCU) and the local ECUs, because it uses a peer-to-peer type network topology. On the other hand, high speed CAN-FD has been studied recently for this bus topology, but its data rate is limited at the range of several mega bps due to the signal waveform distortion caused by the multiple reflections at the non-terminated stubs.This paper describes a novel distortion cancelling for the bus topology as the pre-emphasis technique, in which the digital signal processing (DSP) compensates the complicated signal distortion caused by the multiple reflections. Moreover, this complex signal processing block is located only at the DCU, not at the local ECUs. Therefore, the increase in cost can be suppressed effectively for the total system. The DCU determines the signal distortion characteristics for each ECU by training in advance, and accordingly pre-emphasizes the transmission signal. When the pre-emphasized signal arrives at the target ECU, the waveform becomes non-distorted. This enables 50-Mbps data transmission even with the bus topology.