Challenges and solutions in receiver testing for automotive wired communications
PhD Julien Henaut,
BitifEye Digital Test Solutions
New technologies like advanced driver-assistance, increase automation level in modern cars. Implementation of these technologies requires reliable multi-gigabit/s communications between scores of in-vehicle sensors and control units. Since data rates of the mainstream car communication technologies are several orders of magnitude lower than necessary, novel communication protocols arise. Automotive Ethernet symmetric protocols provide a backbone for vehicle communications. Other applications like data acquisition from cameras and LIDARs or sending data to displays, motivate development of asymmetric protocols, such as Automotive SerDes.
To allow simple interoperability between chipsets, new protocols require more complex and rigorous compliance testing than the earlier automotive standards. Such testing includes measuring quality of the transmitted signal and characterization of the communication channel. Compliance testing should also take into account the fact that in automotive environment signals undergo severe disturbances due to power losses, noise and crosstalk. Even if a signal was perfect at the transmitter, it would get distorted when reaching receiver, and recovering data from this degraded signal can be a challenge. Thus, to ensure successful data communication, transmitter testing is not sufficient and receiver physical layer (Rx PHY) testing is necessary.
Rx PHY Test specifications are defined today for most of the multi-gigabit communication protocols. The principal goal of Rx PHY tests is the verification of the bit error rate under physical layer disturbances such as crosstalk or symbol rate deviations. Further tests can improve the reliability. In the first part of this talk, BitifEye would like to share what we have learnt from our 15 years of experience in developing Rx PHY Testing solutions, describe the most important tests required for a proper characterisation of the receiver and the benefits they bring for both test houses and design engineers.
Rx PHY tests are usually more complicated than Transmitter PHY tests and involve more equipment. While for testing transmitter it is sufficient to have an off-the-shelf oscilloscope that analyse the signal produced by the transmitter (eye characteristic), Rx tests require to recreate a compliant transmitter, capable of generating a controlled distorted signal, and to analyse the impact of the distortions on the transmission. Generator can be either a part of a Bit-Error-Rate Tester (BERT), an Arbitrary Waveform Generator or a media convertor, translating the signal into the given standard. Error detector is either a part of BERT or a built-in block of the Device-Under-Test.
After describing the tests for characterising a receiver, BitifEye will present the advantages and drawbacks of the 3 possible approaches to transmitter emulation, the challenges in designing a proper Rx PHY testing and offer the audience the elements to decide on the most suitable solutions for SerDes Alliance.