The Importance of Accurate S-Parameters for PAM-4 Applications

PAM-4 (4-level pulse amplitude modulation) has been introduced in high-speed serial data technology to reduce the bandwidth demands of ultra-high data rates. It uses only half the bandwidth per bit that would be required of conventional NRZ (non-return to zero) modulation. But at the same time, PAM-4 signaling complicates design and test at every turn. Evaluation of channels is now just as important to system development as serializer / deserializer (SerDes) testing and the challenges presented require a higher level of test and measurement performance than ever before. This paper investigates the evaluation complexities of PAM-4 interconnects at high data rates.