Analog Multi-Tone Signaling for High-Speed Backplane Electrical Links

Implementing a multi-tone (MT) architecture for high-speed backplane electrical links is difficult given the tight power and complexity constraints in this application. This paper proposes an approach that incorporates a baseband (BB) channel and a few passband (PB) channels. In this MT system inter- channel interference (ICI) and inter-symbol interference (ISI) are eliminated through fractionally spaced equalization at the transmitter and feedback equalization at the receiver. The design is modeled as a MIMO system, and optimal equalizer coefficients to minimize the transmit peak voltage are found by casting the optimization as a Second Order Conic (SOC) problem. In addition, for systems that need adaptation, we show how equalizer and power allocation coefficients can be obtained (sub optimally) using Zero Forcing (ZF) optimization. The effect of transmitter and receiver clock jitter are modeled in a way that can be included in both SOC and ZF optimizations, and the performance of this system is compared to more conventional baseband examples. It is shown that this AMT system can be built with complexity/power similar to a comparable performance baseband system, but has the ability to scale to higher bit rates.