Dual-Diode Unified SWIPT for High Data Rates with Adaptive Detection

TL;DR

A low-complexity adaptive detector that learns the nonlinear state transition dynamics and performs decision-directed detection with linear complexity is designed and approaches maximum likelihood sequence detection (MLSD) performance in memory-dominated regimes, while avoiding the exponential search required by classical sequence detection.

Abstract

Due to their low-complexity and energy-efficiency, unified simultaneous wireless information and power transfer (U-SWIPT) receivers are especially suitable for low-power Internet of Things (IoT) applications. Towards accurately modeling practical operating conditions, in this study, we provide a unified transient framework for a dual-diode U-SWIPT that jointly accounts for diode nonlinearity and capacitor-induced memory effects. The proposed model accurately describes the inherent time dependence of the rectifier, highlighting its fundamental impact on both energy harvesting (EH) and information decoding (ID) processes. Based on the provided memory-aware model, we design a low-complexity adaptive detector that learns the nonlinear state transition dynamics and performs decision-directed detection with linear complexity. The proposed detection scheme approaches maximum likelihood sequence detection (MLSD) performance in memory-dominated regimes, while avoiding the exponential search required by classical sequence detection. Overall, these results demonstrate that properly exploiting rectifier memory provides a better tradeoff between data rate and reliability for U-SWIPT receivers.

Figures (4)

• Figure 1: Considered U-SWIPT receiver, illustrating the nodes for EH and ID. Depending on the system needs and priorities, the rectifier output is selectively used for information decoding (ID) or energy harvesting (EH).
• Figure 2: Four conduction states of the dual-diode U-SWIPT receiver.
• Figure 3: Transient response of the dual-diode U-SWIPT receiver for transmission of 15 bits using BASK with $T_s = 4~\mu\text{s}$. The digits above the trace show the transmitted bitstream. End-of-symbol samples ($t = kT_s^{-}$) are marked with circles/squares for the high-capacitance case ($C = 10~\text{nF}$) and triangles/diamonds for the low-capacitance case ($C = 2~\text{nF}$). Circuit parameters: $f = 800~\text{MHz}$, $R_s = 50~\Omega$, $R_L = 1~\text{k}\Omega$, $R_{\text{on}} = 5~\Omega$, $R_{\text{off}} = 10~\text{M}\Omega$, $V_{\text{on}} = 0.25~\text{V}$.
• Figure 4: BER performance with respect to SNR for different schemes