Abstract: Simultaneous wireless power and signal transmission(SWPST) systems typically suffer from low power density, complex system architecture, and significant mutual interference between energy and signal channels. To overcome these limitations, a high-frequency injection SWPST system based on a single-switch inverter is proposed. The system topology is presented, and the operating principle along with the soft-switching characteristics of the P#-type single-switch inverter is analyzed in detail. Equivalent circuit models for both energy transmission and signal transmission channels are established, and the effects of key system parameters on the signal transmission rate and power transfer gain are investigated. Furthermore, based on the voltage gain analysis of the mutual coupling between energy and signal channels, a system parameter optimization method is proposed to suppress crosstalk and improve the signal transmission gain, enabling reliable bidirectional communication. A 120 W experimental prototype is developed to validate the theoretical analysis. Experimental results demonstrate that the system maintains constant-current output characteristics, achieves a signal transmission rate of 240 kbit/s with zero bit error rate, and reaches a maximum power transfer efficiency of 88.7%, confirming the feasibility and effectiveness of the proposed approach.