## 1 Introduction  
The application of wireless power transmission (WPT) technology [1, 2, 3] is more and more extensive. Compared with the conventional wired charging method, it avoids the wear of the joint during the charging of the equipment, as well as the sparks and other safety hazards generated during the insertion and extraction process. It is safe, reliable, flexible and convenient. WPT covers many fields [4, 5] such as medicine [6], industry and electric vehicles, but in most application scenarios, higher requirements are proposed for the performance of wireless transmission systems, such as real-time control, signal transmission, etc. It requires the system to achieve information interaction while performing wireless power transmission; that is, power and information synchronous transmission technology [7, 8]. At present, the power and information synchronous transmission technology of a wireless power transmission system can be divided into three types: ratio frequency technologies [9, 10], dual channel transmission technology [11, 12] and single-channel transmission technology [13, 14]. The ratio frequency technology is a communication method which uses electromagnetic wave to realize the information transmission and exchange. With the development of radio frequency communication technology, it has been integrated into every corner of production and life, such as RFID, BlueTooth, Wi-Fi, Zigbee [15] and so on. However, it also has many problems, such as the long duration of a 'handshake' in communication and the limitation of application field. The dual-channel transmission technology is used to establish an additional channel based on the original power transmission channel. Reference [16] used dual-channel transmission technology, through low-frequency transmission power and high-frequency transmission of information, used in the medical field to achieve simultaneous transmission. Its data transmission rate is fast, but its structure is complex, and there is interference between signal and power, which makes the bit error rate high. Compared with the dual-channel technology, the single-channel transmission technology indicates that the power and the information share a transmission channel. The system structure is simple and avoids the cross coupling between the two channels in the dual channel transmission technology. It has become a hotspot in the research of simultaneous communication. Single-channel transmission technology can be divided into carrier modulation [17] and power modulation. In Reference [18], a double-sided LCC compensation topology for power transmission is adopted, and the data transmission channel is composed of a four-resonance dual-rejection structure used to realize synchronous transmission of power and information. There are many methods of power modulation. Reference [19] realized the synchronous transmission of power and signal by controlling the phase of current and voltage. Reference [20] used the baseband signal to change the magnitude of the input voltage amplitude for signal transmission, which is a traditional amplitude modulation method. This method not only solves the problem of power and information interference, but also reduces the bit error rate. However, the information transmission rate is low, and the output voltage is susceptible to fluctuations. At the same time, the addition of DC-DC modulation circuit makes the system structure more complex, and the system baud rate is affected. The existing phase-shift modulation power and information simultaneous transmission methods [21; 22] transmit power through the fundamental wave, changing the third harmonic amplitude to transmit information, and achieve power and information simultaneous transmission. The application of the phase-shifted full-bridge (PSFB) [23; 24; 25] means the system no longer needs to be controlled by an external modulation circuit, and the switch tube can achieve zero voltage switching (ZVS). The above power and information transmission technologies can only transmit two-bit signals: '0'and '1'.