Apple Inc.
Methods and Apparatus for Performing Demodulation using Maximum Likelihood Sequence Matching in a Wireless Charging Device

Abstract:

A wireless power transmitting device transmits wireless power signals to a wireless power receiving device using a wireless power transmitting coil. The wireless power receiving device may transmit data packets to the wireless power transmitting device. The wireless power transmitting device may include a data receiver that is coupled to the wireless power transmitting coil and that receives the transmitted data packets. The data receiver may be configured to demodulate the received data packets. The data packets may include at least preamble bits, start bits, and data bits encoded as biphase half-bit signals in accordance with a predefined wireless power transfer protocol. During demodulation, the receiver may perform preamble detection, start bit detection, and data bit detection by comparing the input signals to corresponding reference patterns using a maximum likelihood sequence detection scheme. Phase recovery may be employed throughout to help provide immunity to phase change.