WIRELESS POWER TRANSFER

A power receiver () communicates to a power transmitter () using load modulation data symbols modulated by a chip sequence with a chip sequence being divided into load time intervals with different modulation loads. The power transmitter () comprises a receiver () which includes a load measurer () determining measured load values of the power transfer signal for load time intervals. A chip determiner circuit () determines a received chip sequence from the measured load values where the received chip sequence comprises a sequence of chip values. Each chip value is determined in response to a difference between measured load values for at least two modulation load time intervals of the chip. A store () stores a set of chip sequences with each chip sequence linked to a data symbol. A detector () detects a received data symbol value in response to a correlation between the received chip sequence and chip sequences of the set of chip sequences.