WIRELESS POWER TRANSFER

:A power transmitter (101) provides power to a power receiver (105) via an inductive power transfer signal which is also used by the power receiver (105) for communication by load modulation. The power transmitter (101) comprises a load detector (209) detecting load variations for the power transfer signal and a preamble presence detector (213) correlates a second chip sequence with load variations and generates a preamble detection if the correlation exceeds a threshold. A load modulation receiver (207) determines load modulation data symbols based on a correlation of the first chip sequence and load variations of the power transfer signal. A synchronizer (215) synchronizes data symbol time intervals for the load modulation receiver (207) in response to a timing of the preamble detection, and the load modulation receiver (207) aligns the correlation of the first chip sequence and load variations to the data symbol time intervals. The power receiver (105) transmits the preamble and data symbols using the corresponding chip sequences.