| 摘要 |
An orthogonal frequency division multiplexing (OFDM) transmitter comprises a modulator 12 for generating mutually orthogonal sub-carriers, each sub-carrier being modulated with a stream of data symbols to be transmitted, an amplifier 18 for amplifying a signal containing the modulated sub-carriers for transmission, and a symbol processor 24. The symbol processor computes a plurality of error vector magnitude (EVM) values for each data symbol to be transmitted, each EVM value being based on a different one of a plurality of candidate back-off values for the amplifier, and selects one of the candidate back-off values to apply to the transmitter for the data symbol based on the EVM values. The selected back-off value may be that which produces the highest signal to noise ratio (SNR), or that for which the EVM value meets a constant target EVM. A peak to average power ratio (PAPR) reduction unit 14 and pre-distorter 16 may also be used. |
