Transmitter and distortion compensating method

A distortion compensating method comprising:

• measuring power of a transmission signal before application of a distortion compensation process for compensating for a distortion in an output of an amplifier in advance by applying a reverse characteristic to the transmission signal before being amplified by the amplifier;
• adjusting a gain for the transmission signal before the application of the distortion compensation process, when power of a transmission signal changes at certain timing based on an average of power measured at the measuring, correspondingly to amplitude of the transmission signal at the certain timing;
• obtaining a distortion compensation coefficient corresponding to a value of power of the transmission signal adjusted at the adjusting from a storage unit storing therein a value of power of a transmission signal and a distortion compensation coefficient that is used in the distortion compensation process in an associated manner;
• applying the distortion compensation process to the transmission signal using the distortion compensation coefficient obtained at the obtaining;
• calculating an update for the distortion compensation coefficient stored in the storage unit and corresponding to the distortion compensation coefficient obtained at the obtaining based on an error between power of the transmission signal amplified by the amplifier and power of the transmission signal before the application of the distortion compensation process;
• and
• updating the distortion compensation coefficient stored in the storage unit using the update calculated at the calculating.

A transmitter comprising:

• a memory;
• and
• a processor coupled to the memory, wherein
• the processor executes a process comprising:
• measuring power of a transmission signal before application of a distortion compensation process for compensating for a distortion in an output of an amplifier in advance by applying a reverse characteristic to the transmission signal before being amplified by the amplifier;
• adjusting a gain for the transmission signal before the application of the distortion compensation process, when power of a transmission signal changes at certain timing based on an average of power measured at the measuring, correspondingly to amplitude of the transmission signal at the certain timing;
• obtaining a distortion compensation coefficient corresponding to a value of power of the transmission signal adjusted at the adjusting from a storage unit storing therein a value of power of a transmission signal and a distortion compensation coefficient that is used in the distortion compensation process in an associated manner;
• applying the distortion compensation process to the transmission signal using the distortion compensation coefficient obtained at the obtaining;
• calculating an update for the distortion compensation coefficient stored in the storage unit and corresponding to the distortion compensation coefficient obtained at the obtaining based on an error between power of the transmission signal amplified by the amplifier and power of the transmission signal before the application of the distortion compensation process;
• and
• updating the distortion compensation coefficient stored in the storage unit using the update calculated at the calculating.