Distortion compensation device, distortion compensation method, and radio transmitter

A distortion compensation method comprising:

• adding a frequency characteristic to an error signal to generate an added error signal, the error signal being a difference between an input signal input to an amplifier and an output signal output from the amplifier;
• computing a distortion compensation coefficient for compensating for a distortion characteristic of the amplifier based on the added error signal;
• and
• performing distortion compensation on the input signal based on the computed distortion compensation coefficient, wherein the frequency characteristic is set such that a first distortion level of the output signal satisfies a first standard value and a second distortion level of the output signal satisfies a second standard value, the first distortion level having a first frequency band lower than a frequency band of the input signal, the second distortion level having a second frequency band higher than the frequency band of the input signal.

A radio transmitter comprising:

• a distortion compensation device;
• a digital-to-analog converter configured to perform digital-to-analog conversion on an output signal of the distortion compensation device;
• a quadrature modulator configured to quadrature-modulate an output of the digital-to-analog converter;
• an amplifier configured to amplify an output of the quadrature modulator;
• and
• an antenna configured to output an output of the amplifier to the outside,
• wherein the distortion compensation device includes:
• a frequency-characteristic adding unit configured to add a frequency characteristic to an error signal to generate an added error signal, the error signal being a difference between an input signal input to the amplifier and an output signal output from the amplifier;
• a distortion-compensation-coefficient updating unit configured to update a distortion compensation coefficient for compensating for a distortion characteristic of the amplifier based on the added error signal;
• and
• a distortion compensation unit configured to perform distortion compensation on the input signal using the updated distortion compensation coefficient,
• wherein the frequency characteristic is set such that a first distortion level of the output signal satisfies a first standard value and a second distortion level of the output signal satisfies a second standard value, the first distortion level having a first frequency band lower than a frequency band of the input signal, the second distortion level having a second frequency band higher than the frequency band of the input signal.