Signal distortion compensating apparatus and method

A distortion compensating method for compensating distortions of an amplifier which amplifies analog signals converted from digital input signals, said method comprising the steps of:

• applying distortion compensation coefficients for compensating distortions of said amplifier to said digital input signals;
• converting said digital signals having said distortion compensation coefficients applied thereto into analog signals and thereafter feeding said analog signals to said amplifier;
• attenuating analog output signals from said amplifier to the reciprocal times the ideal gain of said amplifier;
• converting said digital input signals into analog signals to find differential signals between said analog signals and said attenuated analog output signals;
• converting said differential signals into digital signals;
• and
• determining a new distortion compensation coefficient on the basis of differential signals converted into said digital signals, to update said distortion compensation coefficients by said new distortion compensation coefficient.

A distortion compensating apparatus for compensating distortions of an amplifier, comprising:

• a first digital-to-analog converter which converts digital input signals into first analog signals;
• an attenuator which attenuates output signals from said amplifier to reciprocal times the ideal gain of said amplifier;
• a first arithmetic circuit which effects in an analog region an arithmetic for obtaining distortion components of said amplifier from the differences between said first analog signals and output signals from said attenuator;
• a second arithmetic circuit which effects in a digital region an arithmetic of distortion compensation coefficients for canceling the distortion components, and which applies said distortion compensation coefficients to said digital input signals depending on the magnitudes of the distortion components;
• and
• a second digital-to-analog converter which converts digital output signals from said second arithmetic circuit into second analog signals and outputs the second analog signals to said amplifier.

A distortion compensating method for compensating distortions of an amplifier, said method comprising the steps of:

• converting digital input signals into first analog signals;
• attenuating output signals from said amplifier to reciprocal times the ideal gain of said amplifier;
• effecting in an analog region an arithmetic for obtaining distortion components of said amplifier from the differences between said first analog signals and the attenuated output signals;
• effecting in a digital region an arithmetic of distortion compensation coefficients for canceling the distortion components, and which applies said distortion compensation coefficients to said digital input signals depending on the magnitudes of the distortion components;
• and
• converting the digital input signals after applying the distortion compensation coefficients, into second analog signals, and outputting the second analog signals to said amplifier.