| 摘要 |
An amplitude compensator utilized in a distortion compensating device which compensates non-linearity in amplitude and phase of an input-output characteristic of a high frequency power amplifier incorporated in a mobile phone in which the input-output amplitude characteristic of the high frequency power amplifier is fitted by a hyperbolic tangent function, and an inverse hyperbolic tangent function is obtained by using two parameters, thereby providing amplitude compensation. A voltage input-output characteristic of the power amplifier is fitted to a hyperbolic function including predetermined parameters and a logarithmic function constituted by the parameters after the fitting and a linear gain of the power amplifier is obtained. An envelope voltage of an envelope signal obtained by detection of a modulated input signal is applied to the logarithmic function to obtain an amplitude compensating value. Based on this amplitude compensating value, an amplitude of the modulated signal is converted and a resulting modulated input signal is inputted to the power amplifier.
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