| 摘要 |
In an automatic predistortion adjusting circuit, a splitter splits an input signal into first and second signals. A predistortion circuit applies first non-linear characteristics to the first signal, a variable attenuator adjusts an amplitude of an output signal of the predistortion circuit, a variable phase shifter adjusts a phase of an output signal of the variable attenuator, and a main amplifier amplifies an output signal of the variable phase shifter, so that second non-linear characteristics opposite to the first non-linear characteristics are applied to an output signal of the main amplifier. A directional coupler takes out a part of an output signal of the main amplifier as a branch signal, and a delay line delays the second signal. An adder adds a delayed signal passed through the dely line to the branch signal. Further, a detector detects an strength of an output signal of the first adder, and a control circuit controls the first non-linear characteristics, an attenuation amount of the variable attenuator and a phase amount of the variable phase shifter in accordance with an output signal of the detector.
|
