이동통신용 고전력증폭기의 선형개선을 위한 디지털 제어기의 설계 및 구현

Abstract

Radio frequency and microwave circuits have nonlinear electric characteristics owing to being used the active device usually.

The eletric characteristics of the power amplifier can be distorted in the gain and phase easily. Also, an intermodulation distortion is formed due to the nonlinear characteristics of power amplifier near the saturation region when more than two different carriers are input to circuit, which are used in digital mobile communication and satellite communication of the multichannel.

Linear power amplifier needs to satisfy the standards of intermodulation distortion in spite of specific output power, the changes of output power level, operating voltage, external temperature and so on.

To be solved these problems, the Back-off, Feedback, Predistortion and Feedforward methods have been developed to linearize the nonlinear characteristics until now.

The controller for linearization of power amplifier is the core of the main amplifier using Feedforward method and this let power amplifier maintain to operate within the proposed time, fit to the specification of the circuit, have the stability and reliability in the worst circumstances.

In the thesis, we designed and fabricated together with the error amplifier and phase converter.

The phase converter has a very flat phase with in the 200 degree at frequency range used. And matching circuit is added to minimize the change of attenuation, it has a good charasteristics of below 0.09 dB when the phase is changed.

And also the error amplifier which is applied linearization technology used the feedforward method in order to realized the linear power amplifier for 40 watt degree in the W-CDMA base station. And then, we confirm that it is possible to realize excellent linear power amplifier from the measurement of IMD characteristics which is shown good results.

So if they could be applied for the main power amplifier it could be helpful to fabricate the linear power amplifier for the W-CDMA station. Also, in the other fields of telecommunication such as digital mobile communication and satellite communication.