Switching characteristics of bias circuits of RF power amplifiers for TD-LTE systems

The RF power amplifiers(PAs) for TDD (Time Division Duplex) systems only turn on in the transmission time slots, which can be realized by the switching control circuits in the bias circuits of the RF PAs. The switching status of the switching control circuit is determined by the envelope detection results of the input RF signals of the RF PA. Therefore, the switching speed of the bias circuits is critical for the performance of the TDD PA. In this paper, the switching characteristics of the bias circuits will be discussed. Then a high speed switching control circuit for Doherty power amplifiers for TD-LTE systems is proposed so as to construct a high quality TDD bias circuit. The experimental results demonstrate that the proposed switching control circuit can effectively improve the speed of the switching speed and satisfy the requirements of the RF power amplifiers in a TD-LTE system.