Information Technology R&D Center of Mitsubishi Electric Corp developed a power amplifier technology that can amplify signals in the frequency band from 1.4G to 4.8GHz with a high efficiency .
It enables to realize an efficiency higher than 40% even with a system whose efficiency tends to be lowered with existing technologies such as a 5G system (fifth-generation mobile communication system). As result, it becomes possible to cover a wireless communication circuit also supporting 4G or 3G with one power amplifier.
The new technology amplifies signals with two amplifiers placed in parallel. In general, the efficiency of an amplifier changes in accordance with the load resistance of the output side. So, the efficiency of one amplifier changes in accordance with the load resistance of the other amplifier connected on the output side.
Therefore, when the input signals (levels and phases) of the two amplifiers are individually controlled, it is possible to find the operating conditions that optimize the combined efficiency of the two amplifiers. This time, Mitsubishi Electric also developed a learning function that optimizes signals input to the two amplifiers in accordance with various amplification factors.
Mitsubishi Electric used a newly-developed control function using learning results and confirmed that it is possible to achieve an efficiency of 40-60% in the bandwidth 10% larger than that of the center frequency (fractional bandwidth: 110%).
Expecting that the new technology will be used for base stations, Mitsubishi Electric made an amplifier by using GaN (gallium nitride) semiconductor, which enables to increase output voltage. The company will test it by using actual wireless communication signals in fiscal 2019, aiming to employ it for base stations at an early date.