In recent years, digital predistortion linearizers have been used in power amplifiers for mobile communications because they are simpler and provide higher power efficiency than conventional feedforward systems. However, in systems that cover a wider frequency band, it is impossible to disregard the frequency characteristics of their various parameters since the degradation that can result causes a decline in output power efficiency which is the most important property of a power amplifier. To date, no detailed studies have been carried out on predistortion compensation systems. Thus, we focused our research on these systems and in this paper we report the simulation and experimental results we obtained for clarifying these effects. In our experiments, we used a W-CDMA power amplifier to determine how much the distortion compensation effect is degraded by the frequency characteristics of analog RF circuits. The results of experiments to determine the relationship between the ACLR (Adjacent Channel Leakage power Ratio) and power efficiency are also reported.

This paper describes GaAs MMICs used in wireless LANs for spread spectrum communications on the ISM band. Both the transmitter and the receiver are incorporated inside the MMIC. In our experiment using prototypes at a center frequency of 2.45 GHz, the transmitter has a saturation output power of 21.4 dBm and the total current consumption is 131.2 mA. The receiver has a noise figure of3.2 dB and a gain of 12.2 dB.