Adaptive Linearization of Frequency Doubler Using DGS

This paper presents adaptive digital predistortion linearization for the frequency doubler of dual band transmitter designed with DGS. The proposed dual band module operates either as an power amplifier for 2.4 GHz band, or as a frequency doubler for 5.8 GHz band according to signal frequency and bias control. The linearized frequency doubler shows significant enhancement in terms of output power, ACPR and EVM. Measured result shows that the frequency doubler has more than 26 dB ACPR improvement at 11 MHz offset from center frequency by the proposed adaptive predistotion. The EVM of the frequency doubler is 4.4% with adaptive predistortion, whereas it is 15.4% with non-adaptive predistortion. The required power back-off has decreased 7 dB to meet the IEEE 802.11 a EVM requirements with 54 Mbps data rate.