The Investigation And Linearization Of Sequential Power Amplifier

The rapid development of the fourth and fifth mobile communication systems have proposed new requirements for the channel capacity and data transmission rate.For instance,the data transmission rate of the forthcoming fifth mobile communication system will reach 10Gpbs.To meet the high-speed data rate,efficient and complex spectrum-modulation techniques have been widely applied in mobile communication a system,which leads to the dramatic increase of peak-to average power ratio(PAPR)and bandwidth for original signal.Power amplifier is the most important device of wireless communication transmitter,which has great influence on the system.Therefore,it is critical to study the performance of power amplifier as efficiency and bandwidth when applied to amplify high-PAPR modulated signal.In this thesis,performance of Sequential power amplifier(SPA)over 3.4GHz-3.6GHz are investigated,especially about the broadband and high-efficiency.The structure of SPA is analyzed at fisrt.The investigations prove that the design of SPA can enhance efficeincy at back-off(BO)level,and the efficiency at BO point varies with the output coupler and the saturated output power ratio of two sub-power amplifiers.For the moduated signal with a PAPR of 6dB and the signal with a PAPR of 8dB,two SPAs(namely,SPA 1 and SPA2)over 3.4GHz-3.8GHz are fabricated,respectively.The measured results show that SPA1 provides saturated output power of 42.4dBm-43.4 dBm.Under the stimulus of a 20MHz signal with a PAPR of 6dB,the 6dB BO average drain efficiency of SPA 1 can reach 44%-54%,and the adjecent channel leakage ratio(ACLR)at BO ouput power is better than-52dBc after digital pre-distortion(DPD).The measured SPA2 delivers 43.2dBm-44.1 dBm saturated output power.Under the stimulus of a 20MHz signal with a PAPR of 8.4dB,the 8.5dB BO efficiency varies from 39%-45%(which is 9%-15%more than that of main PA),and the output ACLR can be lower than-47.4 dBc with DPD.Addtionally,when stimulated by a 40MHz signal with a 7.3dB PAPR,the SPA2 can achieve an ACLR of-45.8dBc after DPD.Lastly,the SPA with modified output combining network is investigated,and a modified SPA over 3.2GHz-3.8GHz is fabricated.The measured modified SPA can provide a saturated output power of 41.8dBm-42.9dBm with the drain efficiency of 55%-65%and achieve the drain efficiency of 54-61%at 7dB-10dB output BO level.To evaluate the performance of the SPA for modulated signal applications,40MHz signal with a PAPR of 9dB is used to test the efficiency and linearity at 3.6GHz.The proposed SPA can deliver an average efficiency of 51%at average the output power of 32dBm,and the output ACLR can reach-44.6dBc after DPD.