| Due to the current high communication rate requirements and spectrum resources limitations of wireless communication systems,modern communication systems use non-constant envelope modulated signals with high peak-to-average power ratio,This requires a long-term staying power back-off zone for power amplifiers that process non-constant envelope modulated signals,to ensure linearity of the system.However,this will result in a significant reduction in the overall efficiency of the power amplifier.And envelope tracking technology can effectively improve the efficiency of the power amplifier in the power back-off zone.Envelope tracking technology is a dynamic power modulation technique that allows the power amplifier to remain in a saturated or gain-compressed region by adjusting the change in the supply voltage at the drain.The core part of the envelope tracking power amplifier system is the envelope amplifier,which requires the envelope amplifier to maintain high efficiency to ensure overall efficiency.This paper focuses on the current mainstream hybrid envelope amplifier architecture and designs a broadband high efficiency envelope amplifier.This paper first designs a parallel hybrid envelope amplifier using 0.18?m 1.8/5V CMOS process.The Cadence spectre simulation results show that the linear amplifier slew rate is about 237V/?s under the equivalent load resistance,the envelope amplifier output power is about 28.02dBm,and the bandwidth is about 57MHz.When inputting the3.84MHz WCDMA signal envelope.The envelope amplifier efficiency is about 80.8%.This performance indicator meets the design requirements.When the 10MHz Wimax signal envelope is input,the envelope amplifier efficiency is about 76.6%,and the output waveform will appear subtle distortion in part of the area due to insufficient output voltage slew rate.In order to increase the bandwidth of the linear amplifier and increase the slew rate of the output voltage,an improved hybrid envelope amplifier is designed in 0.18?m1.8/5V CMOS process.An adaptive bias current source linear amplifier with bandwidth improvement is proposed:the slew rate and the overall circuit transconductance can be improved;At the same time,increase the DC gain and output swing of the transconductance amplifier(the first stage of the linear amplifier).The Cadence spectre simulation results show that the slew rate of the linear amplifier is about 646V/?s under the equivalent load resistance,the envelope amplifier's output power is about 28.39dBm,and the bandwidth is about 70.5MHz,and the efficiency is obtained when inputting the10MHz Wimax signal envelope.It reached 79.2%.This performance indicator meets the design requirements.At the same time,the layout design was completed using Cadence virtuoso,and the area of the layout was about 0.6mm~2. |
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