Study And Design Of Ultra-Wideband Radio Frequency Power Amplifiers

With the development of wireless communication technology,it has been widely used in civilian and military applications.In addition,many applications have placed high demands on the working bandwidth of wireless communication systems,making broadband technology become a hot topic in current research.As a very important sub-circuit in the transmitter of wireless communication systems,the power amplifier(PA)determines the output power and efficiency of the whole transmitter,and has a great impact on the performance of the wireless transmitter.GaAs pHEMT is widely used in the design of RF power amplifier due to its high electron mobility and high breakdown voltage.Based on the win PP25-21 0.25um GaAs pHEMT process,this thesis studies the ultra-wideband power amplifiers and designs two ultra-wideband power amplifiers with frequency band of 2-18GHz and 0.03-3GHz respectively.Based on 0.25um GaAs pHEMT process,a distributed power amplifier with frequency band of 2-18GHz was designed.The amplifier can provide optimum load impedance for each transisitor by reducing the size of transistor and the characteristic impedance of drain transmission lines.Additional drain shunt capacitors are introduced to balance phase velocity between input and output transmission lines and improve the output power and efficiency.Using RC parallel circuit in series with the gate of FETs to increase the cutoff frequency of input transmission lines and improve the circuit stability.The drain bias inductor of the power amplifier is designed by ourself in order to meet the current density requirements.The simulation results show this power amplifier achieves a small signal gain of 10.7±1.2 dB,and the saturated output power of 29.3±0.5 dBm with the power added efficiency is 33%-47%.Based on 0.25um GaAs pHEMT process,an ultra-wideband power amplifier with frequency band of 0.03-3GHz was designed.The power amplifier adopts a two-stage structure to achieve a gain greater than 20dB.The influence of output matching circuit on the performance of power amplifier was analyzed.By introducing a stack structure at the output stage,the output matching network can be eliminated,and the loss and area can be reduced.In order to achieve good input matching and inter-stage matching,this thesis designs a broadband matching circuit with simple structure.By introducing consumable components into the matching circuit,the gain flatness of the power amplifier can be adjusted while the matching function is completed.The simulation results show that in the 0.03-3.2GHz frequency band,the power amplifier achieves a small signal gain of 28.4±0.9dB,and the saturated output power of 32.5±0.6dBm with the power added efficiency is 43%-52%.