Research On A Push-pull Microwave Generator By SiC Photoconductive Semiconductors

In recent years,microwave photonics and solid-state high-power microwave devices have developed rapidly.The scheme of generating microwave by photoconductive semiconductor has attracted extensive attention.With the increasingly complex electromagnetic environment,solid-state microwave devices like Ga N-base transistor amplifier or SiC base photoconductive semiconductor have the unique advantages of wide band gap,low loss,compact volume and weight,antielectromagnetic interference and so on.As a wide band gap photoconductive semiconductor material,silicon carbide(SiC)has excellent characteristics such as low jitter,fast response and good linearity.It can be used to produce high-power microwave with adjustable frequency,pulse width and repetition rate.Triggered by the higher efficiency of the push-pull circuit than that of single transistor amplifier circuit,we proposed a push-pull photoconductive microwave amplifier circuit by analogy with transistor push-pull circuit,which can effectively improve the energy conversion efficiency from DC to RF.The main work of this paper includes:1.The working principle of photoconductive microwave amplifier is described,and its unique advantages are demonstrated in comparison with traditional electric vacuum microwave devices.Focusing on the conversion efficiency from DC power to RF output energy,a push-pull circuit design scheme to improve the photoconductive microwave amplifier is proposed.The energy efficiency of a push-pull photoconductive microwave amplifier is analyzed through theoretical calculation,simulation and experimental verification.2.The output of different frequencies under the condition of fixed pulse width is analyzed by the single pulse laser as the input signal.The two PCSSs is triggered by the splitting delay distance in the optical path as the independent variable,and the delay scheme with the highest output efficiency is used to adjust the parameters such as pulse width and frequency.3.The energy efficiency of Gaussian continuous wave with 30% duty cycle as input signal is theoretically calculated on the condition of laser input with fixed pulse width and frequency.The PSpice simulation model is established for further analysis.The correctness and guiding significance of the simulation model are verified by some simple and low-power experiments.4.A push-pull photoconductive semiconductor frequency modulated microwave generation experiment is designed with a continuously tunable laser as the input signal.Taking the input laser modulation frequency as the independent variable,the relationship between energy efficiency and frequency is obtained through simulation and experiment.Under the guidance of theoretical calculation and simulation model,the influence of input laser with different duty cycle and peak power on push-pull conversion efficiency is analyzed.