Design Of High Power Microwave Solid-state Source Based On PLL Technology

Microwave solid-state source is an essential part of the RF microwave system.Satellite navigation,mobile communication,RFID and other key technologies closely related to human life need to use microwave solid-state source.With the rapid development of science and technology,microwave solid-state source also began to replace the magnetron,TWT,carcinotron and other electrical vacuum devices,and further integrated into the traditional microwave application fields such as industry,medical and household appliances.On the basis of a lot of research,this paper has done the following work:1.In this paper,the theory of PLL technology and the structure of PLL circuit are analyzed in detail,and a PLL circuit with output signal frequency of 915MHz and power of?6d Bm is successfully realized by combining the required PLL circuit indexes,from device selection to schematic design to physical production.2.Based on the phase-locked loop circuit realized in the first point above,the cascade power amplifier circuit is analyzed theoretically and its LDMOS transistor is selected.The cascade RF power amplifier circuit is divided into three parts:the front stage power amplifier circuit,the push stage power amplifier circuit and the last stage power amplifier circuit.The input and output matching circuits of these three parts are given in this paper,and the small signal of each part is given.Finally,the simulation results of cascaded power amplifiers are given.The working frequency range of the cascade power amplifier is 890MHz-950MHz,and the bandwidth is 60MHz.The gain at the 915MHz frequency point is S₂₁=48.8d B.3.Based on the RF link architecture of the solid-state source system constituted by the first and second points above,the DC-DC conversion circuit is selected and designed.The high-efficiency DC-DC conversion is carried out by using the buck circuit,which reduces the 48V to 12V,and then reduces the 12V to 5V,2.8V and 2.5V respectively through three LDO three terminal linear regulators.4.Based on the whole circuit of the solid-state source system composed of the first,second and third points,the shielding cavity is designed,combined with the shielding cavity to Joint commissioning,the high power solid state source is realized,and the output power is 54.82d Bm(303.4W),the second harmonic suppression is-42.71d Bc,the third harmonic suppression is-59.61d Bc,and the efficiency is?70%.The overall scale of the solid-state source is 145.8×126.8×30.2mm³,with compact structure and good performance.5.At the end of this paper,a network structure for broadband complex impedance matching is proposed,the structure is composed of parallel sector open circuit branches of step impedance transmission lines,In this paper,it is applied to the matching circuit of the last stage power amplifier in the cascade power amplifier circuit,and the simulation results show that the relative bandwidth is 51%.The network structure has a significant effect of broadening the matching circuit bandwidth.