Microwave Broadband Pin Switch Study

Microwave switch is the basic component of the microwave control circuit, which is widely used in the radar, electronic-war, microwave communication, satellite communication and microwave measurement systems etc. Single Pole Double Throw Switch (SPDT) mainly completes the conversion of the signal between two different channels. The control element used commonly is PIN diode and GaAs MESFET and two kinds of broadband and high isolation PIN SPDT are discussed by theory and experiment in this paper.The first two chapters introduce the development of microwave broadband switch, the basic theory of PIN diode and circuit structure. In the third chapter the design of the series-shunt PIN switch is presented. The quantity of PIN diode used in each channel is decided by broad band and high isolation with the help of EDA software. Component models and analysis of some parasitic parameter in PIN diode and circuits are applied in a lot of simulation and optimization to compensate the circuits. To improve the working band of switch, bonding wire inductor should be used to bias circuit. This method reduces the influence of working circuit. The improved T intersection compensates the parasitic parameter and increases the frequency band.In the forth chapter the shunt PIN switch is discussed to achieve the broad band and high isolation. This kind of circuit structure is very flexible at the choice of frequency band. Different methods are applied by different kinds of switches. At last the PIN SPDT switches are researched on experiment and measured results achieve the requirements. The results are analyzed by theories and effects of restraining frequency band are summarized from the circuit technics. These results will provide the basis of improving design.