Design And Application Of Microwave Switch Circuit

Microwave switch is an important component of the control circuits, which is widely used in areas of radar, satellite communications, electronic warfare and microwave measurements. Switch’s main effects are to control the signal on or off and change the signal between different channels. With the development of various types of semiconductor transistors, switch can be mainry designed by PIN diode, GaN high electron mobility transistor (HEMT) and so on. In this paper, I designed SPST-single pole single throw and SPDT-single pole double throw switches both by these two tubes. The parameters of insertion loss, return loss, isolation and other aspects are completely prominent. The main contents of this paper are as follows:Firstly, I researched in the design method of switches based on PIN diode in depth. And then combining microstrip circuit and active circuit theories, compromising the advantages and disadvantages of both series and shunt types, I designed SPST switch and L-band T/R module SPDT switch by choosing series-shunt type which is suitable for switches’design. The switches which are processed by printed circuit board have been test. The results are good agreement with the theoretical simulation results with excellent performance.Secondly,1 studied in the fundamental charateristics of GaN HEMI tube based on GaN designing technology, and then analyzed the basic principles of switches composed by this tube. Combining the novel R-C-R circuit which can produce as a band-rejection filter at the specified frequency, I designed the switch monolithic microwave integrated circuit (MMIC) which has high isolation performance based on dual-gate GaN HEMT tube. The isolation is over 60 dB in the bandwidth of 63%.Thirdly, I researched in the switch-based multi-state impedance matching network’s design methods. This structure can be mainly used in the 1:4 power dividers and four array antennas, achieving impedance matching under different conditions by the number of switches as less as possible. This circuit is compact and easy to be achieved.The proposed switches have good parameters of low insertion loss and high isolation based on PIN diode and GaN HEMT tube. The structure is compact and easy to be realized, can be used in different microwave fields such as communication and radar systems.