P-band SIW Single-ridge High Power Wideband Circulator

The circulator is an indispensable and important part of transceiver system,which is widely used in communication system and radar system.With the emergence and popularity of the new generation of communication technology,microwave devices are faced with more complex and higher requirements of the application environment,which can be simply summarized as miniaturization,easy integration,for specific circumstances,it is required to meet the front two requirements while have a high power capacity at the same time.For the traditional planar circuit such as microstrip line,it is easy to realize miniaturization,but with low power capacity.Power capacity of Waveguide is large enough,but its volume is too large to integrate.Substrate integrated waveguide(SIW)provides a feasible solution to make device have both high power capacity and small size,which has become a hot topic mowadays.Based on the above problems and solutions,this paper designs the P-band SIW and RSIW transmission lines,and designs the P-band circulator with the RSIW transmission lines.Firstly,a 950 MHz central frequency SIW is designed.Then,a substrate integrated ridge waveguide(RSIW)is designed by adding ridges to the SIW.After ridges are added,the size of the SIW is further reduced and the operating bandwidth is further widened.Then,a narrow-band P-band circulator with a relative bandwidth of 5.3% and a wideband P-band circulator with a relative bandwidth of 43.6% are designed using RSIW.In order to expand the working bandwidth of the circulator,a variety of expanding methods are discussed,and the relative bandwidth of the circulator is increased to 52.6%.The final design results are as follows: operating frequency is 700-1200 MHz,S11 <-16 dB,S31 <-15 dB,S21 < 0.5dB,calculated CW power capacity is about 1.6k W,the size of one of three ports is 140mm×30mm.It has reached the requirements of miniaturization and high power capacity.Finally,the calculation method of effective Q value of SIW circulator is discussed,and the formula of effective Q value covering several important parameters is given.Using the formula to calculate the effective Q value can quickly judge the performance of the circulator,which is conducive to speed up the design and debugging period of the circulator.