Research On Meter Wave High Power Lumped-element Circulator

As a non-reciprocal passive microwave device,the circulator has been an important part of microwave communication systems since its inception.Due to the unidirectional transmission characteristics of the circulator,it can ensure isolation between many microwave transmitters and receivers,such as transceiver shared antennas.At the same time it plays an important role in satellite communication and radar communication.Until now,the circulator has been everywhere,both military and civilian.Conventional circulator types include waveguide junction circulators,lumped elements junction circulators,line junction circulators,microstrip junction circulators,and the like.With the development of microwave technology,miniaturization has become a popular trend of modern products.However,it can be seen from the theory of the band line junction circulator that the lower the operating frequency is,the larger the ferrite wafer radius R is,especially in the meter band,and the size of the band line junction circulator is too large.However,the size of the lumped elemrnts circulator does not have much to do with the frequency.Therefore,this paper further solves the problems of meter-band devices,impedance conversion and device miniaturization by using the method of combining lumped elements with distributed elements.Based on the traditional lumped elements circulator with only the problem of electric coupling or magnetic coupling,a central structure with both electric and magnetic coupling is designed.In order to obtain wider bandwidth,the band lines whose characteristic impedance is independent of frequency are selected as the transmission lines outside the junction.Firstly,the circulator designed in this paper has a center frequency of 60.44 MHz,a return loss and isolation of more than 20 dB,an insertion loss of less than 0.5 dB,and a relative bandwidth of 73.99%.The center frequency is 390 MHz and the bandwidth is 220 MHz.The center frequency is 681 MHz and the bandwidth is 306 MHz.On this basis,the arc central conductor of the circulator is slotted,and the central frequency is 690.55 MHz,the bandwidth is 326.9 MHz,and a bandwidth spread of 20.9 MHz,and the overall size of the circulator in all frequency bands is less than 59mm × 56mm × 25mm.In order to obtain more bandwidth,a two-stage chebyshev converter is designed based on the central frequency of 681 MHz.When the fluctuation in the passband is ignored,the result that the center frequency is 700 MHz and the bandwidth is 400 MHz with the same performance before matching is obtained.Because the length of each stage matched transmission line is one quarter of the wavelength,in order to meet the needs of miniaturization,this paper uses series inductance and parallel capacitance to replace each stage matched transmission line.Drawings are completed using AutoCAD software and sent to the relevant factory for processing.The vector network analyzer was used to debug the circulatorswith two frequency ranges of 20 MHz-300 MHz and 200 MHz-1200 MHz,and the debugging experience was summarized.