Study On The Design Of Microwave Limit Circuit Based On GaN Schottky Diode

In today's mainstream wireless communication field,with the development of high operating frequency,high integration and miniaturization of electronic equipment,equipment systems are becoming more and more complex,increasing sensitivity,in order to ensure that equipment can cope with the impact of high-power microwave,more professional microwave protection design is required.Therefore,microwave limit circuit in the receiving end of the communication system is an indispensable part,microwave circuit mainly plays the role of controlling input power,in the input microwave power is small to ensure the loss of the signal pass,and in the receiving of high-power microwave attenuation,so as to protect the receiving system low noise,mixing,wave detection and other circuit core components from being burned,to ensure the normal operation of the system.Therefore,the research topic of this paper has very important application value for communication system,especially radar receiving system.Firstly,as the basis of the study of limit circuit,the lateral GaN Schottky diode model is studied in this paper.The test characterization,model building and parameter extraction of GaN SBD device are obtained by the positive current-voltage characteristic curve,capacitor-voltage characteristic curve and reverse characteristic curve of the device,and the test results prove that the switch characteristic of the device are stable and excellent.The on voltage is as low as 0.45 V,zero-bias capacitor 0.5p F,the device's cut-off frequency is up to 50.5GHz,the device is at-20 V reverse bias,the leakage is maintained at about20?A,under the 100?A breakdown condition,The breakdown voltage of the device at a distance of 4?m of the cathode and anode reaches 150V;According to the test results,a GaN SBD device model with ideal diode and parasitic capacitor in parallel is established;Extraction of ADS Model parameters of GaN SBD Devices.The final strength is 0.73 e V,the ideal factor is 1.13,the junction capacitance is 0.22 p F,and the parasitic capacitance is0.28 p F.Then,in the study of the limit circuit,the limit effect in the form of single-stage,two-stage,three-stage and four-stage limit circuit is compared,and finally the rectifier characteristics of Schottky diode are used to improve the isolation of the limit circuit,and a simple structure,safe and reliable,fast response time,short recovery time,high power toleranceand low spike leakage are not derived from the four-stage GaN SBD limit circuit.The circuit achieves insertion loss is 1.375 d B,excellent portability,the starting level is only0.828 d Bm,the limit level is 2d Bm,in the input signal power is greater than 40 d Bm,still maintain a good limit performance,to achieve the goal of high power stability limit.This paper also compares the performance of PIN diode with GaN SBD limit circuit,showing the advantages of the horizontal GaN SBD limit circuit performance developed by this research group.Finally,this paper designs the C-band and S-band four-stage pair tube GaN SBD limit structure,adjusts the circuit and microstrip wire parameters and finally optimizes the S-band and C-band pair tube GaN SBD limit circuit in line with the limit circuit index.The results show that under the condition of not affecting insertion loss and portability,the limit level is reduced,the circuit sensitivity is improved and the limit performance is still maintained when the input signal power is greater than 40 d Bm,the conclusion shows that the construction of the limit structure is ideal,and provides reference value for the design of microwave protection of limiter production and communication radar.