The Reascher Of Improving The Security And Reliability Of Microwave Physiotherapy Instrument

Microwave technology is widely used in clinical treatment.At present,almost all the microwave physiotherapy instruments use radiation antenna as microwave-heat coupler.Reflection of the antenna may be large when loads change,and the power absorbed by the load may be less than the calibrated power,thus the curative effect is not guaranteed.Furthermore,increased reflection will cause the magnetron unstable through load-traction principle and microwave leakage.As a result,the leaked microwave is harmful to other normal sites and medical staff.Most instruments which use 8-bit MCU as control chips for microwave source are short of necessary protection design,and there are other shortcomings such as lack of integration,unintelligenct,non-safety and non-reliability.In order to improve the safety and reliability of microwave physiotherapy instrument,a microwave physiotherapy instrument is designed and produced in this project.Specialized research is conducted on the microwave physiotherapy coupler and a safe microwave physiotherapy coupler is realized.In this paper,microwave physiotherapy coupler based on transmission line is designed to tackle the problem of microwave leakage.When the microwave physiotherapy coupler is not attached to the physiotherapy tissue(unloaded),the microwave transmits as slow-wave,and the slow-wave only carrys energy along the line without radiation;therefore,there is no microwave leakage;when the microwave physiotherapeutic coupler is attached to the physiotherapy tissue(loaded),microwave transmits as fast-wave on the transmission line with radiation,and biological tissues would absorb the microwave energy.In this project,structures of transmission line are designed as microstrip meander-line slow-wave structure or microstrip ring slow wave structure;totally,7 microwave physiotherapy couplers are realized.Most of the existing microwave physiotherapy instruments lack protection design,such as reflected power and load detection,which makes it impossible to determine whether the loads match the physiotherapeutic coupler,and it may cause microwave leakage.Reflected-power detection and load detection modules are designed.The feedback microwave energy is converted into DC voltage by a microwave rectifier circuit.The microwave source control system monitors the feedback of DC voltage signal in real time;the magnitude of the voltage signal can manifest whether the physiotherapeutic coupler matches the load,and it can value the current output power.If the real output power fail to match the preset value or the load do not match well with the physiotherapeutic coupler,the system will automatically give an alarm and take appropriate protection action.The results of the microwave physiotherapy coupler tests show when the microwave physiotherapeutic coupler is unloaded,the distance of leakage microwave with power density of 5mW/cm~2 is below 15cm,which is far less than the traditional physiotherapy coupler’s 350cm;when the microwave physiotherapeutic coupler is loaded,there is no microware leakage.On the contrary,the traditional physiotherapy couplers have microware leakage.The whole instrument is tested,and the results show that the microwave physiotherapy instrument can output power according to that of the user set;if the load and the physiotherapeutic coupler is not well matched,the system will alarm.In summary,the microwave physiotherapy instrument can function normally and stably,and safety and reliability have been improved.