System and Characterization Method for Controlled Microwave Heating in Medical Applications

This paper presents a custom-built 10 W microwave heating device for medical applications, along with a method for characterizing the system heating response. Closed-loop proportional-integral-derivative (PID) temperature control requires optimization of the controller gains to achieve proper response parameters such as fast rise time and minimum steady-state error. This in turn requires the characterization of the microwave heating system (plant). The microwave heating (average) power is adjusted through pulse-width-modulation (PWM), and the temperature response is measured by infrared radiometry. The preliminary results presented in this paper are for microwave heating on tissue phantom brought to 35°C (surface body temperature). The best fit response through PID autotune application in MATLAB, for 20, 40 and 60% PWM (2, 4, and 6 W power respectively) demonstrates that a first order system reasonably and consistently represents the microwave heating response.