Useful Matlab Tool for Radio Frequency Designer

This article deals with the design and construction of the microwave applicator with transversal electro-magnetic (TEM) wave, which is filled by distilled water. We have constructed an applicator that works on the frequency f = 434MHz with aperture size of 100mm x 75mm. The applicator is made of the copper. Design of dimensions of the applicator and simulation of the specific absorption rate (SAR) distribution were created in program SEMCAD X LIGHT 13. We have designed an image segmentation algorithm based on histogram fuzzification and k-means algorithms and a simple graphical user interface for computing of SAR distribution area, both in the MATLAB environment. Introduction Design of the microwave applicators for thermo – therapeutic applications is useful in hyperthermia oncology, which is a promising method of oncology treatment [1]. There is a need for simulation of the thermal effect of the applicator on the applied tissue. In design, there is an often spelled question: how does the applicator radiate into the tissue and what is the shape and size of the effective aperture area? In nowadays market, there is a variety of simulators of electromagnetic field which offers us a great variety of running the simulations as well as really advanced visualization of the computed results. There are often very attractive output images in visualizing the results and showing the proportional radiated power from the antenna or the attenuation of a certain material according to its permittivity and conductivity but there is a need for the scalar interpretation. Thus, the MATLAB with the image processing toolbox can be useful in summarizing the whole area of radiated field from the aperture. The algorithm from statistical and machine learning theory such as histogram fuzzification and K-means clustering are available candidates for performing the automatical results. Subsequently, we design the graphical user interface (GUI) to easily pick up the correspondent colours from the chart with the intended range of the radiated power. Subsequently, the total size of the radiated power area of the chosen range will be instantly shown, and the relative percentage of the aperture will be computed. The same principle can be applied on the cross sectional view of the antenna or applicator, and it can be simply separated from the sections of the chosen energy dissipation. This knowledge will help the radio frequency designers to effectively compare the antennas. Moreover, the applicator can be listed in the statistical database with a known scalar of an effective size of the aperture. 1 Microwave Thermotherapy As for utilization of microwave technique in thermotherapy, especially in local hyperthermia, applicators suitable for heating of tissue are being constructed. Microwave thermotherapy is useful in tumors treating. It may be used in cancer treatment to kill or weaken tumor cells with limited effects on healthy cells. Tumor cells have problem with dissipating of the heat because of a disorganized vascular structure. Therefore, hyperthermia may cause cancerous cells to undergo apoptosis in direct response to applied heat while the healthy cells can easily maintain a normal temperature. Moreover, when the cancerous cells do not die outright, they may become more sensible to ionizing radiation treatment or to certain chemotherapies. Thus, the therapy can be applied in smaller doses. There are number of thermotherapy methods, including focused ultrasound, infrared sauna, radio or microwavefrequency radiation, and magnetic nanoparticle therapy. 2 Design of the Applicator From the analytical point of view, we can consider the analogy of the applicator as a transmission line where the one end represents the shorted circuit and the other end represents the connection between the applicator and the biological tissue [2] (see figure 2.1.). Figure 2.1: Electric circuit analogy of the applicator The biological tissue can be modeled electrically [2], as a parallel connection of the resistor and capacitor. Using the equation (2.1) we will obtain a