Development of microwave antenna for cancer treatment

For cancer treatment,microwave thermotherapy method is widely used especially for liver cancer treatment by using a coaxial biomedical applicator device. This device is used to transfer heat from microwave generator to liver tissue in order to kill cancerous tissue. Neglecting the impedance matching between the applicator and the liver tissue can lead power reflection to the power supply or loss into the surrounding healthy tissue. The impedance of the applicator is hugely dependent on the structure and dielectric material used as the insulator for the biomedical applicator. In this work, we aim to study the best structure of the applicator, which can minimize the impedance mismatch. There are two phases required in order to achieve the aim. In first phase, parameter of the applicator has been estimated using the characteristic of impedance for coaxial structure. In phase two, the biomedical coaxial applicator is designed using the electromagnetic simulator software and the results were analyzed to identify the best parameter used for the design. The result of return loss obtained at 2.45 GHz is −25.42 dB with impedance of 21.23. From the value of return loss, 0.29% of power will be reflected to the generator or surrounding tissue while another 99.71% of power will be transmitted into the cancer cell. Based on the finding, most power is transmitted efficiently to the liver and less power is reflected to the surrounding which means it is harmless to the surrounding tissue

Flat lens design using phase correction technique for horn antenna applications

A design of a flat dielectric lens is presented in this study to enhance directivity of a pyramidal horn antenna. The horn antenna is proposed to cover frequency of medical imaging system, which is between 5 and 6 GHz, and dielectric lens is designed based on phase correction techniques. The spherical waves produced by conventional horn antenna is being transform to planar waves by resorting flat lens in order to achieve a highly directive radiation in the farfield region. This is done by drilling numerous holes with different diameters through the dielectric material to produce different phase delay. The radiation characteristics of the lens are simulated using CST Microwave Studio and then compared with measured results. The results showed a good performance for radiation pattern when the lens is attached. This proposed design shows a significant increment of sidelobe level and 3-dB beamwidth between 5 and 6 GHz

Flat lens design using phase correction technique for horn antenna applications

A design of a flat dielectric lens is presented in this study to enhance directivity of a pyramidal horn antenna. The horn antenna is proposed to cover frequency of medical imaging system, which is between 5 and 6 GHz, and dielectric lens is designed based on phase correction techniques. The spherical waves produced by conventional horn antenna is being transform to planar waves by resorting flat lens in order to achieve a highly directive radiation in the farfield region. This is done by drilling numerous holes with different diameters through the dielectric material to produce different phase delay. The radiation characteristics of the lens are simulated using CST Microwave Studio and then compared with measured results. The results showed a good performance for radiation pattern when the lens is attached. This proposed design shows a significant increment of sidelobe level and 3-dB beamwidth between 5 and 6 GHz

Fabrication and characterization of epoxy resin–barium titanate at G-band using waveguide technique

In this paper, fabrication process of epoxy resin-barium titanate nanocomposite and measurement of its complex permittivity are presented. The material is prepared by mechanical mixing of epoxy resin and barium titanate nanopowder. The nanocomposite is intended to be used as high permittivity microstrip antenna substrate, which requires accurate measurement of its electrical characteristics. Thus, characterization of materials is done using waveguide technique, which does not require a precise machining of sample's width and thickness, and does not utilize small reflection coefficient, which can cause error in measurement. The complex permittivity of the nanocomposite is measured in G-band (4 to 6 GHz). Then, the measured values are compared with prediction method, Lichtnecker and Maxwell-Garnet method. The results show that the measured permittivity of composite materials are in good range with prediction method, while the measurements of loss tangent show that the developed materials are low-loss and suitable to be used as substrate of antenna