Erdal Korkmaz

Reconfigurable fractal tree antenna for multiband applications

This paper evaluates reconfigurable specification of the fractal tree antenna. Fractal tree antenna fed by a 50 ohms round coax from its middle. Making PIN-diodes on or off state, the characteristic of antenna changes and it results changes in the operation frequency and radiation pattern. The proposed antenna demonstrates reconfigurable frequency range from 1.51 GHz up to 8.6 GHz. Analysis of the antenna has been done by means of commercial software CST Microwave Studio to discuss the impression of different dimensional parameters by controlling the PIN diode switches on radiation pattern, directivity and operational frequency.

A Compact Microstrip Spiral Antenna Embedded in Water Bolus for Hyperthermia Applications

This paper presents the design, simulation, fabrication, and measurement of a circular spiral microstrip antenna embedded in distilled water bolus. The antenna is mainly designed to operate at 434 MHz ISM band to be used for a hyperthermia applicator. The performance of the antenna is compared to a conventional patch antenna also embedded in water bolus. The results show that spiral antenna has significant narrower radiation pattern and is capable to operate at multiple frequencies as well. Narrow beam of the antenna is desired to design a multiantenna arrangement with less coupling and a better focusing resolution which can be crucial for deep regional hyperthermia applications. The option of other frequencies is desirable to have a better control over the penetration depth versus focusing depending on the application region.

Antenna arrangement considerations for microwave hyperthermia applications

This paper presents the adequateness of a rectangular spiral shaped patch antenna and a Vivaldi antenna having narrow beam width to use for antenna arrangements in microwave hyperthermia applications. The results obtained from simplified leg model show the adequateness of the small size spiral antenna due to its capability to operate at multi frequencies and narrow beam width. In addition its small lateral size is promising to use it in multi antenna configuration system for microwave hyperthermia application for cancer treatment.

Design of a tri band 5-fingers shaped microstrip patch antenna with an adjustable resistor

This paper presents a tri band 5-fingers shaped microstrip patch antenna, which resonates initially at dual band of 3.2 GHz and 5.2 GHz frequencies for VSWR <; 2. The antenna is modified by adding an adjustable resistor between the conductor and the reflecting plane giving a third resonant frequency of 2.4 GHz. A decrease in the return loss at 2.4 GHz is observed by modifying the value of the resistance. Impedance bandwidth and the resonant frequencies are examined with respect to the variability of the parameters of the antenna and the position of the adjustable resistor. The size of the antenna has been reduced by 57.9% in length and 14.06% in width. The proposed antenna can be used for 4G, WLAN, and Wi-MAX. The antenna is designed and optimized by using the commercial CST software.

Design of compact microstrip antennas embedded in water bolus for hyperthermia applications

This paper presents the design of a circularly shaped spiral microstrip antenna and a conventional patch antenna both are embedded inside a distilled water bolus. The adequateness of the antennas is investigated for hyperthermia applications. The novelty of the spiral antenna is, it has a narrower radiation pattern and resonates at multiple frequencies to have a better control over the penetration depth and focusing considerations.

Simulation of a rectangular spiral shaped microstrip patch antenna

For some applications it is required to design antennas operating at lower frequencies, have relatively low lateral size and a narrow beam broadside radiation pattern. To that end a new rectangular spiral shaped microstrip antenna is designed and simulated by using of commercial software CST Microwave Studio. The parameters are optimized to have an operation frequency around 1–3.5 GHz, maximum lateral size of 3.5 cm, a minimum directivity of 6 dBi and a HPBW less than 90°. The achieved results are promising and are tunable to specific parameters.

Electromagnetic modeling of a female breast hyperthermia applicator

A female breast hyperthermia applicator is designed with twelve microstrip spiral antennas embedded in distilled water and operating at 434 MHz. The antennas are directed towards the tumor and its phases are individually adjusted to have a positive interference at the tumor location. The simulated temperature distribution and SAR values at the tissues obtained by means of SEMCAD X are presented.

Design and optimization of bow-tie optical antennas

This paper presents numerical simulations of bow-tie optical antennas with different base angles, apex length and bending corners. The sensitivity of optical antennas with respect to possible fabrication limitations is analyzed and an optimum design is proposed. Results show that the field confinement and enhancement can be improved with changing of particular parameters of the bow-tie optical antennas.

Development of a hyperthermia applicator with compact microstrip antennas

The adequateness of a circularly shaped spiral microstrip antenna and a conventional patch antenna is investigated for hyperthermia applicator design. A head model is simulated by using of both antenna types to observe the field distributions. The results show that the novel spiral antenna is more adequate for hyperthermia applicator.

Optical Energy Transfer Mechanisms: From Naphthalene to Biacetyl in Liquids and from Pyrazine to Biacetyl

Optical energy transfer from naphthalene to biacetyl in liquids at room temperature is studied. Electronically excited naphthalene with 200–260 nm ultraviolet (UV) light emits photons in its emission band and the emitted photons are absorbed by biacetyl, which, in turn, excites biacetyl phosphorescence. The resulting phosphorescence is very stable with emission peak at 545 nm for different excitation wavelengths from 200 to 260 nm. Similar optical energy transfer is also observed from pyrazine to biacetyl. The sensitization of biacetyl by several aromatic donors has been investigated in detail. An aromatic donor, pyrazine, is raised to its first excited singlet state by absorption of ultraviolet radiation. Excitation wavelengths were selected in the first - band of pyrazine. Intersystem crossing in pyrazine is sufficiently fast to give a triplet yield of almost unity as determined by the biacetyl method. The optical excess energy in the biacetyl will be released as light, which is sensitized fluorescence. Biacetyl is the simplest molecule among a wide range of -dicarbonyl compounds, which is important for photophysics and photochemistry applications.