Ayhan Yazgan

Novel composite method for determining the location of the transmitter using Particle Swarm Optimization

In this study, the Time Difference of Arrival Averaging (TDOAA) method is studied to minimize the estimation error and increase the accuracy for emitter location finding using Particle Swarm Optimization (PSO). We combined TDOAA method with both classic and improved version of PSO and found out a considerable performance increase on the location finding of the transmitter. The improved PSO is to combine different tasks of implementations of PSO for a single decision. Therefore the improved PSO also means more accuracy but price is paid for more complexity. However, the increase on complexity does not prohibit applying the technique, since coherence time for decision may well tolerate more complexity when using todays state of art microprocessors processing power.

Optically reconfigurable fractal antennas for RoF systems

This study presents the operating frequency reconfigurability for the Sierpinski gasket fractal antenna. This design may be a good candidate for RF over fiber (RoF) systems in which the built-in optical systems have already been included. Doped silicon with a suitable laser light is considered as a switching component.

The tradeoff between bit error rate and link distance for a constant signal to noise ratio in Coherent Optical OFDM systems

Recently, fiber optical communication and Orthogonal Frequency Division Multiplexing (OFDM) method are combined to obtain both advantages in a communication link called CO-OFDM. In this research, bit error rate (BER)-Distance variations are investigated for a constant signal to noise ratio (SNR) in CO-OFDM systems. Results also show the performance of the CO-OFDM system at different data rates and distances for one RF carrier and one optical carrier. There are 111 channels (C and L bands) can be used (191.4 to 185.9 THz) at 50 GHz spacing according to the Telecommunication Standardization Sector (ITU-T) standards. Wavelength Division Multiplexing (WDM) is the key factor to reach 1.7 Tb/s (111∗16 Gb/s) using only one optical cable utilizing C and L bands. In this research, CO-OFDM technique is modeled and simulated designing a Monte Carlo simulation. To the best of our knowledge, this work shows the first BER-Distance variations in a CO-OFDM communication link.

High impedance monopole antenna for indoor terahertz wireless communication systems

In this study, a wideband terahertz antenna for indoor wireless communication systems is proposed. Antenna has high input impedance which is reasonable for terahertz systems due to the high output impedance of terahertz sources. Proposed antenna has been designed to operate in 0.67 THz which is one of the appropriate frequencies considering the atmospheric attenuation conditions for short range indoor terahertz wireless communication systems. Designed antenna has 0.8 kohm input impedance at the center of the band and approximately 100 GHz −10 dB bandwidth at 0.67 THz.

A novel rectangular microstrip antenna for ultra-wideband applications with dual band-notched characteristic

In this study, a printed microstrip monopole antenna with band-notched property for wide band communication systems is presented. The antenna is intended to operate in two bands. By using two symmetric rectangular slots on the radiating patch, a notched band 5-6GHz, not to interfere with WLAN, is obtained. Additionally, an M-shaped slot to acquire another notch band at 8-9GHz is formed on the microstrip feed line not to be affected by C-band satellite communication system. Antenna simulations are realized using HFSS and CST high frequency simulators.

The effects of sea environmental conditions on the underwater acoustic communication systems

This research is focused on the effect of the most important environmental conditions (temperature, salinity and wind speed) and distance between transmitter and receiver for the underwater acoustic communication (UWAC) system. These conditions may change the characteristics of the communication channel and need to be taken into account during implementation process. As an example, we chose different regions from Turkey to figure out the most suitable areas for UWAC.

Optimization of receiver arrangements for emitter location finding using time difference of arrival

In this study, particle swarm optimization (PSO) is applied to the time difference of arrival (TDOA) method to determine the emitter location. In addition, receiver arrangements have been optimized to reduce the positioning error. Depending upon the position of the emitter, the receiver arrangements which move the Cramer-Rao lower bound (CRLB) to the lowest value is calculated by PSO.

Examination of the effect of fixing laser phase noise in Coherent Optical OFDM systems with different channel parameters

In this research, the effect of laser phase noise fixing is investigated for different optical channel parameters such as dispersion, attenuation and link distance for Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM) systems. The effect of laser phase noise is examined at different data rates and link distances utilizing only one RF and optical carrier. In this research Phase Shift Keying (PSK) is used as a digital modulation format to maintain the maximum data rate with the acceptable BER value. By fixing the laser phase noise 1.7 Tb/s (111∗16 Gb/s) can be obtained from 191.4 to 185.9 THz at 50 GHz spacing over 1000 km link distance using only one optical cable in C and L bands according to the Telecommunication Standardization Sector (ITU-T). In that case high level modulation formats (N-PSK) should be performed with DWDM technique.

The effect of PIN diode characteristics on the antenna reconfiguration part of cognitive radio

In this paper, frequency reconfiguration of an antenna system is analyzed by means of the PIN diode as a switching element. A printed monopole antenna has been designed and fabricated by combining the PIN diode with RF choke inductors and current limiting resistors. According to both simulation and experimental results, the effect of PIN diode should be taken into consideration for the communication systems in which the electronic antenna reconfiguration is utilized such as cognitive radio.

The state of art of terahertz sources: A communication perspective at a glance

Terahertz band lying between infrared and microwave is a very promising part of electromagnetic spectrum for spectroscopy, space applications and different kind of imaging applications such as medical and security. Recently, this special band has attracted the attention of communication society because of its huge bandwidth and therefore ability of very high speed wireless communications. One of the challenges still on the table is to obtain efficient terahertz sources. In this paper, recent studies on the topic of efficient terahertz sources are reviewed comparatively. Especially for the communication concept, taking into account the efficiency, it can be said that the trend goes to the optical photoconductive materials method including plasmonic electrodes.