Al-Furat Journal of Innovations in Electronics and Computer Engineering

A dual bands circular slot based on a substrate integrated waveguide (SIW) antenna is presented in this paper for K-band
applications. The proposed antenna structure is consisting of a microstrip antenna with two circular-shape slots etched on the top of
radiation plane and located one on top of the other for bandwidth enhancement. This antenna has been printed on an FR-4 substrate
with a dielectric constant 4.3 of and thickness of 1.5 mm. The optimized antenna resonates at 22.45 GHZ and 25GHZ with a fractional
bandwidth of 1.20 GHZ about (5.353 %) and 1.50 GHZ about (5.994 %), respectively. The achieved peak gain is about 6.14 dB and
4.72 dB over the operating frequencies, respectively, this makes it suitable for K applications with good matching and return loss
characteristics. Design model and performance evaluation of a proposed antenna has been executed by EM simulator, CST
Microwave Studio.

a microwave microfluidic microstrip spilt ring resonator is presented in this paper for liquid sensing and characterization.
The sensor is designed to operate at frequency of 1.4 GHz and quality factor of 360. The sensor has been tested with several solvents
to verify its sensitivity where the resonant frequency and losses vary with each solvent. The shift in the resonant frequency and the
change in the insertion loss have been used to extract the values of the complex permittivity of the solvent. The measured complex
permittivities of the solvents have been compared with the theoretical values with very good agreement. This sensor can be utilized in
many industrial and medical application where the characterization of liquids are needed.

In this paper, a reconfigurable bandpass filter based on meander open loop resonators called split ring
resonators (SRRs) in square shapes is proposed. The proposed filter is able to tune its centre frequency and bandwidth
by changing DC voltages applied to varactor diodes loaded on SRRs simultaneously. Two groups of varactor diodes are
placed where the equivalent electrical length and electrical coupling can be effectively influenced. The first group of
varactor diodes is attached to open ends of SRRs to obtain variable electrical lengths, leading to a tunable resonant
frequency, while the second group is inserted between the two SRRs as a step to store more electrical energy which in
turn leads to govern the required bandwidth freely. Consequently, the proposed filter can vary its centre frequency and
bandwidth independently. All diodes utilized in the proposed design are reverse biased to get a wide range of variable
capacitance. The microstrip technology is adopted in all simulation and fabrication. The substrate used in the
fabrication is a FR4 with dielectric constant 4.5 and thickness 1.5mm. The filter response has two transmission zeros
located below and above the passband to improve the filter selectivity due to asymmetrical locations of feeding lines. The
proposed filter has been designed, simulated, fabricated, and measured where both the measured and simulated results
are in good agreement. However, only a filter with static response is manufactured because the required equipment is
not available. The two coupled SRRs generate second order responses. The tuning range of bandwidth from 404MHz to
960MHz has been achieved, while the centre resonant frequency is widely changed from 0.92GHz to 2.06GHz to cover
the most important wireless applications.

The speedy growing of communication technology and visual services, larger capacity and higher-speed transmissions are required in contemporary underwater applications, which produce the present aquatic systems finally flop to meets requirements. A recently emerging technique in the scope of wireless communication is underwater optical wireless communications (UOWC). Due to using an optical signal, we can achieve a high data rate (approximately Gbps) over medium communication link ranges because of the harsh environment in the underwater channel where optical signals are faced many difficulties in transmission such as absorption and scattering. So, the main problem in the UOWC system performance is the short link range. In this paper, a DPSK with Coherent Detection CD-Optical OFDM with a various number of OFDM subcarriers has been designed and simulated under high turbulence water. Concerning their bit error data rate (BER) achievements, the comparing bit error rate impose is corresponding to 10-5. The simulation results show the achieved communication distances by the suggested system for deferent OFDM subcarriers indexes (128, 256, 512 and 1024) are 3.9m, 4.8m, 5m, and 5.9m respectively. It is clear when we increase the number of OFDM subcarriers the link rage will be increased linearly due to the combating of the inter-symbol interference (ISI) effect. The design and simulation have been accomplished using the optisystemTM tool.

Heterogeneous systems merging a different wireless networks to provide a maximum system capacity and to improve spectrum efficiency. In the Heterogeneous systems the problem of Resources Allocation (RA) and interference management considered as important challenges to maximize a total system capacity. An Orthogonal Frequency Division Multiplexing (OFDM) cognitive radio network is proposed in this paper to a group of small cells assisted by amplify and forward AF two-way relays, with perfect sensing. The RA and relay selection proposed in this paper as a formulation problem, to maximize the total transmission rate for small cell networks within one macro cell. The genetic algorithm GA used as optimization technique to solve this optimization problem. The results showed the ability of this algorithm to effectively determine the frequency and power values that distributed over 256 levels. To solve the problem of cross-tier interference from macro cell base station to small cell users, a theoretical analysis has been performed to calculate it and which included in calculation the total capacity according to Shannon's theory. All equations have been derived and theoretically calculated in this paper, in addition to getting higher transmission rate.