فهرست مطالب غلامرضا باقرسلیمی

In this research the effect of a radio-over-fiber (RoF) subsystem on the total degradation (TD) performance of uplink wideband code division multiple access (WCDMA) is assessed in the presence of near-far effect. The study considers the use of pilot-aided channel estimation to neutralize the optical subsystem nonlinearities for different channel conditions, estimation intervals, and near-far factors (NFF). The results demonstrate that the proposed equalization technique almost compensates for the joint impact of the optical subsystem nonlinearity and the near-far effect irrespective of spreading factor, large signal distortion, estimation interval, and user number.

Today، along with the advances in circuit printing technology it has become possible to fabricate band lines integrated with circuit elements. The band lines are known as microstrip lines and the whole packages are called microstrip antennas. The microstrip antennas have three layers، including conductive patch layer، dielectric sub layer، and ground conductive layer. One of the most important problems of prevalent antennas is their inflexibility، which was addressed in the current paper using textile based structure with proper flexibility and flexural stiffness. This was done using ink jet printing techniques followed by electrolytic plating to provide diverse antenna patterns based on nickel particles. The coated surface was characterized by scanning electron microscope، elemental analysis and optical microscope. Moreover، the washing fastness and the other physical and mechanical specifications were measured using standard techniques. The elemental analysis of metal-coated fabric clearly indicated a high level of nickel. Furthermore، the morphological investigation proved the formation of homogenous nickel nanoparticle in a diameter range of 100-500 nm with an evident boundary and semi-spherical shape. In addition، the cumulative presence of particles in a sequence followed a cabbage-like structure originating from metallic crystals. The washing fastness tests revealed a high stability in electrical resistance after several washing steps. In the meantime، the antenna gain and the corresponding bandwidth were measured using spectrum analyzer. The results indicated a 1 kHz increase in bandwidth and 11 dB decrease in antenna gain for a large size compared to a small one. Meanwhile، the bandwidth of rectangular pattern showed a 0. 2 kHz increase and 2. 5 kHz decrease compared to spiral pattern. Finally، the four-probe electrical conductivity test demonstrated a high level of conductivity around 2632 S/cm.

In recent years, the highly conductive patterned fabric has been field of interest for many researchers by focusing on medical and electrical application of flexible and wearable electronic devices. In the meantime, inkjet printing technology as a high precision technique has been extensively successful in flexible electronic device industry. Compared to other techniques, the ink jet printing is most preferred due to low process time, expenses, waste material and also its great capability for creation of flexible conductive pattern. In current study, the polyester fabric was employed for temperature and pH optimization in nickel electroless plating process. The fabrication process composed of three steps including the etching, activation and electroless plating. The etching process provides necessary condition for inkjet printing in activation step followed by electroless plating. The formation of a multi cavity structure on PET fabric after etching process and a continues metallic phase composed of nickel nano crystals(20-100nm) after plating process are two major finding from AFM, SEM and optical microscopic images. The four probe conductivity measurements showed a range of conductivity around 2632± 35 S/cm. Range of patterns including spiral or flat panels with applications in antenna and sensors show the technique perfection. The capacitance measurements also represent a range between 10-20 nF.