Hamed Abbasi

Compact microstrip lowpass filter with wide stopband and sharp roll-off using tapered resonator

In this article, a novel microstrip lowpass filter (LPF) with specifications such as sharp cut-off, wide stopband, low insertion loss and high return loss using tapered resonator is presented. The LPF has cut-off frequency of 1.11 GHz, where unwanted harmonics are suppressed by novel tapered cells. The bandwidth is enhanced, and the size is reduced as compared to the conventional tapered filter. The transition band is approximately 0.29 GHz from 1.11 to 1.4 GHz with corresponding attenuation levels of –3 and –20 dB, respectively. The stopband with greater than –20 dB rejection is from 1.4 to 8.9 GHz, insertion loss in the passband is less than 0.1 dB, return loss is less than –18 dB and the overall size of the filter is 0.12 × 0.073 λg. The proposed filter is fabricated and measured. The simulation and measurement results are in good agreement. This LPF is designed for microwave communication applications, especially wireless video transmitters.

Compact Microstrip Lowpass Filter with Sharp Roll-off and Wide Stopband Using Semicircle Ended Stub Resonator

In this paper, a semicircle ended stub resonator, cascaded to a modifled radial patch to design a compact lowpass fllter with sharp roll-ofi and wide stopband is proposed. This fllter has 3dB cutofi frequency at 1.54GHz. The transition band is only 0.26GHz from 1.54GHz to 1.8GHz with corresponding attenuation levels of i3dB and i20dB respectively. Maximum insertion loss is 0.1dB in the passband, and the stopband bandwidth with the attenuation level better than i20dB is extended from 1.8GHz up to 13.93GHz. So, a wide stopband is achieved. The proposed fllter is designed, fabricated and measured, where there is a good agreement between the simulation and measurement results. The results show that a roll-ofi rate of 65.4dB/GHz together with a relative stopband bandwidth of 154% with the suppression level of i20dB is obtained while achieving a high flgure of merit (FOM) of 23509.

Fabrication and Nonlinear Refractive Index Measurement of Colloidal Silver Nanoparticles

In this paper we report the measurement of nonlinear refractive index of colloidal Ag nanoparticles and fabrication of Ag nanoparticles. In order to fabricate the colloidal silver nanoparticles laser ablation method has been used. A silver coin as a target (purity 99.9 %) was ablated by a Q-Switched Nd: YAG laser with a fluence of about 91 mJ/cm 2 at a repetition rate of 10 Hz at room temperature. In order to characterize these particles transmission electron microscopy (TEM) and spectrophotometry (from UV to NIR) have been used. The average size of fabricated nanoparticles is ~ 20 nm. The importance of morphology of nanoparticles has been investigated. We used the Z-scan technique to investigate the nonlinear refractive index of Ag nanoparticles. The excitation source was a CW 532nm Second harmonic Nd:YAG laser with a beam power of 55 mW. Mostly used applications of silver nanoparticles have been studied; silver nanoparticles are considered as biocompatible and low in toxicity and have good potential for biological applications. Lately silver nanoparticles have found a novel approach in different fields of medicine, biology and industry. In this paper n 2 refers to nonlinear refractive index ,ΔT p-v is the difference between the normalized peak and the valley transmittance. s is the aperture linear transmittance. L eff is the effective thickness of the sample. EIS, SPR, TEM and SEM refer to: electrical impedance spectroscopy, surface plasmon resonance, transmission electron microscope and scanning electron microscope, respectively.

Preparation of Colloidal Silver Nanoparticles by Laser Ablation; Evaluation and Study on its Developed Applications

In this work we report the preparation of colloidal silver nanoparticles. In order to prepare the silver nanoparticles laser ablation method has been used.A silver coin as a target (purity 99.9 %) was ablated by a Q-Switched Nd:YAG laser with a fluence of about 91 mJ/cm2 at a repetition rate of 10 Hz at room temperature. In order to evaluate these particles transmission electron microscopy (TEM) and spectrophotometry (from UV to NIR) have been used. The average size of prepared nanoparticles is ~ 20 nm. The importance of morphology of nanoparticles has been investigated. Developed applications of silver nanoparticles have been studied,silver nanoparticles are considered as biocompatible and low in toxicity and have good potential for biological applications. Lately silver nanoparticles have found a novel approach in different fields of medicine, biology and industry.

Microstrip lowpass filter with wide stopband and sharp roll-off using modified radial stub resonator

In this paper, a microstrip lowpass filter with wide stopband and sharp roll-off is presented. The proposed filter consists of a modified radial stub resonator which is cascaded by four suppressing cells. To reduce the overall size, the transmission lines are folded. The cut-off frequency of the proposed filter is 1.19 GHz. The transition band is approximately 0.2 GHz from 1.19 to 1.39 GHz with corresponding attenuation levels of 3–20 dB. The stopband is from 1.39 to 19 GHz with attenuation level of

Design of Class-EM Power Amplifier at any DC Voltage Source Considering Nonlinear Capacitances

ABSTRACT In this paper, the effects of the DC input voltage source on the class-EM power amplifier design and specifications at 4 MHz operating frequency are investigated. The most important parameters of the class-EM power amplifier are the output power, output power capability, maximum voltage and current of the MOSFETs and power conversion efficiency which are all dependent on the input DC power supply. In this paper, IRFZ24N and IRF510 transistors have been used for the presented designs. The measured efficiency and output power at DC source voltage of the main circuit equal to 12 V for the proposed class-EM power amplifier with IRFZ24N are 96.2% and 21.78 W, respectively. The measured results for IRFZ24N are consistent with simulation and analysis results.

A novel microstrip lowpass filter with sharp roll-off and ultra-wide stopband using SICMRC

This paper presents a novel microstrip lowpass filter with sharp roll-off and ultra-wide stopband using stepped-impedance resonator and bended transmission line structure. The filter includes stepped-impedance prototype filter and stepped-impedance compact microstrip resonator cells that are combined in one structure. The proposed filter has good specifications such as sharp roll-off, ultra-wide stopband and low insertion loss. The transition band is approximately 0.25 GHz from 1.75 to 2 GHz with corresponding attenuation levels of −3 and −40 dB. The attenuation level in the stopband is better than −20 dB that is achieved from 1.94 to 23 GHz, and the insertion loss in the passband is less than 0.4 dB. The proposed filter is fabricated and measured, and the simulation and measurement results are found to be in good agreement with each other.

Studying the Recent Improvements in Holograms for Three-Dimensional Display

Displayers tend to become three-dimensional. The most advantage of holographic 3D displays is the possibility to observe 3D images without using glasses. The quality of created images by this method has surprised everyone. In this paper, the experimental steps of making a transmission hologram have been mentioned. In what follows, current advances of this science-art will be discussed. The aim of this paper is to study the recent improvements in creating three-dimensional images and videos by means of holographic techniques. In the last section we discuss the potentials of holography to be applied in future.