ELECTRONIC INDUSTRIES
Year:2018 | Volume:8 | Issue:4 |Papers Count:15

The purpose of this paper is designing a communications system and the required protocols for store and forward (S&F) payload of a LEO satellite. Considering users' dispersion in diverse places, split channel reservation multiple access (SRMA) technique, is applied through users to access the uplink channel. Different modulation methods are analyzed and PSK modulation and non-coherent FSK modulation are suggested for payload downlink and uplink, respectively. An error detection technique based on Reed-Solomon (255, 233) is used in the payload to improve the link performance and SR-ARQ approach is selected which is more efficient than other ARQ techniques. Moreover, communication protocols of the users' network, file transmitting to the satellite and file receiving from that along with their implementation are explained in terms of software. Finally, an appropriate hardware is proposed for this subsystem. Comparison of our design and the design strategy suggested in [4] show that onboard hardware complexity of current paper is less than [4]. Furthermore, our coding, modulation and protocol and Doppler compensation scenario is more efficient than [4].

In this paper design and implementation of a new and compact ultra wide band antenna for on body communication is addressed. In order to reduce the interference body system, WLAN and WiMAX rejection bands are used. These rejection bands are introduced by using newly suggested metamaterials loading technique. The EBG structure is used as the metamaterials. In addition, a specific absorption rate was simulated using CST Microwave Studio software. A good agreement has been observed between the simulation and experimental results. Considering the specific features of the proposed antenna, it can be appropriate for the on body applications in communication.

In this paper, a Low Noise Variable Gain Amplifier in Ka-frequency band is designed. This amplifier is digitally controlled by using switching transistors which change the gain with an accuracy of 5-bit resolution (32 steps). The output phase shift should be minimized within a Dynamic Range of 15 dB. The proposed structure includes a Low Noise Amplifier and a Variable Gain Amplifier, with common-source structure and degenerative inductor. In the proposed structure, the main gain is achieved by LNA and the switching control bits are used in two stages of the VGA. Simulation illustrates a Noise Figure of 5. 6 dB; bandwidth of 5. 34 GHz; S11, S22 less than-14 dB and Dynamic Range of 15 dB. By using a “ compensating inductor” in the source of switching transistors, the amount of phase shift was reduced, such that within the bandwidth of 1. 5 GHz it is less than 5 degrees. The post-layout simulation results, show a Dynamic Range of 18. 7 dB; a bandwidth of 2. 5 GHz; Noise Figure of 6. 4 dB and return losses less than-10 dB. In addition to it, In EM analysis, all inductors and major RF paths are evaluated by “ Sonnet” software.

he Josephson Fluxonic Diode is a long Josephson Junction that uses oppositely directed magnetic flux quanta, associated with current votrices and antivortices, as its basis operation. the movement of the vortices creates a changing phase. this in turn creates a voltage drop. in this paper, discrete JJ is proposed instead of continues JJ in JFD. Also, by numerical calculation of the discrete sine-Gordon equation, the manner of the carriers is discussed in discrete JJ. Numerically study of the dynamics of JFD based on discrete JJ shows a rectification. Because of it is easy to adjust the value of the junction parammeters, and it is possible to have single flux quantum stuffed in a small area by adjusting the discreetness parameter, it is expected that the useful and practical Josephson fluxonic devices can be made by discrete JJs.

Sounds detection in the water is one of the main challenges of researchers in the sonar field. This challenge will become more complex when the depth of the sea is low or published sound is negligible. Usually Target detection in sonar system is performed with a fix defined threshold that it will increase the detection error. The purpose of this paper is to present a new target detection method in passive sonar using adaptive threshold. In the proposed method, adaptive threshold due to the statistical analysis and Bayesian classifier applied in both time and frequency domains. Particle Filter is used to calculate prior pdf in Bayesian classifier. Finally target detection point is calculated after fusion detection points in time and frequency domains by adaptive filter. The results indicate that the proposed method has better performance (23%) than recent methods in passive sonar target detection issue.

In this paper, design, fabrication and experimental results of a dual-band bandpass filter for global system for mobile communications (GSM) in center frequency f_1=1. 84GHz and worldwide interoperability for microwave access (WiMAX) in center frequency f_2=3. 5GHz are presented. The proposed dual-band filter for use in a simultaneous dual-band Power Amplifier is harmonically designed. Since, the second until fifth harmonics in the power amplifier output power and efficiency will play an important role size, good removal of these harmonics is important. Many multiband filters and circuits designed none have done to eliminate harmonic precision. The proposed dual-band bandpass filter configuration comprises of dual quad-section stepped impedance resonators with a J-inverter in between. With a combination of two bandpass and special Bandstop filters, accurately and completely remove all the harmonics. Ideal circuit components are provided with the relevant formula. After filter design, simulation and fabrication and the results of the internal characteristics both bands is measured.

In this paper, the modeling of a thin layer in (finite-difference time-domain) FDTD lattice is considered. The layer can be nonlinear, anisotropic, dispersive and etc. in this paper, the nondispersive medium containing a dispersive thin layer with Debye model is studied. It is assumed that the thickness of the layer is smaller than the size of FDTD cell. Accordingly, the cells containing the layer are inhomogeneous. The equivalent circuit approach is used in order to the homogenization of inhomogeneous FDTD cells. The proposed method gives accurate results for both normal and tangential electric/magnetic field components. The proposed method doesn’ t require to additional computational effort during the simulation, also reduces the memory and computational time requirements.

CWI is one of the most important error sources that makes the error in measuring Time Of Arrival (TOA) and then decreasing the navigation accuracy in Loran system. This paper presents a novel algorithm to remove CWI. It coincides with analyzing the structure of Loran pulses in time domain plus to presenting a new phase code. The aforementioned algorithm has not complex computations. Additionally, the proposed method has better performance than ones which are conventional. It improves the effectiveness and accuracy in navigation system. The simulation results show that Signal to Interference Rate (SIR) in the output of the proposed algorithm is highly independent from SIR of the received signal and the limiting factor in this algorithm is only Signal to Noise Rate (SNR) of the received signal. The proposed algorithm for the measurement of the (TOA) makes mainly rejecting the effect of synchronous interference. This algorithm is equal to-15 dB for the factor of signal to interference and improves the error of TOA up to 693 times the averaging and phase decoding algorithms. This progress stems from decreasing the received SIR originated from asynchronous CWI up to 3 dB, which it can be rejected using a band pass filter.

In this paper, we simulate junctionless tunnel field effect transistor (JLTFET) by Silvaco Atlas. Two devices which utilize double material gate (DMG) and heterostructure (H) ideas are simulated and investigated. We propose double material gate hetero-structure JLTFET (DMG-H-JLTFET) using these two ideas. These devices have discussed at ON and OFF state with energy band diagram. Simulation results show that DMG-H-JLTFET has a larger ON current, a smaller subthreshold slope, a larger ION/IOFF and smaller threshold voltage as compared with other devices. Furthermore, we calculated the transconductance and the cut-off frequency with respect to gate voltage for these devices, which indicates that performance of proposed device is superior. Hence, DMG-H-JLTFET is suitable for analog and digital applications.

With the advent of hybrid compensators, it has become possible to improve energy transfer by the least investment cost and the rapid control of power system problems. In this paper, Adaptive Neuro-Fuzzy Inference System (ANFIS) method is applied to control Rotary Hybrid Flow Controller parameters as a new member of hybrid compensators. Also, the proposed control strategy is simulated to determine the total fuel cost, power losses and system loadability as objective functions in IEEE 14 bus test system using Matlab software. Furthermore, in order to highlight the ability of ANFIS method, the results are compared to OPF model from economical and technical points of view. The results demonstrate the effectiveness of the intelligent method to improve the power system operation.

By the use of graphene in graphene/silicon schottky junction solar cell, we can benefit from the unique characteristics of graphene not only as an electrode but also as an absorbing material. In this paper we have proposed two new structures for the solar cell based on graphene/silicon junction. In these new structures, it is possible to collect the optical carriers generated in graphene as well as silicon and this is the reason of enhancement in the efficiency of the solar cell. The intrinsic electric field made by the schottky barrier between graphene and silicon in graphene/silicon schottky junction, separates the electron-hole pairs generated in silicon under radiation and cause the photo current in external circuit. In our new structures, we have benefited from graphene as an absorber by producing an extra electric field on the surface of graphene layer. The effect of surface metallization on band diagram of graphene will make this electric field. Conventional metallization of graphene solar cells has window-shape structure. In this structure, graphene is used just as a semitransparent electrode. The two proposed metallizations have asymmetrical and interdigitated finger shapes. The simulation is done by TCAD Silvaco software and declares that in conventional graphene/silicon schottky junction solar cell with window like metallization, the PCE is 2. 7% whereas in solar cell with asymmetrical metallization by two different work functions, the PCE reaches to 3. 5%. By the use of interdigitated finger structure metallization, the PCE would increase to 4. 3%.

In this paper, a new structure is provided for the dispersion compensating photonic crystal fibers in order to broaden the chromatic dispersion and increase the dispersion compensating capability in a wide wavelength range. In the recommended model, putting a star structure instead of the first ring of the internal clad of the square lattice fiber, the dispersion of the fiber is broadened, and the fiber will have the capability of dispersion compensating of the whole E to U telecommunication bands. With the fiber mentioned, in the 1. 55μ m wavelength, the dispersion coefficient will be-553ps/ (nm. km) and the minimal dispersion coefficient will be-1205ps/ (nm. km) in the 1. 71μ m wavelength. The simulation of this fiber is done using the finite difference time domain numerical method.

Nowadays, as tampering attacks getting more attention, data protection Radio Frequency Identification tag (RFID) becomes more important. The watermarking approach prevents unauthorized changes on the content of such labels. Due to the limitations of such tags like their simple structure, scarcity of memory bits and its binary content, using conventional methods likes watermarking and hash function are impossible. Thus, the approaches that can be applied to binary data with low size are used. This paper is based on a special algorithm of neural networks that is used to create the hash and the watermarking code that causes fewer number of valuable bits of memory to be consumed. In the proposed algorithm, all watermarking bits are securely protected and locations of the watermark bits is not detectable. This method not only has no need for secrecy watermarking algorithms, but also has other benefits such as ease and speed of implementation. Another advantage of the proposed approach is the two-step algorithm with its keys and using pseudo-random bits location makes watermark's probability of detection very difficult and inaccessible, and also increase the robustness of the method.

In this paper is investigated a voltage source converter fed with battery system, boost converter, solar cell and a star triangle connection transformer for power quality improvement. Three-phase reference frame theory is proposed to control the four-wire distributed Static Synchronous Compensator (STATCOM) that is consists of a voltage source converter with a dc link capacitor. The proposed DSTATCOM is provided the reactive compensation, source harmonic reduction and compensation of neutral point current in common coupling PCC. Photovoltaic cell with battery and boost converter is used to supply the DC link of VSC voltage source. The main advantage of this method is compensation continuously throughout the day. Also the star triangle transformer is supplied for zero current and neutral current harmonic. To determine the reference current to generate the VSC fire angles, the overall system is designed and is validated in MATLAB environment.

In this paper, it is designed and simulated a 4 input AND all-optical gate based on Kerr-type nonlinear ring resonator using 2D-photonic crystal with silicon rods embedded into air as square lattice. It is utilized silicon Nano-crystal (Si-NC) with nonlinear Kerr coefficient in the ring resonator structure. The ring resonator parameters such as rod radius, refractive index, ring radius and lattice constant are selected in the proposed optical device to operate in c telecommunication window (1550 nm). Finite Difference Time Domain (FDTD) method And Plane Wave Expansion (PWE) method are used for simulations. The Kerr nonlinear effect causes to obtain resonance frequency shift in output characteristics. The input threshold for altering the gate logical state is around 150 mW/ µ m and its time response is 0. 85 ps. The simulation results show that the ratio contrast between the logical state 0 and 1 for the proposed AND logical gate is more than 28 dB.