نشریه صنایع الکترونیک
سال پنجم شماره 1 (پیاپی 16، بهار 1393)

One of the requirements in the exploiting satellite is creating communication links between satellites and the station.This object requires accurate tracking of the satellite when passing over the station. There are several methods for tracking and control the antenna. In this paper, some new operational methods of the semiautomated methods in satellite searching will offer.Utilizing these methods, there would be no need to use sophisticated common ways of automatic monopulse, step and intelligence tracking. Through these semiautomatic methods, tracking will be done using some software techniques to reach exact simple inexpensive results. These methods were tested operationally on NOAA weather satellites tracking. Received images after applying this method show tracking was improved.

In this paper, a novel algorithm for image encryption based on self-adaptive method and hash function is proposed. In the suggested self-adaptive method, an image is equally divided into four sub-images, all of which are encrypted by using the masks that is generated by other part. This will significantly increase the resistance of the cryptosystem against known/chosen plaintext and differential attacks. In the next process, the salsa20 hash function is modified to generate a key stream. Then the final encryption key stream (by correlating the keystream and plaintext) is used to encrypt 8×8 block images in only two rounds of diffusion process that resulting in both key sensitivity and plaintext sensitivity. Experimental results such as key space analysis (>2512), differential analysis ((NPCR>99.61% and UACI>33.45%)), information entropy (entropy 7.9975) and … show that the proposed image encryption algorithm is secure and reliable against the all attacks.

In this paper, a current mode D-latch and improvement of its speed and performance are investigated. The primary structure of current mode D-latches was altered frequently. Speed and power consumption are the maintwo factors in designing such circuits. In this work, two ideas are investigated, using an active inductance load in the holding section and utilizing transistor capacitor for coupling the input and eliminating low frequency effects. The active inductor at the output cancels capacitance effects and thus speeds up the response. Accordingly, rise and fall times are reduced significantly. The circuit is implemented by means of 90-nm CMOS transistors and the supply voltage is 1 V. Based on simulation results, in the squared pulse frequency of 10 GHz the delay is 1.11 ps, rise times 3.64 ps, and fall time 3.57 ps. The peak-to-peak differential output sweep voltage is 0.464 V. The static power dissipation of the circuit is 200 μW. Simulation results show that the input signals with up to 40 GHz frequency can be applied to the new presented latch in the cost of only 400 fs peak-to-peak jitter. These characteristics made the circuit suitable for the ultra-high speed communications.

Various models are presented for reproducing nonlinear biological neural dynamics, which the Izhikevich model is one of the best of them in complexity and accuracy. Silicon neuron is a compact transistor-based circuit for implementing neural models. In this paper, we present a compact ultra low-power low area silicon neuron of the Izhikevich model based on log-domain integrators. In the proposed circuit, area and static power are decreasedby reducing the value of capacitors and bias currents. Moreover, we have a ultra low dynamic power consumption by reducing voltage swing of the comparator. Also, In the peak current detector a practical huge resistance current source is used. The simulations performed in standard CMOS 180nm technology. Accordingto our experiments, the power and area are enhanced from 1.65nW and 1100μm2 to 650pW and 180μm2, respectively. Our design at present reproduces 12 of cortical patterns with only 3 tuning parameters.

Delay tolerant networks (DTNs) are wireless networks with intermittent connections. Node mobility, dynamic topology, limited energy of nodes and etc make these networks unreliable. DTNs have many applications such as satellites, space communications, war fields, wild life tracking and etc. Since there is not usually a permanent path between source node and destination, traditional routing algorithms in ad hoc networks do not work properly in DTNs. Limited sources of nodes such as buffer and energy, make researchers consider these factors when designing routing protocols. These methods are designed based on duplicating the message received. Then, the node sends the copy to all of the nodes it encounters. In this case, the message will be given to final receipt with more reliability. Duplicating messages cause sources wasting. In this paper, DTN reliability is improved by increasing message delivery ratio and decreasing message drop from node buffers. This can be done by considering the message copies scattered in network. Regarding message delivery ratio, message drop, and delay, number of message copies is determined. This helps to improve network reliability. The proposed method which is called Crouting is compared with PRoPHET, ER, First Contact Routing and Direct Delivery Routing. Crouting improves delivery ratio on average by 5% compared to ER and PRoPHET, 11% more than First Contact Routing and Direct Delivery Routing. Message drop, on average, reduces to 30% compared to Direct Delivery and First Contact Routing. Crouting message drop has on average, reduced to 80% compared to ER and PRoPHET.

Synthetic aperture radar (SAR) images have very applications in the field of target recognition, mineral detection, weather forecasting, agricultural, etc. due to their high spatial resolution and imaging technology. However, the process of this type of images is difficult because of the existence of speckle noise. Nowadays, texture region segmentation based on designing a Kernel function with proper parameters is a real challenge. In this paper, a new parameter estimation algorithm has been proposed to design an efficient Kernel function for texture segmentation of SAR images. In this method, the Curvelet transform is applied to the SAR image only in one step and the inner layer coefficients as texture features are extracted. Then, a new Kernel function is formed based on the kurtosis value of the Curvelet coefficients energy (KCE). In the next step, the segmentation of different textures is applied by using the estimated KCE Kernel function. Experimental results on both simulated and real SAR images demonstrate that the proposed algorithm is effective for segmentation and description of different textures in SAR images, and it has also the less segmentation error in comparison with other methods.

In this paper, we present a successful implementation of a cost-effective direct laser lithography system, using a Blu-Ray optical head. In general, laser lithography systems can be divided into two parts, an optical system and a motion stage. In this work, optical system is provided by a Blue-Ray assembly, containing a 405 nm semiconductor diode laser and 0.85 NA objective lens. The laser beam along the surface of substrate is kept on focus point by an autofocus subsystem, implemented by the laser of optical head and fabricated electronic boards.Motion stage is a three axis nano-positioner which is synchronous with optical head. Experimental results show that the resolution of the lithography system is about 3 μm. However, because of good parameters of Blu-Ray optical head a smallest feature size of about 500 nm can be obtained.

Authentication is an important parameter of a satellite network for providing its security needs. Meanwhile, in recent years several papers have been presented to meet this need. In this paper, a secure authentication scheme for mobile satellite communication systems have been proposed which is secure against of the denial of service attack in addition to providing security needs considered in the literature. This meansthat in the update phase of the temporary identity of the user, if the connection between the user and the network controller be corrupted for some reasons, it is possible to re-establish the session authentication. In this scheme does not use thehigh complex computation, such as public key cryptography or secret key cryptography and scheme is only based on hash function and exclusive-OR operations and Compared with otherschemes, the proposed scheme has a lower computation cost. In additional, this scheme is resistant against the attacks such as stolen-verifier, denial of service, insertion, impersonation, replay attack and the loss of the smart card.