نشریه صنایع الکترونیک
سال پنجم شماره 4 (پیاپی 19، زمستان 1393)

Software product line is a set of software-intensive systems that share common parts and is designed to provide proactive planning and reuse through a set of shared reusable software assets. In Service Oriented product lines - in which, the shared assets are comprised of software services - the alignment of services with the business is an important goal due to service-orientation. Identifying and specifying services and their variability in a way that they are aligned with business, cannot be merely possible using the feature models. Therefore, an importantchallenge in service-oriented product lines is the identification of business-aligned services and their variability using business processes. The contribution of this paper is identifying the aforementioned services and their variability by partitioning the graph of business process family models into sets of activities forming services by leveraging an evolutionary algorithm. The identified services satisfy design metrics and are described in terms of a service-variability model. They are acceptable from the viewpoint of both product line and service-oriented design metrics as well as structural similarity with designs by architects.

In this paper double flyback half bridge converter using zero voltage switching has been designed and implemented. This converter is a combination of two flyback converters with active clamp which are paralleled. They are using common switches. efficiency increase and switching losses decrease are the result of zero voltage switching. In this case the switches voltage stress is equal to input voltage. In addition, parallel structure results in transformer copper losses and diode conduction losses decrease. Consequently this structure has a high efficiency and is proper in applications with high input voltage because of low switch voltage stress and applications with high output current because of current division between converters. A new double flyback converter with output voltage of 12 volts and output current of 16 amperes has been designed and implemented to demonstrate the above claims. These arguments has been introduced and discussed in several sections in this paper respectively.

In this paper a bandgap voltage reference(BVR) with MOSFET transistors in strong inversion region is presented. The proposed circuit has high PSRR and low temperature sensitivity. In this design PSRR is enhanced by using a feedback loop and a regulated voltage for the core of BVR. The proposed bandgap voltage reference, simulated in a 0.18µm CMOS technology, exhibits the output voltage and temperature coefficient in the temperature range of -20 to 100 °c equal to 466.7 mV and 29.1ppm⁄(°c), respectively. The PSRR at lower frequencies is 109 dB. This circuit dissipates 42 μW from 1.2 supply voltage at room temperature.

In this paper, a very low phase noise oscillator is proposed. Phase noise of the proposed VCO is lower than the lowest attainable phase noise of the conventional topologies. In the proposed circuit a fourth-order tank is employed, also the the current waveform injected the tank is class-C which provide the best DC to RF efficiency. Phase noise of the proposed oscillator has been theoretically investigated and closed-form formulae have been derived that shows the amount of phase noise improvement achieved by using the proposed circuit for different tank elements. 6 dB phase noise improvement in current-limited regime is achieved by using the proposed technique with same tank elements in comparison with the conventional topologies. In order to verify the derived formulae, the results of the calculations have been compared against simulation results. Their match are excellent.

The importance of linearity and noise arises a lot of challenges in mixer design. A new technique is presented in this paper in order to improve mixer linearity, which tries to make the circuit more linear by means of displacing switching and transconductance stages and producing second harmonic of the fundamental signal using a frequency doubler and then injecting it to the basic circuit from two auxiliary paths. In this topology, quadrature oscillator is used for appropriate operation of the switching stage. Because of using frequency doublers, the problem of local oscillator signal leakage and DC offset in direct-conversion and heterodyne receivers is reduced, and also, this doublers make the design procedure of this topology easier. Obtained results from simulations in ADS software using TSMC 0.18 um technology, show that linearity characteristics (IIP3 and IIP2) are improved in this topology compared to conventional gilbert cell topologies.

Recently, the ever-increasing multimedia communication traffic has demanded security in distribution including encryption of data. In this paper, a novel image encryption schema is proposed to improve Hill algorithm based on using the principle of magic cube transformation to shuffle the position of image pixels and modify the pixel values. The technique involves three steps. In the first step, the half partition of sub images is encrypted with improved Hill algorithm and is compounded with other partition to get better results. In the second step, we have shuffled the position of all image pixels based on Rubik's magic cube rotation. Finally, the image is encrypted using the improved Hill encryption algorithm. To evaluate the effectiveness of the encryption method, visual tests, histogram analysis, qualitative analysis tests and correlation analysis is used which in Compared with the original Hill algorithm. The experimental results have shown that the proposed algorithm has better scrambling degree and less correlation between adjacent pixels, regarding the Chaos it has a bigger key space.

Regarding to extraordinary significance and application of carbon nanotubes in different industries, producing methods and effective parameters could alternate the diverse carbon nanotubes properties. In this study for the first time, the influential parameters (with economic and industry concept) manipulating the properties of multi-wall carbon nanotubes are investigated by neural network grown by thermal chemical vapor deposition. The six growth parameters which were catalyst thickness, pressure of acetylene gas, temperature and time of pre-treatment and growth were used as input data for the determination of the CNT’s diameter and length. Experimental evaluation showed near coalescence relation between simulation data and operating outcomes. The error level for diameter and length was 5.5% and 7.8%, respectively. Measuring of field emission property demonstrated ideal current density at 5-8 applied voltage. Consequently, using of the network model for determining of diameter and length of carbon nanotubes could decrease the test repetitions in an appropriate matter.

Spin-torque nano-oscillators (STNOs) are able to transfer dc current to RF voltage have shown a great potential for application as sub-micron elements in the next generation microwave generators, tunable with current and magnetic field. In this paper, fabrication and characterization of STNOs will be presented. Output frequency of the STNO as a function of current and magnetic field will be investigated. Based on the achievements and modeling, we predict a sub-THz response of the STNOs via tuning the magnetic anisotropy of the free layer. Finally, results exhibit application of STNOs as wide band microwave signal generators in next generation of integrated micro-electronic components.