Modeling and Analysis of Scheduling for Distributed Real-time Embedded Systems

Aimed at the deficiencies of resources based time Petri nets （RBTPN） in doing scheduling analysis for distributed real-time embedded systems, the assemblage condition of complex scheduling sequences is presented to easily compute scheduling length and simplify scheduling analysis. Based on this, a new hierarchical RBTPN model is proposed. The model introduces the definition of transition border set, and represents it as an abstract transition. The abstract transition possesses all resources of the set, and has the highest priority of each resource; the cxecution time of abstract transition is the longest time of all possible scheduling sequences. According to the characteristics and assemblage condition of RBTPN, the refinement conditions of transition border set are given, and the conditions ensure the correction of scheduling analysis. As a result, it is easy for us to understand the scheduling model and perform scheduling analysis.

NOVEL SPECTRUM SENSING METHOD BASED ON THE SPATIAL SPECTRUM FOR COGNITIVE RADIO SYSTEMS

Spectrum sensing is the key problem for Cognitive Radio(CR) systems.A method based on the Peak-to-Average Amplitude-Ratio(PAAR) of the Spatial Spectrum(SS) of the received signals is proposed to sense the available spectrum for the cognitive users with the help of the multiple antennas at the receiver of the cognitive users.The greatest advantage of the new method is that it requires no information of the noise power and is free of the noise power uncertainty.Both the simulation and the analytical results show that the proposed method is robust to noise uncertainty,and greatly outperform the classical Energy Detector(ED) method.

Robust stabilization of state delayed discrete-time Takagi-Sugeno fuzzy systems with input saturation via an anti-windup fuzzy design

We consider the robust stabilization problem for discrete-time Takagi-Sugeno （T S） fuzzy systems with time- varied delays subjected to input saturation. We design static and dynamic anti-windup fuzzy controllers to ensure the convergence of all admissible initial states within the domain of attraction. Based on the project lemma and classical sector conditions, the conditions for the existence of solutions to this problem are obtained and expressed in terms of a set of linear matrix inequalities. Finally, a numerical example is provided to illustrate the effectiveness of the proposed design approach.

Tunable polarization of high numerical-aperture objective with phase plate

The intensity distribution of depolarized field in the focal region of a high numerical-aperture optical system was investigated and found that the depolarization effect is tunable by the plate. The depolarization effect gains with the increase of the inner convergence angle of the phase plate, goes through a dramatic descent when the angle is larger than 30°, and begins to come back when the angle reaches a threshold of respectively 60°and 65° for the orthogonal diffractive field and the longitudinal diffractive fields. This reveals two convergence points where the depolarization effect is the strongest and weakest, respectively, suggesting that the pure phase plate can be a promising method for altering depolarization diffractive fields and constructing optical instruments.

Focal evolution induced by combination of nonspiral and spiral phase plates

Focusing properties of Gaussian beam induced by nonspiral and spiral phase plates are investigated nu-merically. The nonspiral phase plate introduces phase singularity to the incident beam, and the spiral one adjusts the radial phase distribution. Intensity distributions in geometrical focal plane show that the parameters of phase plates can alter the intensity distributions considerably. And local dark focal spots may be obtained, the focal spot may evolve into a circle, a two-peak spot, or a curve line, which indicates that the combination of nonspiral and spiral phase plates can be used to form novel focal spots.

Axial multiple foci of radially polarized hollow Gaussian beam

Axial multiple loci patterns of radially polarized hollow Gaussian beam （HGB） with radial wavefront distribution is investigated theoretically. The wavefront phase distribution is cosine function of radial coordinate. Simulation results show that the multiple foci patterns can be adjusted considerably by the beam order of HGB and cosine parameter that indicates the phase change degree. The foci number fluctuates on increasing cosine parameter for certain beam order. And when the beam order is small, there occur five foci in focal region, and the cases are more frequently than that under the condition of higher beam order. Gradient force distributions are also given to show that the multiple foci of radially polarized HCB may be applied to construct tunable optical traps.

Mechanically scanned leaky-wave antenna based on a topological one-way waveguide

We propose a uniform backfire-to-endfire leaky-wave antenna(LWA)based on a topological one-way waveguide under external bias magnetic field.We systematically analyze the dispersion,showing that the proposed structure supports leaky mode arisen from total internal reflection.By means of tuning frequency or magnetic field,we obtain fixed-bias frequency and fixed-frequency bias LWA with continuous beam scanning from backward,broadside to forward direction.More importantly,we,for the first time,demonstrate that this proposed LWA shows mechanical tunability,allowing us to manipulate the radiation direction from backward,broadside to forward direction by mechanically tuning the air layer thickness.The simulated results show that our system exhibits super low 3dB beam width,high radiation efficiency as well as high antenna gain.Being provided such multiple controlled(especially mechanically)beam scanning manners,the present LWA paves an advanced approach for continuous beam scanning,holding a great potential for applications in modern communication and radar system.