MULTIPLE DIRECTION INTERFERENCE SUPPRESSION BY UNIFORM LINEAR PHASED ARRAY SIDELOBE EFFICIENT CANCELLER

Background. For radar systems, the beam pattern of a uniform linear array (ULA) is synthesized to ensure signal selectivity by direction. A specific ULA sidelobe is cancelled by rescaling the beam weights. In particular, this is done by increasing the number of sensors and shortening the scanning step. However, a noticeable limitation is a loss of the transmitted power. Therefore, the problem is to optimally balance the number of sensors versus effective ULA sidelobe cancellation. Objective. In order to ensure multiple direction interference suppression, the goal is to find an optimal number of ULA radar sensors for the beam pattern synthesis. The criterion is to determine such a minimum of these sensors at which mainlobes towards useful signal directions are evened as much as possible. Methods. To achieve the said goal, the ULA sidelobe cancellation is simulated. The simulation is configured and carried out by using MATLAB® R2020b Phased Array System ToolboxTM functions based on an algorithm of the sidelobe cancellation. Results. By increasing the number of ULA sensors, the beam pattern lobes are not only thinned but also change in their power. In particular, the interference direction sidelobes become relatively stronger. The number of sensors is limited by the three influencing factors: the thinned-array curse transmitted power loss, the aperture size, and the sidelobes intensification. Conclusions. An optimal number of ULA radar sensors for the beam pattern synthesis can be found when the scanning step is equal to the least distance between adjacent interference directions. At the start, the number of sensors is set at the number of useful signal directions. If the mainlobes towards useful signal directions are not evened enough, the set of interference directions is corrected. Keywords: radar phased array; beam pattern; interference direction; sidelobe cancellation; aperture size.

DETERMINATION OF THE OPTIMAL SCANNING STEP FOR EVALUATION OF IMAGE RECONSTRUCTION QUALITY IN MAGNETOACOUSTIC TOMOGRAPHY WITH MAGNETIC INDUCTION

Magnetoacoustic Tomography with Magnetic Induction (MAT-MI) is a new hybrid imaging modality especially dedicated for non-invasive electrical conductivity imaging of low-conductivity objects such as e.g. biological tissues. The purpose of the present paper is to determine the optimal scanning step assuring the best quality of image reconstruction. In order to resolve this problem a special image reconstruction quality indicator based on binarization has been applied. Taking into account different numbers of measuring points and various image processing algorithms, the conditions allowing successful image reconstruction have been provided in the paper. Finally, the image reconstruction examples for objects’ complex shapes have been analyzed.

Object Scanning of Windows Kernel Driver Based on Pool Tag Quick Scanning

In the memory forensics, the Pool Tag Scanning based on the memory pool tag requires a detailed search of the physical memory when scanning the kernel driver object, which is very inefficient. The object scanning of Windows kernel driver by using the pool tag quick scanning is proposed. The method uses the quick pool tag scanning to reduce the memory range of the scan, and then scan the driver object according to the characteristics of the kernel driver object quickly, to help investigator to determine whether the driver is normal. Experimental results shows that the scanning efficiency for object scanning of kernel driver is improved greatly by using the quick pool tag scanning technology and the time spent in the scanning step is reduced while ensuring the false alarm rate is same.

A Novel Scanning Method Applied to New-Style Solar Telescope Based on Autoguiding System

To expand field of view (FOV) of telescope, the method of special scanning often is used, but, for some telescopes with special structure in optics and machine, the conventional scanning methods are unsuitable. This paper proposes a novel scanning method based on autoguiding system so as to expand the FOV of fiber array solar optical telescope (FASOT) in possession of the special structure in optics and machine. Meanwhile, corresponding experiments are conducted in the FASOT prototype, FASOT-1B, in order to demonstrate that, for both FASOT and FASOT-1B, the proposed scanning method is feasible. First of all, on the basis of the software and hardware characteristics of FASOT and FASOT-1B, the three key technologies related to the proposed scanning method are described: quickly locating and pointing the first scanning step, the closed-loop controlling of multistep scanning, and the disturbance suppression of every scanning step based on Kalman filter. Afterwards, experiments are conducted and corresponding results show that the proposed scanning method is robust for the random disturbances forced on every scanning step and able to meet the scanning requirement of both FASOT and FASOT-1B .

Research on the effect of coverage rate on the surface quality in laser direct writing process

Direct writing technique is usually used in femtosecond laser two-photon micromachining. The size of the scanning step is an important factor affecting the surface quality and machining efficiency of micro devices. According to the mechanism of two-photon polymerization, combining the distribution function of light intensity and the free radical concentration theory, we establish the mathematical model of coverage of solidification unit, then analyze the effect of coverage on the machining quality and efficiency. Using the principle of exposure equivalence, we also obtained the analytic expressions of the relationship among the surface quality characteristic parameters of microdevices and the scanning step, and carried out the numerical simulation and experiment. The results show that the scanning step has little influence on the surface quality of the line when it is much smaller than the size of the solidification unit. However, with increasing scanning step, the smoothness of line surface is reduced rapidly, and the surface quality becomes much worse.

Evaluation of SEE on a 32-bit Microprocessor by Laser Test and Heavy Ion Test

In this paper the SEE (single event effects) of different parts of device were explored on a 32-bit microprocessor with a five-stage instruction pipeline by laser test and heavy ion test. The cross section curves for different function units were obtained and the comparison of the dates obtained from laser test and heavy ion tests was made. In addition, laser test under different scanning steps were made which indicate that when the scanning step length is in small steps which is considerably equivalent to the laser spot size, there is little change in the number of single event errors caused by each laser pulse. Wherever with the scanning step increasing, the number of single event errors caused by each laser pulse will be reduced. Experiment results suggest that there are differences between laser test and the heavy ion test but have a similar trend. The pulsed laser is an extremely powerful and low-cost technique for SEE testing and will provide invaluable information in characterizing SEE in integrate circuits.