Phase Perturbation Method (PPM) is introduced as a new phase-only synthesis method to design reflectarray antennas so as their sidelobe level is reduced. In this method, only the reflected phase of conventional unit cells are perturbed from their required values. To this end, two approaches namely the conventional Optimization method and newly introduced Phase to Amplitude Approximation (PAA) method are proposed. Finally, a reflectarray antenna is designed and fabricated to have a low sidelobe level and its performance is investigated.

In this paper, a millimeter-wave power divider based on gap waveguide technology is designed for use in the feeding network of a slot array antenna. The simulation results demonstrate that the proposed structure has about 10% matching input bandwidth in the 58-64 GHz frequency range. The significant advantage of using gap waveguide technology is that there is no requirement of good electrical contact among different metallic parts of the low-loss structure which considerably simplifies the manufacturing processes and mechanical assembly at millimeter-waves applications. Finally, a planar slot array antenna is designed with sidelobe level of-23 dB and bandwidth of 4. 1% at the center frequency of 60 GHz. The gain of antenna is higher than 21. 7 dB over the operation bandwidth from 58. 8 to 61. 25 GHz, corresponding to efficiency larger than 88%.

The purpose of this article is design and development of an aperture coupling microstrip array antenna with high gain, high bandwidth, low side-lobe level. work with optimally design of element started. Then, the complete 512 element array was fed to all the elements by feeding and distributing the same power and gain was obtained over 30 dB. To reduce the side-lobe level, the feed network is designed with Taylor distribution so that the specific range required for each element, which is different from the other elements, is obtained and also, all elements of the array are fed in phase. The elements that are in the middle of the array receive the most power and the elements that are in the besides of the array receive the least power. This structure is designed with 512 elements in an array of 32 × 16, and the operating frequency of the antenna is 12. 5 to 14. 9 GHz, equivalent to 17% of bandwidth in the Ku band. The gain of this antenna is 29 dB and gain variations over the entire frequency range is low, which is desirable and the side-lobe level also varies between-22 dB and-29 dB on both of the E-plane and H-plane. Finally, a metal reflector plate was used to lower the Backlobe level, reaching F/B levels above 35 dB. The overall dimensions of the antenna are 576 mm × 288 mm.

The most common radar EP technique to prevent effects of impulsive interferences is SLB. In classical SLB structure, an auxiliary antenna and receiver channel are employed to discriminate between the main beam signal and the unwanted signals entering through the sidelobes of the main antenna. In this paper, we have proposed a new SLB structure which utilizes multiple auxiliary antennas. Then, by using an envelope-detection based demodulation, we have presented a group of processing logics including AND, OR and SUM to control the switch. Additionally, we have suggested a new method for setting the detection and blanking thresholds. Simulation results show that the proposed methods using multiple auxiliary antennas, outperform the conventional structure in terms of reducing the number of false target blips on radar PPI.

In recent years, different researches have been done in the context of the sidelobe level suppression for the military and civilian porposes. In these studies, various methods have been considered to reduce the sidelobe level, such as: edging the antenna in different cases, surface impedance tuning, placing metal pills on the reflector surface, placing resonant and non-resonant elements on the edges around the antenna. In this article, the effect of focal length and diameter of parabolic reflector antenna on the suppression of the sidelobe level has been investigated and obtained by optimization without the use of complex and costly structures. Depending on the need for the maximum gain, the small size or the minimum sidelobe level, the antenna can be designed. According to the purpose of the minimum sidelobe level, the proposed antenna has a working frequency of 12. 5GHz, gain of 39. 07dBi, 4. 967λ (11. 9 Cm) depth, 39. 24λ (94. 11 Cm) diameter, 19. 375λ (46. 47 Cm) focal length,-44. 91dB and-43. 5dB Sidelobe level in E and H-Plane respectively. This antenna has sidelobe levels of-30. 76 and-47. 15 at frequencies of 6. 5 and 18. 5GHz.

This article presents a novel 4×8 SIW Butler matrix (BM) with sidelobe level (SLL) suppression. The BM operates at 60 GHz and is implemented with a new design to achieve a compact size, which would be attractive for future mmWave wireless systems. This beamforming network uses straight SIW phase shifters with two apertures or two metal posts to pursue a smaller circuit area than with curved line phase shifters. Using a stepwise procedure and analyzing the design equations, the crossover and other components of the BM are also designed and optimized. The reflection and isolation coefficients are lower than-10 dB for all input ports and insertion loss magnitude imbalance is below 2. 4 dB within the band from 57 GHz to 67 GHz. The slot array antenna fed by the BM shows an SLL lower than-21 dB for inputs 1 and 4 and lower than-14. 5 dB for inputs 2 and 3 and provides ± 45° beam switching.

Background and Aims: Lasers with different characteristics have been used to stimulate orthodontic tooth movement. Considering the contradictory findings in this regard, this study was designed to assess the effect of low level laser therapy (LLLT) on the rate of orthodontic tooth movement.Materials and Methods: In this randomized clinical trial study, 12 patients (4 boys and 8 girls; average age: 16.9±3.4) with extracted upper first premolars and required canine retraction into extraction site were included. While in both sides canines were retracted by NiTi coil spring, one side was exposed to GaAlAs laser (890 nm). LLLT was done (on the buccal and palatal mucosa by slow movement of probe) at the beginning of the first month. Impression and cast fabrication performed at the beginning of retraction, one and two months later. The amount of retraction on the cast was measured with the aid of a reference plaque fabricated on the rogae using a digital caliper. Data were analyzed using paired sample T-test and one-sample Kolmogorov-Simirnov test.Results: There was no significant difference in the amounts of canine movement between laser exposed and control sides (P>0.05).Conclusion: The energy dose of laser used in this study (72 J per each tooth) was not appropriate for increasing dental movement.

Always antenna structures with low sidelobe levels are a main goal during antenna design. In this paper, a new method for reduction of radiation patter sidelobe level in phased array antenna with uniform and non-uniform weighting is presented. In this method, by change of array elements weight or adding several elements, such as SLC technique, the pattern with low side lobe level can be achieved.According to the design, in an array with uniform weighting value of SLL in third sidelobe to next more than -10 dB can be reduced so that main beam-width changes less than %3 and variations of gain is negligible.Since in applications use non-uniform weighting so, here a new method for sidelobe level reduction in phased array antennas radiation pattern by Taylor weighting is presented. In this method, by use of uniform weighting results, the weight vector of array modify so that sidelobe reduction in resultant pattern is perceptible. In this method, the value of SLL in third sidelobe to next, ratio to primary Taylor weighting can be reduced so that main beam-width approximately %1 to %2 changes and variation of array gain is negligible. Since in phased array antennas, location of main-lobe can be set electronically by applied proper phase in arbitrary angle, performance of this method in pattern scanning is considered and shown in both way that this method is independent from main-lobe location.

In order to properly understand the subsurface structures, the issue of inversion of geophysical data has received much attention from researchers. Since accurate reconstruction of the shape and boundaries of the mass using gravimetric data is very important in some issues, it is important to use an effective and efficient method that has a high ability to draw and reconstruct the boundaries of a mass. In recent years, the level set method introduced by Asher and Stein has been widely used to solve this problem. From the expansion of the level set function in some bases of the problem, the effective number of parameters is greatly reduced and an optimization problem is created which its behavior is better than the least squares problem. As a result, the level set parameterization method will be presented for the reconstruction of inversion models. A common advantage of the parametric level set method is the careful examination of the boundary for optimum sensitivities, which significantly reduces the dimensional problem, and many of the difficulties of traditional level set methods, such as regularization, reconstruction, and basis function. Level set parameterization is performed by radial basis functions (RBF),which causes an optimal problem with an average number of parameters and high flexibility,and the computational and optimization process for Newton's method is more accurate and smooth. The model is described by the zero contour of a level-set function, which in turn is represented by a relatively small number of radial basis functions. This formulation includes some additional parameters such as the width of the radial basis functions and the smoothness of the Heaviside function. The latter is of particular importance as it controls the sensitivity to changes in the model. In this algorithm adaptively chooses the required smoothness parameter and tests the method on a suite of idealized Earth models. In this evolutionary approach, the reduction gradient method usually requires many iterations for convergence, and the functions are weakened for low-sensitivity problems. Although the use of Quasi-Newton methods to improve the level set function increases the degree of convergence, they are computationally challenging, and for large problems and relatively finer grids, a system of equations must be solved in each iteration. Moreover, based on the fact that the number of underlying parameters in a parametric approach is usually much less than the number of pixels resulting from the discretization of the level set function, we make a use of a Newton-type method to solve the underlying optimization problem. In this research, the algorithm is used to investigate its strengths and weaknesses for applying geophysical gravity data, coding and programming, and it is tested using several two-dimensional synthetic models. Finally, the method is tested on gravity data from the Mobrun ore body, north east of Noranda, Quebec, Canada. The results of this study show that the application of the optimization algorithm of the level set function will lead to a relatively more accurate and realistic detection of mass boundaries. It shows that the tested mass has spread from a depth of 10 meters to a depth of 160 meters.