Current Issue : July - September Volume : 2011 Issue Number : 3 Articles : 7 Articles
Electromagnetic bandgap (EBG) structures can help in the reduction of mutual coupling by their capabilities of suppressing surface wave's propagation in a specific frequency range. In this work, a dual-layer EBG structure, which had a lower resonant frequency than the single-layer one, is proposed in order to reduce the mutual coupling between E-plane coupled microstrip antenna array. As this EBG structure significantly made the series capacitance between neighbor cells larger, a drastic reduction of the unit cell size was achieved. The simulated and experimental results show that the proposed structure has a significant 19?dB mutual coupling reduction....
This paper proposes a novel way to compact the constellation points in QAM modulation schemes and exploits this compaction to reduce the peak to average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. The compaction is accomplished using one dimensional product code (PC). Significant PAPR reduction is achieved by carefully mapping the points in the compact version of the constellation to their radial symmetric points and choosing for transmission signalling points which result in lower PAPRs. Specifically, the complementary cumulative distribution function (CCDF) of the modified OFDM signal shows about five dB improvement in PAPR at a clipping probability of 10-4 over the original OFDM signal. This performance is comparable to that in similar PAPR reduction schemes; however, it is achieved using simple single parity check (SPC) product code and at lower average power....
This research is to describe the recent development of a new automated and high-speed gas filling system in industrial applications. It aims at the introduction, study, and analysis of automated and high-speed gas filling mechanisms in industry. Automation is not only significantly increasing the production speed but also more accurately controlling product quality. Automated mechanical system can maintain consistent quality, shorten lead time, simplify material handling, optimize work flow, and meet the product demand for flexibility and convertibility in production. Computer-aided engineering design can quickly model automated machinery systems, shorten the product development cycles, and improve engineering integral processes of product design, development, engineering analysis, and production. This paper introduces a newly developed automated and high-speed gas filling system and focuses on computer-aided design, modeling, and simulation of this new mechanism. Compared with the current conventional systems, this new automated gas filling system has more reliable sealing function and higher production rates. The prototype of this automated machinery system has also been tested for functional verification. Both computer-aided analysis and prototype testing results indicate that this automated and high-speed gas filling mechanical system works well with high production quantity and reliable product quality....
In the near future, RF front-ends of GNSS receivers may become very complicated when multifrequency signals are available from at least four global navigation systems. Based on the direct RF sampling technique, fully digitized receiver front-ends may solve the problem. In this paper, a direct digitization RF front-end scheme is presented. At first, a simplified sampling rate selection method is adopted to determine the optimal value. Then, the entire spectrum of GNSS signal is directly digitized through RF sampling at a very fast sampling rate. After that, the decimation and filtering network is designed to lower the sampling rate efficiently. It also realizes the digital downconversion of the signal of interest and the separation of narrow band signals from different navigation systems. The scheme can be flexibly implemented in software. Its effectiveness is proved through the experiment using simulated and true signals....
The design of a two-element antenna array using the substrate integrated waveguide (SIW) technique and operating at 10?GHz is presented. The proposed antenna array consists of two SIW phase shifter sections with two SIW slot antennas. The phase shifting is achieved by changing the position of two inductive posts inserted inside each element of the array. Numerical simulations and experimental measurements have been carried out for three differential phases between the two antenna array elements, namely, 0�°, 22.5�°, and 67.5�°. A prototype for each differential phase has been fabricated and measured. Results have shown a fairly good agreement between theory and experiments. In fact, a reflection coefficient of better than 20?dB has been achieved around 10?GHZ. The E-plane radiation pattern has shown a beam scan between 5�° and 18�° and demonstrated the feasibility of designing an SIW antenna phased array....
A design method of compact dual-polarized antennas has been proposed for multiple input and multiple output (MIMO) handset application. For the sake of high isolation in dual polarizations, a printed monopole and a hybrid slot antenna are combined using a coplanar waveguide (CPW) and microstrip hybrid feeding structure. The proposed topology will result in orthogonal current distribution modes for the different polarizations, which effectively reduces the mutual coupling of the two modes. The operation mechanism of the feeding structure is analyzed in principle and verified by simulation. Simulated and measured results show this compact dual-polarized antenna achieves isolation between the two ports of better than 25?dB, and the relative bandwidth is wider than 23.5%....
Based on the kineto-elastodynamic assumptions, the dynamic model of the six-degree-of-freedom parallel structure seismic simulator is developed by virtue of the finite element method and the substructure synthesis technique. The kineto-elastodynamic characteristics represented by the natural frequency, the sensitivity analysis, the energy ratios, and the displacement response of the moving platform are investigated. It is shown that the second-order natural frequency is much higher than the first-order natural frequency, and the first-order natural frequency is sensitive to the radius of the strut and the radius of the lead screw. In order to\r\nimprove the dynamic characteristic of the manipulator, the mass of the moving platform should be reduced or the stiffness of the strut should be increased especially for the sixth strut. For the investigated trajectory, the displacement response of the moving platform along the x direction is smaller than these displacement responses along the y direction and along the z direction. The\r\nangular displacement response of the moving platform rotating about z-axis is slightly larger than those angular displacement responses rotating about the x-axis and about the y-axis....
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