Tri‐band and quad‐band dual L‐slot coupled circularly polarized dielectric resonator antennas

In this paper, two Dielectric Resonator Antenna (DRA) models fed through a pair of diagonally coupled asymmetric L‐slots are incorporated on the ground plane of size 44 X 44 mm² with a strip line feed underneath the substrate are presented. The proposed DRA‐1 is a triband antenna, resonates at 5.2GHz, 6.7GHz and 9.85GHz with a gain of 5.6dBi, 5.66dBi and 9.8dBi respectively. The bandwidth offered at Circularly Polarized (CP) band by DRA‐1 is 1.95 GHz (6‐7.95 GHz). The proposed second model DRA‐2 operates at 5 GHz, 6.4 GHz, 7.8 GHz and 10.3 GHz with a peak gain of 5.5dBi, 5dBi, 6.1dBi and 7.8dBi respectively. The quad‐band DRA‐2 offers two CP bands with bandwidths of 1.3GHz (7‐8.3 GHz) and 1.2 GHz (9.8‐11 GHz). The multiple operating bands of the proposed DRAs are appropriate for different wireless applications such as WLAN, C‐Band and X‐Band range of frequencies.     

Design of Tri-Band MIMO Antenna with Improved Isolation using DGS and Vias

Wireless Personal Communications - An antenna which is used for multipurpose like WiMAX, RADAR altimeter and X-band applications proposed. A tri-band multiple-input–multiple-output antenna...     

Reduced PFC emissions and gas consumption using a c-C/sub 4/F/sub 8/-based PECVD chamber clean chemistry

Perfluorocompounds (PFCs) used in semiconductor manufacturing are potential contributors to greenhouse gas-driven climate change. PFCs emitted from plasma enhanced chemical vapor deposition (PECVD) chamber cleans can be a significant portion of the total PFC emissions for a typical semiconductor fabrication facility. Previous work adopting octafluorocyclobutane (c-C/sub 4/F/sub 8/) clean chemistries to reduce gas consumption and PFC emissions have been reported on applied materials and novellus PECVD tools. In this study, c-C/sub 4/F/sub 8/ was evaluated as an alternative chamber clean gas on Mattson ASPEN II PECVD tools. A statistical design of experiment (DOE) methodology and tool emission analysis by Fourier transform infrared spectrometry were used to develop a low gas consumption and low PFC emission process. This c-C/sub 4/F/sub 8/ process reduced the clean gas consumption by 65% and PFC emission by 78%, compared to our current C/sub 2/F/sub 6/ clean with no impact on deposited film properties or process repeatability.     

A Multi-band Multi-slot MIMO Antenna with Enhanced Isolation

Communication fields are growing rapidly in the recent era, so transmitting the multimedia contents through an open channel becomes a challenging task. The multimedia contents that are transmitted through this channel are highly prone to vulnerabilities and attacks. Therefore, secure and efficient data communication is considered as a major concern in the multimedia communication systems. So, major efforts are taken by researchers to safeguard the originality of each image. In a conventional system, the secure image communication process was achieved by compressing the content first, and then encryption is performed over the compressed data. Even though it met the required security and compression ratio, but some applications may require the reverse system. In this method, the encryption process is conducted prior to compression to improve the privacy of user data. Moreover, the initial concentration is given for improving content privacy rather than concentrating on size reduction. This paper proposes a reversed system that uses block based perceptual encryption algorithm for encryption and vector quantization (VQ) with hybrid Lloyd–Buzo–Gray (LBG)-Adaptive Deer Hunting Optimization (ADHO) algorithm (VQ-LBG-ADHO) for compression. So, the content secrecy gets improved. The involvement of this adaptive optimization method enhances the performance of VQ in the compression process. This method highly concentrates on secure communication, so the reverse process is followed in this method. It not only improves the image secrecy, however, it further enhances the image quality. The performance of this secure communication process is compared with state-of-the-art algorithms, and the results reveal that the proposed method outperforms the other existing methods.

     

A Geometric Modeller Based on the Exact Octtree Representation of Polyhedra

Geometric Modellers based on a Boundary Representation scheme are well suited for display operations, but boolean operations require algorithms with quadratic complexity. Using a class of extended octtrees which is presented here, boolean operations become linear, while exact recomputation of the boundary model in the case of polyhedral objects is possible, and memory requirements are less than in classical octtree encodings. Some bounds on the memory savings are given and discussed. The DMI system, a Geometric Modeller based on a hybrid model Boundary - Extended Octtrees, is presented, discussing the main operations and the interface between both models. Some modelling examples are shown. Finally, a generalization of the extended octtree encoding which allows the exact representation of objects limited by sculptured surfaces is presented.