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Arceo D.,Pacific Advanced Technology | Arceo D.,Arizona State University | Balanis C.A.,Arizona State University
IEEE Antennas and Wireless Propagation Letters | Year: 2011

A three-element compact Yagi-Uda antenna is proposed that maintains a high absolute gain and low VSWR over a 10% fractional bandwidth with an element spacing of 0.053λ. The proposed Yagi-Uda antenna uses a director and reflector to create a dual resonance and approach superdirectivity at each resonant frequency. By adjusting the reflector and director's resonant frequency, the gain and bandwidth of the antenna can be maximized. The driven element has one folded arm to increase the impedance of the antenna. The reflector and director elements are bowtie designs to increase the bandwidth. The measured impedance and gain agrees well with the computational model. © 2011 IEEE. Source


Arceo D.,Pacific Advanced Technology | Arceo D.,Arizona State University | Balanis C.A.,Arizona State University
IEEE Antennas and Wireless Propagation Letters | Year: 2012

The proposed multiport impedance-matching feed network simultaneously optimizes the operating bandwidth and gain of a two-element superdirective antenna array. Maximum directivity of an $N$-element isotropic radiator approaches N2 as the element spacing approaches zero. Additionally, the operating bandwidth of superdirective antenna arrays is narrowband. Utilizing a multiport impedance-matching network will increase the operating bandwidth. Special consideration is required in designing the circuit so that the losses introduced by the matching network do not significantly degrade the absolute gain of the antenna array. © 2002-2011 IEEE. Source


Hinnrichs M.,Pacific Advanced Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Recent advances in micro-optical element fabrication using gray scale technology have opened up the opportunity to create simultaneous multi-spectral imaging with fine structure diffractive lenses. This paper will discuss an approach that uses diffractive optical lenses configured in an array (lenslet array) and placed in close proximity to the focal plane array which enables a small compact simultaneous multispectral imaging camera[1]. The lenslet array is designed so that all lenslets have a common focal length with each lenslet tuned for a different wavelength. The number of simultaneous spectral images is determined by the number of individually configured lenslets in the array. The number of spectral images can be increased by a factor of 2 when using it with a dual-band focal plane array (MWIR/LWIR) by exploiting multiple diffraction orders. In addition, modulation of the focal length of the lenslet array with piezoelectric actuation will enable spectral bin fill-in allowing additional spectral coverage while giving up simultaneity. Different lenslet array spectral imaging concept designs are presented in this paper along with a unique concept for prefiltering the radiation focused on the detector. This approach to spectral imaging has applications in the detection of chemical agents in both aerosolized form and as a liquid on a surface. It also can be applied to the detection of weaponized biological agent and IED detection in various forms from manufacturing to deployment and post detection during forensic analysis. © 2011 SPIE. Source


Zhou X.,Zhejiang University of Technology | Li Y.,City University of Hong Kong | He B.,Fuzhou University | Bai T.,Pacific Advanced Technology
IEEE Transactions on Industrial Informatics | Year: 2014

Tracking multiple moving targets in a video is a challenge because of several factors, including noisy video data, varying number of targets, and mutual occlusion problems. The Gaussian mixture probability hypothesis density (GM-PHD) filter, which aims to recursively propagate the intensity associated with the multi-target posterior density, can overcome the difficulty caused by the data association. This paper develops a multi-target visual tracking system that combines the GM-PHD filter with object detection. First, a new birth intensity estimation algorithm based on entropy distribution and coverage rate is proposed to automatically and accurately track the newborn targets in a noisy video. Then, a robust game-theoretical mutual occlusion handling algorithm with an improved spatial color appearance model is proposed to effectively track the targets in mutual occlusion. The spatial color appearance model is improved by incorporating interferences of other targets within the occlusion region. Finally, the experiments conducted on publicly available videos demonstrate the good performance of the proposed visual tracking system. © 2012 IEEE. Source


Hinnrichs M.,Pacific Advanced Technology
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

Using diffractive micro-lenses configured in an array and placed in close proximity to the focal plane array will enable a small compact simultaneous multispectral imaging camera. This approach can be applied to spectral regions from the ultraviolet (UV) to the long-wave infrared (LWIR). The number of simultaneously imaged spectral bands is determined by the number of individually configured diffractive optical micro-lenses (lenslet) in the array. Each lenslet images at a different wavelength determined by the blaze and set at the time of manufacturing based on application. In addition, modulation of the focal length of the lenslet array with piezoelectric or electro-static actuation will enable spectral band fill-in allowing hyperspectral imaging. Using the lenslet array with dual-band detectors will increase the number of simultaneous spectral images by a factor of two when utilizing multiple diffraction orders. Configurations and concept designs will be presented for detection application for biological/chemical agents, buried IED's and reconnaissance. The simultaneous detection of multiple spectral images in a single frame of data enhances the image processing capability by eliminating temporal differences between colors and enabling a handheld instrument that is insensitive to motion. © 2012 SPIE. Source

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