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ABSTRACT: A cross-correlating 186-GHz passive millimeter-wave imager has been built. The key components in the signal processing hardware are two 186-GHz receivers and a broadband complex correlator. To evaluate the performance of this imager, its point-spread function, beam pattern, baseline vector, and their variations with the scanning direction have been experimentally measured and derived. Some of these results are needed for optimizing the imager's parameter settings. Others are required for implementing the modulated-beam and modulated-scene algorithms proposed in a previous paper dealing with the imager's fringe in its point-spread function. These results will also reveal any problems in the construction process of the imager. The theoretical bases for these measurements are analyzed. Novel algorithms for deriving each antenna's point-spread function and beam pattern, as well as the imager's baseline vector from the measurement results of the imager's point-spread function and beam pattern are proposed and successfully applied in the measurements. Experimental results are presented and discussed.
IEEE Transactions on Microwave Theory and Techniques 11/2009; · 1.85 Impact Factor
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ABSTRACT: Two methods, the modulated scene method and modulated beam method, are proposed in this paper to manage the fringe in a T-shaped correlating millimeter-wave imaging system. The modulated scene method incorporates the fringe into the scene to form a fringe-modulated scene. The pencil beam that corresponds to the beam of the system with a zero baseline scans the modulated scene to form an image. To recover the image of the original scene, an algorithm that involves demodulation and spectrum patching is used to process the original image after deconvolution. The resulting image is a super-resolution image of the scene. The advantage of the modulated scene method is that a phase shifter is not required. The modulated beam method incorporates the fringe into the beam. By dynamically adjusting the phase of a local oscillator, the fringe scans together with the beam. The advantages of this method are that demodulation is unnecessary and only a single output (real or imaginary) from the complex correlator is necessary to generate a super-resolution image. A disadvantage is that a rapidly adjustable phase shifter is needed. The performance of these methods is theoretically analyzed and tested with simulated data.
IEEE Transactions on Microwave Theory and Techniques 07/2007; · 1.85 Impact Factor
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ABSTRACT: A variety of photonic crystal structures have been patterned using an electron beam lithography instrument developed by modifying a scanning electron microscope. The cumulative dose lithography technique developed for use with this instrument has enabled dense structures such as photonic crystals to be efficiently fabricated. This technique overcomes the need for large pattern data files and minimises the number of shapes to expose in order to produce the final structures. This has the advantages of reducing the time spent blanking and unblanking the beam and minimizing the effect of artifacts due to beam blanking on a large number of shapes. The lithography pattern data files are also reduced in size and the characteristic benefits of electron beam lithography are retained. These include the wide range of line widths available and the ability to rapidly vary the topology of the fabricated structures by changing only the pattern data files since no exposing mask is required.
Optoelectronic and Microelectronic Materials and Devices, 2006 Conference on; 01/2007
