• Journal of the Optical Society of Korea
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• v.13 no.4
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• pp.445-450
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• 2009

Fingerprint recognition using a joint transform correlator (JTC) is the most well-known technology among optical fingerprint recognition methods. The JTC method optically compares the reference fingerprint image with the sample fingerprint image then examines match or non-match by acquiring a correlation peak. In contrast to the JTC method, this paper presents a new method to examine fingerprint recognition by producing a computer generated hologram (CGH) of those two fingerprint images and directly comparing them. As a result, we present some parameters to show that fingerprint recognition capability of the CGH direct comparison method is superior to that of the JTC method.

• Journal of the Optical Society of Korea
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• v.18 no.4
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• pp.388-394
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• 2014

In this paper, we propose a three-dimensional (3D) image correlator by use of computational integral imaging reconstruction based on the modified convolution property of periodic functions (CPPF) for recognition of partially occluded objects. In the proposed correlator, elemental images of the reference and target objects are picked up by a lenslet array, and subsequently are transformed to a sub-image array which contains different perspectives according to the viewing direction. The modified version of the CPPF is applied to the sub-images. This enables us to produce the plane sub-image arrays without the magnification and superimposition processes used in the conventional methods. With the modified CPPF and the sub-image arrays, we reconstruct the reference and target plane sub-image arrays according to the reconstruction plane. 3D object recognition is performed through cross-correlations between the reference and the target plane sub-image arrays. To show the feasibility of the proposed method, some preliminary experiments on the target objects are carried out and the results are presented. Experimental results reveal that the use of plane sub-image arrays enables us to improve the correlation performance, compared to the conventional method using the computational integral imaging reconstruction algorithm.

• Journal of the Institute of Convergence Signal Processing
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• v.16 no.4
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• pp.139-148
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• 2015

In this paper, the optimum coding method is proposed by using open library in order to improve the performance of a software correlator developed for Korea-Japan Joint VLBI Correlator(KJJVC). The correlation system for VLBI observing system is generally implemented with hardware using ASIC or FPGA because the computational quantity is increased geometrically according to the participated observatory number. However, the software correlation system is recently constructed at a massive server such as a cluster using software according to the development of computing power. Since VLBI correlator implemented with hardware is able to conduct data processing with real-time or quasi real-time compared with mostly observational time, software correlation has to perform optimal data processing in coding work so as to have the same performance as that of the hardware. Therefore, in this paper, the experimental comparison was conducted by open-source based fftw library released in FFT processing stage, which is the most important part of the correlator system for performing optimum coding work in software development phase, such as general method using fftw library or methods using SSE(Streaming SIMD Extensions), shared memory, or OpenMP, and method using merged techniques listed above. Through the experimental results, the proposed optimum coding method for improving the performance of developed software correlator using fftw library, shared memory and OpenMP is effectively confirmed by reducing correlation time compared with conventional method.

• Journal of Navigation and Port Research
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• v.31 no.5 s.121
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• pp.409-414
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• 2007

The effect of multipath is especially serious in urban area and sea surface where buildings and water reflect GPS signal. Multipath brings about the performance degradation on many GPS application because the presence of multipath causes the diminution of pseudorange measurement accuracy in turn position accuracy. In this paper, a multipath mitigation named weighted correlation method is implemented on software GPS receiver, in which the asymmetric correlation function is compensated by modifying the late correlation value. Asymmetry compensation is obtained as weighted sum of two correlators which have different early-late chip spaces. This structure is adopted to lessen the computation load lower keeping up performance similar to that. The performance of implemented multipath mitigation technique is evaluated using GPS signal and multipath signal generated by GPS signal generator and software GPS receiver. The test results show that the weighted correlation method gives hefter performance than the standard correlator and the narrow correlator.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7C
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• pp.715-723
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• 2009

In this paper, we propose a new detection method called dual-cell combining (DCC) detection for the acquisition in time of spread spectrum codes in the presence of residual frequency offset (RFO). When the RFO exists, the correlation peak used for detection during the acquisition process is split into two neighboring peaks with smaller amplitudes, resulting in considerable degradation in the overall acquisition performance of conventional methods. In the DCC detection method, the decision variable for detection is formed by combining two consecutive correlator outputs so that the influence of the reduction in the correlation peak due to the RFO can be alleviated. Numerical results show that the DCC detection method can offer better mean-time-to-synchrouization performance than the conventional method based on the cell-by-cell detection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.289-293
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• 2013

In the noncoherent methods for UWB-IR (ultra-wideband impulse radio), block coded modulation (BCM) is better than the transmitted reference (TR) systems in terms of the energy efficiency and data rate. However, even BCM suffers from the performance degradation in the presence of strong inter-frame interference and inter symbol interference. We propose the transmitted reference based on the BCM (TR-BCM) which is the hybrid system of TR and BCM. Performance evaluation shows that the performance of TR-BCM is better than that of BCM in the high SNR range.