• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.2
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• pp.27-32
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• 2004

Absolute optical angle sensor is described that is an essentially digital opto-electronic device. Its purpose is to resolve the relative and absolute angle position of coded disk using Pseudorandom-code and Geometry-code. In this technique, the angular position of disk is determined in coarse sense first by Pseudorandom-code. A further fine angular position data based on Pixel count is obtained by Geometry-code which result 0.006$^{\circ}$ resolution of the system provided that 7 ${\mu}{\textrm}{m}$ line image sensor are used. The proposed technique is novel in a number of aspects, such that it has the non-contact reflective nature, high resolution of the system, relatively simple code pattern, and inherent digital nature of the sensor. And what is more the system can be easily modified to torque sensor by applying two coded disks in a manner that observe the difference in absolute angular displacement. The digital opto-electronic nature of the proposed sensor, along with its reporting of both torque and angle, makes the system ideal for use in intelligent vehicle systems. In this communication, we propose a technique that utilizes Pseudorandom-code and Geometry-code to determine accurate angular position of coded disk. We present the experimental results to demonstrate the validity of the idea.

• Journal of Satellite, Information and Communications
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• v.12 no.1
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• pp.120-124
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• 2017

In this paper, effect of antenna diversity on pseudorandom noise (PN) code acquisition performance is analyzed and simulated for a direct sequence/code division multiple access (DS/CDMA) overlay system where a CDMA user and a narrowband user coexist in the same frequency band. From the simulation results, it is shown that the antenna diversity is very effective in improving the PN acquisition performance. The results of this paper can be applied to design of synchronization scheme for a DS/CDMA overlay environment.

• ETRI Journal
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• v.27 no.3
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• pp.273-279
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• 2005

Toward code division multiple access (CDMA) communications and data protection, we propose and analyze pseudorandom noise (PN) sequences generated from a 2-dimensional array structure of shift-registers. For any positive integers m and n, we construct PN sequences of period $2^{mm}-1$ using an $m{\times}n$ array of registers and show that we can generate all shifted PN sequences as required by IS-95x with the proper linear combination of available sequences.

• ETRI Journal
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• v.28 no.4
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• pp.513-516
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• 2006

Experimental demonstration of bipolar spectral encoding code-division multiple-access with modified pseudorandom noise codes is presented. Bipolar spectral encoding is achieved with an erbium-doped fiber amplifier amplified spontaneous emission source and arrayed waveguide gratings. The bit-error rate performance of 1.25 Gbps signal transmission over 80 km single mode fiber is measured in a multiple-user environment.

• Journal of Power System Engineering
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• v.19 no.3
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• pp.11-15
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• 2015

In this paper, the multi-point hydrogen detection system based on the combination of the hetero-core optical fiber SPR hydrogen tip sensor and interrogator by pseudorandom noise (PN) code correlation reflectometry has been developed. In a light intensity-based experiment with an LED operating at 850 nm, it has been presented that a transmitted loss change of 0.32dB was induced with a response time of 25 s for 4% $H_2$ in $N_2$ in the case of the 25-nm Au, 60-nm $Ta_2O_5$, and 5-nm Pd multi-layers film. The proposed sensor characteristic shows excellent reproducibility in terms of loss level and time response for the in- and out- $H_2$ action. In addition, in the experiment for multi-point hydrogen detection, all sensors show the real-time response for 4% hydrogen adding with reproducible working. As a result, the real-time multi-point hydrogen detection could be realized by means of the combination of interrogating system and hetero-core optical fiber SPR hydrogen tip sensors.

• Journal of the Korean Society for Nondestructive Testing
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• v.14 no.3
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• pp.185-193
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• 1994

Conventional ultrasonic flaw detection system uses a large amplitude narrow pulse to excite a transducer. However, these systems are limited in pulse energy. An excessively large amplitude causes a dielectric breakage of the transducer, and an excessively long pulse causes decrease of the resolution. Using the pulse compression, a long pulse of pseudorandom signal can be used without sacrificing resolution by signal correlation. In the present work, the pulse compression technique was implemented into an ultrasonic system. Golay code was used as a pseudorandom signal in this system, since pair sum of autocorrelations has no sidelobe. The equivalent input pulse of the Golay code was derived to analyze the pulse compression system. Throughout the experiment, the pulse compression technique has demonstrated for its improved SNR(signal to noise ratio) by reducing the system's white noise. And the experimental data also indicated that the SNR enhancement was propotional to the square root of the code length used. The technique seems to perform particularly well with highly energy-absorbent materials such as polymers, plastics and rubbers.

• Journal of IKEEE
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• v.13 no.1
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• pp.65-70
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• 2009

We propose an ultrashort pulse optical code-division multiple-access (O-CDMA) scheme based on a pseudorandom binary M-sequence spectral phase encoding and decoding of coherent mode-locked laser pulses and perform a numerical simulation to analyze its feasibility. We demonstrate the ability to properly decode any of the multiple (eight) 10 Gbit/s users by the matched code selection of the spectral phase decoder. The peak power signal to noise ratio of properly and improperly decoded $8{\times}10 Gb/s$ signals could be greater than 15 for 127 M-sequence coding.

• ETRI Journal
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• v.26 no.1
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• pp.13-20
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• 2004

We propose a new optical code division multiple access (OCDMA) scheme for reducing multiple access interference (MAI) and enhancing performance for optical subscriber access networks using modified pseudorandom noise (PN)-coded fiber Bragg gratings with bipolar OCDMA decoders. Through the bipolar OCDMA decoder and the modified PN codes, MAI among users is effectively depressed. As the data are encoded either by a unipolar signature sequence of the modified PN code or its complement according to whether the data bit is 1 or 0, the bit error ratio (BER) can be more improved with the same signal to interference plus noise ratio over the conventional on-off shift keying-based OCDMA system. We prove by numerical analysis that the BER of the proposed bipolar OCDMA system is better than the conventional unipolar OCDMA system. We also analyze the spectral power distortion effects of the broadband light source.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.1
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• pp.1-13
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• 2024

In this paper, we investigate the signal design of six (USA, EU, Russia, China, Japan, and India) countries for Global Navigation Satellite Systems (GNSS). Recently, a navigation satellite system that is capable of high-precision and reliable Positioning, Navigation, Timing (PNT) services has been developed. Prior to system design, a survey of the signal design for other GNSS systems should precede to ensure compatibility and interoperability with other GNSS. The signal design includes carrier frequency, Pseudorandom Noise (PRN) code, modulation, navigation service, etc. Specifically, GNSS is allocated L1, L2, and L5 bands, with recent additions of the L6 and S bands. GNSS uses PRN code (such as Gold, Weil, etc) to distinguish satellites that transmit signals simultaneously on the same frequency band. For modulation, both Binary Phase Shift Keying (BPSK) and Binary Offset Carrier (BOC) have been widely used to avoid collision in the frequency spectrum, and alternating BOCs are adopted to distinguish pilot and data components. Through the survey of other GNSS' signal designs, we provide insights for guiding the design of new satellite navigation systems.

• The KIPS Transactions:PartC
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• v.13C no.3 s.106
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• pp.311-316
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• 2006

We propose the optical sensor network using optical CDMA with bipolar receiver and modified Pseudorandom Noise codes which are widely used in the wireless communication network. We numerically analyze the performances in the optical sensor network. In the proposed network, multiple access interferences between two sensors are suppressed by performing synchronization between the optical encoder and the optical decoder and adjusting the delay times of optical delay lines. Numerical simulations confirm that the performance can be acquired by suppressing the beat noise among optical signals as the number of sensors increases.