• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.484-487
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• 2004

Symmetric directional couplers are widely used in interferometers, switches, and various signal processing devices. Recently, several optical couplers using multimode fibers were reported, but these suffer from inefficient coupling of light into a branching fiber and/or low directivity. This paper presents the measurement and analysis of loss in the connection of optical fibers via the optical directional couplers. The functionality of the device is based on the principle that is symmetrical, the power in excited mode can be unambiguously directed into one of the output channel by varying and of its parameters. In this experiment, we measure the power of loss in the optical directional coupler at various radius of curvature. Before the measurement of loss in x-coupler, we polish the contact of the fiber surface in order that light can penetrate through another port. The results show that, when the radius of curvature is increased, the loss power is decreased and also approaches of the straight line case.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.28-31
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• 2004

This paper describe analysis active microstrip antenna with low noise amplifier at 900 MHz for mobile communication. The microstrip patch antenna is integrated with low noise amplifier on a permittivity 4.5 (Epoxy-FR4) and thickness of substrate 1.6 mm. Low noise amplifier is designed by using GaAs FETs. The analysis characteristics of antenna include return loss, input impedance, vswr, radiation pattarn, bandwidth and gain of antenna. Mesurement gain of antenna is shown 19.2435 dBi.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.46-49
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• 2002

One problem of vision-based eye-gazed detection is that it gives low resolution. Base on the displacement of the eyes, we proposed method for vision-based eye-gaze detection. While looking at difference positions on the screen, the distance of the centers of the eyes change accordingly. This relationship is derived and used to map the displacement to the distance in the screen. The experiments are performed to measure the accuracy and resolution to verify the proposed method. The results shown the accuracy of the screen mapping function for the horizontal plane are 76.47% and the error of this function be 23.53%

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.192-195
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• 2002

About 90% of Thai-style addresses have similar features; e.g. the beginning of each address line is diagonal. In this paper, we propose a method for locating destination address block (DAB) on Thai envelopes based on features of Thai-style addresses. Firstly, we decompose image into smaller blocks and remove all blocks not meeting criteria. Secondly, we search for the DAB candidates. Lastly, heuristic rules and typical features are applied to identify the destination address block. Experimental results using 2,700 envelopes of handwritten and machine printed Thai envelopes show a successful address extraction rate of 91%.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.585-588
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• 2004

This paper describes design and verification of the motion estimation and compensation unit using full search algorithm. Video processor is the key device of video communication systems. Motion estimation is the key module of video processor. The technologies of motion estimation and compensation unit are the core technologies for wireless video telecommunications system, portable multimedia systems. In this design, Verilog simulator and logic synthesis tools are used for hardware design and verification. In this paper, motion estimation and compensation unit are designed using FPGA, coded in Verilog HDL, and simulated and verified using Xilinx FPGA.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.147-150
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• 2004

In this paper, we propose a reduced-state sequence estimation (RSSE) for trellis coded modulation (TCM) in OFDM with two-stage IDFT/ DFTs, MMSE-LE, and interleaving on frequency selective Rayleigh fading channels. The Viterbi algorithm (VA) is used to search for the best path through the reduced-state trellis combined with equalization and TCM decoding. Computer simulations confirm the bit error probability of the proposed scheme.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.277-280
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• 2005

In this paper, we propose a frequency synthesizer for dualband repeater. The dual-band RF technology for applications to the wireless repeater for CDMA and WCDMA mobile communications has been developed in this paper. The dualband PLL module consisted of dual-band VCO and one PLL IC has been developed. The main technological efforts for the dual-band PLL module is to suppress the intermodulation distortion by applying the miniature ceramic filter using the slow wave characteristics. The dual-band miniature RF module including dual-band PLL module and one MCU controller is very attractive for applications to the miniature dual-band RF mobile repeaters.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.175-178
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• 2005

In this paper, a carrier frequency offset (CFO) estimator is proposed for the interleaved OFDMA uplink systems. It is based on the estimation of signal parameters via rotational invariance technique (ESPRIT). Compared with the Cao's estimator, the proposed estimator has low computational complexity. Simulation results demonstrate that the proposed estimator performs better than Cao's estimator at the relatively low SNR region. Hence, the proposed estimator is more applicable to the practical environments than the Cao’s estimator.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1079-1082
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• 2005

In this paper, a secure system is studied and designed for omenetworking middleware based on sensor network security algorithm. Many sensor networks have mission-critical tasks, so it is clear that security needs to be taken into account at design procedure. First, We study homenetworking middleware model in Jini. And we design a security system is applied by SPINS algorithm for moddleware model. Then we firgure out proper secrecy, authentication, broadcast authentication mechanisms in this model.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.7-10
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• 2005

Ad hoc MAC protocols using directional antennas can be used to improve the network capacity. Directional antennas have a Deafness problem and decrease throughput of the network caused by increasing backoff duration. Dual channel protocols have been proposed to mitigate the Deafness and hidden node problems. In this paper, we propose a dual channel MAC protocol using a directional antenna to mitigate the Deafness problem and increase the network capacity. The performance of the proposed Ad hoc MAC protocol is confirmed by computer simulations using Qualnet ver. 3.8 simulator.