• Journal of IKEEE
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• v.16 no.1
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• pp.20-27
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• 2012

In order to overcome jamming, a hysteresis tunable monolithic comparator circuit based on a 0.35 ${\mu}m$ CMOS process is suggested, designed, fabricated, measured and analyzed in this paper. To tune the threshold voltage of the hysteresis in the comparator circuit, two external digital bits are used with supply voltage of 3.3V. An improved variable hysteresis comparator circuit controlled by serial digital bits is suggested, designed and simulated to overcome jamming in modern warfare.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.254-260
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• 1999

Meteor Burst Communication can provide effective and economical means of communication where long distance VHF NLOS data transmission is needed; often ranges more than 1000 km. It has been, however, so far considered unsuitable for short distance application because of phenomenal decrease in burst durations, which leads to decreation of total duty rate of the system. This paper extensively analyzes characteristics of shot distance MB(Meteor Burst) path and shows the low duty rate may be improved by increasing burst rate through adapting antenna beam width to cover entire hot-spot region in the space and, by compensating effective burst length through cutting down man-made noises introduced by antenna. Based on the analysis, we are developed a small-opening-cavity antenna, especially designed for short distance MB path. In operation, the antenna is to be buried under ground surface so as to improve directivity and reduces noise introduction. The antenna exhibits power gain of 3 dB with 90 degree beam width and thus enables to illuminate entire hot-spot regions with the elevation angle of 8-90 degree which is the case of transmission less than 100 km. Directivity horizontal to earth surface is suppressed to minimum which enables to cut man-made noises from near-by sources down to more than 3 dB from the level reported with conventional 4 element Yagi. A series of experiments performed on 100 km MB paths have conformed that, with the antenna installed at receiving site, the burst rate and duration time have been noticed to increase by 10 and 20 percent respectively from the values obtained by conventional 4-element Yagi antenna under same testing condition.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.6
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• pp.788-801
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• 1998

Meteor Burst Communication can provide effective and economical means of communication where long distance VHF NLOS data transmission is needed ; often ranges more than 1000 km. It has been, however, so far considered unsuitable for short distance application because of phenomenal decrease in burst durations, which leads to decreation of total duty rate of the system. This paper extensively analyzes characteristics of shot distance MB(Meteor Burst) path and shows the low duty rate may be improved by increasing burst rate through adapting antennal beam width to cover entire hot-spot region in the space and, by compensating effective burst length throughcutting down man-made noises introduced by antennal. Based on the analysis, we are developed a small-opening-cavity antennal, especially designed for short distance MB path. In operation, the antenna is to be buried under ground surface so as to improve directivity and reduces noise introduction. The antennal exhibits power gain of 3 dB with 90 degree beam width and thus enables to illuminate entire hot-spot regions with the elevation angle of 8-90 degree which is the case of transmission less than 100 km. Directivity horizontal to earth surface is suppressed to minimum which enables to cut man-made noises from near-by sources down to more than 3 dB from the level reported with conventional 4 element Yagi. A series of experiments performed on 100km MB paths have conformed that, with the antenna installed at receiving site, the burst rate and duration time have been noticed to increase by 10 and 20 percent respectively from the values obtained by conventional 4-element Yagi antennal under same testing condition.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.9
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• pp.11-17
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• 2004

This paper describes the implementation of monolithic optical transceiver circuitry being used as a part of the fiber optic modules. It has been fabricated in 0.6 ${\mu}{\textrm}{m}$ 2-poly 3-metal silicon CMOS analog technology and operates at 155.52 Mbps(STM-1) data rates. It drives laser diode to transmit intensity modulated optical signal according to 155.52 Mbps electrical data from system. Also, it receives 155.52 Mbps optical data that transmitted from other systems and converts it to electrical data using photo diode and amplifier. To avoid noise and interference between transmitter and receiver on one chip, layout techniques such as special placement, power supply separation, guard ring, and protection wall were used in the design. The die area is 4 ${\times}$ 4 $\textrm{mm}^2$, and it has 32.3 ps rms and 335.9 ps peak to peak jitter on loopback testing. the measured power dissipation of whole chip is 1.15 W(230 mW) with a single 5 V supply.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.2
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• pp.71-77
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• 2009

A novel phase-locked loop(PLL) architecture with multiple charge pumps for fast locking has been proposed. The proposed PLL has three charge pumps. The effective capacitance and resistance of the loop filter can be scaled up/down according to the locking status by controlling the direction and magnitude of each charge pump current. The fast locking PLL that changes its loop bandwidth through controlling charge pumps depending on locking status has been designed. The capacitor usually occupying the larger portion of the chip is also minimized with the proposed scheme. Therefore, the PLL size of $990{\mu}m\;{\times}\;670{\mu}m$ including resistors and capacitors at the bandwidth of 29.9KHz has been achieved. It has been fabricated with 3.3V $0.35{\mu}m$ CMOS process. The locking time is less than $6{\mu}s$ with the measured phase noise of -90.45dBc/Hz @1MHz at 851.2MHz output frequency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.331-340
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• 2006

In this Paper, we propose to extend the TSS-LS(Two-Step Search scheme with Linear search based Second step) scheme which was already proposed by the authors for coherent UWB(Ultra Wide Band) systems, to rapid and reliable acquisition of noncoherent UWB systems in multipath channels. The proposed noncoherent TSS-LS employing simple energy window banks utilizes two different thresholds and search windows to achieve fast acquisition. Furthermore, the linear search is adopted for the second step in the proposed scheme to correctly find the starting point in the range of effective delay spread of the multipath channels, and to obtain reliable BER(Bit Error Rate) performance of the noncoherent UWB systems. Simulation results with multipath channel models by IEEE 802.15.3a show that the proposed two-step search scheme can achieve significant reduction of the required mean acquisition time as compared to general search schemes. ]n addition, the proposed scheme achieves quite good BER performance for large signal-to-noise ratios, which is favorably comparable to the case of ideal perfect timing.