• Journal of Astronomy and Space Sciences
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• v.24 no.4
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• pp.397-408
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• 2007

Diplexer is one of core devices needed to communicate with satellite using single ground antenna by separating uplink and downlink signal. This paper presents the design of the S-band diplexer for LEO TT&C application, especially for KOMPSAT (KOrea Multi-Purpose SATellite). To cope with requirements such as high handling power, low insertion loss, air-cavity resonator with high quality factor was considered as one of design drivers. Design was started with predicting unloaded Q and equivalent circuit from the structure of air-cavity resonator. For the convenience of adjustment, the coupling factor placed between resonators was estimated from COTSEM (Electro-Magnetic) simulator, EESOF $ADS^{TM}$, and expressed with 2-order polynomial regression. To improve the isolation between transmitting part (Tx) and receiving part (Rx), the inductive and capacitive attenuation poles were inserted between $4^{th}\;and\;6^{th}$ resonator respectively. The fabricated diplexer consists of two bandpass filters and each filter has eight resonants. From the measurement, it was shown that major requirements such as 0.5dB of insertion loss, 20dB of return loss and 100dB of isolation were fully satisfied within passband.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.12
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• pp.1297-1307
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• 2009

The purpose of this paper is to propose a detection algorithm and a tracking algorithm based on silent time using MB-OFDM UWB(Multi-Band Orthogonal Frequency Division Multiplexing Ultra Wide Band) receiver in order to satisfy DAA(Detect And Avoid) regulation of Korea to permit UWB in 3.1~4.8 GHz. In DAA regulation of Korea, if UWB device receives a signal more than -80 dBm/MHz from the victim system during UWB operation, the UWB system should avoid the collision within 2 sec. In this paper, we proposed the detection algorithm to detect the victim signal received by －80 dBm/MHz for the avoidance process that changes the operating UWB frequency to other UWB frequency and the subcarrier tracking algorithm to follow up the subcarrier positions of the victim signal for the tonenulling avoidance process that decreases the TX power of subcarriers occupied by the victim signal by -70 dBm/MHz. The performance of the detection algorithm and the tracking algorithm suggested in this paper is verified in simulation results considering various conditions.

• Journal of Advanced Navigation Technology
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• v.12 no.2
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• pp.146-153
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• 2008

Due to the extremely short pulse in the Ultra-Wideband (UWB) technology, the accurate synchronization acquisition method is very important for both high data-rate WPAN and low data-rate WPAN. In this paper, we propose the synchronization acquisition algorithm based on two-step signal search method to acquire the synchronization in the UWB multi-path channel. At the first step, the search window is divided by two and the window that has higher power is chosen as a next search window. This operation is repeated until the measure power of the search window is smaller than the threshold value. At the second step, we employ Linear Search algorithm to the search window obtained at the first step for fine search. The proposed algorithm is proved that the synchronization acquisition is faster than the parallel search algorithm and it shows good performance in environment of the SNR extreme changes by the simulation.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.11
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• pp.141-148
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• 2012

A design of a 32-bit fourth-stage decimation filter decimation filter used in sigma-delta analog-to-digital (A/D) converter is proposed in this work. A four-stage decimation filter with down-sampling factor of 512 and 32-bit output is developed. A multi-stage cascaded integrator-comb (CIC) filter, which reduces the sampling rate by 64, is used in the first stage. Three half-band FIR filters are used after the CIC filter, each of which reduces the sampling rate by two. The pipeline structure is applied in the CIC filter to reduce the power consumption of the CIC. The Canonic Signed Digit (CSD) arithmetic is used to optimize the multiplier structure of the FIR filter. This filter is implemented based on a semi-custom design flow and a 130nm CMOS standard cell library. This decimation filter operates at 98.304 MHz and provides 32-bit output data at an audio frequency of 192 kHz with power consumption of $697{\mu}W$. In comparison to the previous work, this design shows a higher performance in resolution, operation frequency and decimation factor with lower power consumption and small logic utilization.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.20
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• pp.8917-8921
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• 2014

Objective: To observe and compare the effects of multi-patch biopsy under conventional white light imaging endoscopy (C-WLI) and precise targeted biopsy under magnifying narrow-band imaging endoscopy (M-NBI) on the endoscopic submucosal dissection (ESD) of early gastric cancers and intraepithelial neoplasias. Methods: According to the way of selecting biopsy specimens, patients were divided into C-WLI and M-NBI groups, 20 cases. The ESD operations of the 2 groups were compared quantitively. Results: The mean frequency of biopsy in M-NBI group was ($1.00{\pm}0.00$), obviously lower than in the C-WLI group ($4.78{\pm}1.02$) (P<0.01).The average total number of selected biopsy specimens was also fewer ($1.45{\pm}0.12$ and $7.82{\pm}2.22$, respectively, P<0.01). There was no significant difference in the time of determining excision extension, marking time and the time of specimen excision of 2 groups during the ESD (P>0.05), whereas submucosal injection time, mucosal dissection time, stopping bleeding time, wound processing time in the M-NBI group were significantly shorter than in the C-WLI group (P<0.01). Conclusion: Precise targeted biopsy under M-NBI can obviously shorten the time of ESD operation, with small quantity of tissues but high pathological positive rate.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.3
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• pp.451-456
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• 2020

In this paper, we studied the method of designing a embedded antenna for mounting on the JTDLS complete aircraft. The proposed antenna satisfies the MIDS-LVT operation frequency band and is designed as a broadband in consideration of expandability. As a result of the design, it was confirmed that the proposed antenna has similar electrical performance to the existing blade antenna and has broadband characteristics. As a result of EM analysis, the antenna was mounted on the top and bottom parts of the aircraft to check the mount of the aircraft, and it was confirmed that both the top and bottom parts had good radiation characteristics. The technology acquired through this study is judged to be applicable to the JTDLS completed aircraft.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1312-1315
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• 2002

This research describes the design of a fully integrated fractional-N frequency synthesizer intended for the local oscillator in IMT-2000 system using 0.18-$\mu\textrm{m}$ CMOS technology and 1.8-V single power supply. The designed fractional-N synthesizer contains following components. Modified charge pump uses active cascode transistors to achieve the high output impedance. A multi-modulus prescaler has modified ECL-like D flip-flop with additional diode-connected transistors for short transient time and high frequency operation. And phase-frequency detector, integrated passive loop filter, LC-tuned VCO having a tuning range from 1.584 to 2.4 ㎓ at 1.8-V power supply, and higher-order sigma-delta modulator are contained. Finally, designed frequency synthesizer provides 5 ㎒ channel spacing with -122.6 dBc/Hz at 1 ㎒ in the WCDMA band and total output power is 28 mW.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.240-243
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• 2001

As electronic industry and radio communication technologies progress, mankind enjoys its abundant life. On the other hand, it becomes possible that the electrical and electronic equipments are on light weight, small size, high speed, broad bandwidth, and operation by small energy. At the same time, many social problems like EMI/EMS by electromagnetic waves occur. Therefore, tile organizations such as CISPR, FCC, ANCI, etc., have provided the standards of electromagnetic wave environments for the countermeasure of the EMC. In this paper, we designed and studied a new EMI filter for multi-tap in the frequency band from 150 kHz to 30 MHz.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.115-125
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• 2005

This paper discusses how to effectively design a next-generation wireless communication system that can possibly provide very high data-rate transmissions and versatile quality services. In order to accommodate the sophisticated user requirements and diversified user environments of the next-generation systems, it should be designed to take an efficient and flexible structure for multiple access and resource allocation. In addition, the design should be optimized for cost-effective usage of resources and for efficient operation in a multi-cell environment. As orthogonal frequency division multiple access (OFDMA) has turned out in recent researches to be one of the most promising multiple access techniques that can possibly meet all those requirements through efficient radio spectrum utilization, we take OFDMA as the basic framework in the next-generation wireless communications system design. So, in this paper, we focus on introducing an OFDMA-based downlink system design that employs the techniques of hybrid multiple access (HMA) and frequency group (FG) in conjunction with intra-frequency group averaging (IFGA). The HMA technique combines various multiple access schemes on the basis of OFDMA system, adopting the multiple access scheme that best fits to the given user condition in terms of mobility, service, and environment. The FG concept and IFGA technique help to reduce the feedback overhead of OFDMA system and the other-cell interference (OCI) problem by grouping the sub-carriers based on coherence band-widths and by harmonizing the channel condition and OCI of the grouped sub-carriers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.11A
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• pp.1086-1095
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• 2007

This paper proposes a novel non-coherent TOA estimation scheme using multiple correlation process on the existence of multiple simultaneously operating piconets (SOPs). Impulse radio-ultra wideband (IR-UWB) based on direct sequence spread spectrum (DSSS) using Gold sequence is employed in order to discriminate each piconet. In order to enhance the characteristic of correlation, this paper presents the method of multiple mask operation (MMO). The time of arrival (TOA) of direct line of sight (DLOS) path is estimated via two step coarse/fine timing detection. To verify the performance of proposed scheme, two distinct channel models approved by IEEE 802.15.4a Task Group (TG) are considered. According to the simulation results, it could conclude that the proposed scheme have performed better performance than the conventional method well even in densed indoor multi-path environment as well as in the existence of multiple SOPs.