• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.7 no.1
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• pp.53-60
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• 1996

The 8W hybrid MIC SSPA has been developed in the frequency range from 14.0 GHz to 14.5 GHz for uplink of KOREASAT's earth station. The whole system was designed of two parts with driving amplifier and high power amplifier to simplify the fabrication process. we reduced weight and volum of power amplifier through arranging the bias circuits in the same housing. The realized SSPA has a small signal gain of $26\pm1dB$within 500 MHz bandwidith, and the input and output return losses are over 7dB and 12dB respectively. The output power of 39.0 ~ 39.2dBm is achieved at the 1dB gain compression point of 14 GHz, 14.25 GHz, and 14.5 GHz. That reveals higher power than 8W of design target. The proposed SSPA manufacture techni- ques in this paper can be applied to the implementation of power amplifiers for some radars and SCPC.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.9
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• pp.895-902
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• 2014

This paper presents a 2-stage CMOS power amplifier for the 1.75 GHz band using a $0.18-{\mu}m$ CMOS process. Using ADS simulation, a power gain of 28 dB and an efficiency of 45 % at an 1dB compression point of 27 dBm were achieved. The implemented CMOS power amplifier delivered an output power of up to 24.8 dBm with a power-added efficiency of 41.3 % and a power gain of 22.9 dB. For a 16-QAM uplink LTE signal, the PA exhibited a power gain of 22.6 dB and an average output power of 23.1 dBm with a PAE of 35.1 % while meeting an ACLR(Adjacent Channel Leakage Ratio) level of -30 dBc.

• Journal of IKEEE
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• v.15 no.3
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• pp.218-226
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• 2011

In this paper, the leaky electric field intensity of outdoor CATV facilities on CDMA mobile service band defined in technical regulation related with CATV is investigated if appropriate or not. From experimental and theoretical analysis results, Maximum allowable power level of CATV leakage should be -110dBm/1.23MHz. Also, the CATV leakage intensity thresholds, which may not nearly give an impact on the uplink performance of CDMA mobile base station for outdoor background noise of -100~-80dBm/1.23MHz to be measured in outdoor environment, couldn't conform to the current CATV technical regulation. Therefore, the leakage intensity in the current CATV technical regulation is rated as a too much low level in view of an overly worst case.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.156-161
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• 2007

In a TDD system, the length of slots can be unequal, and the number of downlink (DL) and uplink (UL) slots per frame can be different as well. The advantage of using TDD is the capability to accommodate asymmetric high-bit-rate services for the DL and It, which will be one of the prominent features in 4G systems. This paper analyzes the performance of TDD system on mobile channel environments like indoor pedestrian and vehicular channel, and proposes optimum modulation/demodulation method in TDD system. A rectangular QAM (RQAM) used in various communication systems has good BER performance but the much more signal amplitudes also have become one of the barriers to implement receiver. While PSK receiver is implemented easily because it has a constant amplitude, but it's BER performance is worse than RQAM. APSK proposed in this paper integrates merits of RQAM and PSK, and minimizes demerits of then And a simple method is also proposed to demodulate the soft symbol. The results indicate that the proposed APSK has a little worse performance than RQAM but the dynamic range of APSK is about 4 dB, 8 dB better than RQAM at 16-ary, 64-ary modulation/demodulation respectively.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.776-781
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• 2005

In this paper, using received channel information, we analyze performance in MIMO multiuser system in low-to-medium mobile speed by selecting each user's constellations, powers, and transmit antennas. Given a target of symbol error, we determine each user's constellations, powers, selected tranprobability smit antennas such that the required signal-to-noise(SNR) is minimized for MMSE, V-BLAST receiver according to each user's information and channel estimation information. When we do power control with antenna selection technique through uplink channels of MIMO system in low-to-medium mobile speed, we analyze system performance with wireless channel information from Base-Station(BS) to Users. By simulation, it has been shown that the proposed antenna selection scheme for transmitting data offer better performance improvement than all transmit antennas for transmitting data.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.11
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• pp.985-991
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• 2015

This paper proposes appropriate locations for site diversity to provide stable satellite communication service in Korea. For this purpose, we analyzed rainfall rate data measured by KMA for 5 years at 88 sites, and the variations of simultaneous occurrence of rainfall rate in pairs of sites using the correlation coefficient. This paper provided contour maps of the spatial ditstribution of rainfall rate correlation, and proposed information on the optimum sites/regions for the operation of muti-uplink satellite systems, in 4 cities which were principal in field of satellite communication in Korea.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.11
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• pp.1142-1155
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• 2014

The classical PCM/PSK/PM scheme has been commonly used for TC & R applications between satellites and ground stations in the S-band. We analyzed TC & R link performance between ground station and the geostationary satellite which employs PCM/PSK/PM, when the satellite are particularly on the Super Synchronous Transfer Orbit(SSTO). The satellite parameters on SSTO are assumed to be those operating on the geostationary orbit, considering heritage aspect. In the uplink, the results shown indicate that sufficient margins over 3 dB are obtained when the EIRP of ground station is greater than 65 dBW. The down link performance is of great interest. By adjusting the telemetry modulation index and ranging modulation index, we could obtain the required margin of 3.0 dB in the down link, and find out the minimum G/T of ground station. In conclusion, the previously operated ground stations during LEOP at COMS launch, can be operational when GEO injection is made using SSTO(65,000 km and 70,000 km).

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.3
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• pp.351-355
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• 2010

The service which is required wide bandwidth is growing in these days, so building up High Speed communication system is being required. The Task Force team of IEEE 802.3ah set the EPON as a standard; next generation subscriber access network. For offering a high quality service, 10G EPON that is changed from 1Gbps uplink downlink bandwidth to 10Gbps is come up. Although Kramer had studied 10G EPON there was a QoS limitation, when load is low, End-to-End maximum delay is increased. This paper is suggesting time synch ronization method, resource reservation method, band width allocation method. We confirmed that 10EPON was able to offer quality service by the result of the OPNET.

• Journal of Advanced Navigation Technology
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• v.16 no.2
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• pp.219-226
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• 2012

Since OFDM(Orthogonal Frequency Division Multiplexing) technology is applied into LTE(Long Term Evolution)/LTE-Advanced system, it is important to estimate the spectrum sharing and to analyze interference in LTE system based on the characteristics of frequency assignment. Therefore, in this paper, a study on the adjacent channel interference between two operators/systems to provide LTE services. For co-existence of LTE systems, the relative capacity loss and the relative throughput loss in uplink and downlink have been simulated to evaluated ACIR(Adjacent Channel Interference Ratio) values with 5% loss rate. Some parameters such as the location of user, aggressor bandwidth, and the separation offset affect the required ACIR value for spectrum sharing, and these results and interference analysis schemes in this article can provide reliable reference for LTE RF standardization and efficient frequency utilization in future.

• Journal of Advanced Navigation Technology
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• v.12 no.6
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• pp.567-573
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• 2008

According to the ICAO's Global Air Navigation Plan for CNS/ATM - Communications, Navigation, and Surveillance - systems, employing digital technologies, including satellite systems together with various levels of automation, are to be applied in support of a seamless global air traffic management system. For the future navigation, the focus of future implementation efforts can be placed entirely on an expected gradual migration toward GNSS-based navigation, Korea has been considered various options for airspace GNSS augmentation system: GBAS, SBAS and GRAS. This paper discusses current status and future trend of GNSS airspace navigation systems, and presents the results of possible augmentation options and scenarios to analyze system availabilities which could lead to the conclusion of the best program for Korea. The results showed that Korea could have sufficient availabilities from en-route to CAT-I approach with ABAS and GBAS. The study was in cooperated with MITRE, an American research company.