• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.1
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• pp.40-46
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• 2002

In this paper we design and fabricate the Skeleton slot antenna which operates dually in GSM 900 and 1800 bands. Its simulation results are also compared with the measured ones. The original Skeleton slot antennas had the problems of unsatisfactory VSWR characteristics and considerably changing horizontal radiation patterns at high frequencies, but the proposed design improves these problems using multi-path feeding network and folding structure. The size of the radiator is 154 $\times$ 106(mm), and its height is 33(mm), and the reflector of 190$\times$190(mm) is used. The material of the radiator and reflector is 1mm-thick aluminum. Using NTC process reduces the mass production cost significantly. The measured return losses are 13.7 % at 900 MHz band and 16.4 % at 1800 MHz band, respectively. The horizontal radiation beam width is stable within $\pm$ 1$^{\circ}$ at both frequency bands.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.12
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• pp.45-51
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• 2011

This paper presents a wideband low-noise amplifier (LNA) covering 800MHz~5.8GHz for various wireless communication standards by utilizing in a 0.13um CMOS technology. Particularly, the LNA consists of two stages to improve the low-noise characteristics, that is, a cascode input stage and an output buffer with noise cancellation technique. Also, a feedback resistor is exploited to help achieve wideband impedance matching and wide bandwidth. Measure results demonstrate the bandwidth of 811MHz~5.8GHz, the maximum gain of 11.7dB within the bandwidth, the noise figure of 2.58~5.11dB. The chip occupies the area of $0.7{\times}0.9mm^2$, including pads. DC measurements reveal the power consumption of 12mW from a single 1.2V supply.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.335-340
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• 2005

In this paper, the triple-band planar monopole antennas are designed for cellular communication, WiBro and WLAN(IEEE802.llb/g) communication and WLAN(IEEE802.lla) communication of 5GHz band. Various types of antennas are designed and examined experimentally as bended in the low and middle band radiation elements to decrease antennas size and increased radiation elements width to improve bandwidth. The proposed antennas are improved by 11% in antenna size with bended low-band radiation elements down and are extended by 30%$\sim$40% in bandwidth by increasing the width of the radiation element at 800MHz band.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.8
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• pp.1485-1492
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• 1994

In this paper, we design and implement the Combline Bandpass Filters for the satellite transponder by using the least-squares curve-fitting method. The Combline Bandpass Filters are located front of the mixer and behind of it, which is the component of down converter. Comparing with the filters which have $\lambda$/4 resonance length. Combline Filter has wide range of stop-band by using $\lambda$/8. So, it is useful to the satellite transponder owing to its low mass and small size. The filters described are realized as coupled rectangular coaxial transmission lines. The choice of this type is due to the ease of machining and wide variations in coupling coefficients rather than the use of the round rod resonators. We determine 800 MHz bandwidths for the combline bandpass filters. By using Chebyshev filter function, we design and implement 4-pole combline filters.

• Journal of Digital Convergence
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• v.12 no.8
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• pp.1-18
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• 2014

Recently, many of the mobile network operators or telcos are introducing the LTE service in order to effectively cope with an explosive increasing mobile traffics due to an expansion of the use of smart phones. The 1.8GHz, 2.6GHz, and 800MHz band classes are most widely used for LTE. In particular, the 1.8GHz band class is the most useful one in terms of the reusability of the existing (2G) network, global harmonization, bandwidth, eco-system of equipments and devices, and so on. In recent years, major countries in the world have allocated the 1.8GHz band spectrum in a wide bandwidth unit suitable for the upcoming LTE-Advanced service. This paper surveyed the 1.8GHz band spectrum allocation policies of the 12 OECD countries, including Republic of Korea. From the survey, we have found that they rebuilt or refarmed the existing holders' bands, recovered the public (i.e., military)-use bands, and allocated the bands in a wide bandwidth and in an equal or similar size.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.5
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• pp.55-59
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• 2014

Multi-band and multi-mode transmitters are needed for SDR and CR. Recently many types of polar transmitters have been studied in order to implement a multi-band and multi-mode transmitter. Polar transmitters have many advantages, such as a simple structure, high efficiency and etc. In this paper we consider the number of D/A bit and the effects of a delay mismatch as design parameters for implementing polar transmitters. From the simulation we know that a 10 bit D/A is sufficient and a delay mismatch must be maintained small than 1/64 chip for satisfying the spectrum mask characteristics. We implement a polar transmitter based on the design parameters and the measured output signal meet the spectrum mask of 800MHz CDMA.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.6
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• pp.57-63
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• 2019

S-parameters were used to analyze the effect of the circuit according to the height of the EMI shield layers. Among the S-parameters, S11, S21, S22, and S31 were used as factors for determining the effect on the circuit function. Simulations were performed using shields made of Graphite and Ferrite, and the frequencies were run from 100 MHz to 1 GHz. As the height of the shield was increased, the value of S21 was getting closer to 0 dB. In addition, the SE value was confirmed to improve the shielding performance according to the thickness of the insulating layer only in a specific frequency band. Based on 800um with thickest silicon dioxide thickness, the FG structure averaged -1 dB in narrow frequency bands between 100 MHz and 300 MHz, showing better efficiency than GF with an average of -2 dB. Although GF structures do not show high efficiency, they exhibit average performance of -3 dB in frequency bands between 100 MHz and 1 GHz rather than FG structures that sway over a wide range. In other words, FG and GF structures have trade-off structures. Therefore, it should be noted that the appropriate structure is selected for use.

• Journal of Broadcast Engineering
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• v.5 no.2
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• pp.273-280
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• 2000

Channel characteristics between the outdoor transmitter far away from the building and receivers inside the building are explored theoretically using ray tracing technique. In this paper, 29 receivers are located on the single floor of the building to observe the variation of channel properties depending on receiver location. For each receiver, amplitudes and phases of ail the possible rays form the transmitter to the receiver are traced to obtain impulse response. Statistical results for rms delay spread and power delay profiles for representative receiver location are given.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.5
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• pp.87-92
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• 2011

In this paper, we got the 800 ~ 900 MHz path loss model for Russia PNG area using the free space model and the Okumura-Hata Model. In order to add new regional properties to the existing path loss model, the mean square error technique is used to obtain the correction factor. The correction factors for the free space and the Hata model are 28, 13 dB respectively. By applying this correction factors, the new Russain PNG path loss model is proposed.

• Electronics and Telecommunications Trends
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• v.28 no.3
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• pp.137-150
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• 2013

본 논문은 경매설계 벤치마크 대상 국가로 거론되고 있는 프랑스를 대상으로 모바일 시장동향, 4G 주파수 경매결과, 정책과정, 그리고 세부 정책내용을 분석하여 조만간 시행될 예정인 국내의 1.8GHz 및 2.6GHz 대역 경매설계에 관한 정책적 시사점을 도출하였다. 본 논문의 분석에 따르면 주파수의 이용 효율성, 공정경쟁 양 측면에서 극단에 가까운 패키징 옵션 대신에 양 측면을 보다 균형되게 접근하여 메커니즘을 통해 자동적으로 결정되도록 하는 패키징 옵션 방안 마련이 필요하다고 사료된다. 이와 함께 미래 10년간의 경쟁 상태에 큰 영향을 줄 수 있는 제 4의 이동통신사의 진입 문제, 주파수 할당의 동시 할당 또는 순차적 할당 등에 대하여도 심도있는 정책적 고민이 병행되어야 한다고 사료된다.