김인석 Ihn S. Kim , 조치성 Chi Sung Jo , 한용인 Yong In Han

DOI: JANT Vol.7(No.1) 1-5, 2003

---

In this paper, the output power level and phase noise property of nine conventional push-push FET DROs (Dielectric Resonator Oscillator) have been experimentally investigated by adding one more identical DR at the drain port. The nine oscillators designed to generate 20 GHz from 10GHz fundamental frequency, have been tested for each of three different power combiners at the output port. It has been observed that the output power level of the push-push FET DROs can be improved by placing the DR while maintaining their phase noise characteristics were approximately the same as before adding the DR.

양연실 Yeon Sil Yang , 박형래 Hyung Rae Park

DOI: JANT Vol.7(No.1) 6-14, 2003

---

In this paper, a non-coherent code tracking loop is designed for 3GPP HSDPA MODEM and its performance is analyzed in terms of steady-state jitter variance and transient response characteristics. Analytical closed-form formula for steady-state jitter variance is first derived for AWGN environments as a function of pulse-shaping filter, timing offset, signal-to-interference ratio, and loop bandwidth. Also obtained is the transient response characteristic of a tracking loop. Finally, the performance of the designed tracking loop is confirmed by computer simulations.

이성렬 Seong Real Lee , 이윤현 Yun Hyun Lee

DOI: JANT Vol.7(No.1) 14-22, 2003

---

We investigated the optimum pump light power compensating distorted WDM signal due to both chromatic dispersion and self phase modulation (SPM). The considered system is 3×40 Gbps intensity modulation direct detection (IM/DD) WDM transmission system with path-averaged intensity approximation (PAIA) mid-span spectral inversion (MSSI) as compensation method. This system have highly nonlinear dispersion shifted fiber (HNL-DSF) as nonlinear medium of optical phase conjugator (OPC) in the mid-way of total transmission line. We confirmed that HNL-DSF is an useful nonlinear medium in OPC for wideband WDM transmission, and the excellent compensation is obtained when the pump light power of HNL-DSF OPC was selected to equalize the conjugated light power into the second half fiber section with the input WDM signal light power depending on total transmission length. By this approach, it is verified the possibility to realize a long-haul high capacities WDM system by using PAIA MSSI compensation method, which have HNL-DSF OPC with optimal pump light power depending on transmission length.

양의장 Eui Jang Yang , 김규환 Kyu Hwan Kim , 함형일 Hyung Il Ham , 강영흥 Yung Heung Kang

DOI: JANT Vol.7(No.1) 22-29, 2003

---

In this paper, we analyze the interference effects between NGSO(Non-Geostationary Orbit) and HAPS(High Altitude Platform System) by dividing into two cases. The one is interference effects of HAPS into NGSO, the another is the interference effectes of NGSO into HAPS. At the result, we can know the interference effect into NGSO mobile station is the highest when position of NGSO is 95%. In this case, we can also know the interference effects from both HAPS and NGSO exceed interference criteria when the number of users are more than 20. And, in the case of the interference effect into HAPS mobile station, we can know it is the highest when elevation angle of NGSO is 87°, and the interference effects from both NGSO and HAPS exceed interference criteria when the number of users is more then 10. Moreover, the interference effect is the minimum, when elevation angle of NGSO is 64°, at this time, in case that the number of users of NGSO equal to the number of user of HAPS, the interference effects exceed interference criteria when the number of users is 190.

이영춘 Young Choon Lee , 박기식 Ki Sik Park , 조성준 Sung Joon Cho

DOI: JANT Vol.7(No.1) 30-37, 2003

---

In this paper, we have analyzed the BER (Bit Error Rate) performance of MC-CDMA systems under indoor wireless environment with class A impulsive noise suggested by Middleton. For the performance evaluation, we considered from strong to weak impulsive noise characteristics. And we have evaluated the degree of performance improvement by using turbo code as a compensation technique to impulsive noise. From the result of analysis, it is found powerful performance improvement scheme must be adopted in the system under impulsive noise environment, and when turbo code scheme is adopted, system BER performance is improved by the 10^2. As the impulsive noise characteristics approaches AWGN characteristics, the degree of performance improvement by adopting turbo code become large.

송은석 Eun Seok Song , 신용준 Yong June Shin , 최덕선 Tok Son Choe , 육종관 Jong Gwan Yook , 박진배 Jin Bae Park , Edward J. Powers

DOI: JANT Vol.7(No.1) 38-50, 2003

---

In this paper, a new high resolution reflectometry scheme, time-frequency domain reflectometry (TFDR), is proposed to detect and locate fault in wiring. Traditional reflectometry methods have been achieved in either the time domain or frequency domain only. However, time-frequency domain reflectometry utilizes time and frequency information of a transient signal to detect and locate the fault. The time-frequency domain reflectometry approach described in this paper is characterized by time-frequency reference signal design and post-processing of the reference and reflected signals to detect and locate the fault. Design of the reference signal in time-frequency domain reflectometry is based on the determination of the frequency bandwidth of the physical properties of cable under test. The detection and estimation of the fault on the time-frequency domain reflectometry relies on the time-frequency domain reflectometry is compared with commercial time domain reflectometry (TDR) instrument. In these experiments provided in this paper, TFDR locates the fault with smaller error than TDR. Knowledge of time and frequency localized information for the reference and reflected signal gained via time-frequency analysis, allows one to detect the fault and estimate the location accurately.

노재성 Jae Sung Roh , 조성준 Sung Joon Cho , 김춘길 Choon Gil Kim

DOI: JANT Vol.7(No.1) 51-58, 2003

---

Generally, multi-path is viewed as an undesirable feature of wireless communications. Therefore, diversity reception and adaptive array schemes are proposed to mitigate its effects. Recently, to increase the spectrum efficiency and the link reliability, multiple-input multiple-output (MIMO) scheme is devised to exploit multi-path in a scattering wireless channel. In this paper, we have evaluated the channel capacity of MIMO Multi-Carrier CDMA system in path correlation fading channel. And, the channel capacity of MIMO system is compared with single-input single-output (SISO) system. Form the results, the MIMO multi-carrier CDMA system with path correlation yields better performance with respect to channel capacity than a SISO system.

마동철 Dong Chul Ma , 기영민 Young Min Ki , 김동구 Dong Ku Kim

DOI: JANT Vol.7(No.1) 59-71, 2003

---

The channel scheduler is suggested the radio resource management method in order to provide service with guaranteeing fairness and throughput to the users who use limited wireless channel. Proportional fairness scheduling algorithm is the channel scheduler used in the AMC(Adaptive Modulation and Coding)/TDM system, and this algorithm increases the throughput considering the user`s time fairness. In this paper is suggested the channel scheduler combining CDM scheme available in AMC/TDM/CDM system. Unlike the system which only uses TDM which provide the only one user at the same slot, this scheduler can service a lot of users since this uses the CDM scheme with multi-cord channel. At every moment, allocation of transmission power to multi-channel users is problematic because of CDM scheme. In this paper, we propose a water-filling scheduling algorithm to solve the problem. Water-filling fairness(WF2) scheduling algorithm watches the average channel environment. So, this modified method guarantees fairness for each user in terms of power and service time.

김영수 Young Soo Kim

DOI: JANT Vol.7(No.1) 71-83, 2003

---

A new beamforming technique is presented for effectively nulling out multiple incoherent interferences incident on an equispaced linear array. The basic idea of the proposed beamformer is based on the matrix property mapping which is basically concerned with the task of recovering a signal from a noise and interference contaminated measurement made on that signal. Computer simulations are shown to illustrate the superior performance achieved with the proposed beamformer relative to that of the conventional LCMV beamformer.

강자영 Jay Kang

DOI: JANT Vol.7(No.1) 82-90, 2003

---

Recently, a new concept of telecommunication system, utilizing stratospheric platforms such as airships or airplanes, has been proposed. This system aims to provide broadband multimedia services, i.e. high-rate multimedia service, high-rate internet service, and leased line service. In this study, operation concept of the system is defined and by allocation required functions on the system and its subsystems, conceptual design of the ground control system for the stratospheric platforms is established and proposed.

학회자료

DOI: JANT Vol.7(No.1) 91-91, 2003

---