• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.7
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• pp.78-86
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• 2010

This paper discusses the programming model of SODA-II that is a baseband processor for software defined radio (SDR) systems. Signal processing On-Demand Architecture Ⅱ (SODA-II) is an on-chip multiprocessor architecture consisting of four processor cores and each core has both an wide SIMD datapath and a scalar datapath. This architecture is appropriate for baseband processing that is a mixture of vector computations and scalar computations. The programming model of the SODA-II is based on C library routines. Because the library routines hide the details of complex SIMD datapath control procedures, end users can easily program the SODA-II without deep understanding on its architecture. In this paper, we discuss the details of library routines and how these routines are exploited in the implementation of baseband signal processing algorithms. As application examples, we show the implementation result of W-CDMA multipath searcher and OFDM demodulator on the SODA-II.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.12
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• pp.1296-1302
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• 2012

In this research, optimization of a dual-band dipole array was performed using genetic algorithm. A non-uniform, aperture-shared linear array was configured with dipoles which resonate at 4 GHz and 9.5 GHz. The excited current distributions on dipoles were computed considering mutual coupling between dipole elements. The current distributions were also computed using method of moment (MoM). The optimization using genetic algorithm was performed to obtain the low sidelobe levels in two operating frequency band. The PSLs of the optimized array for 4 GHz and 9.5 GHz are -15.7 dB and -17 dB, respectively. Comparison between computed and simulated results are also discussed.

• The KIPS Transactions:PartC
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• v.12C no.5 s.101
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• pp.709-716
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• 2005

QoS is an important requirement of the FTTH (Fiber To The Home) subscriber in access network using E-PON (Ethernet Passive Optical Network). In this research, we describe the structure of the access network and propose a bandwidth guarantee scheme for subscriber and service according to the requirements of the subscriber, service and system. This scheme uses two kinds of the classification table, which are called 'service classification table' and 'subscriber classification table.' Using the classification table, we can identify the flow of the subscriber and service. Also, we compute the number of hash table entry to minimize the loss ratio of flows using the M/G/k/k queueing model. Finally, we apply the DRR scheduling through virtual queueing per subscriber instead of the aggregated class.

• 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.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.3
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• pp.1-9
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• 2003

In this paper, we designed a highly suppressed sidelobe ladder type RF SAW bandpass filter based on 1-port resonator, for 800 MHz mobile communication system. In order to get the highest device characteristics, we optimized some important parameters such as the electrode thickness, electrode lambda weghting of the reflectors, and static capacitance ratio. Furthermore, we fabricated the Tx and Rx. filter using optimized parameters. Implemented filters can be used in 800 MHz mobile communication system and external impedance matching circuits are not needed. RF filter was fabricated on 36$^{\circ}$LiTaO$_3$ substrates with Al-Cu (W 3 %)and mounted 3.8mm$\times$3.8mm$\times$1.5mm SMD package. Developed filters has 2.3 dB insertion loss in the 25 MHz pass-band, 33MHz with 3-dB insertion loss, stop-band rejection of 30 dB, passband ripple is less than 0.5 The power durability of the filters measured about 3.5W and the maximum temperature variation within -2$0^{\circ}C$~8$0^{\circ}C$ was 0.09 dB/$^{\circ}C$ of 3-dB insertion loss.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.5
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• pp.430-433
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• 2017

This paper presents a S/C/X-band LNA MMIC with resistive feedback structure in 0.25 um GaN HEMT process. The GaN devices have advantages as a high output power device having high breakdown voltage, energy band gap and stability at high temperature. Since the receiver using the GaN device with high linearity can be implemented without a limiter, the noise figure of the receiver can be improved and the size of receiver module can be reduced. The proposed GaN LNA MMIC based on 0.25 um GaN HEMT device is achieved the gain of > 15 dB, the noise figure of < 3 dB, the input return loss of > 13 dB, and the output return loss of > 8 dB in the S/C/X-band. The current consumption of GaN LNA MMIC is 70 mA with the drain voltage 20 V and the gate voltage -3 V.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.5
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• pp.201-206
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• 2015

A new electronically stopband tunable filter is proposed with three-input single-output using Operational Transconductance Amplifier (OTA) in this paper. The proposed filter provides band pass, low pass and high pass multifunctional responses. Centre frequency ($f_c$) and quality factor (Q) of the realized filters could independently tuned without disturbing each other. Various network sensitivity and non-ideal characteristic analysis are done to check the sensitivity and parasitic effect of different circuit parameters. The CMOS realization of filter is done with 1.8V-0.18um process parameters and HSPICE simulation results are presented to assert the presented theory.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.11
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• pp.29-34
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• 1999

In this paper, a current comparative frequency automatic tuning circuit for the CMOS gm-C bandpass filters are designed with the new architecture. And also, when the designed circuit is compared to the typical tuning circuit, the designed circuit has very simple architecture that is composed of the current comparator and charge pump and operating in 3V power supply. The proposed tuning circuit automatically compensates the difference between the operating current of the transconductor and the specified reference Current. Using CMOS 0.8um parameter a biquad gm-C bandpass filter with center frequency($f_\circ$=60MHz) is designed, and according to the transistor size the variation of the center frequency is simulated. As the HSPICE simulation results, the tuning operation of the proposed current comparative frequency automatic tuning circuit is verified.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.9
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• pp.76-84
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• 1999

EZW proposed by Shapiro is based on a zerotree constructed in a way that a parent coefficient in a subband is related to four child coefficients in the next finer subband of similar orientation. This fixed treeing based on 1-to-4 parent-child is suitable to exploti hierachical correlations among subbands but not to exploit spatial correlations within a subband. A new treeing by Joo, et al. is suggested to simulatneously exploit those two correlatins by extending parent-child relationship in a flexible way. The flexible treeing leads to increasing the number of symbols and lowering entorpy comparing to the fixed treeing, and therefore a better compression can be resulted. In this paper, we suggest two techniques to suppress the increasing of symbols. First, a probing bit is generated to avoid redundant scan for insignivicant coefficients. Second, since all subbands do not always require the same kind of symbol-set, produced symbols are re-symbolized into binary codes according to a pre-defined procedure. Owing to those techniques, all symbols are generated as binary codes. The binary symbols can be entropy-coded by an adaptive arithmetic coding. Moerover, the binary symbol stream can give comparatively good performances without help of additional entropy coding. Our proposed coding scheme is suggested in two modes: binary coding mode and arithmetic coding mode. We evaluate the effectivenessof our modifications by comparing with the original EZW.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1925-1926
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• 2008

본 논문에서는 UHF TV방송 전 대역 Ch.14(473MHz)$\sim$Ch.69(803MHz)까지의 모든 채널에서 동작하는 유도결합구조의 RF동조회로를 설계하였다. 기존 자기결합구조의 RF동조회로는 PCB 양면을 사용하여야 하고 수작업으로 Air Coil 간격을 조절해야만 한다. 부품의 집적화와 양산 효율성 측면에서 자기결합구조의 단점을 해결할 수 있도록 하기 위해 본 논문에서 제안한 유도결합구조는 수동부품인 칩인덕터와 칩커패시터 및 가변용량 다이오드만을 사용하여 RF동조회로를 설계하였다. 칩인덕터는 Air Coil에 비해 낮은 소자 Q값을 가진다. 상대적으로 낮은 Q값을 갖는 칩인덕터를 사용하기 때문에 이를 보완하기 위해 Peaking용 칩인덕터를 설계 디자인에 적용하였다. 가변형 대역통과필터로 동작하기 위해 자기결합구조와 동일하게 가변용량 다이오드를 이용하였다. UHF TV방송 전 대역(470$\sim$806MHz)에서 -2.88 $\sim$ -3.97dB의 삽입손실 특성 및 -8dB 이상의 반사손실 특성과 330MHz의 중심주파수 변화 범위를 갖는다. 현재 상용중인 지상파 튜너에 적용되고 있는 자기결합구조의 RF동조회로를 대치하여 적용될 수 있을 것이다.