• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.1
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• pp.24-28
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• 2010

This paper is presented on the antenna design for notepc platform. We present the antenna with combination of electric-magnetic radiator for dual-band Wireless Local Area Network (WLAN) service and a High Speed Downlink Packet Access (HSDPA) service. Due to the limited antenna space in notepc platform, the antennas for various wireless communication service should be located at a very small area. In this paper, the magnetic-type radiator works for high frequency band (1.7 - 2.1 GHz) application and the electric-type radiator works for low frequency band (820 - 960 MHz) application. This combination produces wide-band characteristics in the high frequency band. Simulation and experimental results of input impedance and gain characteristics of the proposed antenna are presented. There are good agreements between the simulated and measured S11 and gain values.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.628-638
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• 2005

The analysis of maximum diversity order and coding gain for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems over time-and frequency-selective (or doubly-selective) channels is addressed in this paper. A novel channel time-space correlation function is developed given the spatially correlated doubly-selective Rayleigh fading channel model. Based on this channel-model assumption, the upper-bound of pairwise error probability (PEP) for MIMO-OFDM systems is derived under the maximum likelihood (ML) detection. For a certain space-frequency code, we quantify the maximum diversity order and deduce the expression of coding gain. In this wort the impact of channel time selectivity is especially studied and a new definition of time diversity is illustrated correspondingly

• Journal of the Korean Institute of Telematics and Electronics
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• v.18 no.6
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• pp.38-43
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• 1981

In this paper an actively compensatedfinite gain amplifie. (FGA) with positive gain using 4 operational amplifiers and resistors is propo sod, and an application is considered in an active RC filter. By cancelling the effect of the GB's up to the third-order term of s on the transfer function, the proposed FGA has the extended frequency range over that of the FGA using 3 operational amplifiers. When this FGA is applied to an active RC filter with Pole frequncy of 100kHz, the magnitude error of the frequency characteristics of the filter is less than 2%.

• 한국가시화정보학회:학술대회논문집
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• 2001.12a
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• pp.14-22
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• 2001

The frequency responses on the sub-pixel evaluation technique were investigated using the Monte-calro Simulation technique. The frequency response by the FFT based cross-correlation gives very good results, however, the gain loss does exist for the small displacement, (less than 0.5 pixel). While, the no gain loss is observed in the Direct Cross-correlation, however, the sub-pixel accuracy was limited to be about 0.1 pixel, i.e., it could not detect the small displacement. To detect the higher accurate sub-pixel displacement, the gradient based technique is the best. For the small interrogation area (e.g., 4x4), only the gradient technique can detect the small displacement correctly.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.41-44
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• 2003

Generally, the frequency of set makes ICI and degrades OPDM system performance. Thus, we propose a pulse shaped OFDM to give robustness against the frequency offset. The proposed OFDM system uses pulse shaping with smooth shape, instead of rectangular pulse shape, to reduce the power of ICI. The proposed scheme always gives performance gain in comparing with the convention one, when the frequency offset exists. In addition, the smoother pulse shape is employed in the proposed system, the more performance gain is obtained.

• ETRI Journal
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• v.26 no.5
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• pp.443-451
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• 2004

Since the publication of Alamouti's famous space-time block code, various quasi-orthogonal space-time block codes (QSTBC) for multi-input multi-output (MIMO) fading channels for more than two transmit antennas have been proposed. It has been shown that these codes cannot achieve full diversity at full rate. In this paper, we present a simple feedback scheme for rich scattering (flat Rayleigh fading) MIMO channels that improves the coding gain and diversity of a QSTBC for 2$^n$ (n=3, 4, ${\cdots}$) transmit antennas. The relevant channel state information is sent back from the receiver to the transmitter quantized to one or two bits per code block. In this way, signal transmission with an improved coding gain and diversity near to the maximum diversity order is achieved. Such high diversity can be exploited with either a maximum-likelihood receiver or low-complexity zero-forcing receiver.

• Journal of IKEEE
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• v.16 no.2
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• pp.116-120
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• 2012

We reported on a high performance InGaAs/InAlAs metamorphic HEMT with 50 nm gate length on a GaAs substrate. The fabricated $50nm{\times}60{\mu}m$ MHEMT showed good DC and RF characteristics. Typical drain current density of 740 mA/mm and extrinsic transconductance(gm) of 1.02 S/mm were obtained with our devices. The current gain cut-off frequency(fT) and maximum oscillation frequency(fmax) obtained for the fabricated MHEMT device were 430 GHz and 406 GHz, respectively.

• Journal of information and communication convergence engineering
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• v.3 no.1
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• pp.28-32
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• 2005

In this paper, we propose a novel test method to effectively detect hard and soft faults in CMOS 2-stage op-amps. The proposed method uses a very high frequency sinusoidal signal that exceeds unit gain bandwidth to maximize the fault effects. Since the proposed test method doesn't require any complex algorithms to generate the test pattern and uses only a single test pattern to detect all target faults, therefore test costs can be much reduced. The area overhead is also very small because the CUT is converted to a unit gain amplifier. Using HSPICE simulation, the results indicated a high degree of fault coverage for hard and soft faults in CMOS 2-stage op-amps. To verify this proposed method, we fabricated a CMOS op-amp that contained various short and open faults through the Hyundai 0.65-um 2-poly 2-metal CMOS process. Experimental results for the fabricated chip have shown that the proposed test method can effectively detect hard and soft faults in CMOS op-amps.

• ETRI Journal
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• v.45 no.4
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• pp.690-703
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• 2023

Multistage amplifiers have become appropriate choices for high-speed electronics and data conversion. Because of the large number of high-impedance nodes, frequency compensation has become the biggest challenge in the design of multistage amplifiers. The new compensation technique in this study uses two differential stages to organize feedforward and feedback paths. Five Miller loops and a 500-pF load capacitor are driven by just two tiny compensating capacitors, each with a capacitance of less than 10 pF. The symbolic transfer function is calculated to estimate the circuit dynamics and HSPICE and TSMC 0.18 ㎛. CMOS technology is used to simulate the proposed five-stage amplifier. A straightforward iterative approach is also used to optimize the circuit parameters given a known cost function. According to simulation and mathematical results, the proposed structure has a DC gain of 190 dB, a gain bandwidth product of 15 MHz, a phase margin of 89°, and a power dissipation of 590 ㎼.

• Journal of IKEEE
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• v.27 no.4
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• pp.391-398
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• 2023

In this paper, we propose an alternative analysis to regulate DC motors using a PID controller with a gain scaling factor. We start by providing a systematic design method for selecting the PID gains of our proposed controller by seeing the effect of ϵ on damping ratio, overshoot and settling time from the frequency response analysis. With the help of matlab (simulink), We proceed to show that the proposed controller provides robust stability against system parameter uncertainty and the effect of the gain scaling factor on steady-state error. The validity of our control method along with the analysis is verified with the simulation results.