• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.12
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• pp.40-48
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• 1998

An offset compensation scheme for rail-to-rail CMOS op-amps with complementary input stages is presented. Two auxiliary amplifiers are used to compensate for the offsets of NMOS and PMOS differential input stages, and ping-pong control is employed for continuous-time operation. A 3V offset-compensated rail-to-rail CMOS op-amp has been designed and fabricated using a 0.8$\mu\textrm{m}$ single-poly, double-metal CMOS process. Measurement results show that offsets are reduced about 20 times by this scheme.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.76-83
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• 2005

In this study a general method for computing offsets of free form curves is presented. In the method arbitrary free form curve is approximated with point series considering required tolerance. The point series are offset precisely using the normal vectors computed at each point and loop removal is carried out by the newly suggested algorithm. The resulting offset points are transformed to lines and arcs using the biarc approximation method. Tangent vectors for approximation of discrete points data are calculated by traditional local interpolation scheme. In order to show the validity and generality of the proposed method , various of offsettings are carried our for the base curves with complex shapes.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.226-229
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• 2003

Under the prsence of the frequency and timing offset, we evaluate the BER performance of the FFH-MA system using noncoherent M-ary FSK modulation in the Rayleigh fading channel. The numerical resuts show that while the frequency and timing offset increases at a given SNR, the BER is severely degraded. The threshold level used in the envelope detector increases with the increase of the frequency and timing offset, and with the proper selection of the threshold level, the BER can be improved under the presence of such offsets.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.2
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• pp.610-628
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• 2012

Dual carrier frequency offsets (CFOs) occur in multiple-input single-output (MISO)-mode DVB-T2 systems, where signals are transmitted simultaneously from two distributed transmitters in a single frequency network (SFN). In this paper, we first derive an optimal compensation frequency for dual CFOs. We also propose an algorithm that optimizes the compensation frequency for the MISO-mode DVB-T2 application. Its performance is compared with the conventional scheme by using a full DVB-T2 simulator.

• International Journal of Automotive Technology
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• v.5 no.1
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• pp.23-31
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• 2004

Secondary movements of piston in the bore clearance are closely related to the side impact to the engine block as well as many tribological problems. Some of the major parameters that influence these kinds of movements are piston profile shapes (barrel and flat), piston pin offsets and the magnitudes of bore clearances. In our study, computational investigations are performed about the piston movements in the bore clearance by changing the skirt profiles and piston offsets. In this work, it is found that curved profile and larger offset magnitude to thrust side provide better performance that has low side impact during the engine cycle.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.34C no.12
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• pp.28-36
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• 1997

In this paper, system application techniques of a low-voltage low-power CMOS comparator are proposed. The proposed techniques employ poly-layer lines instead of conventional dummy cells to improve the accuracy of comparators which are located in both ends of a comparator array. This technique is easily applicable for hihg-density systems such as memory. The proposed circuits are implemented using a 0.6 um signle-poly double-metal n-well CMOS technology and the dissipated power is 0.38 mW. at a 20MHz clock speed based on a 3V supply. The comparator offsets are measured separately and compared for system applications. Using the proposed techniues, the measured comparator offsets are reduced by 40% of a conventional case.

• Journal of Communications and Networks
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• v.15 no.2
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• pp.191-197
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• 2013

In this paper, a mobile relay station (MRS) for vehicles with a beamforming antenna is considered to increase the reliability of the transmission link, particularly for the MRS at the cell boundary. A cell searching and direction-of-arrival estimation method for an MRS with a uniform linear array is proposed for OFDM-based cellular systems in a multipath environment, even with the existence of the symbol timing offsets and carrier frequency offsets. The performance of the proposed method is evaluated by computer simulation using the standard profile of IEEE 802.16e.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1043-1048
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• 2011

In this paper, a newsynchronization technique applied to burst-mode communication is proposed. A synchronization technique is to estimate carrier frequency and phase offsets in a noisy channel environment. A fundamental problem for estimating the parameters(carrier phase and frequency offsets) in burst-mode transmission is that the ways of pursuing estimation accuracy and transmission efficiency are always trade-off. To solve this problem, a new carrier recovery technique is proposed to improve the transmission efficiency with reliable performance especially at low S/N. In the proposed technique, the synchronization parameters are first estimated based on a data-aided feed-forward estimation scheme. Then, a phase tracker using decision-directed DPLL estimates the phase offset for the data portion of the burst data. From simulation results, it shows fast synchronization with shorter preamble maintaining reasonable BER performance at low S/N.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.417-425
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• 2007

While the cyclic prefix lengths of downlink OFDMA(Orthogonal Frequency Division Multiple Access) systems are determined based on the maximum delay spreads encountered in cellular environments, the guard interval of uplink OFDMA systems should consider the timing offsets of uplink signals as well as the delay spread lengths. Especially in the cases of initial accesses, handovers, and considerable time elapsed without data transmissions between base and mobile stations in a large cell, uplink timing offsets can be large and a very long guard interval length may be required. In order to keep the small size of the cyclic prefix in uplink OFDMA systems, the systems require a method of extending the guard intervals for users with large timing offsets without affecting the cyclic prefix length of the system. This paper proposes a method extending the guard intervals of individual users in uplink OFDMA systems.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.344-346
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• 2004

IKONOS 1m satellite imagery is particularly well suited for 3-D feature extraction and 1 :5,000 scale topographic mapping. Because the image line and sample calculated by given RPCs have the error of more than 11m, in order to be able to perform feature extraction and topographic mapping, rational polynomial coefficients(RPCs) camera model that are derived from the very complex IKONOS sensor model to describe the object-image geometry must be refined by several Ground Control Points(GCPs). This paper presents a quantitative evaluation of the geometric accuracy that can be achieved with IKONOS imagery by refining the offset and scaling factors of RPCs using several GCPs. If only two GCPs are available, the offsets and scale factors of image line and sample are updated. If we have more than three GCPs, four parameters of the offsets and scale factors of image line and sample are refined first, and then six parameters of the offsets and scale factors of latitude, longitude and height are updated. The stereo images acquired by IKONOS satellite are tested using six ground points. First, the RPCs model was refined using 2 GCPs and 4 check points acquired by GPS. The results from IKONOS stereo images are reported and these show that the RMSE of check point acquired from left images and right are 1.021m and 1.447m. And then we update the RPCs model using 4 GCPs and 2 check points. The RMSE of geometric accuracy is 0.621 m in left image and 0.816m in right image.