• Journal of the Institute of Electronics Engineers of Korea SD
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• v.49 no.7
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• pp.30-38
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• 2012

This paper presents packet detection, frequency offset estimation architecture and performance analysis for OFDM-based wireless personal area network (WPAN) systems. Packet detection structure is used to find the start point of a packet exactly in WPAN system as the correlation value passes the constant threshold value. The applied autocorrelation structure of the algorithm can be implemented simply compared to conventional packet detection algorithms. The proposed frequency offset estimation architecture is designed for phase rotation process structure, internal bit reduction to reduce hardware size and the frequency offset adjustment block to reduce look-up table size unlike the conventional structure. If the received signal can be compensated by estimated frequency offset through the correction block, it can reduce the impact on the frequency offset. Through the performance result, the proposed structure has lower hardware complexity and gate count compared to the conventional structure. Thus, the proposed structure for OFDM-based WPAN systems can be applied to the initial synchronization process and high-speed low-power WPAN chips.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.1861-1868
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• 2014

In wireless communication systems, a frequency offset exist at the received signal due to the transmitter-receiver oscillator mismatch and Doppler effect in mobile environments. Those offsets rotate the received signal's phase and degrade the receiver performance. Hence, estimation and compensation of the frequency offset is crucial at the receiver. This paper proposes a new frequency offset estimation technique based on partial correlation. The proposed method requires less computational complexity than that of the conventional method. In addition, since the proposed one can estimate a wide range of frequency offset without estimation accuracy loss, the application of the method is desirable for the communication environments that have a large frequency offset. In order to verify the performance of our proposed scheme, a series of computer simulations have been carried out and compared against those of the conventional method.

• KSTLE International Journal
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• v.3 no.2
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• pp.84-89
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• 2002

Clearance movements of engine piston are very related to the piston impact to the engine block as well as many tribological problems. Some of the major parameters that influence these kinds of performances are piston profiles, piston offsets and clearance magnitudes. In our study, computational investigation is performed about the piston movements in the clearance between piston and cylinder liner by changing the skirt profiles and piston offsets. Our results show that curved profile and more offset magnitude to thrust side have better performance that has low side impact during the engine cycle.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.419-419
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• 2006

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.190-194
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• 2006

This research investigates vehicle structure acceleration and vehicle deformation with RCAR crash test. To investigate vehicle damage characteristics in an individual case, it is possible to RCAR low speed crash test. In this study, two tests were conducted to evaluate difference between RCAR new condition and RCAR old condition. A two large vehicles were subjected to a frontal crash test at a speed of 15km/h with an offset of 40% $10^{\circ}$ angle barrier and flat barrier. The results of the 15km/h with an offset of 40% $10^{\circ}$ angle barrier revealed high acceleration value on the vehicle structure and high repair cost compared to the RCAR 15km/h with an offset of 40% flat barrier. So in order to improve damage characteristics in low speed crash of vehicle structure and body component of the monocoque type passenger vehicles, the end of front side member and front back beam should be designed with optimum level and to supply the end of front side member as a partial condition approx 300mm.

• Journal of electromagnetic engineering and science
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• v.4 no.3
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• pp.137-142
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• 2004

In this paper, we present a new current-current negative feedback(CCNF) differential voltage-controlled oscillator (VCO) with 1/f induced low-frequency noise suppressed. By means of the CCNF, the 1/f induced low-frequency noise is removed from the proposed CCNF VCO. Also, high-frequency noise is stopped from being down-converted into phase noise by means of the increased output impedance through the CCNF and the feedback capacitor $C_f. The proposed CCNF VCO represents 11-dB reduction in phase noise at 10 kHz offset, compared with the conventional differential VCO. The phase noise of the proposed CCNF VCO is measured as - 87 dBc/Hz at 10 kHz offset frequency from 5.5-GHz carrier. The proposed CCNF VCO consumes 14.0 mA at 2.0 V supply voltage, and shows single-ended output power of - 12 dBm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2A
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• pp.176-186
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• 2006

In this paper, we propose an enhanced symbol detector algorithm for 2.45GHz LR-WPAN(Low-Rate Wireless Personal Area Network) receiver. Because the frequency offset of $\pm$80ppm on 2.45GHz band is recommended in IEEE 802.15.4 LR-WPAN(Low-Rate Wireless Personal Area Network) specification, a symbol detector algorithm having stable operation in the channel environment with large frequency offset is required. For robustness to the frequency offset, non-coherent detection-based symbol detector algorithm is typically applied in the LR-WPAN receiver modem. However, the noncoherent symbol detector has increased performance degradation and hardware complexity due to squaring loss of I/Q squaring operation. Therefore we propose a coherent detection-based symbol detector algorithm with frequency offset compensation using a preamble symbol. The proposed algorithm is more suitable for LR-WPAN receiver aimed at low-cost, low-power and low-complexity than the non-coherent symbol detector, since it can reduce performance degradation due to squaring loss of I/Q squaring operation and implementation complexity. Simulation results show that the proposed algorithm has performance improvement of about 1dB in various channel environments.

• Journal of Korea Multimedia Society
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• v.18 no.4
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• pp.452-459
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• 2015

Three synchronization issues, i.e., phase, frequency, and symbol time, have to be properly controlled to achieve distributed beamforming gain. In this paper, the impacts of synchronization errors in distributed beamforming are analyzed for both single-carrier and OFDM systems. When the channel is constant over a symbol duration, the performance degradation due to phase offset is the same for both single-carrier and OFDM systems. For symbol timing offset in OFDM systems, high frequency subcarriers are more susceptible as compared to low frequency ones. Frequency offset is critical in OFDM systems since it leads to interference from the other subcarriers as well as power loss in the desired signal.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.301-302
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• 2008

In this paper, we present an algorithm which decrease a frequency offset effect for 868MHz IEEE 802.15.4b LR - WPAN (Low Rate - Wireless Personal Area Network) receiver. The proposed method improve the robustness to frequency offset and receiver's stability using the multiple delay differential filter of receiver correlator.

• 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.