• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.4A
• /
• pp.440-449
• /
• 2008

In this paper, we propose a 16-QAM carrier recovery loop which is suitable for the implementation of Inmarsat M4 system receiver. Because the frequency offset of ${\pm}924\;Hz$ on signal bandwidth 33.6 kHz is recommended in Inmarsat M4 system specification, carrier recovery loop having stable operation in the channel environment with large relative frequency offset is required. the carrier recovery loop which adopts only PLL can't be stable in relatively large frequency offset environment. Therefore, we propose a carrier recovery loop which has stable operation in large relative frequency offset environment for Inmarsat M4 system. The proposed carrier recovery loop employed differential filter-based noncoherent UW detector which is robust to frequency offset, CP-AFC for initial frequency offset acquisition using UW signal, and 16-QAM DD-PLL for phase tracking using data signal to overcome large relative frequency offset and achieve stable carrier recovery performance. Simulation results show that the proposed carrier recovery loop has stable operation and satisfactory performance in large relative frequency offset environment for Inmarsat M4 system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.11
• /
• pp.1074-1080
• /
• 2013

The low phase noise and wideband frequency synthesizer has been designed by using YTO. Offset PLL structure is used for reducing a division ratio of feedback loop. The phase noise modeling is applied to optimize loop filter of PLL and YTO module. And DDS is used as reference signal of frequency synthesizer for fine resolution. The fabricated wideband frequency synthesizer has the output frequency of 3.2 GHz to 6.8 GHz, phase noise of -107 dBc/Hz at 10 kHz offset from the carrier and frequency resolution of 1 Hz. The measured phase noise is well agreed with the simulated one.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.3 no.1
• /
• pp.31-37
• /
• 2010

This paper proposes a novel method for pilot-aided integer frequency offset (IFO) estimation in orthogonal frequency division multiplexing (OFDM)-based digital video broadcasting-terrestrial (DVB-T) systems. The conventional method proposed for estimating the IFO uses only partial information of combinations that pilots can provide, which stems from a rigorous assumption that the channel responses of pilots used for estimating the IFO change very rapidly. In this paper, we propose an efficient IFO estimation method exploiting additional information of combinations that pilots can provide to improve the performance of the IFO estimation. The simulation results show that the proposed method outperforms the conventional method in terms of the IFO detection probability.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.7A
• /
• pp.627-634
• /
• 2011

In this paper, a new frequency offset estimation method in OFDM system is suggested. To measure fractional part of frequency offset, the repetition feature of cyclic prefix and that of training sequence is adopted. Both method shows relatively large frequency offset estimation error under low SNR circumstances, but this error can be greatly reduced by joint measurement of cyclic prefix and inversely repeated training symbol such as primary advanced preamble (PA-preamble) of IEEE 802.16m IMT-Advanced WiMax system. In this paper, the performance of suggested frequency offset estimation method is verified in IEEE 802.16m IMT Advanced WiMax system, using its PA-preamble and cyclic prefixes of A-preambles.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.9
• /
• pp.1699-1709
• /
• 2015

Moving terminals like high-speed-train undergo high Doppler frequency shift, and this leads to carrier frequency offsets that have to be compensated to avoid degradation of communication performance. In multiple access mechanism like OFDMA, base-stations need complex hardware to compensate the uplink frequency offset. In this paper, we propose a method, which can reduce burden of the base-station and makes frequency offset estimation and compensation simple. This method contains transmitting new synchronization signal, estimating frequency offsets in base-station, transmitting feedback information to terminal, and compensating the offset in uplink transmission. Simulation results show the proposed method operates well in high Doppler frequency shift conditions of 500 km/h which is the requirements of 5G mobile communication.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.6C
• /
• pp.626-633
• /
• 2009

ISO/IEC/WD 24753 defines new modem specifications for a long-range RFID communications and application protocol for a sensor tag system. According to the standard, the frequency offset of the tag is 4%. In general wireless communications systems, it is known that a coherent receiver is superior to a non-coherent receiver. However, if the frequency offset is large, it is difficult to restore the original data accurately with a coherent receiver, and the performance of a coherent receiver is easily degraded. In this paper, a non-coherent receiver structure is adopted to solve the frequency offset problem of long-range RFID communications. We designed a frequency estimation block to find an optimal frequency from the received signal with 4% frequency offset and proposed a start frame delimiter (SFD) detection algorithm to determine the start position of the payload. The frequency estimation block finds the optimal frequency from the received signal using 9-correlators. And the SFD detection block searches the received signal to find the start position of the payload with dual correlator. We implemented a long-range RFID reader with the proposed methods and evaluated its performance in a wired/wireless test network. The implemented long-range RFID reader showed more superior performance than the commercial RFID reader in terms of recognition range.

• Journal of Power Electronics
• /
• v.15 no.6
• /
• pp.1593-1600
• /
• 2015

This paper proposes a novel compensation algorithm of current offset error for single-phase linear compressor in home appliances. In a half-bridge inverter, current offset error may cause unbalanced DC-link voltage when the DC-link is comprised of two serially connected capacitors. To compensate the current measurement error, the synchronous reference frame transformation is used for detecting the measurement error. When an offset error occurs in the output current of the half-bridge inverter, the d-axis current has a ripple with frequency equal to the fundamental frequency. With the use of a proportional-resonant controller, the ripple component can be removed, and offset error can be compensated. The proposed compensation method can easily be implemented without much computation and additional hardware circuit. The validity of the proposed algorithm is verified through experimental results.

• 전자공학회논문지 IE
• /
• v.45 no.1
• /
• pp.24-30
• /
• 2008

In this paper, Digital MultiTone(DMT) is an emerging multi-carrier modulation scheme, which has been adopted for VDSL(Very high speed Digital Subscribe Line). A problem of DMT is its sensitivity to frequency offset between the transmitted and received carrier frequencies. This frequency offset introduces inter-carrier interference(ICI) in the DMT symbol. This paper is proposed an ICI cancelation scheme using Kalman Filtering. The performance of the proposed method is compared with conventional methods in terms of bit error rate performance, bandwidth efficiency, and computational complexity. Through simulations, it is shown that for high values of the frequency offset and for higher order modulation schemes, the EKF(Enhanced Kalman Filtering) method perform better than the others.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.11
• /
• pp.1280-1287
• /
• 2012

The 3.2~6.5 GHz wideband YTO(YIG Tuned Oscillator) module is designed, fabricated and measured. To improve the phase noise characteristic of the YTO module, offset PLL(Phase Locked Loop) structure with sampling mixer is applied. This YTO module is composed of sampling mixer, phase detector, loop filter, current driver, and YTO. The phase noise of the fabricated YTO module is measured as -100 dBc/Hz at 10 kHz offset frequency, which approximates the predicted result at the center frequency of 4.5 GHz. This YTO module presents over 10 dB improved phase noise compared to conventional PLL module from operating frequency.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2018.11a
• /
• pp.310-312
• /
• 2018

In this paper, We stduy addtional consideration and method to treat carrier frquency offset on defined system parameter & requirements in IALA G1139, previous studied consecutively. We studied the method to treat carrier frequency offset by extending length of training symbol and by differential modulation. This study will publish and argue in IALA ENAV22. We will decide a method to treat carrier frequency offset from result of IALA ENAV22.