• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.283-286
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• 1999

A 2㎓, low noise, low power CMOS voltage-controlled oscillator (VCO) with an integrated LC resonator is presented. The design of VCO relies heavily on the on-chip spiral inductor. An optimized spiral inductor with Q-factor of nearly 8 is achieved and used for the VCO. The simulated result of phase noise is as low as -l14 ㏈c/Hz at an offset frequency of a 600KHz from a 2㎓ carrier frequency. The VCO is tuned with standard available junction capacitors, resulting in an about 400MHz tuning range (20%). Implemented in a five-metal 0.25${\mu}{\textrm}{m}$ standard CMOS process, the VCO consumes only 2㎽ from a single 2.5V supply. It occupies an active area of 620${\mu}{\textrm}{m}$$\times$720${\mu}{\textrm}{m}$.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1928-1931
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• 2002

Orthogonal Frequency Division Multiplexing or OFDM is a form of multi-carrier modulation technique. High spectral efficiency, robustness to channel fading, immunity to impulse interference, uniform average spectral density, capability of handling very strong echoes and less on linear distortion are among the favorite properties of OFDM. Even though there are many advantages of OFDM, t has two main drawbacks: high Peak to Average Power Ratio (PAPR) and frequency of offset. In this paper, the issue of PAPR in OFDM is discussed. A new algorithm is proposed to reduce PAPR by selecting the input sequences property using a lookup table.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.4
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• pp.817-823
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• 2010

MC-DS-CDMA is technique where a single data symbol is transmitted at multiple subcarriers which are orthogonal to each other. With this technique, frequency diversity can be achieved. The performance of PSAM MC-DS-CDMA system with the application of MRRC antenna diversity is analyzed. The BER performance of this system over multipath fading environment is evaluated, considering the channel estimation error, carrier frequency offset, and the nonlinear high power amplifier.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1955-1957
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• 2003

This paper presents a novel defected ground structure (DGS) and its application to a microwave oscillator. The presented oscillator is designed so as to use the suggested defected ground structure as a feedback loop inducing a negative resistance as well as a frequency-selective circuit. Applying the feedback loop between the drain and the gate of a FET device produces precise phase conversion in the feedback loop. The equivalent circuit parameters of the DGS are extracted by using a three-dimensional EM calculations and simple circuit analysis method. The implemented 1.07 GHz oscillator exhibits 0 dBm output power with over 15% dc-to-RF power efficiency and -106 dBc/Hz phase noise at 100 kHz offset from carrier.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1506-1508
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• 2005

VCO(voltage controlled oscillator) using mobile communication device decides direct characteristics as parts that affect important in stable oscillation and distortion characteristics of system. VCO used 900 MHz band was designed by the transformation of Colpitts circuit form use ADS that consider Q-factor to minimize phase noise. VCO manufactured together evaluation board and voltage control oscillator to FR-4 PCB. VCO experimented chracteristics after control through resonance department tuning. In our research, the designed VCO has 15.5 dBm output level at the bias condition of 6V and 10mA and the operating frequency range of 917 MHz$\sim$937 MHz band. Phase noise is -98.28 dBc/Hz at 1 MHz frequency offset from the carrier.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.858-866
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• 2005

This paper proposes the method of frequency synchronization using the spectrum correlation in ATSC terrestrial DTV system. If the spectrum around pilot is severely distorted by multipath or mobile reception environment, the conventional algorithm using the pilot signal makes the estimation error of the frequency offset. Because the proposed algorithm acquires frequency synchronization using the correlation between the received specalm and the standard spectrum without the use of pilot, the proposed method can acquire frequency synchronization faster and more accurate than conventional algorithm. And this paper proposes new method for ATSC frequency synchronization without the use of pilot.

• Journal of IKEEE
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• v.16 no.2
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• pp.121-126
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• 2012

In this paper, a push-push VCDRO (Voltage Controlled Dielectric Resonator Oscillator) with a modified frequency tuning structure is investigated. The push-push VCDRO designed at 16GHz is manufactured using a LTCC (Low Temperature Co-fired Ceramic) technology to reduce the circuit size. The frequency tuning structure is embedded in intermediate layer of A6 substrate by an advantage of LTCC process. Experimental results show that the fundamental frequency suppression is above 30dBc, the frequency tuning range is 0.43MHz over control voltage of 0 to 12V, and phase noise of push-push VCDRO presents a good performance of -103dBc/Hz at 100KHz offset frequency from carrier.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4A
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• pp.402-411
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• 2006

In OFDMA system, multiple users transmit signal through the subcarriers assigned to the user. Capabilities of high data-rate transmission in OFDMA system come from the ability to compensate the ICI (Inter Carrier Interference) using a single-tap equalizer and to implement transmitter and receiver by employing high speed FFT circuitry. Issues of time and frequency synchronization in OFDM system is quite essential to preserve the orthogonality among subcarriers not to produce ICI. In this paper, we Int analyze the preamble used in 802.16 d/e and WiBro system. Then we propose an effective timing synchronization algorithm, which is more accurate than the conventional one in the sense of timing position, and integral frequency offset estimation scheme for the simultaneouse estimation of the fractional and integral frequency offset. Through the simulation utilizing the proposed synchronization algorithm and structure, we show that the performance degradation due to the adjacent channel interference can be mitigated for the than conventional ones.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.6
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• pp.1-5
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• 2011

We present the Multi-band orthogonal frequency division multiplexing ultra-wideband (MB-OFDM UWB) technology for increasing the transmission reach of wireless speaker systems. The proposed scheme adopts the Reed-Solomon coding for preventing the random error perfectly and shows the SNR gain in low bit error rate (BER) especially. So, we can increase the maximum reach of MB-OFDM UWB technology since the receiver sensitivity is improved. The simulation environment includes most effects of realistic channel environments such as Additive White Gaussian Noise (AWGN), CM1 channel model, Sampling frequency offset (SFO), Carrier frequency offset (CFO) to improve the simulation accuracy. The simulation results show that the proposed scheme can give a maximum 2 dB SNR gain and increase the transmission reach up to 12.6m.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.5
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• pp.9-14
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• 2013

This paper is designed frequency multiplier with low phase noise using DLL technique. The VCDL is designed using a differential structure to reduce common-mode noise. The proposed frequency multiplier is fabricated in a 65nm, 1.2V TSMC CMOS process, and the operating frequency range from 10MHz to 24MHz was measured. The SSB phase noise is measured to be -125dBc/Hz at 1MHz from 38.4MHz carrier. A total area of $0.032mm^2$were consumed in the chip, including the output buffer. Total current is 1.8mA at 1.2V supply voltage.