• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.472-473
• /
• 2008

This paper presents a charge pump used in frequency synthesizer for PHS application. The up/down current mismatch of charge pump has a critical effect on the phase noise and spur performance in frequency synthesizer. Therefore, the mismatch compensation scheme is proposed in this paper. And, the measurement results show that the mismatch can be reduced below 5 %.

• Journal of electromagnetic engineering and science
• /
• v.16 no.4
• /
• pp.206-209
• /
• 2016

This letter proposes a reconfigurable directional coupler that uses a variable impedance mismatch reflector to achieve high isolation characteristics in the antenna front end. The reconfigurable coupler consists of a directional coupler and a single-pole four-throw (SP4T) switch with different load impedances as a variable load mismatch reflector. Selection of the load impedance by the reflector allows cancellation of the reflected signal due to antenna load mismatch and the leakage from the input to isolation port of the directional coupler, resulting in high isolation characteristics. The performance of the proposed architecture in separating the received (Rx) signal from the transmitted (Tx) signal in the antenna front end was verified by implementing and testing the reconfigurable coupler at 917 MHz for UHF radio-frequency identification (RFID) applications. The proposed reconfigurable directional coupler showed an improvement in the isolation characteristics of more than 20 dB at the operation frequency band.

• ETRI Journal
• /
• v.28 no.2
• /
• pp.231-234
• /
• 2006

The cancellation performance of a linearization loop is limited by the degree of an amplitude imbalance and a phase imbalance. A delay mismatch causes a phase variation as a function of frequency. Therefore, the cancellation performance and linearization bandwidth are limited by a delay mismatch. The expression for the effects of an amplitude imbalance, a phase imbalance, and a delay mismatch on the characteristics of a linearization loop is derived and analyzed. The simulation results are compared with the results obtained by means of using a commercial simulation tool and the exact agreement is reported. The derived equation could be used in designing a linearization loop and predicting the cancellation performance of the linearization loop usefully. Some useful characteristics, known from the simulation results obtained by using the derived equation, of a linearization loop for designing and implementing feedforward amplifiers are described in detail.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.11
• /
• pp.3-10
• /
• 2014

Direct conversion receiver(DCR) gets noticed for integration and cost reduction of wireless communication systems instead of the heterodyne receiver which uses complex filter. But DCR has several factors in performance degradation. One of them is I/Q imbalance phenomenon, that is amplitude and phase mismatch between real and imaginary part of receiver. Accordingly, researches are being carried to improve the I/Q imbalance problem. However, the tendency of the broaden bandwidth of communication systems, low pass filter(LPF) mismatch problem affects severely in I/Q mismatch phenomenon at the DCR. To study this problem, we generated 10MHz broadband signal and shifted it ${\pm}8MHz$ from the center frequency. The signal is affected by LPF mismatch and it appears as frequency selective distortion. Thus, LPF mismatch model is added to I/Q imbalance model which conventionally dealt with amplitude and phase mismatches. In addition, we proposed the compensation method for each factors of mismatch. As the simulation results, the proposed I/Q mismatch compensator resolves the frequency selective distortion which occurred by the existing LPF mismatch.

• Proceedings of the Optical Society of Korea Conference
• /
• 2003.02a
• /
• pp.222-223
• /
• 2003

As laser pulse width becomes shortened from nanoseconds to femtoseconds, the effects caused by the dispersions of nonlinear optical mediums, such as group velocity mismatch and group velocity dispersion become considerably significant. The group velocity mismatch and group velocity dispersion are the major factors that lead to a decrease of frequency conversion efficiency and pulse spreading for picosecond and femtosecond pulses. (omitted)

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.25 no.4
• /
• pp.565-571
• /
• 2021

In this paper, a compensation scheme of frequency selective IQ mismatch for high-performance radar systems based on commercial RFIC's is proposed. Besides, an optimization model and its solution based on the dimension reduction scheme using singular value decomposition are also proposed to design the optimal IQ mismatch compensation digital filter with complex coefficients. The performance of the proposed method had been analyzed through experiments using the IQ mismatch measurement and compensation system implemented on an FPGA board with a target RFIC and compared with the previous method. The experiment result showed a performance improvement of the proposed method over the existing one without noticeable increments in complexities. These performance analysis results showed that the limitation of using commercial RFIC's in high-performance radar systems due to the undesirable maximum SNR cap caused by their IQ mismatches could be overcome by employing the proposed method.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.48 no.2
• /
• pp.35-43
• /
• 2011

In this paper, an analysis on I/Q mismatch characteristics of a quadrature LC VCO(Voltage controlled oscillator) is presented. Based on this analysis, a new I/Q mismatch compensator is proposed. The proposed I/Q mismatch compensator utilizes an amplitude mismatch detector rather than the conventional phase mismatch detector requiring much more wide frequency bandwidth. To verify the proposed circuit, a 2.5GHz quadrature LC VCO was designed in a $0.18{\mu}m$ CMOS process and tested. Test results show that an amplitude mismatch detector achieves similar I/Q mismatch compensation performance as that of the conventional phase mismatch detector. The I/Q mismatch compensator consumes 0.4mA from 1.8V supply voltage and occupies $0.04mm^2$.

• Journal of Institute of Control, Robotics and Systems
• /
• v.20 no.5
• /
• pp.563-569
• /
• 2014

This article focuses on a hemispherical resonator gyro driven by the Coriolis effect. A hemispherical shell, called a resonator, is maintained in the resonance state by amplitude control and phase locking control. Parametric excitation has been used to control the amplitude. For rate measurement mode or FTR mode, nodal points have been kept to an amplitude of zero. Angular rate measurement has been demonstrated by rotating a resonator. Frequency mismatch between two stiffness principal axes is a major cause of low performance: vibrating pattern drift and reduced control effectiveness. This mismatch has been reduced significantly by the addition of small mass. A negative spring effect, which lowers resonance frequencies, has been verified experimentally.

• Journal of the Semiconductor & Display Technology
• /
• v.1 no.1
• /
• pp.1-7
• /
• 2002

Modem technology depends on the reliability of extremely high precision equipments. In the production of semiconductor wafer, optical and electron microscopes, ion-beam, laser device must maintain their alignments within a sub-micrometer. This equipment requires a vibration free environment to provide its proper function. Therefore, this high technology equipments require very strict environmental vibration criteria because it is used as basic data for the design of building structure and structural dynamics of equipment. In this paper, the new approach is proposed to investigate the mismatch problem of time and frequency domain for vibration criteria of sensitive equipment. The proposed approach is based on a vibration measurement data and a relative transfer function which can be obtained by experiment or analysis.

• Journal of Korean Academy of Nursing Administration
• /
• v.18 no.3
• /
• pp.310-319
• /
• 2012

Purpose: The purpose of this study was to analyze emotional labor factors influencing job satisfaction, intent to leave, and nursing performance of clinical nurses. Method: The participants were 384 clinical nurses working in a hospital. Study design was cross sectional survey. Subcategories of emotional labor (frequency of emotional labor, attentiveness of emotional display, mismatch of emotions) of emotional labor were dependent variables. Job satisfaction, intent to leave, and nursing performance were independent variables. Data were analyzed by hierarchial multiple regression. Results: The strength of emotional labor of nurses was similar for all participants in spite of differences in age, position, and clinical career. Total score for emotional labor was 3.21, frequency of emotional labor 3.34, attentiveness of emotional display 3.41, and mismatch of emotions 2.87. Mismatch of emotions influenced job satisfaction (F=12.53, p<.001) $R^2$ 27%, intent to leave (F=8.51, p<.001) $R^2$ 19%, and nursing performance (F=5.80, p<.001) $R^2$ 15%, Conclusion: These findings indicate that the factor (mismatch of emotion) is an important variable for clinical nurses in human resource management. Therefore, nurse managers should consider this factor for the improvement of organizational effectiveness.