• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.2A
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• pp.183-190
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• 2008

The balanced Tx diversity with same data on two antennas can have better or lower performance than STBC Tx diversity, depending on the difference between each phase of two channels when the received signal is processed with MRRC. Therefore, using the feedback information based on the phase estimation in each channels, the better scheme of the balanced Tx diversity and STBC Tx diversity can be selected. However, when the phase condition changes during the transmission as the selected Tx. diversity scheme, the decoded bit can be erroneous because the previously estimated phase and newly estimated phase is different. In this case, the receiver should request the re-transmission of the just received signal to the transmitter part. Through computer simulation, it is shown that the combined scheme of the balanced Tx diversity and STBC Tx. diversity has better performance than STBC Tx diversity.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.3
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• pp.630-635
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• 2010

In this paper, a new discrete static output feedback variable structure controller based on a new dynamic-type sliding surface and output feedback discrete version of the disturbance observer is suggested for the control of uncertain linear systems. The reaching phase is completely removed by introducing a new proposed dynamic-type sliding surface. The output feedback discrete version of disturbance observer is derived for effective compensation of uncertainties and disturbance. A corresponding control with disturbance compensation is selected to guarantee the quasi sliding mode on the predetermined dynamic-type sliding surface for guaranteeing the designed output in the dynamic-type sliding surface from any initial condition for all the parameter variations and disturbances. Using Lyapunov function, the closed loop stability and the existence condition of the quasi sliding mode is proved. Finally, an illustrative example is presented to show the effectiveness of the algorithm.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.6 no.2
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• pp.23-30
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• 2012

In this study, we developed a wireless rehabilitation auditory feedback gait training system for symmetrical weight-bearing in patient with CVA. The device consists of an instantaneous shoe equipped with two load-cell sensors. Auditory feedback can be applied according to the weight-bearing. For gait patterns analysis, cadence, walking velocity, stance/swing phase ratio and gait cycle were examined. The clinical test with six healthy volunteers and two hemiplegic patients was performed applying the auditory feedback system. Both normal subjects and hemiplegic patients were increased strength on weight-bearing in affected limb, walking velocity, and cadence after biofeedback device. Also, the stance time with weight-bearing was increased while the swing time was decreased in gait phase. It can be expected that by using the feedback system, the patient with lower limb disorder will be able to reach a better quality of weight-bearing during gait.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.617-620
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• 2003

In this paper, a monolithic VCO has been designed for Wireless Local Area Network(WLAN) applications. The differential form VCO is constructed using positive feedback with capacitor and phase shift for low phase noise performance. The VCO shows the phase noise of -92.725 dBc/Hz at an offset frequency of 10KHz and the tunning range of 5.822~6.154GHz.

• 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 Electromagnetic Engineering and Science
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• v.8 no.1
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• pp.94-99
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• 1997

There are several factors that have influence on the phase noise of an oscillator. But one of the major factors is the flicker noise of a transistor, since the phase noise of an oscillator is generated by mixing the carrier with the low frequency noise near the DC having the characteristic of 1/f. In this paper, we have presented a method on reducing the phase noise of an oscillator by using a low-frequency feedback circuit based on an active bias circuit, and have fabricated a DRO for a DBS receiver. Measurement results show that the phase noise is -92 dBc/Hz at the 10 KHz offset frequency, and from these results we have found out that the reduction method is very effective.

• Physical Therapy Korea
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• v.8 no.4
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• pp.81-89
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• 2001

There are two independent mechanisms to control the segmental reflex gain in humans during gait. They are presynaptic inhibition and homosynaptic depression. Through the mechanism of the presynaptic inhibition, the muscle spindle afferent feedback can be properly gated during eccentric phase of gait. The modulation of the presynaptic inhibition is reflected in the level of H-reflex at a constant EMG level. During the eccentric muscle activation presynaptic inhibition should increase to account for the lower amplitude level of H-reflex at a constant level of EMG. Homosynaptic depression is another mechanism responsible for regulating the effectiveness of the muscle spindle afferent feedback. Both the presynaptic inhibition and the monosynaptic depression are responsible for modulating reflex gain during gait initiation. Reflex modulation is influenced not only as a passive consequence of the alpha motor neuron excitation level, but also through supraspinal mechanisms. Spastic paretic patients show the impaired soleus H-reflex modulation either during the initial stance phase, or during the swing phase. This abnormal modulatory mechanism can partially and artificially be restored by the application of peripheral stimulus to the sole of the foot, provided that the segmental circuitry remains functional.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.1
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• pp.1-9
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• 2003

This paper deals with the nodal admittance approach steady-state frequency domain analysis of the three-phase self-excited induction generator (SEIG) driven by the variable speed prime mover as the wind turbine. The steady-state performance analysis of this power conditioner designed for the renewable energy is based on the principle of equating the input mechanical power of the three-phase SEIG to the output mechanical power of the variable speed prime mover mentioned above. Us-ing the approximate frequency domain based equivalent circuit of the three-phase SEIG. The main features of the present algorithm of the steady-state performance analysis of the three-phase SEIG treated here are that the variable speed prime mover characteristics are included in the approximate equivalent circuit of the three-phase SEIG under the condition of the speed changes of the prime mover without complex computations processes. Furthermore, a feedback closed-loop voltage regulation of the three-phase SEIG as a power conditioner which is driven by variable speed prime movers such as the wind turbine(WT) employing the static VAR compensator(SVC) circuit composed of the thyristor phase controlled reactor(TCR) and the thyristor switched capacitor(TSC) controlled by the PI controller is designed and considered for wind-turbine driving power conditioner.

• Korean Journal of Optics and Photonics
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• v.16 no.6
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• pp.527-534
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• 2005

We investigate the pulsation characteristics in a multi-section DFB laser which is composed of one DFB section, phase tuning section, and gain section. Multi-section DFB lasers with anti-phase (AP) complex-coupled (CC) DFB structure show wide current ranges of gain and phase tuning sections fer stable pulsations compared to those with in-phase CC DFB structure or index-coupled DFB structure. For multi-section DFB lasers with AP CC DFB structure, the current range of a gain section for stable pulsations increases and the tuning range of the pulsation frequency increases as a coupling strength or a gain coupling coefficient increases Also, the tuning range using the phase variation in a phase tuning section increases. For a fixed coupling strength, the current ranges of gain and phase tuning sections for stable pulsations increase and the tuning range of the pulsation frequency increases as the length of a DFB section increases.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.3
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• pp.707-714
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• 2010

Since an LFSR(linear feedback shift register) as a pattern generator has solely linear dependency in itself, it generates sequences by moving the bit positions for pattern generation. So the correlation between the generated patterns is high and thus reduces the possibility of fault detection. To overcome these problems many researchers studied to have goodness of randomness between the output test patterns. In this paper, we propose the new and effective method to construct phase shifter as PRPG(pseudo random pattern generator).