• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.7
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• pp.3-8
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• 2014

We consider a limited feedback based hybrid beamforming which reduces the energy of feedback information. In the millimeter wave channel, some rays with large ray gain dominate energy of the channel. Using this point, we propose a channel feedback scheme that employs limited number of channel rays. Also, we provide a hybrid beamforming scheme for the limited feedback system. Based on the simulation results, the proposed scheme shows a comparable data rate performance with conventional schemes, while it remarkably reduces energy of channel feedback.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.9
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• pp.1573-1595
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• 2011

In this paper, the outage performance of multiuser multiple-input single-output (MISO) systems exploiting joint spatial and multiuser diversities is investigated for Rayleigh fading channels with outdated feedback. First, we derive closed-form exact outage probabilities for the joint diversity schemes that combine user scheduling with different spatial diversity techniques, including: 1) transmit maximum-ratio combining (TMRC); 2) transmit antenna selection (TAS); and 3) orthogonal space-time block coding (OSTBC). Then the asymptotic outage probabilities are analyzed to gain more insights into the effect of feedback delay. It is observed that with outdated feedback, the asymptotic diversity order of the multiuser OSTBC (M-OSTBC) scheme is equal to the number of transmit antennas at the base station, while that of the multiuser TMRC (M-TMRC) and the multiuser TAS (M-TAS) schemes reduce to one. Further by comparing the asymptotic outage probabilities, it is found that the M-TMRC scheme outperforms the M-TAS scheme, and the M-OSTBC scheme can perform best in the outage regime of practical interest when the feedback delay is large. Theoretical analysis is verified by simulation results.

• Journal of electromagnetic engineering and science
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• v.10 no.1
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• pp.25-27
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• 2010

This paper presents a gain and phase mismatch calibration technique for an image-reject RF receiver. The gain mismatch is calibrated by directly measuring the output signal amplitudes of two signal paths. The phase mismatch is calibrated by measuring the output amplitude of the final IF output at the image band. The calibration of the gain and phase mismatch is performed at power-up, and the normal operation of the RF receiver does not interfere with the mismatch calibration circuit. To verify the proposed technique, a 2.4-GHz Weaver image-reject receiver with the gain and phase mismatch calibration circuit is implemented in a 0.18-${\mu}m$ CMOS technology. The overall receiver achieves a voltage gain of 45 dB and a noise figure of 4.8 dB. The image rejection ratio(IRR) is improved from 31 dB to 59.76 dB even with 1 dB and $5^{\circ}$ mismatch in gain and phase, respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.744-747
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• 2005

This research studied 6-Axes Articulated Robot Manipulator's gain Tuning in consideration of dynamic. First of all, search fur proportional gain of velocity control loop by dynamic signal analyzer. Proportional gain of velocity control loop is connected to dynamic signal analyzer. Next Select free Proportional Gain value. And Select amplitude X of sinusoidal properly so that enough Velocity Feedback Signal may be paid as there is no group to utensil department. Next step, We can get Bode Diagram of Closed loop transfer function response examination in interested frequency. Integral calculus for gain of velocity loop is depended on integral calculus correction's number. We can obtain open loop transfer function by integrator. And we can know bode diagram's special quality from calculated open loop transfer function. With this, Velocity Control Loop's Parameter as inner loop is controlled. Next In moving, when vibration occurs, it controls notch filter. And finally, we have to control fred-forward filter parameter for elevation of control performance.

• Proceedings of the IEEK Conference
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• 2003.07c
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• pp.2489-2492
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• 2003

In this paper, observer-based H$\sub$$\infty$/ controller design method for singular systems with time-varying delay by Just one LMI condition is presented. The sufficient condition for the existence of controller and the controller design method are presented by one perfect LMI approach. The design procedure involves solving an LMI. Since the obtained condition can be expressed as an LMI form, all variables including feedback gain and observer gain can be calculated simultaneously by Schur complement and changes of variables.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.920-925
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• 1993

For a multi-input, multi-output system, it is widely known that feedback control gain presents extra freedom pole placement problem. An eigenstructure assignment utilizes this freedom for assignment of all or some elements of the closed-loop eigenvectors. In this paper, a nonlinear optimization technique is adopted to obtain a small gain controller that assigns closed-loop eigenvalues and elements of eigenvectors simultaneously. To illustrate the approach, a numerical example of the Airplane mode decoupling using an advanced fighter is shown.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.355-360
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• 1991

A method of autopilot gain-scheduling is presented for missiles which have heavy aerodynamic coupling between pitch and yaw channels due to high maneuverability. Pitch and yaw, autopilot are cross-coupled, and their feedback gains are scheduled by total acceleration and bank angle for given Mach number and height. Bank angle information is obtained by using a simple estimator. By computer simulation, it is shown that the proposed method is superior to other existing methods.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.5
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• pp.1702-1716
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• 2015

Customer product reviews have become great influencers of purchase decision making. To assist potential customers, online stores provide various ways to sort customer reviews. Different methods have been developed to identify and recommend useful reviews to customers, primarily using feedback provided by customers about the helpfulness of reviews. Most of the methods consider the preferences of all users to determine whether reviews are helpful, and all users receive the same recommendations.

• Journal of Communications and Networks
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• v.9 no.3
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• pp.213-218
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• 2007

Methods for symbol-by-symbol channel feedback and adaptation of symbol durations have been recently proposed. In this paper, we quantitatively analyze the gain in error-constrained data throughput due to such an extremely rapid adaptation of symbol durations to fast-time-varying channels. The results show that a symbol-by-symbol adaptation can achieve a throughput gain by orders of magnitude over a frame-by-frame adaptation.

• ETRI Journal
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• v.25 no.6
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• pp.531-534
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• 2003

This report describes the effect of optical delay on the suppression of the power transient excursion in a combined gain-controlled erbium-doped fiber amplifier with an internal optical feedback loop (OFL). A simple homogeneous model showed that the optical delay caused a phase change in the oscillation of the surviving and laser channels, which resulted in a reduction of the overall power transient excursion. In addition to the reduction, a real system with a 1528.7-nm OFL shifted the oscillation upward or downward according to channel removal or addition, whereas another one with a 1560.9-nm OFL did not. This different transient behavior reflected a control-wavelength dependence on optical automatic gain control, where spectral-hole burning dominated over relaxation oscillation for 1528.7 nm, and vice versa for 1560.9 nm.