• Title/Summary/Keyword: Amplitude imbalance

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Current-Steered Active Balun with Phase Correction

  • Park, Ji An;Jin, Ho Jeong;Cho, Choon Sik
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.15 no.6
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    • pp.629-633
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    • 2015
  • An active balun using current steering for phase correction is presented. The proposed active balun is constructed with two different unit balun structures based on current steering to reduce phase and amplitude errors. This type of topology can be compared with the conventional phase and amplitude correction techniques which do not incorporate the current steering. Designed and fabricated active balun in $0.18{\mu}m$ CMOS process operates over 0.95 - 1.45 GHz band, showing input reflection coefficient under -15 dB, phase error of $11^{\circ}$ and gain error of 0.5 dB. Gain is measured to be 0.3 dB maximum and power consumption of 7.2 mW is measured.

Analysis of the Cancellation Performance of a linearization loop

  • Kang, Sang-Gee;Yi, Hui-Min;Hong, Sung-Yong
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2003.11a
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    • pp.183-187
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    • 2003
  • The expression for the effects of an amplitude imbalance, a phase imbalance and a delay mismatch on the characteristics of a linearization loop in feedforward amplifiers 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.

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Comparison of Subtalar Joint Range of Motion and Dorsiflexor Muscle Activity Between Normal and Pes Planus Feet (정상발과 평발에서의 목말밑 관절가동범위와 등쪽굽힘근의 근활성도 비교)

  • Koh, Eun-Kyung;Jung, Do-Young
    • Journal of the Korean Society of Physical Medicine
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    • v.13 no.2
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    • pp.129-135
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    • 2018
  • PURPOSE: The imbalance of pretibial muscles can be a factor contributing to the development of pes planus. However, no study has yet compared the muscle activity of the tibials anterior (TA) to that of the extensor digitorum longus (EDL). The purpose of this study was to determine whether there are differences in the electromyographic (EMG) TA and EDL amplitude indexes (AIs) between normal and pes planus feet. METHODS: A total of 14 subjects with normal feet and 15 subjects with bilateral pes planus participated in this study. TA and EDL muscle activities were measured using a wireless EMG system and the angles of ankle dorsiflexion and eversion of the subtalar joint were measured using a universal goniometer during active ankle dorsiflexion in the prone position. AI was calculated as follows: $\text{amplitude_{TA}-amplitude_{EDL}/(amplitude_{TA}+amplitude_{EDL})}/2{\times}100$. RESULTS: The AIs of the TA and EDL were significantly lower in pes planus feet than in normal feet (p<.05). The angle of subtalar eversion was significantly greater in pes planus feet than in normal feet during active ankle dorsiflexon (p<.05). However, there was no significant difference in the angle of ankle dorsiflexion between normal feet and pes planus feet (p>.05). CONCLUSION: This study showed that TA muscle activation was lower in pes planus feet than in normal feet, resulting from greater eversion range of motion during active ankle dorsiflexion. We suggest that the imbalance of ankle dorsiflexors must be considered in pes planus management.

Performance Analysis of OFDM Communication System with the IQ Imbalance and Phase Noise (IQ Imbalance와 위상 잡음을 고려한 OFDM 통신 시스템의 성능 분석)

  • Kim, Sang-Kyun;Ryu, Heung-Gyoon;Kang, Byung-Su;Lee, Kwang-Chun
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.18 no.7
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    • pp.757-765
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    • 2007
  • OFDM system is an excellent high speed transmission method but it is seriously sensitive to the phase noise and IQ imbalance. Therefore, in this paper, we analyze the communication performance of the OFDM communication system with IQ imbalance and phase noise. Phase noise's variance can be calculated by integral calculus of phase noise power spectrum. From simulation results, it can be shown that the BER performances show different change according to the phase noise variance and IQ imbalance amount. When amplitude imbalance is ${\varepsilon}$=0.2; 0.3; 0.4 and phase imbalance is ${\phi}=10^0$, and distribution of phase noise is ${\sigma}^2=0.012$, BER is degraded by 2.88 dB, 3.61 dB, 4.09 dB in $10^{-5}$ in the respect of the SNR penalty.

A study on wideband strip-line balun using a power divider and a phase converter (전력 분배기와 위상 변환기를 이용한 광대역 스트립라인 발룬에 관한 연구)

  • Lee, Chang-Seok;Park, Ung-Hee
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.12 no.7
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    • pp.1160-1164
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    • 2008
  • This paper presents an wideband stripline balun. And, the proposed balun is composed of one power divider and two phase converters on stripline substrate. The target characteristics of the proposed balun is the combination loss of below -0.05 dB, an amplitude imbalance of ${\pm}0.5\;dB$ and a phase imbalance of $180{\pm}10$ degrees, with the reflection coefficient(S11) of below -10 dB over frequencies ranging from 500 to 1500 MHz. The fabricated balun occupies the area of $12(W){\times}220(L){\times}2.3(T)\;mm3$. Experimental measurement shows that the fabricated balun has an amplitude imbalance of ${\pm}0.7\;dB$, a phase imbalance of $180{\pm}8$ degrees and an insertion loss of about -2 dB with the reflection coefficient(S11) of below -10 dB over frequencies ranging from 500 to 1,500 MHz.

Analysis and Control of Neutral Point Current Deviation in Grid Tied 3-Level NPC Converter under Various Grid Unbalanced Conditions (다양한 불평형 계통 상황에서 계통 연계형 3-레벨 NPC 컨버터의 중성점 전류 변동에 대한 해석 및 제어)

  • Choi, Jaehoon;Suh, Yongsug
    • The Transactions of the Korean Institute of Power Electronics
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    • v.25 no.5
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    • pp.385-393
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    • 2020
  • This study introduces an analysis and control method for the variation of neutral point current in a grid-tied three-level neutral point clamped (NPC) converter under various grid imbalance operating conditions. Various fault cases with unbalanced amplitude and phase are systematically categorized and described using a unified metric called the imbalance factor. The fundamental component of neutral point current is generated under grid imbalance cases. The pattern and behavior of this fundamental component of neutral point current highly depend on the imbalance factor regardless of the particular type of grid fault cases. The control scheme for regulating the negative sequential component of AC input current effectively reduces the size of the fundamental component of neutral point current under a wide range of grid imbalance cases. The control scheme will enable a grid-tied three-level NPC converter to operate reliably and stably under various types of grid faults.

Some Further Consideration for the Image Retrieving of Synthetic Aperture Radiometer

  • Liu, Hao;Wu, Ji;Wu, Qiong
    • Proceedings of the KSRS Conference
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    • 2003.11a
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    • pp.1349-1351
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    • 2003
  • In this paper, theoretical channels model of Synthetic Aperture Radiometer is presented. Based on this model, how amplitude imbalance, phase imbalance and mutual coupling between the different channels effect brightness temperature image retrieving is analyzed. The computer simulation results are also presented to find out the cause of the along-track streaks usually appeared in the retrieved brightness temperature image. In addition, a new system calibration approach is introduced to solve this problem.

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Sensing Technique of Mass Imbalance for Condition Monitoring of Wind Turbine Blade (풍력발전기 블레이드 상태 모니터링을 위한 질량 불균형 감지기법)

  • Lee, Jong Won
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.15 no.1
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    • pp.209-214
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    • 2011
  • A method to detect rotor mass imbalance, which is one of the typical faults of wind turbine, is presented for effective condition monitoring of wind turbine. Dynamic analysis for a three-bladed horizontal-axis wind turbine was carried out with adding mass to a blade for inflicting the rotor mass imbalance. It has been found that the added mass induce a resulting centrifugal force to nacelle and this leads to a transverse (relative to the rotor axis) oscillation of the nacelle. It has been also found that the amplitude of the oscillation is almost linearly increased as the added mass is increased.

Enhanced Spatial Modulation of Indoor Visible Light Communication

  • Shan, Ye;Li, Ming;Jin, Minglu
    • Journal of information and communication convergence engineering
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    • v.13 no.1
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    • pp.1-6
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    • 2015
  • In this study, we consider visible light communication in an indoor line-of-sight environment. It has been proved that among the multiple input multiple output (MIMO) techniques, spatial modulation (SM) performs better than repetition coding (RC) and spatial multiplexing (SMP). On the basis of a combination of SM and pulse amplitude modulation (PAM), here, we propose an enhanced SM algorithm to improve the bit error rate. Traditional SM activates only one light-emitting diode (LED) at one time, and the proposed enhanced SM activates two LEDs at one time and reduces the intensity levels of PAM by half. Under the condition of a highly correlated channel, power imbalance is used to improve the algorithm performance. The comparison between the two schemes is implemented at the same signal-to-noise ratio. The simulation results illustrate that the enhanced SM outperforms the traditional SM in both highly correlated and lowly correlated channels. Furthermore, the proposed enhanced SM scheme can increase the transmission rate in most cases.

I/Q Imbalance Compensation Method for the Direct Conversion Receiver with Low Pass Filter Mismatch (저역 통과 필터 불일치를 포함한 직접 변환 수신기의 I/Q 불균형 보상 기법)

  • Yun, Seonhui;Ahn, Jaemin
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.11
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    • pp.3-10
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    • 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.