• ETRI Journal
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• v.26 no.5
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• pp.501-504
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• 2004

This paper presents a simple gain/phase blind compensation algorithm with an automatic gain control (AGC) function for the adoption of the AGC function and compensation for gain/phase imbalances in quadrature phase shift keying (QPSK) direct conversion receivers (DCRs). The AGC function is interactively operated with the compensation algorithm for gain/phase imbalances. By detecting the gain sum and difference values between the I-channel and Q-channel, the combined AGC and gain imbalance compensation algorithm provides a simpler DCR architecture.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.1
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• pp.100-106
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• 2009

This paper deals with an estimation problem of the gain and phase imbalances between the in-phase and quadrature components in the quadrature receivers which are widely used in wireless communications. It is shown that the estimates derived from the suggested auto-calibration algorithm is asymptotically minimum-variance unbiased as a function of the sampling time. In order to show this characteristic, the probability density functions of the estimates for the gain and phase imbalances are derived first. Then the mean and variance functions are investigated analytically or numerically based on the density functions.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.3
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• pp.113-119
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• 1998

In this paper, the error sidelobe level and signal to noise loss from the numerical analysis using the modelling of quadrature coherent detector in the case that the channel imbalance and with local oscillator leakage is considered. From the numerical results, the error sidelobe level and signal to noise loss that with the gain and phase imbalance(0.8(dB)J5(dog)) is (-21.322[dB], -0.0071[dB]), (-11.6839[dB], -0.0059[dB]) in the case that the channel imbalance and with local oscillator leakage is considered.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.517-520
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• 2000

This paper deals with the statistical analysis of an autocalibration procedure for the gain and phase imbalances between the in-phase (I) and quadrature (Q) components in quadrature receivers. In real implementation, the imbalances of the gain and phase exist and degrade the performance of the receiver. In this paper we investigate the statistical characteristic of the estimates in an on-line imbalance estimation method for the receiver under the assumption of an additive white Gaussian noise environment.

• Korean Journal of Optics and Photonics
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• v.8 no.3
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• pp.209-212
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• 1997

Spectral gain variation characteristics of the silica-based erbium doped fiber amplifiers is investigated in the 1545-1557 nm wavelength region. For a given length of the erbium doped fiber, the gain($G_0$) with minimum spectral gain variation is uniquely determined. The spectral gain imbalance DG is nearly proportional to the difference between G0 and the operating gain(G) with the proportional constant of 0.1-0.2 dB/dB. For the gain flattened EDFA at the input power of -20 dBm/ch. and the gain of 21 dB, the output power and the optical signal to noise variations after 12 cascaded EDFAs were 5 dB and 3 dB, respectively.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.2
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• pp.90-95
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• 2009

All-optical fiber-type gain flattening filer (GFF) for an EDFA (Erbium doped fiber amplifier) were fabricated by using a FBT (fiber biconical tapered) process and the performance of the GFF was tested and athermal package was proposed. Historically, the chief contributor to gain unevenness has been the EDFA. Due to the inherent gain response of the EDFA's operation, there is always a modest imbalance in the gain applied as a function of wavelength. FBT methods have been used to make fiber type couplers and WDM filter since 1980. Attractivity of this methods was simple, cost effective and thermal stability. Simulation program tool is made to design target GFF profile for this paper. Fiber coupler manufacturing machine is modified for the GFF process. The final GFF is obtained by cascading 4 unit filter that has 6 taper stage. Test result shows 1 dB of wavelength flatness in the C band. Polarization dependent loss is under 0.15dB. The center wavelength variation is below ${\pm}$0.35nm at the temperature range of $20^{\circ}C$ to $70^{\circ}C$.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1896-1898
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• 2001

An offset problem caused by the static parasitic capacitors is analyzed and then some techniques to reduce their effect on the capacitive position sensor are presented. Also new offset compensation technique is proposed that by adjusting the magnitudes of the modulating signals independently, the charge imbalance between electrodes caused by the parasitic capacitors is eliminated without sensor gain variation. Simulation results are given to validate the proposed compensation technique.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.11
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• pp.1275-1284
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• 2010

100 MHz bandwidth and 1 Gbit/s data speed are needed in LTE-advanced for the next generation mobile communication system. Therefore, spectrum aggregation method has been studied recently to extend usable frequency bands. Also bandwidth utilization is increased since vacant frequencies are used to communicate. However, transceiver structure requires the digital RF and SDR. Therefore, frequency synthesizer and PA must operate over wide-bandwidth and RF impairments also increases in transceiver. Uplink of LTE advanced uses DFT-S OFDM using plural power amplifier. The effect of ICI increases in frequency domain of receiver due to phase noise and IQ imbalance. In this paper, we analyze influences of ICI in frequency domain of receiver considering phase noise and IQ imbalance in multiband system. Also, we separate phase noise and IQ imbalance effect from channel response in frequency domain of uplink system. And we propose a method to estimate the channel exactly and to compensate IQ imbalance and phase noise. Simulation result shows that the proposed method achieves the 2 dB performance gain of BER=$10^{-4}$.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.457-459
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• 2005

In this paper the BER consideration of a quadrature receiver that has an autocalibration method is considered. The analysis is based on the derivation of the statistical characteristics of the imbalances in gain and phase between in-phase and quadrature components that may cause severe performance degradation of the receiver. The density. mean and variance functions of the estimates of gain and phase imbalances are discussed. Then it is shown that the estimates are asymptotically minimum variance unbiased with respect to the integration time in sampling. A brief consideration on the BER calculation follows.

• Journal of Korean Medicine Rehabilitation
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• v.18 no.1
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• pp.33-46
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• 2008

Objectives : Obesity is a metabolic disease resulted from various causes including nutritional disproportion, hormonal imbalance, and hypothalamic nuclei disorder. Samhwang-tang(Sanhuang-tang, SHT) is composed of 5 herbs (Ephedrae Herba, Scutellariae Radix, Typhae pollen, Acori Rhizoma and Ansu Semen) and is frequently used for obese patients. This study investigated anti-obesity effects of SHT on the rats. Methods : Obesity was induced by high fat diet (HFD), monosodium L-glutamate injection (MSG) and ovariectomy (OVX) in the Sprague-Dawley rats. Water extract of SHT was treated for 2 weeks, then changes of body weight gain and epididymal fat cell size were measured. In OVX animals, c-Fos and neuropeptide Y (NPY) expressions in hypothalamic nuclei were observed with immunohistochemistry. Results : SHT treatment demonstrated significant decrease of body weight gain in obesity induced by HFD and OVX, but not in obesity induced by MSG. SHT treatment demonstrated significant decrease of fat cell size in obesity induced by HFD, but not in obesity induced by MSG. On c-Fos and NPY expressions in hypothalamic nuclei, SHT treatment resulted significant decrease of immuno-reactivity of c-Fos and NPY in obesity induced by OVX. Conclusions : These results suggest that SHT has a weight loss effect against obesity induced by nutritional disproportion of diet intake and hormonal imbalance, especially without central nervous system disorder.