• ETRI Journal
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• v.46 no.2
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• pp.238-249
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• 2024

Equivalent-time sampling can improve measurement or sensing systems because it enables a broader frequency band and higher delay resolution for periodic signals with lower sampling rates than a Nyquist receiver. Meanwhile, a digital down-conversion (DDC) technique can be implemented using a straightforward radio frequency (RF) circuit. It avoids timing skew and in-phase/quadrature gain imbalance instead of requiring a high-speed analog-to-digital converter to sample an intermediate frequency (IF) signal. Therefore, when equivalent-time sampling and DDC techniques are combined, a significant synergy can be achieved. This study provides a parameter design methodology for optimal equivalent-time sampling using DDC.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.11
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• pp.2391-2396
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• 2010

The power-controlled six-port element that can control the local oscillator signal power and receiving RF signal power was designed and implemented in this paper. The direct conversion six-port element configuration was proposed, which provides the constant six-port output power by controlling the six-port input power with various signal strength. The direct conversion six-port element protects the power detector element of six-port receiver from the saturation status and compensates the transmission performance degradation. For implementation of power-controlled six-port element, the power-controlled six-port element including the power controller was analyzed. The implemented power-controlled six-port element shows the power control capability of 36 dB and gain imbalance of about 1.6 dB, phase imbalance of about $4^{\circ}$ in the frequency range of 1.69 GHz. The measured results show the good performance as direct conversion front-end element.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.4
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• pp.76-85
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• 2008

In this paper, a 800 MHz 1 W cartesian feedback linearized power amplifier is designed and fabricated for TETRA handset application. For amplification of TETRA signal with 200 kHz narrow bandwidth, amplifier linearization performance of more than 30 dBc is improved through the cartesian feedback linearizer at the offset Sequency of ${\pm}25$ kHz. It is clear that the linearization performance is affected by imbalance of gain and phase between I/Q signals and also DC offset. The linearization performance can be maximized by the compensation of those influences. Cartesian feedback is suitable for a liearization technique of narrow band signal with QAM and another modulation signals, as well.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3A
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• pp.225-234
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• 2008

Orthogonal Frequency Division Multiplexing (OFDM) systems utilizing direct conversion receiver suffer from frequency selective (FS) and frequency independent (FI) phase and gain imbalances caused by imperfect local oscillator and low pass filter. In this paper, we analyze the impacts of the transmit/receive IQ imbalances on the system and propose the estimation and compensation schemes for those imbalances. The preamble signals coded by Alamouti scheme in the frequency domain could be used in the estimation of relatively large IQ imbalances with FS and FI characteristics and the estimation results are used for the compensation of distortions caused by the FI and FS IQ imbalances. The optimal maximum likelihood (ML) receiver or suboptimal ordered successive interference cancallation (OSIC) receiver utilizing the estimation results show symbol error rate (SER) performance improvement compared to zero-forcing (ZF) technique due to diversity gain inherent in the frequency domain IQ imbalances combined with the frequency selective channels.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.6
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• pp.573-582
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• 2010

In this paper, X-band transceiver for high resolution wideband SAR systems is designed and fabricated. Also as a technique for enhancing the performance, error compensation algorithm is presented. The transceiver for SAR system is composed of transmitter, receiver, switch matrix and frequency generator. The receiver especially has 2 channel mono-pulse structure for ground moving target indication. The transceiver is able to provide the deramping signal for high resolution mode and select the receive bandwidth for receiving according to the operation mode. The transceiver had over 300 MHz bandwidth in X-band and 13.3 dBm output power which is appropriate to drive the T/R module. The receiver gain and noise figure was 39 dB and 3.96 dB respectively. The receive dynamic range was 30 dB and amplitude imbalance and phase imbalance of I/Q channel was ${\pm}$0.38 dBm and ${\pm}$3.47 degree respectively. The transceiver meets the required electrical performances through the individual tests. This paper shows the pulse error term depending on SAR performance was analyzed and range IRF was enhanced by applying the compensation technique.

• CELLMED
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• v.13 no.14
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• pp.17.1-17.23
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• 2023

Menopause is a physiological phase experienced by all women as part of normal aging known as menopause. Per se, menopause is not a disease, but hormonal imbalance may lead to menopausal symptoms in some women. The unani physician described that in Sinn-i-Inḥiṭāṭ/ Sinn al-Yās, Burūdat (coldness) increases lead to Ihtibās al-Tamth (amenorrhea) that can occur naturally. Besides, Khilt Dam (blood) production decreases from the liver, slight production occurs, tends towards Burūdat. Therefore, at this age, Ihtibās al-Tamth is associated with Alāmāt Sinn al-Yās(menopausalsymptoms) including weight gain, loss of appetite, hirsutism, fatigue, headache, backache, arthralgia, neck pain, general myalgia, nervousness, anxiety, depression, and insomnia. The traditional Unani manuscripts are enriched with knowledge for the management of Alāmāt Sinn al-Yās. Consequently, an extensive exploration of classical texts concerning the management of Alāmāt Sinn al-Yās was undertaken. Moreover, PubMed, Scopus, Google Scholar, and other indexing databases were thoroughly explored for evidence-based approaches to managing menopausalsymptoms. The principle management as per Unani texts is to treat the cause of Alāmāt Sinn al-Yās. Unani medicines with emmenagogue, anti-inflammatory, analgesic, cardioprotective, and neuroprotective properties are beneficial for the amelioration of Alāmāt Sinn al-Yās. Unani Herbs such as Asgandh, Aslusūs, Khārkhasak, Tagar, Shuneez, Ustukhuddus, Zafran, and Majūn Najāh possess properties and are proven scientifically for their efficacy in Alāmāt Sinn al-Yās. Hence, the substantiation and preservation of traditional knowledge assume paramount importance in facilitating prospective research and proving invaluable in the modern era. Moreover, the conduct of randomized controlled trials, systematic reviews, and meta-analyses becomes imperative.