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5G NR 통신을 위한 GaAs HBT 3.5 GHz 대역 도허티 전력 증폭기
손정택,임정택,이재은,송재혁,김준형,백민석,이은규,김철영 한국전자파학회 2023 한국전자파학회논문지 Vol.34 No.12
This paper discusses the design of a 3.5-GHz band Doherty power amplifier using a 0.5-μm GaAs process. The design was optimized through load-pull simulations, employing the second harmonic trap filter at the output of the peaking amplifier to maintain high linearity. Measurement results of the fabricated power amplifier showed a maximum saturated power of 27.8 dBm and power-added afficiency (PAE) of 34.3 % in the 3.5 GHz band. Additionally, with a 5G NR 64-QAM 100-MHz modulated signal, it achieved a linear output power of 22 dBm with an EVM of 5.6 % and a linear output power added efficiency of 19.8 %.
0.5-μm GaAs pHEMT 공정을 이용한 4.4∼5.0 GHz 저잡음 증폭기
손정택,임정택,이재은,송재혁,김준형,백민석,이은규,김철영 한국전자파학회 2023 한국전자파학회논문지 Vol.34 No.12
This paper discusses the design of a 4.4∼5.0 GHz low-noise amplifier (LNA) using a 0.5-μm GaAs pHEMT process. The transistor size was optimized to address the mismatch between optimal noise and input impedance owing to the unique noise sources of the transistor and parasitic characteristics, achieving a low noise figure with high input and noise optimal impedance matching without additional inter-stage loss components. The designed low-noise amplifier consumed 48 mW of power in the 4.4∼5.0 GHz range, demonstrating more than 23 dB of gain and a low noise figure of less than 0.9 dB. The size of the fabricated circuit was 1.8×1.4 mm2 .
22.5–27GHz High Suppression Frequency Tripler with Excellent Output Power Flatness in 65nm CMOS
손정택,최한웅,김철영 한국과학기술원 반도체설계교육센터 2021 IDEC Journal of Integrated Circuits and Systems Vol.7 No.2
This paper presents a high harmonic suppression frequency tripler with an excellent output power flatness in 65nm CMOS process. In order to achieve a high first, second and forth harmonic suppression, the highly balanced different transformer is employed. The proposed tripler multiplies 7.5 - 9GHz to 22.5 - 27GHz with ±1.5-dB ripple. It suppresses the harmonic up to 40-dBc and consumes a DC power of 20 mW at a maximum operating point. The tripler occupies a 0.259 × 0.742 mm2.
Hemoglobin A1c May Be an Inadequate Diagnostic Tool for Diabetes Mellitus in Anemic Subjects
손정일,이상열,우정택,황진경,진상욱,전숙,오승준,김성운,김영설 대한당뇨병학회 2013 Diabetes and Metabolism Journal Vol.37 No.5
Background: Recently, a hemoglobin A1c (HbA1c) level of 6.5% has been determined to be a criterion for diabetes mellitus (DM), and it is a widely used marker for the diagnosis of DM. However, HbA1c may be influenced by a number of factors. Anemia is one of the most prevalent diseases with an influence on HbA1c; however, its effect on HbA1c varies based on the variable pathophysiology of anemia. The aim of this study was to determine the effect of anemia on HbA1c levels. Methods: Anemic subjects (n=112) and age- and sex-matched controls (n=217) who were drug naive and suspected of having DM were enrolled. The subjects underwent an oral glucose tolerance test and HbA1c simultaneously. We compared mean HbA1c and its sensitivity and specificity for diagnosing DM between each subgroup. Results: Clinical characteristics were found to be similar between each subgroup. Also, when glucose levels were within the normal range, the difference in mean HbA1c was not significant (P=0.580). However, when plasma glucose levels were above the diagnostic cutoff for prediabetes and DM, the mean HbA1c of the anemic subgroup was modestly higher than in the nonanemic group. The specificity of HbA1c for diagnosis of DM was significantly lower in the anemic subgroup (P<0.05). Conclusion: These results suggest that the diagnostic significance of HbA1c might be limited in anemic patients.
Evaluation of Dynamic Recrystallization Behaviors in Hot-Extruded AA5083 Through Hot Torsion Tests
손광태,이지운,정택균,최현진,김상욱,Shae K. Kim,윤영옥,현숭근 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.1
Hot torsion tests were carried out to evaluate the dynamic recrystallization (DRX) behaviors of hot-extruded AA5083 at various deformation conditions. Flow curves showed the peak followed by the flow softening to the steady-state or to the failure strain, indicating that the DRX occurred during deformation. The peak stress increased as the temperature decreased and the strain rate increased. Constitutive relationship and Zener-Hollomon (Z) parameter were used to evaluate the DRX characteristics. Peak and steady-state stresses were generalized by the dimensionless parameter, Z/A, to reveal the DRX mechanism. The empirical relationship of the DRXed grain size with the deformation conditions was established, and decreased with increasing Z parameter. The relationship for the fraction of DRXed grains was established as a function of the effective strain at given deformation conditions from the experimental data. The Avrami relationship based on micro-hardness measurement was used to describe the DRX kinetics, and was fitted well with the observed DRX fraction.
Insufficient Experience in Thyroid Fine-Needle Aspiration Leads to Misdiagnosis of Thyroid Cancer
손정일,이상열,우정택,박원서,변종규,김유진,변자민,진상욱,존석,오승준,김성운,김영설 대한내분비학회 2014 Endocrinology and metabolism Vol.29 No.3
Background: Fine-needle aspiration (FNA) of the thyroid is a widely accepted confirmatory test for thyroid cancer with high sensitivity and specificity. FNA is a simple procedure that is learned by many clinicians to enable accurate diagnosis of thyroid cancer. However, it is assumed that because the FNA test is a relatively simple procedure, its cytologic results are reliable regardless of the operator’s experience. The aim of this study was to evaluate the differences in the diagnostic indices of FNA between operators with different levels of experience. Methods: A total of 694 thyroid FNA specimens from 469 patients were reviewed, and were separated based on the experience of the clinicians who performed the procedure. One hundred and ninety were categorized in the experienced group, and 504 in the inexperienced group. All FNA results were then compared with histological data from surgically resected specimens, and the sample adequacy and diagnostic accuracy of the groups were compared. Results: The age, gender, and nodule size and characteristics were similar in both groups. The sample adequacy rate was not significantly different between the experienced and nonexperienced groups (96.3% vs. 95.4%, P=0.682). However, the non-experienced group had a higher false-negative rate than the experienced group (6.4% vs. 17.2%, P=0.038), and the sensitivity of the FNA test also tended to be lower in the nonexperienced group (95.6% vs. 88.9%, P=0.065). Conclusion: These results suggest that FNA operators who have less experience may miss cases of thyroid cancer by performing the procedure incorrectly. As such, the experience of the FNA operator should be considered when diagnosing thyroid cancer. When clinicians are being trained in FNA, more effort should be made to increase the accuracy of the procedure; therefore, enhanced teaching programs and/or a more detailed feedback system are recommended.
GPS용 RF Front-End 수신단을 위한 L 대역 저잡음 증폭기 개발
이병찬,손정택,임정택,이재은,송재혁,김준형,백민석,박종성,이은규,김철영 한국전자파학회 2024 한국전자파학회논문지 Vol.34 No.2
GPS의 프론트-엔드 수신단에서는 잡음 지수가 매우 중요하며 잡음 지수가 낮고 크기가 작은 저잡음 증폭기를 요구한다. 본 논문에서는 0.18 μm CMOS 공정을 이용한 L 대역 저잡음 증폭기의 설계에 관한 내용이다. 저잡음 특성을 위해입력단 직렬 인덕터를 제거하고 트랜지스터의 유효폭(effective width)을 늘려 임피던스 정합을 이루어 냈으며 작은 칩크기를 위해 높은 인덕턴스를 요구하는 인덕터들을 적층 구조로 제작하였다. 제작된 저잡음 증폭기는 1.4 GHz부터 2.1 GHz에 이르는 대역에서 2.5 dB 이하의 잡음 지수, 10.57 dB 이상의 반사손실, 17.3 dB의 최고 이득, 1.05 mm×0.78 mm의크기를 달성하였다. In the front-end receiver of a GPS, the noise figure is extremely important and requires a low-noise amplifier with a low noise figure and small size. This study aims to investigate the design of an L-band low-noise amplifier using the 0.18-μm CMOS process. For low-noise characteristics, the input series inductor was removed, the effective width of the transistor was increased to achieve impedance matching, and the inductors requiring high inductance had laminated structures with small chip sizes. The low-noise amplifier achieved a noise figure of less than 2.5 dB, a return loss of more than 10.57 dB, a peak gain of 17.3 dB, and a size of 1.05 mm×0.78 mm in frequency from 1.4∼2.1 GHz.
저칼륨혈증 및 저인산혈증으로 유발된 방실전도장애를 동반한 갑상샘 중독성 주기성 마비 1례
김현수,위정국,손정일,최문찬,오승준,우정택,김성운,김진우,김영설,전숙 대한응급의학회 2011 대한응급의학회지 Vol.22 No.5
Thyrotoxic periodic paralysis (TPP) occurs in 2% of the asian patients with hyperthyroidism and is characterized by bilateral flaccid paralysis of the extremity, especially lower limbs. It is well-known that hypokalemia is usually accompanied by TPP. However, hypophosphatemia is usually mild and well neglected. Although paralysis is generally recovered without treatment, in some cases, patients with TPP may die due to cardiopulmonary complications, such as cardiac arrhythmia. Therefore, proper and rapid replacement of potassium is essential. But it should be acknowledged that replacement may cause a rebound. TPP is often unrecognized and over-treated in the emergency room due to its non-specific symptoms. This is why clinicians must be familiar with this disease and its diagnostic clues such as Echocardiography change and clinical features. This is a case report of a 29-year-old male presenting with TPP accompanied by hypokalemia, hypophosphatemia and second degree atrioventricular block, who showed rebound hyperkalemia and hyperphosphatemia after rapid replacement of electrolytes. EKG changed to the normal sinus rhythm in the end after the correction of the electrolytes.