필더의 선택도를 포함한 새로운 IP3 계산에 관한 연구

김학선 대전산업대학교 반도체기술연구소 1999 半導體技術硏究所報 Vol.1 No.-

수신기의 3차 인터셉트 포인트(Third order Intercept Point: IP3)는 수신기 회로나 시스템의 최소 수신감도와 밀접한 관계를 갖는 선형성을 평가하는 척도로 사용되고 있다. 본 논문에서는 종속 연결된 수신 시스템의 IP3를 개선하기 위하여, 이전에는 계산되지 않았던 수신 단에서 사용되는 필터의 선택도를 고려한 새로운 계산 방법을 제시하였다. 수식의 유도 결과 필터의 선택도를 높임으로써 시스템 전체의 IP3를 증가 시킬 수 있음을 입증하였다. The third order intercept point is used to calculate the linearity of receiver systems that is closely related to the minimum sensitivity. This paper presents a modification of the traditional receiver intercept point (IP) cascading equation for the third order IM case. The new mathematical derivation for the third order IP cascading equation incorporates the effect of adding selectivity (S) between receiver stages to improve the overall receiver input IP3.

기가주파수대 멀티플렉서 설계에 관한 연구

김학선,최병하,이형재 한국통신학회 1990 韓國通信學會論文誌 Vol.15 No.2

갈륨비소를 사용한 SCFL을 채택하여 4:1 시분할 멀티플랙서를 설계하였다. 설계된 멀티플렉서는 2:1 시분할 주파수 분할기를 사용하여 2:1 멀티플렉서 2단을 사용하였다. 시뮬레이션 결과, 최고 동작 주파수는 6.25GHz이었고 전력소모는 192mW이었다. 따라서 최대 출력 bit율은 12.5Gbit/sec를 얻었다. 이 결과 기존의 멀티플렉서에 비해 속도 및 전력소모 면에서 상당히 개선된 것이다. A 4:1 Time Division Multiplexer(MUX) had been designed in using GaAs Source Coupled FET Logic(SCFL), Designed Multiplexer uses a time division frequency divider and two stage of singnal combining 2:1 multiplexer. The performance of the multiplexer is verified by PSPICE simulation. Designed circuit operates up to 12.5Gbit/s with a power dissipation of 192mW. These performance are more advanced than other reported multiplexer in the speed and power dissipation.

초고속 4 : 1 멀티플렉서의 설계 ( Design of the High-Speed 4 : 1 Multiplexer )

김학선,최병하,이형재 대한전자공학회 1989 대한전자공학회 학술대회 Vol.1989 No.1

抒情的 世界에 投射된 原型의 아니무스

金學善 한국아동문학학회 1996 한국아동문학연구 Vol.- No.5

흰쥐의 척수손상 망상체핵 유발 전위의 변화

김학선,김상수,심대무,김태요,임경수,김종환 대한척추외과학회 1999 대한척추외과학회지 Vol.6 No.1

목적 : 척수의 손상 후 운동 회복은 세로토닌계 축삭이 재생하여 운동 신경원과 새로운 접합부를 형성하여 이루어진다고 믿어진다. 해부학적으로 신경사가 재생된다면 전기 생리적 방법으로도 이를 증명할 수 있어야 한다. 이와 관련하여 흉추부에 척수손상을 입은 쥐에서 뒷다리 운동을 회복하는 시기는 대뇌피질을 자극하여 유발된 운동 유 발 전위의 회복과 밀접한 관계가 있는 것으로 알려졌다. 이러한 사실을 확인하고 회복 기전을 밝히는데 도움이 되고자 백서 제 5-6 흉추간 척수의 배측 1/4을 남기고 손상을 준 후 망상체 척수로 유발 전위를 측정하였다. 대상 및 방법 : 80 마리의 백서를 무균 수술을 통하여 제 5-6 흉추간을 제 11 번 칼을 이용하여 손상을 준후 손상 직후부터 최장 6 1일간 망상체 척추로 유발 전위를 측정하였다. 손상준 동측의 망상체 핵을 자극하고, 유발 전위의 측정은 제 2-3 요추간에 후궁 절제술후 2 M Nacl (1.5-2.0 M Ohm)으로 채워진 미세 전극을 사용하였다. 망상체핵 자극에 의한 운동 유발 전위 발생을 감지하기 위하여 제 6 흉추에서 경막외 측정을 하는 동시에 유리 미세 전극을 이용하여 제 2-3 요추부 척수내 측정을 수행하였다. 결과 : 요추의 배측 전방에서 형성된 장전위를 양측에서 측정하여 다음과 같은 결과를 얻었다. 1) 제 5-6 흉추간에 서 손상을 준 직후 동측의 제 2-3 요추간에서는 장전위가 거의 소멸 하였고, 반대측은 변함이 없이 유지 되었다. 감 소된 손상측의 장전위는 손상후 1주부터 회복 되었으며, 이후 크기가 점차 증가하여 4주 째에는 건측의 장전위 보 다 오히려 4배나 증가 하였다. 2) 장전위의 크기가 측정된 요추부의 척수을 배측에서부터 적은 간격으로 지도화 하 였다. 건측에서는 회백질의 배측 경계부에서 가장 크고, 이에 비하여 손상된측에서는 배측에서 약간 요측으로 이동 하였다. 결론 : 망상체핵 유발 전위가 가장 크게 기록되는 척수내의 위치를 조사한 결과 회백질부와 복측 백질 경계부에서 배측으로 이동하였음을 발견하였다. 따라서 망상체핵 유발 전위가 다시 나타나는 것은 왼쪽에서 완전히 절단되었던 망상핵 척수로가 남아있던 오른쪽으로부터 척수의 중앙선을 건너 재생되어 복측 회백질부의 운동 신경원과 연결을 이루기 때문으로 추정되었다. 배측의 망상 척수로 유발 전위는 손상후 시간의 경과에 따라 회복 되었으며, 4 주 이 후에는 건측 보다 크게 회복 되었다. 이또한 망상체 척수로 유발 전위는 동측과 반대측을 경유하여 내려오며, 손상 후 재조합되어 회복함을 보여준다. Study design : There is a prospective study of 80 Sprague-Dawley rats which were made at the spinal cord lesion T5/6 level, sparing only one ventral quadrant. We monitered medullary reticulospinal neurons(RtN) evoked potentials at the L2/3 level which laminectomy was performed. Objective : to investigate changes in the physiological responses of motor neurons to stimulation of the medullary reticular formation following partial spinal cord lesions sparing only the ventral quadrant. Summery and Back ground data : There were many report that the animals with spinal cord lesion recovered well-coordinated fourlimb locomotion within 2-3 weeks. The time course of the functional recovery of this hindlimb locomotion was correlated with the recovery of motor evoked potentials(MEP), which originate from reticular nuclei. Therefore, it was hypothesized that the return of locomotor function after incomplete spinal cord injury may partially rely on the reorganization of descending inputs to ventral horn neurons previously occupied by damaged afferents. Materials and methods : Total 80 Sprague-Dawley rats were used in this study. Under sterile conditions, spinal cord lesions were made at the T5/6 level using a No. 11 blade, sparing only one ventral quadrant. The animals allowed to survive from one day to 61 days. To monitor RtN evoked potentials, laminectomies were performed at L2/3 level. Field potentials were recorded using a glass microelectrode filled with 2 M NaCl(1.5-2.0 M Ohm). Cord dorsum potentials were also epidurally monitored at L2/3 using a pair of teflon-coated wires. The gigantocellular reticular nucleus ipsilateral to the spared ventral cord was stimulated using a monopolar tungsten microelectrode. Results : The field potentials generated in the ventral horn of the lumbar cord were recorded bilaterally. In some animals field potentials were monitored just before and right after the spinal cord lesion. 1) Following spinal cord lesion at T5/6, the amplitude of RtN evoked potentials declined significantly in the L2/3 ventral gray matter of the completely lesioned side. Field potentials monitored below the ipsilaterally spared ventral quadrant remained unchanged. Depressed RtN evoked potentials in the ventral cord gradually increased during the next four weeks, and finally reached greater than 4 times of the amplitude monitored on the contralateral side. 2) The sites in which field potentials could be monitored in the lumbar spinal cord were mapped. In normal rats, the largest field was monitored near the ventral margin of the gray matter. On the other hand, in spinal cord injured animals, the largest field potentials were located in more dorsal aspects of the ventral horn, suggesting a structural reorganization of the descending inputs has taken place. Conclusion : The RtN evoked potentials in the ventral horn increased gradually for several weeks after the injury. The returned RtN evoked potentials below the completely lesioned side of spinal cord were larger than those seen in normal spinal cord. The time course of returning evoked potentials below the lesioned side of the spinal cord seems to coincide with the restitution of same-side hindlimb locomotion.

구내 무선 통신 서비스 동향 분석

김학선 한국조명전기설비학회 2004 조명.전기설비 Vol.18 No.2

유비쿼터스 컴퓨팅 시대가 매우 빠르게 도래하면서 가정이나 회사의 정보 가전기기들이 초고속, 대용량을 전송하는 고속의 디지털 가전기기들로 바뀌어 가고 있으며 이들을 하나의 네트워크로 구성하고자 하는 요구가 증가하고 있다. IEEE 802.11과 IEEE 802.15.3a Task Group에서는 대량의 정보를 고속으로 통신하는 기술의 표준화를 위해 연구하고 있으며, 간단한 시스템을 이용하여 저속의 통신을 저렴한 가격으로 이루려는 또 하나의 주류인 ZigBee (IEEE802.15.4), Bluetooth (IEEE802.15.1) 시스템이 개발되고 있다. (중략)

갈륨비소 MESFET를 이용한 고이득 연산 증폭기의 입력단 설계

김학선,김은노,이형재 한국통신학회 1992 한국통신학회논문지 Vol.17 No.1

In the high speed analog system satellite communication system, video signal processing and optical fiber interface circuits, GaAs high gain operational amplifier is advantageous due to obtain a high gain because of its low transconductance and other drawbacks, such as low frequency dispersion and process variation. Therefore in this paper, a circuit techniques for improving the voltage gain for GaAs MESFET amplifier is presented. Also, various types of existing current mirror and current mirror proposed are compared.To obtain the high differential gain, bootstrap gain enhancement technique is used and common mode feedback is employed in differential amplifier.The simulation results show that gain is higher than that of basic amplifier about 18.6dB, and stability and frequency performance of differential amplifier are much improved.

SPICE에서의 BJT F-1 잡음 해석 파라미터의 추출에 관한 연구 ( A Study on the BJT F-1 Noise Parameter Extraction for SPICE )

김학선,이형재 대한전자공학회 1995 대한전자공학회 학술대회 Vol.1995 No.11

Comparison of Surgical Outcomes in Thoracolumbar Fractures Operated with Posterior Constructs Having Varying Fixation Length with Selective Anterior Fusion

김학선,Seung Yup Lee,Ankur Nanda,Ju Young Kim,박진오,문성환,이환모,김호중,Huan Wei,문은수 연세대학교의과대학 2009 Yonsei medical journal Vol.50 No.4

Purpose: Surgical treatment in the case of thoracolumbar burst fractures is very controversial. Posterior instrumentation is most frequently used, however, but the number of levels to be instrumented still remains a matter of debate. Materials and Methods: A total of 94 patients who had a single burst fracture between T11 and L2 were selected and were managed using posterior instrumentation with anterior fusion when necessary. They were divided into three groups as follows; Group I (n = 28) included patients who were operated by intermediate segment fixation, Group II (n = 32) included patients operated by long segment fixation, and Group III (n = 34) included those operated by intermediate segment fixation with a pair of additional screws in the fractured vertebra. The mean follow-up period was twenty one months. The outcomes were analyzed in terms of kyphosis angle (KA), regional kyphosis angle (RA), sagittal index (SI), anterior height compression rate, Frankel classification, and Oswestry Disability Index questionnaire. Results: In Groups II and III, the correction values of KA, RA, and SI were much better than in Group I. At the final follow up, the correction values of KA (6.3 and 12.1, respectively) and SI (6.2 and 12.0, respectively) were in Groups II and III found to be better in the latter. Conclusion: The intermediate segment fixation with an additional pair of screws at the fracture level vertebra gives results that are comparable or even better than long segment fixation and gives an advantage of preserving an extra mobile segment. Purpose: Surgical treatment in the case of thoracolumbar burst fractures is very controversial. Posterior instrumentation is most frequently used, however, but the number of levels to be instrumented still remains a matter of debate. Materials and Methods: A total of 94 patients who had a single burst fracture between T11 and L2 were selected and were managed using posterior instrumentation with anterior fusion when necessary. They were divided into three groups as follows; Group I (n = 28) included patients who were operated by intermediate segment fixation, Group II (n = 32) included patients operated by long segment fixation, and Group III (n = 34) included those operated by intermediate segment fixation with a pair of additional screws in the fractured vertebra. The mean follow-up period was twenty one months. The outcomes were analyzed in terms of kyphosis angle (KA), regional kyphosis angle (RA), sagittal index (SI), anterior height compression rate, Frankel classification, and Oswestry Disability Index questionnaire. Results: In Groups II and III, the correction values of KA, RA, and SI were much better than in Group I. At the final follow up, the correction values of KA (6.3 and 12.1, respectively) and SI (6.2 and 12.0, respectively) were in Groups II and III found to be better in the latter. Conclusion: The intermediate segment fixation with an additional pair of screws at the fracture level vertebra gives results that are comparable or even better than long segment fixation and gives an advantage of preserving an extra mobile segment.

콜피츠 전압제어 발진기 동작의 새로운 해석 및 구현에 관한 연구

김학선,황인갑,이형재 한국통신학회 1994 한국통신학회논문지 Vol.19 No.12

In this paper, We analyze Colpitts type voltage contrqlled oscillator(VCO) used in personal handheld phone using a nonlinear analysis with third-order model. The resul shows the non-exponentially decaying shifting bias superimposed on the oscillator output which is different with the exponentially decaying shifting bias from the linear analysis. The stable oscillation criterion during a frequency change in a design of VOC can be also determined using proposed non-linear analysis. The theory is confirmed using PSPICE simulation and the experimental result of GaAs VCO matched very well with the theory.