1,721,346 research outputs found
Oblique injection depth correction by two parallel OCT sensors guided handheld SMART injector
Get PDFWe present a SMART injector with two parallel common-path optical coherence tomography fibers to enable angle measurements and injection depth corrections for oblique subretinal injection. The two optical fibers are attached to opposite sides of a 33 G needle with known offsets and designed to pass through a 23 G trocar that has an inner diameter of 0.65 mm. By attaching a SMART system to a rotational stage, the measured angles are calibrated for minimal error from reference angles. A commercial eye model was used to evaluate the control performance, and injection experiments were performed on a phantom made of agarose gel and a porcine eye. © 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.1
Low frequency oscillations assessed by diffuse speckle contrast analysis for foot angiosome concept
Get PDFAn angiosome refers to a 3D tissue volume that is vascularized by a single artery and is a relatively new concept that is useful in vascular surgery; however, the direct relationship between arterial blood flow and micro-perfusion is still controversial. Here, we propose a diffuse speckle contrast analysis (DSCA), which is an emerging tissue perfusion monitoring modality, to investigate the correlations among low frequency oscillations (LFOs) measured from different areas on the feet of healthy subjects. We obtained reproducible results from the correlation analyses of LFOs, and their physiological implications were discussed. In order to confirm the changes in the frequency oscillations, we analyzed and compared the power spectral density changes due to heart rate variability in the electrocardiographic signal during reactive hyperemia and head-up tilt protocols. © 2020, The Author(s).1
A study on confocal heterodyne interference system using beam scanning method and compensation of the optical path difference
No full text학위논문(석사) - 한국과학기술원 : 기계공학전공, 2005.2, [ vii, 82 p. ]수년전부터 공초점의 원리와 디퍼렌셜 헤테로다인간섭의 원리를 동시에 이용한 시스템이 만들어져 오고 있으나, 그 대부분의 연구가 스테이지 스캐닝방법으로서 시간이 많이 걸리는 단점이 있었다. 본 연구에서는 시편의 정보를 빨리 얻기위해 빔스캐닝 방식을 채택한 공초점 헤테로다인 간섭측정시스템을 제안하였다. 그러나, 스캐닝 중 시스템 구성요소에 의해 발생하는 두 일차빔 사이의 광경로차가 문제가 된다. 따라서 이에 대한 보상이 필요하며 그 보상절차를 제안하였다. 또한 파장의 4분의 1을 넘는 높이단차의 시편을 FOV의 네 곳에서 비교 측정하였으며, 그 결과를 분석하였다.한국과학기술원 : 기계공학전공
A Single-Chip K-Band CMOS FMCW Radar Transceiver
No full textThis paper presents a K-band FMCW radar transceiver IC, which is integrated in 0.13-μm CMOS technology. In the transmitter part, the class-C topology is adopted in the VCO block to achieve good phase noise performance. In the receiver part, the high gain of the LNA sufficiently suppresses the noise of the next stages to achieve a good noise figure in the receiver and the linearity of the receiver was improved by adoption of a gain control block, thereby achieving a wide dynamic range. As a result, a conversion gain of 35.7 dB, a P1dB of -12.7 dBm, and a DSB noise figure of 5.5 dB are achieved in the receiver part. The tuning range of 23.8~24.5 GHz and the phase noise of -103.1 dBc/Hz @ 1MHz offset are achieved in the transmitter part. The transceiver chip consumes 181.5 mW from a 1.5 V power supply. Using this chip, the K-band FMCW radar module is implemented and verified by measurement of the distance of an object
A 1.83 GHz 28.5 dBm CMOS Power Up-Mixer
No full textA power up-mixer is proposed in this letter. A merged CMOS linear power amplifier (PA) and mixer allows low current consumption and smaller chip size than a conventional integrated transmitter including a mixer and a CMOS linear PA. The chip is fabricated in a 0.18 mu m CMOS process and in an integrated-passive-device. Measurements show a drain efficiency of 27% at 27.2 dBm of 1 dB compression point (P1dB) output power from 1.75 to 1.95 GHz. Power conversion gain is 26.4 dB and LO leakage is -43 dBc
A 79 GHz g(m)-boosted Sub-Harmonic Mixer with High Conversion Gain in 65nm CMOS
No full textIn this paper, a 79 GHz gm-boosted subharmonic mixer with high conversion gain is presented. As a gm-boosting technique, a transformer based feedback network with an NMOS bleeding path is proposed to achieve high conversion gain. The differential LO-driven subharmonic mixer has a simple structure and operates at low LO power. The measurement results show a conversion gain of 1.6 dB at a LO power of −5 dBm, a noise figure of 13 dB, and a 2LO-to-RF isolation of 38 dB. The power consumption of the sub-harmonic mixer is 12 mW. The circuit was fabricated using 65-nm CMOS technology with a chip area of 0.69×0.45 mm
Cerebral Blood Flow Monitoring by Diffuse Speckle Contrast Analysis during MCAO Surgery in the Rat
No full textThe rodent model has been used frequently to understand stroke pathophysiology, due to its low cost and the large spectrum of genetic strains available. Here, we present a diffuse speckle contrast analysis system (DSCA) with a 1 × 2 optical switch that was used to non-invasively assess cerebral blood flow (CBF) changes in the rat during intraluminal suturing for middle cerebral artery occlusion (MCAO) surgery. The blood flow index (BFI) in the left hemisphere was lower than that in the right hemisphere because the left middle cerebral artery was occluded. Furthermore, the performance of the DSCA system was compared with that of commercial laser Doppler flowmetry. The changes in the BFI measured by the two systems were correlated strongly. The DSCA system was less sensitive to motion artifacts and able to measure relatively deep tissue flow in the rat’s brain. In conclusion, the DSCA system secured CBF monitoring during surgery in a rodent model without craniotomy. © 2017 Current Optics and Photonics.1
Millimeter wave UWB pulse radar front-end ICs
No full textThe 26 GHz and 79 GHz UWB frequency bands are used for short-range radar applications for automobile. In this paper, single chip front-end ICs for both frequency bands are presented. The pulsed oscillator at 26 GHz can produce UWB short pulses. It consumes power only during short duty cycles; thus, it allows a power-efficient radar. A stereo radar, which comprises two synchronized radars, is demonstrated with the ICs. Hybrid beam forming techniques based on base-band delay are also demonstrated. The pulsed front-end architecture of the proposed 79 GHz UWB pulse radar is discussed, which is expected to reduce power consumption. The performance of some circuit elements is also reported
CMOS LNA with Darlington-pair for UWB systems
No full textA 3-5 GHz ultra-wideband CMOS low-noise amplifier fabricated using 0.18 mu m CMOS process is presented. To achieve wideband characteristics, a two-frequency matching method for input matching is proposed. A cutoff-frequency (f(T)) doubler using Darlington-pair is employed to achieve high gain from 2.4 to 5.4 GHz. The LNA achieves an average gain of 21 dB, input return loss less than -10 dB, and a noise figure of 2.85-4.5 dB at a power consumption of 23 mW The input 1 dB gain compression point (P1 dB) and IIP3 are -22 and -14 dBm at 4 GHz, respectively
Design and Analysis of 239 GHz CMOS Push-Push Transformer-Based VCO With High Efficiency and Wide Tuning Range
No full textA push-push transformer-based voltage-controlled oscillator (VCO) is proposed and analyzed to achieve high efficiency and a wide tuning range at sub-terahertz (THz) frequencies. Analyses show that the coupling factor of the transformer to obtain high output power (P-OUT) has to be carefully chosen by consideration of gate-to-drain voltage gain as well as matching impedances seen from the drain and to the gate of a VCO transistor at the 2nd harmonic frequency (2f(o)). Analysis also shows that the transformer-based resonator allows a wide tuning range. In addition, it has been shown that the introduction of a parallel inductor to a varactor leads to high P-OUT and low phase noise. The proposed 239 GHz VCO with a 65 nm CMOS process demonstrates the high efficiency of 1.45%, the P-OUT of -4.8 dBm, and the wide tuning range of 12.5% with a supply voltage of 1.2 V
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