• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.4 s.346
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• pp.67-74
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• 2006

We present the design of a radiometer in W-band which operates simultaneously with a single antenna configured FMCW radar. We choose a total power radiometer(TPR) which shares an antenna and a front-end with the radar for miniaturizing the system. We separate the radiometer signal from the radar signal using a diplexer in IF band. Because the radiometer has an unwanted transmitter section due to the common use of the MMW front-end with the radar, some additional noise signals caused by the transmitter degrade the sensitivity of the radiometer system. To compensate the degradation of sensitivity, we use matching circuits and a diode detector configured as the voltage doubler. Through some experiments, we have verified that the designed radiometer system has good performances in detecting metal targets tying at several hundred meters.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.2
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• pp.128-136
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• 2001

This paper evaluates the performance of an optic link in a frequency conversion based fiber-radio system. The proposed link structure simplifies a BS(base station) via making the MMW(millimeter wave) optical pilot tone generated in the CS(control station) be used in the uplink as well as in the downlink. To acquire the optical pilot tone, an EOM(electro-optic modulator) in the CS is biased in three different ways, i.e., MAB(maximum bias), MIB(minimum bias), QB(quadrature bias). We, depending on the biasing of the EOM, evaluate the link performances in two cases; one is for constant laser source power and the other for constant received DC optical power at a PD(photo detector). Based on the simulation results on the downlink CNR and the uplink SFDR(spurious free dynamic range), we finally deduce the effective EOM biasing for each case.

• Journal of Sensor Science and Technology
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• v.30 no.6
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• pp.436-440
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• 2021

The impact of the gate length (L_g) on the DC and high-frequency characteristics of indium-rich In_0.8Ga_0.2As channel high-electron mobility transistors (HEMTs) on a 3-inch InP substrate was inverstigated. HEMTs with a source-to-drain spacing (L_SD) of 0.8 ㎛ with different values of L_g ranging from 1 ㎛ to 19 nm were fabricated, and their DC and RF responses were measured and analyzed in detail. In addition, a T-shaped gate with a gate stem height as high as 200 nm was utilized to minimize the parasitic gate capacitance during device fabrication. The threshold voltage (V_T) roll-off behavior against L_g was observed clearly, and the maximum transconductance (g_{m_max}) improved as L_g scaled down to 19 nm. In particular, the device with an L_g of 19 nm with an L_SD of 0.8 mm exhibited an excellent combination of DC and RF characteristics, such as a g_{m_max} of 2.5 mS/㎛, On resistance (R_ON) of 261 Ω·㎛, current-gain cutoff frequency (f_T) of 738 GHz, and maximum oscillation frequency (f_max) of 492 GHz. The results indicate that the reduction of L_g to 19 nm improves the DC and RF characteristics of InGaAs HEMTs, and a possible increase in the parasitic capacitance component, associated with T-shap, remains negligible in the device architecture.

• Journal of the Korean Orthopaedic Association
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• v.56 no.1
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• pp.51-60
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• 2021

Purpose: Radiocarpal dislocation (RCD), which is caused by high-energy trauma, often involves radial styloid fractures and short radiolunate ligament (SRLL) injuries. Although SRLL injuries may occur as a simple rupture at the attachment site of radius, it may occur with a relatively large avulsed-fragment in the volar rim of the lunate facet of the radius. This study aimed to differentiate the injury type of SRLL and assess the differences in the treatment results depending on the treatment methods that have been applied in RCD with radial styloid fractures. Materials and Methods: Eighteen patients managed surgically with RCD were enrolled in this study. The patients were classified as Group 1 and Group 2 by using the Dumontier method. In this study, Group 2 was subdivided into 2A (purely ligamentous or small avulsion fracture of the volar rim of lunate facet) and 2B (large avulsed-fragment enough to internal fixation) according to the injury type of SRLL. Groups 2A and 2B were treated with direct repair and screw fixation, respectively. Pain, range of motion of the wrist joint, grip strength, and complications on final radiographs were examined. The outcomes were evaluated using patient-rated wrist evaluation (PRWE), and modified Mayo wrist score (MMWS). Results: All patients were Group 2 (six and twelve patients in 2A and 2B, respectively). The mean flexion to extension arch recovered 79%,and the mean grip strength was 72.9% of the uninjured side. Group 2A showed better recovery in extension, flexion and pronation than Group 2B, but there was no difference in radial deviation, ulnar deviation, supination, grip strength and pain. No differences in the PRWE and MMWS were observed between two groups. Complications included traumatic arthritis in seven patients and residual instability in five patients. Conclusion: When the SRLL was injured, the involvement of a large avulsion fracture on the anterior plane of the radiolunate did not affect the test results. On the other hand, it should be observed cautiously because avulsion fractures tend to disturb the joint's reduction through rotation or displacement. In addition, anatomical reduction and sturdy internal fixation are important for restoring the function of the SRLL.