• JSTS:Journal of Semiconductor Technology and Science
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• v.8 no.4
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• pp.295-301
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• 2008

Recently, the demand on mm-wave (millimeter-wave) applications has increased dramatically. While circuits operating in the mm-wave frequency band have been traditionally implemented in III-V or SiGe technologies, recent advances in Si MOSFET operation speed enabled mm-wave circuits realized in a Si CMOS technology. In this work, a 58 GHz CMOS LC cross-coupled VCO (Voltage Controlled Oscillator) was fabricated in a $0.13-{\mu}m$ Si RF CMOS technology. In the course of the circuit design, active device models were modified for improved accuracy in the mm-wave range and EM (electromagnetic) simulation was heavily employed for passive device performance predicttion and interconnection parasitic extraction. The measured operating frequency ranged from 56.5 to 58.5 GHz with a tuning voltage swept from 0 to 2.3 V. The minimum phase noise of -96 dBc/Hz at 5 MHz offset was achieved. The output power varied around -20 dBm over the measured tuning range. The circuit drew current (including buffer current) of 10 mA from 1.5 V supply voltage. The FOM (Figure-Of-Merit) was estimated to be -165.5 dBc/Hz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.9
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• pp.892-899
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• 2013

This paper discusses difficulties in precise measurements of the scattering parameters in (sub-)millimeter-wave range and tips for more accurate measurements, and provides measurement examples in the G-band(140~220 GHz). First, one investigates the differences in operating principles of scattering parameters measurement systems used in microwave and (sub-)millimeter-wave ranges and describes tips for better operation of the (sub-)millimeter-wave scattering parameters measurement system. In addition, one describes tips for better transmission properties and connection repeatability of waveguides and a precise measurement method for devices with small reflection coefficients.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.223-227
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• 2006

The millimeter-wave radar is positioned as a key, basic ITS technology supporting safe driving, because millimeter wave allows radar to see small distant objects. This system is considered the collision-avoidance radar available in some cars. This system employs poised radar operating within the frequency range $76\sim77GHz$. Radar systems create two major problems(false images and system-to-system interference). False echoes cause driving hazards. These problems can be eliminated through the use of EM wave absorber. Therefore, we designed and fabricated EM wave absorber using permalloy. It has the thickness of 1.4 mm with composition of permalloy:CPE=70:30 wt% and absorption ability higher than 18 dB in the frequency range $76\sim77GHz$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.12
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• pp.7-11
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• 2007

In this paper, we proposed the dual-mode stepped impedance ring resonator bandpass filter for MMIC (Microwave Monolithic Integrated Circuit) applications using the dielectric-supported air-gapped microstrip line (DAML). The ring resonator fabricated by surface micromachining technology. This filter consists of a DAML resonator layer and a CPW feed line. The DAML ring resonator is elevated with $10{\mu}m$ height from GaAs substrate surface. This bandpass filter is $1-{\lambda}g$ type stepped impedance ring resonator including dual-mode resonance. From the measurements, we obtained attenuation of over 15 dB and insertion loss of 2.65 dB at the center frequency of 97 GHz. Relative bandwidth is about 12 % at 97 GHz. Furthermore, the proposed bandpass filter is useful to integrate with conventional MMICs.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.857-860
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• 2005

We reported 94 GHz, low conversion loss, and high isolation single balanced active-gate mixer based on 70 nm gate length InGaAs/InAlAs metamorphic high electron mobility transistors (MHEMTs). This mixer showed that the conversion loss and isolation characteristics were 2.5 ${\sim}$ 2.8 dB and under -30 dB, respectively, in the range of 93.65 ${\sim}$ 94.25 GHz. The low conversion loss of the mixer is mainly attributed to the high-performance of the MHEMTs exhibiting a maximum drain current density of 607 mA/mm, a extrinsic transconductance of 1015 mS/mm, a current gain cutoff frequency ($f_t$) of 330 GHz, and a maximum oscillation frequency ($f_{max}$) of 425 GHz. High isolation characteristics are due to hybrid ring coupler which adopted dielectric-supported air-gapped microstrip line (DAML) structure using surface micromachined technology. To our knowledge, these results are the best performance demonstrated from 94 GHz single balanced mixer utilizing GaAs-based HEMTs in terms of conversion loss as well as isolation characteristics.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.8
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• pp.45-51
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• 2007

We designed and fabricated the planar graded-gap injector GaAs Gm diodes with $1.6{\mu}m$ active length for operation at 94 GHz. The fabrication of the Gunn diode is based on MESA etching, Ohmic metalization, and overlay metalization. The measured negative resistance characteristics of the graded-gap injector GaAs Gunn diodes are examined for two different device structures changing the distance between the cathode and the anode electrodes. Also, we discuss the DC results under the forward and the reverse biases concerning the role of the graded-gap injector. It is shown that the structure having the shorter distance between the cathode and the anode electrode has higher peak current, higher breakdown voltage, and lower threshold voltage than those of the larger distance.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.1
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• pp.159-165
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• 2018

In this paper, a low-loss wideband waveguide transducer is proposed for millimeter-wave communication and radar applications. A conventional E-plane probe transducer is generally designed using thin and flexible substrate at millimeter-wave frequencies, considering the very small waveguide size. However, it results in serious performance degradation caused by the bending of the substrate. In order to alleviate this problem and provide a reliable performance, we propose an extended E-plane probe transducer where the probe substrate is extended to and fix ed in the slit area formed in the waveguide wall. It is fabricated using $127{\mu}m$-thick substrate with dielectric constant of 2.2. The measurement in the back-to-hack configuration shows the excellent insertion loss of 1.35 dB (${\pm}0.35dB$) including the loss of 3 cm-long thru waveguide and return loss better than 13.8 dB over entire W-band (75-110 GHz). Therefore, it can be effectively applied for millimeter-wave high-speed communications and high-sensitivity radars.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.5
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• pp.123-129
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• 2018

Recently, as required wireless communication traffic increase, millimeter wave mobile technologies that can secure broadband spectrum are gaining attention. However, the path loss is high in the millimeter wave channel. Massive MIMO system is being researched in which can complement the path loss by beamforming by equiped large-scale antenna at the base station. While legacy beamforming techniques have analog and digital methods, practical difficulties exist for application to massive MIMO systems in terms of system complexity and cost. Therefore, this paper studies a hybrid beamforming scheme for massive MIMO system in the millimeter wave band. Also this paper considers spatial multiplexing scheme to serve multi-users with multiple received antennas. Gains of the beamforming and the spatial multiplexing schemes are evaluated by analyzing the spectral efficiency.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.5
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• pp.163-167
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• 2016

We have developed a millimeter-wave radiometer system for applications in the fields of medical imaging. In this paper, we introduced the brightness temperature measurement in the human body using Millimeter-wave Radiometer. Calibration of sensitivity of the radiometer system is essential to measure equivalent temperature (brightness temperature) of objects. We have developed, as a calibration source, a new type of black body for the millimeter wave region with temperature control capability. The system noise figure and temperature sensitivity of the system measured using the blackbody are 3.3 dB and 0.1 K, respectively. The brightness temperature of human body through clothes was measured to be around $38^{\circ}$[C].

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.7
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• pp.728-736
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• 2014

Due to the recent development of mobile wireless telecommunication, RRHs(Remote Radio Heads) are widely being utilized to expand the cell coverage. Wire-link, an existing connection between DU(Digital Unit) and RRH through fiber cables, is considered to have limitations in relation to cost for a wide range of applications. This paper focuses on replacing the wire-link by wireless transmission using millimeter-wave, and implementing cellular network system through RRH from a remote location. After an influence element analysis on millimeter-wave wireless link transmissions, a comparative analysis between wireless link and an existing fiber link method will be made by utilizing currently commercialized LTE(Long Term Evolution), to prove the compatibility of millimeter-wave wireless link RRH method in replacing fiber link method without a significant decline in data transmission performance.