• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.96-99
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• 2003

This paper presents the development of a Ku-band Low Noise Amplifier with the Noise figure of 1.4dBmax, the gain of 35dB, and the In/Out Return toss of -22dB/-18dB in the frequency range from 14 to 14.5GHz for Satellite transponders. All RF components were assembled using a hybrid technology with 15-mil thin-film substrates. The mechanical and thermal design of the housing was performed considering a vibration and a vacuum of space environment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.6
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• pp.843-849
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• 1998

A voltage controlled oscillator using dielectric resonator for 2.4 GHz WLL System is designed and fabricated. To improve the phase noise characteristic resonator is used as an inductor of VCO. At the bias condition of 5 V and 10 mA, the output power and phase noise in the operating frequency range of 2210~2240 MHz are 0 dBm and 100 dBc/Hz 10 kHz offset from the carrier, respectively. The phase noise and harmonic response of fabricated VCO are suitable for WLL system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.3
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• pp.365-371
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• 2000

In this paper, we introduce a noise reduction method using polarizers in a wireless optical interconnections. If we use polarizers in a differential detector, the noise reduction capability is improved. In a case that two optical signal beams of similar wavelength are overlapped in space and crosstalk is a serious problems, we can detect each channel separately without crosstalk using two orthogonal polarizers. This method is very simple and easy to use.

• Journal of electromagnetic engineering and science
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• v.4 no.1
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• pp.37-42
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• 2004

In this paper, LNB(low noise block) downconverter MMIC is designed for Ku-band satellite communication system using InGaP/GaAs HBT high linear process. Designed MMIC consists of low noise amplifier, double balanced mixer, and IF amplifier with a total chip area of 2.6${\times}$1.1 $\textrm{mm}^2$. Designed MMIC has the characteristics of over 37.5 ㏈ conversion gain, 14 ㏈ noise figure, ripple of 3 ㏈, and output-referred $P_{1dB}$TEX>(1 ㏈ compression power) of 2.5 ㏈m with total power dissipation of 3 V, 50 mA.

• Journal of electromagnetic engineering and science
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• v.7 no.2
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• pp.64-68
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• 2007

An InGaP/GaAs HBT based differential Colpitts voltage control oscillator(VCO) is presented in this paper. In the VCO core, two switching transistors are introduced to steer the core bias current to save power. An LC tank with an inductor quality factor(Q) of 11.4 is used to generate oscillation frequency. It has a superior phase noise characteristics of -130.12 dBc/Hz and -105.3 at 1 MHz and 100 kHz frequency offsets respectively from the carrier frequency(1.566 GHz) when supplied with a control voltage of 0 volt. It dissipates output power of -5.3 dBm. Two pairs of on-chip base collector (BC) diodes are used in the tank circuit to increase the VCO tuning range(168 MHz). This VCO occupies the area of $1.070{\times}0.90mm^2$ including buffer and pads.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.851-852
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• 2006

This paper presents methods to reduce acoustic noise in interior permanent magnet (IPM) motor. Mechanical and magnetic sources are considered to reduce noise of the machine, and structural and electromagnetic designs are performed. In the structural design to reduce mechanical source, the structural resonances are moved to higher frequency for enhancement of stiffness. Then, the electromagnetic design to reduce magnetic source, the amplitudes of magnetic force harmonics are reduced by using objective function of response surface methodology (RSM). The validity of the design process and objective functions is confirmed with their calculated and experimental results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.622-629
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• 2001

An engineering model VCO with a good phase noise for Ku-band satellite transponder is designed using a nonlinear design methodology. It generates frequencies from 1,745 and 1,755 MHz with control voltages from 0 to 5 V DC. This unit requires 7 mA of current from 5 V DC supply voltage. Phase noise characteristics of the manufactured VCO exhibit -114 dBc/Hz @10 kHz offset and -131 dBc/Hz @100 kHz of offset and its output power is 5 dBm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.1
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• pp.110-115
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• 2000

A K-band GaAs MMIC receiver module has been developed using 0.15 ${\mu}{\textrm}{m}$ HEMT technology process. It incorporates two front end low noise amplifiers, a double balanced diode mixer, and filters. The RF input frequency ranges 20.1 to 21 GHz and the IF output 1.1 to 2 GHz. Test results show an overall conversion gain of more than 27 dB, and less than a 2.2 dB noise figure. The image-rejection ratio greater than 21 dB has been obtained. The isolation between RF and IF ports is better than 27 dB, and between LO and IF is more than 50 dB.

• Journal of electromagnetic engineering and science
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• v.17 no.1
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• pp.39-43
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• 2017

In this paper, a systematic and statistical calibration technique was implemented to calibrate a high-speed signal converting system containing multiple digital-to-analog converters (DACs). The systematic error (especially the imbalance between DACs) in the current combining network of the multi-DAC system was modeled and corrected by calculating the path coefficients for individual DACs with wideband reference signals. Furthermore, by applying a Kalman filter to suppress noise from quantization and clock jitter, accurate coefficients with minimum noise were identified. For correcting an arbitrary waveform generator with two DACs, a co-simulation platform was implemented to estimate the system degradation and its corrected performance. Simulation results showed that after correction with 4.8 Gbps QAM signal, the signal-to-noise-ratio improved by approximately 4.5 dB and the error-vector-magnitude improved from 4.1% to 1.12% over 0.96 GHz bandwidth.

• Carbon letters
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• v.13 no.1
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• pp.17-22
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• 2012

Currently, graphene is a topic of very active research in fields from science to potential applications. For various radio-frequency (RF) circuit applications including low-noise amplifiers, the unique ambipolar nature of graphene field-effect transistors can be utilized for high-performance frequency multipliers, mixers and high-speed radiometers. Potential integration of graphene on Silicon substrates with complementary metal-oxide-semiconductor compatibility would also benefit future RF systems. The future success of the RF circuit applications depends on vertical and lateral scaling of graphene metal-oxide-semiconductor field-effect transistors to minimize parasitics and improve gate modulation efficiency in the channel. In this paper, we highlight recent progress in graphene materials, devices, and circuits for RF applications. For passive RF applications, we show its transparent electromagnetic shielding in Ku-band and transparent antenna, where its success depends on quality of materials. We also attempt to discuss future applications and challenges of graphene.