• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.2
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• pp.100-105
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• 2006

In this paper, a low noise amplifier(LNA) in a receiver of a low noise block down converter (LNB) for direct broadcasting service(DBS) is implemented using GaAs HEMT. The LNA is designed for the bandwidth of 11.7 GHz-12.2 GHz. The two-stage LNA consists of a input matching circuit, a output matching circuit, DC-blocks and RF-chokes. Experimental results of the LNA show the noise figure less than 1.4 dB, the gain greater than 23 dB and the flatness of 1 dB in the bandwidth of 11.7 to 12.2 GHz.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2318-2320
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• 2005

In this paper, a low noise amplifier(LNA) in a receiver of a Low Noise Block Down Converter (LNB) for direct broadcasting service(DBS) is implemented using GaAs HEMT. The LNA is designed for the bandwidth of 11.7GHz-12.2GHz. The 2stage-LNA consists of a input matching circuit, a output matching circuit, DC-blocks and RF-chokes. The result of a simulation of the LNA using Advanced Design System(ADS) shows the noise figure less than 1.4dB, the gain greater than 23dB and the flatness of 1dB in the bandwidth of 11.7 to 12.2GHz.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.472-474
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• 2004

In this study, we investigated the characteristics of the input impedance and the gain of a ‘Folded dipole antenna with stub’ by the Method of Moments. The center frequency in this study is 200MHz, the radius of wire is 0.5nm, and the distance between two linear dipoles is 2cm. The inside variation of stub length within 18cm and the outside variation of stub length 4.5cm ive the value of SWR(Standing Wave Ratio) within 3. This means that the impedance matching between the ‘Folded dipole antenna with stub’ and receiver can easily be performed without a supplementary matching circuit.

• Journal of IKEEE
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• v.23 no.2
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• pp.403-406
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• 2019

We propose a low-loss on-chip transformer using an auxiliary primary part (APP) for an output matching network for fully integrated CMOS power amplifiers. The APP is designed using a fifth metal layer while the primary and secondary parts are designed using a sixth metal layer with a width smaller than that of the primary and secondary parts of the transformer to minimize the substrate loss and the parasitic capacitance between the primary and secondary parts. By adapting the APP in the on-chip transformer, we obtain an improved maximum available gain value without the need for any additional chip area. The feasibility of the proposed APP structure is successfully verified.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.3
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• pp.413-419
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• 1987

In this paper, self-oscillating mixer is designed by small signal S-parameter and series feedback circuit. The input-output matching circuit is accomplished from double stub and additional matching stub. The self-oscillating mixer is oscillating itself and amplifies without any external local oscillator and an intermediate frequency amplifier, so it has advantages in its economical and system simplification. The experimental results show the maximum conversion gain 1.5d B and the noise figure 6.5d B at RF center frequency 4GHz and IF 1.1GHz` output oscillating power 4d Bm, efficiency 13.4%, stability -10MHz/V and -0.5MHz/\ulcornerC at oscillating frequency 5.1GHz.The rejection band loss characteristics in band pass filter and low pass filter are -40d B and -30d B, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.53-61
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• 2014

In this paper, we present the design, fabrication and measurement of high efficiency GaN HEMT power amplifier using harmonic matching technique. In order to achieve high efficiency, harmonic load-pull simulation is performed, that is, the optimum load impedances are determined at $2^{nd}$ and $3^{rd}$ harmonic frequencies as well as at the fundamental. Then, the output matching circuit is designed based on harmonic load-pull simulation. The measurement of the fabricated power amplifier shows the linear gain of 20 dB and $P_{1dB}$(1 dB gain compression point) of 33.7 dBm at 1.85 GHz. The maximum power added efficiency(PAE) of 80.9 % is achieved at the output power of 38.6 dBm, which belongs to best efficiency performance among the reported high efficiency power amplifiers. For W-CDMA input signal, the power amplifier shows a PAE of 27.8 % at the average output power of 28.4 dBm, where an ACLR (Adjacent Channel Leakage Ratio) is measured to be -38.8 dBc. Digital predistortion using polynomial fitting was implemented to linearize the power amplifiers, which allowed about 6.2 dB improvement of an ACLR performance.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.197-200
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• 2005

This paper presents the design of a broadband hybrid mixer using dual-gate FET topology with a low-pass filter which improves return loss of output to isolate RF and LO signal. The low-pass filter shows the isolation whose RF and LO signal is better than 40 dBc at 2 GHz and 5 GHz band. The dual-gate mixer which has been designed by using cascade topology operates when the lower FET is biased in linear region and the upper FET is in saturation. The input matching circuit has been designed to have conversion gain from 2 GHz to 6 GHz. The designed mixer with low-pass filter shows the conversion gain of better than 7 dB from 2 GHz to 6 GHz at a low LO power level of 0 dBm with the fixed IF frequency of 21.4 MHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.164-164
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• 2009

A multilayer piezoelectric transformer(MPT) for step-down voltage was made by ceramic stack process. And then, the characteristics of piezoelectric transformer, such as resonance frequency, matching impedance, electro-mechanical coupling coefficient, voltage gain, heat generation and efficiency, are analyzed. The piezoelectric transformer consists of a lead zirconate titanate ceramic with a high electromechanical quality factor. The piezoelectric transformer, with a multilayered construction in the thickness direction, was formed with dimensions 15mm long, 15mm wide and 5mm thick.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.136-140
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• 1990

A hybrid wideband amplifier having bandwidth from 5MHz to 2000MHz with a gain of 10db$\pm$3dB is designed and implemented by using a lossy matched network and GaAs FET. The implemented amplifier circuit operates as a capacitor-resistor(C-R) coupled amplifier circuit in the low frequency range (below 800 MHz) in which {{{{ LEFT $\mid$ S_{21 } RIGHT $\mid$ }} for the GaAs FET is constant. It also operates as a lossless impedance matching circuit in the microwave frequency range in which S21 for the GaAs FET has a slope of approximately -6dB/octave. Using this configuration technique, Two stage GaAs FET amplifier implemented is measured to 10dB gain within a 3dB fluctuation over the frequency band from 5 to 2000MHz.

• Journal of information and communication convergence engineering
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• v.9 no.5
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• pp.483-486
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• 2011

In this study, a fan-beam microstrip array antenna for an X-band radar was designed and fabricated using a novel technique. A microstrip array structure was used to obtain a high-gain and narrow horizontal beam-width. The feeding point is located at the center of the antenna because of its $360^{\circ}$ rotational characteristic. The measured results indicate a gain of 23dBi, and a horizontal and vertical beamwidth of $3.57^{\circ}$, $26.12^{\circ}$, respectively. The proposed antenna performed adequately and managed to meet the specifications.