• 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 IEEK Conference
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• 2008.06a
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• pp.469-471
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• 2008

The charge pump affects the performance of PLL. In designing the charge pump, we need to consider various issues such as current mismatch, charge sharing, feedthrough, charge injection, and leakage current. This paper propose the new charge pump circuit which is improved in terms of the current match over the existing high-speed charge pump. The simple method used for reducing current mismatch is the technique that uses a cascode in order to increase the output resistance of the charge pump. However the method limits the output voltage range of the charge pump. So the method is hard to apply as the supply voltage is lowered. Thus this paper proposes a new charge pump circuit using an op amp instead of the cascode. And the new charge pump circuit has an excellent current matching characteristics over a wide output range.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.756-761
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• 2009

In this paper, a X band voltage controlled oscillator is proposed. The oscillator uses a transistor as an oscillating element and its oscillating frequencies are controlled by the tuning voltage of varactor diode. Using the circuit simulation tools, the matching circuits between the transistor and varactor diode, its input and output matching circuits, and a feedback circuits are designed. The measured results of the fabricated oscillator show that its oscillation frequencies are from 10.50GHz to 10.88GHz according to the turning voltages of 1V to 18V, its output power levels are about 4.3dBm, and its phase noise is around -43.5dBc/Hz at 100kHz offset frequency of 10.5GHz.

• Journal of electromagnetic engineering and science
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• v.16 no.1
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• pp.52-56
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• 2016

This paper suggests a class-F power amplifier with split open-end stubs to provide a broadband high-efficiency operation. These stubs are designed to have wide bandwidth by splitting wide open-end stubs into narrower stubs connected in shunt in an output matching network for class-F operation. In contrast to conventional wideband class-F designs, which theoretically need a large number of matching lines, this method requires fewer transmission lines, resulting in a compact circuit implementation. In addition, the open-end stubs are designed with slant ends to achieve additional wide bandwidth. To verify the suggested design, a 10-W class-F power amplifier operating at 1.7 GHz was implemented using a commercial GaN transistor. The measurement results showed a peak drain efficiency of 82.1% and 750 MHz of bandwidth for an efficiency higher than 63%. Additionally, the maximum output power was 14.45 W at 1.7 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.8
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• pp.788-793
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• 2004

This paper proposes new configuration for the dual power amplifier that operates at 5.8 GHz for the wireless LAN and 1.8 GHz for the PCS. It dose not select the input signal but amplify the dual band signals simultaneously. Broadband diplexer is used at the input to separate the dual band signals. Output power of each amplifier is 1 W. The PBG is employed to improve the performance of power amplifier. Generally, the PBG is employed at the end of output matching network. But in this paper, the PBG is employed in the load pull output matching circuit of amplifer to maximize the output power.

• Journal of electromagnetic engineering and science
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• v.16 no.1
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• pp.44-51
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• 2016

A commercial $0.25{\mu}m$ GaN process is used to implement 6-18 GHz wideband power amplifier (PA) monolithic microwave integrated circuits (MMICs). GaN HEMTs are advantageous for enhancing RF power due to high breakdown voltages. However, the large-signal models provided by the foundry service cannot guarantee model accuracy up to frequencies close to their maximum oscillation frequency ($F_{max}$). Generally, the optimum output load point of a PA varies severely according to frequency, which creates difficulties in generating watt-level output power through the octave bandwidth. This study overcomes these issues by the development of in-house large-signal models that include a thermal model and by applying distributed L-C output load matching to reactive matched amplifiers. The proposed GaN PAs have successfully accomplished output power over 5 W through the octave bandwidth.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.353-364
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• 1998

This paper presents a systematic approach to the modeling of power electronic circuits with systemlongrightarrowlevel simulation l languages. It is shown that a circuit model reduces to one of four basic types according to input/output conditions. The e elementary models for single series components and shunt components are derived which are integrated to develop a m model of given converter circuit. The constraints imposed on the model development-matching input/output conditions a and avoiding algebraic loop-are discussed in relation to the realization example of a buck converter circuit model. It is s shown that the constraints can always be fullfilled by introducing fictitious interface blocks, which is generalized to the c concept of model transformation.

• ETRI Journal
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• v.32 no.1
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• pp.151-153
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• 2010

A highly efficient linear and compactly integrated series-type Doherty power amplifier (PA) has been developed for wideband code-division multiple access handset applications. To overcome the size limit of a typical Doherty amplifier, all circuit elements, such as matching circuits and impedance transformers, are fully integrated into a single monolithic microwave integrated circuit (MMIC). The implemented PA shows a very low idle current of 25 mA and an excellent power-added efficiency of 25.1% at an output power of 19 dBm by using an extended Doherty concept. Accordingly, its average current consumption was reduced by 51% and 41% in urban and suburban environments, respectively, when compared with a class-AB PA. By adding a simple predistorter to the PA, the PA showed an adjacent channel leakage ratio better than -42 dBc over the whole output power range.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.3
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• pp.139-144
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• 2003

We report the results of extensive mixed mode simulations and theoretical analysis to quantify the contribution of the edge direct tunneling (EDT) current on the total gate leakage current of 80nm NMOSFET with SiO2 gate dielectric. It is shown that EDT has a profound impact on basic analog circuit building blocks such as sample-hold (S/H) circuit and the current mirror circuit. A transistor design methodology with zero gate-source/drain overlap is proposed to mitigate the EDT effect. This results in lower voltage droop in S/H application and better current matching in current mirror application. It is demonstrated that decreasing the overlap length also improves the basic analog circuit performance metrics of the transistor. The transistor with zero gate-source/drain overlap, results in better transconductance, input resistance, output resistance, intrinsic gain and unity gain transition frequency.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.1125-1128
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• 2003

This paper presents the design method of a Colpitts type oscillator with coplanar waveguide(CPW) structures in the range of Ka-band frequency for transmitter and receiver modules. Series short stubs of CPW patterns provide inductances and capacitances in the range of Ka-band which can be expressed as a CLC-$\pi$ equivalent circuit. The experimentation has employed ro4003 substrates as a CPW substrate which has a dielectric constant of 3.38 and a signal and ground space of 100um. A method of momentum simulation for the CPW patterns has performed with an ADS software tool of Hewlett-Packard Corp. Inductance and capacitance circuits of a Colpitts oscillator was interconnected to a MESFET with CPW bend structures of including the input and output impedance matching circuits of the active transistor. Circuit parameters for impedance matching were determined through the network conversion to the equivalent length of CPW transmission lines by using T-network 1 $\pi$-network conversion circuit. A Colpitts oscillator was fabricated on the substrate of a area of 8.5mm x 17.4mm with a MESFET of Fujitsu FMM5704X and CPW series short stubs. The design suggested the possibility of realizing oscillators on a planar surface for the wireless system of tansmitter and receiver modules in the frequency range of 30GHz