• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.2
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• pp.18-26
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• 2015

In this paper, we studied the method for analyzing and estimating the parameters that induce I/Q imbalance in the repeater using direct conversion RF. In repeater, amplitude, phase, and filter mismatch are generated in the receiving-end which converts RF signal to baseband signal. And amplitude and phase mismatch are generated in the transmitting-end which converts baseband signal to RF signal. Accordingly, we modeled the parameters that cause I/Q imbalance in the structure of the repeater in order, and proposed a feedback test structure from the transmitting-end to the receiving-end for estimating the corresponding parameters. By comparing the test transmitting signal and received signal, it is possible to estimate the I/Q imbalance parameters which occurred from mixed components of real and imaginary part. And it was confirmed that I/Q imbalance phenomenon has been properly compensated with estimated parameters at the direct conversion RF repeater.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.11
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• pp.1254-1264
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• 2008

This paper suggests an extended memory polynomial model that improves accuracy in modeling memory effects of RF power amplifiers(PAs), and verifies effectiveness of the suggested method. The extended memory polynomial model includes cross-terms that are products of input terms that have different delay values to improve the limited accuracy of basic memory polynomial model that includes the diagonal terms of Volterra kernels. The complexity of the memoryless model, memory polynomial model, and the suggested model are compared. The extended memory polynomial model is represented with a matrix equation, and the Volterra kernels are extracted using least square method. In addition, the structure of digital predistorter and digital signal processing(DSP) algorithm based on the suggested model and indirect learning method are proposed to implement a digital predistortion linearization. To verify the suggested model, the predicted output of the model is compared with the measured output for a 10W GaN HEMT RF PA and 30 W LDMOS RF PA using 2.3 GHz WiBro input signal, and adjacent-channel power ratio(ACPR) performance with the proposed digital predistortion is measured. The proposed model increases model accuracy for the PAs, and improves the linearization performance by reducing ACPR.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.3
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• pp.20-26
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• 2000

In this work, the degradation of g$_{m}$ , f$_{T}$ and f$_{max}$ of RF-CMOS devices have been characterized at elevated temperature. Since MOS transistors in RF applications are usually in saturation region, a simple empirical model for temperature dependence of g$_{m}$ at any measurement bias has been suggested. Because f$_{T}$ and f$_{max}$ of CMOS devices are proportional to g$_{m}$, the temperature dependence of f$_{T}$ and f$_{max}$ could be obtained from the temperature dependence of g$_{m}$. It was found that the degradation of f$_{T}$ and f$_{max}$ at elevated temperature was due to the degradation of g$_{m}$. From the correlation between DC and RF performances of CMOS devices, we can predict the enhanced f$_{T}$ and f$_{max}$ performances at low temperature.

• Journal of IKEEE
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• v.27 no.4
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• pp.650-656
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• 2023

This paper implements a channel model for mmWave bands using an NS-3-based 5G system-level simulator and analyzes the reliability and validity of the implemented model through RF performance verification. The channel model for RF performance verification in the mmWave bands consider parameters such as characteristics defined in 3GPP TR 38.901, beam-forming, antenna configuration, scenarios, among others. Furthermore, the simulation results verify compliance within the ranges permitted by the 3GPP standards and verify reliability in indoor environmental scenarios by exploiting the Radio Environment Map (REM). Therefore, the channel model implemented in this study is applicable to the actual design and establishment of 5G networks, presenting a method to evaluate and validate RF performance by adjusting various parameters.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.12 s.354
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• pp.33-39
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• 2006

An empirical nonlinear model with intrinsic nonlinear elements has been newly developed to predict the RF nonlinear characteristics of nano-scale bulk MOSFET accurately over the wide bias range. Using an extraction method suitable for nano-scale MOSFET, the bias-dependent data of intrinsic model parameters have been accurately obtained from measured S-parameters. The intrinsic nonlinear capacitance and drain current equations have been empirically obtained through 3-dimensional curve-fitting to their bias-dependent curves. The modeled S-parameters of 60nm MOSFET have good agreements with measured ones up to 20GHz in the wide bias range, verifying the accuracy of the nano-scale MOSFET model.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.7
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• pp.624-630
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• 2006

ZnO deposition parameters are not independent and have a nonlinear and complex property. To propose a method that could verify and predict the relations of process variables, neural network was used. At first, ZnO thin films were deposited by using RF magnetron sputtering process with various conditions. Si, GaAs, and Glass were used as substrates. The temperature, work pressure, and RF power of the substrate were $50\sim500^{\circ}C$, 15 mTorr, and $180\sim210W$, respectively : the purity of the target was ZnO 4 N. Structural properties of ZnO thin films were estimated by using XRD (0002) peak intensity. The structure of neural network was a form of 4-7-1 that have one hidden layer. In training a network, learning rate and momentum were selected as 0.2, 0.6 respectively. A backpropagation neural network were performed with XRD (0002) peak data. After training a network, the temperature of substrate was evaluated as the most important parameter by sensitivity analysis and response surface. As a result, neural network could capture nonlinear and complex relationships between process parameters and predict structural properties of ZnO thin films with a limited set of experiments.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.5
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• pp.11-16
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• 2017

The frequency dependent input resistance observed in RF MOSFETs is analyzed in detail by deriving pole and zero frequency equations from a simplified input equivalent circuit. Using this theoretical analysis, we find that the reduction effect of the input resistance in the low frequency region arises from the channel resistance between source and pinch-off region in the saturation region. This channel resistance effect on the low frequency reduction of the input resistance is physically validated by performing small-signal equivalent circuit modeling with varying the channel resistance.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.5
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• pp.54-61
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• 1999

We suggested a macro medel for MOS transistors, which incorporates the distributed substrate resistance by using a method which utilizes external diodes on SPICE MOS model. By fitting the simulated s-parameters to the measures ones, we obtained a model set for the W=200TEX>$\mu\textrm{m}$ and L=0.8TEX>$\mu\textrm{m}$ NMOS transistor, and also analyzed the effects of distributed substrate resistance in the RF range. By comparing the physical parameters calculated from simulated s-parameters such as ac resistances and capacitances with the measured ones, we confirmed the validity of the simulation results. For the frequencies below 10GHz, it seems appropriated to use a simple macro model which utilizes the existing SPICE MOS model with junction diodes, after including one lumped resistor each for gate and substrate nodes.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.27-30
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• 2007

This paper deals with an equivalent circuit model for RF passive components. Rational functions are obtained from the frequency responses of EM simulation by using Foster canonical partial fraction expressions. The Vector Fitting(VF) and the Adaptive Frequency Sampling(AFS) scheme are also implemented to obtain the rational functions. A passivity enforcement algorithm is applied to ensure the stability of the equivalent circuit model. In order to verify the schemes, S parameters of the equivalent circuit model is compared to those of EM simulation in case of the microstrip line structure with 3 slots in ground.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.1
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• pp.1-5
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• 2009

In this paper, we propose a method that applies Vector Fitting (VF) technique to the equivalent circuit model for RF passive components. These days wireless communication system is getting smaller and smaller. So EMI/EMC is an issue in RF. We can solve PI/SI (Power Integrity/Signal Integrity) that one of EMI/EMC problem apply IFFT for 3D EM simulation multiple with input signal. That is time consuming task. Therefore equivalent circuit model using RF passive component is important. VF schemes are implemented to obtain the rational functions. S parameters of the equivalent circuit model is compared to those of EM simulation in case of the microstrip line structure.