Kwangho Kim

Design, Analysis, and Equivalent Circuit Modeling of Dual Band PIFA Using a Stub for Performance Enhancement

This work presents a new method for enhancing the performance of a dual band Planer Inverted-F Antenna (PIFA) and its lumped equivalent circuit formulation. The performance of a PIFA in terms of return loss, bandwidth, gain, and efficiency is improved with the addition of the proposed open stub in the radiating element of the PIFA without disturbing the operating resonance frequencies of the antenna. In specific cases, various simulated and fabricated PIFA models illustrate that the return loss, bandwidth, gain, and efficiency values of antennas with longer optimum open stub lengths can be enhanced up to 4.6 dB, 17%, 1.8 dBi, and 12.4% respectively, when compared with models that do not have open stubs. The proposed open stub is small and does not interfere with the surrounding active modules; therefore, this method is extremely attractive from a practical implementation point of view. The second presented work is a simple procedure for the development of a lumped equivalent circuit model of a dual band PIFA using the rational approximation of its frequency domain response. In this method, the PIFA’s measured frequency response is approximated to a rational function using a vector fitting technique and then electrical circuit parameters are extracted from it. The measured results show good agreement with the electrical circuit results. A correlation study between circuit elements and physical open stub lengths in various antenna models is also discussed in detail; this information could be useful for the enhancement of the performance of a PIFA as well as for its systematic design. The computed radiated power obtained using the electrical model is in agreement with the radiated power results obtained through the full wave electromagnetic simulations of the antenna models. The presented approach offers the advantage of saving computation time for full wave EM simulations. In addition, the electrical circuit depicting almost perfect characteristics for return loss and radiated power can be shared with antenna users without sharing the actual antenna structure in cases involving confidentiality limitations.

Voltage Transfer Characteristics of an Insulation Transformer Up to 1 MHz

This paper proposes a novel method that analyzes voltage transfer characteristics from the primary to the secondary side of an insulation transformer. Raw data of transfer characteristics were obtained from the S -parameter measurement using vector network analyzer. To characterize transfer characteristics of an insulation transformer, the proposed method uses ABCD parameters, which are transformed from the measured S-parameters. This method enables us to predict the transferred pulse voltage waveforms in the secondary side as well as to predict the frequency-dependent gain of the insulation transformer. It is confirmed that the predicted voltage waveforms and gains in the secondary side coincide to the measured voltage waveforms quite accurately, which shows the validness of the proposed method.

Analysis of filtering characteristics for coplanar symmetrical meander lines

This paper presents an analysis of the filtering characteristic for a coplanar symmetrical meander lines structure. The effects of geometrical parameters, which are length of vertical and horizontal elements as well as the distance of the gap between two symmetrical lines, on the filtering property of the structure are discussed. A novel direct derivation of the filtering performance of the coplanar configuration based on our proposed circuit model is also addressed. The mentioned analysis could be a useful guidance in the design stage of a uniplanar filter to enhance the signal and power integrity as well as immunity of Integrated circuits.

Total Simulation for the Noise Prediction of Motor Driving System in EV/HEV System

The noise prediction of motor driving system is one of the most important parts in EV/HEV, as the number of power electronic devices increases. This paper describes the mechanism of noise making process and proposes a simulation model of motor driving system for the prediction of the conducted noise. Theoretical calculations and model based simulations were carried out. DOD-dependent-battery parameters were extracted by AC analysis, and an inverter model including dynamic diode was used. Furthermore, 2-D EM tool was used for the motor modeling and was combined with the circuit models of battery and inverter. The simulated voltages, currents and spectrums in the motor driving system showed qualitatively meaningful results, suggesting the validness of the suggested modeling methods.

Analysis of electromagnetic field interference between an antenna and a multiple-noise source using active scattering parameters

This paper proposes an analysis method for electromagnetic field interference between an antenna and adjacent noise sources, using active scattering parameters. Electromagnetic field interference can be analyzed by measurement or simulation of the scattering parameters. In this paper, a multiple-band antenna and a multiple-noise source were designed and fabricated to analyze the electromagnetic field interference between them. The proposed analysis method employs active scattering parameters, whose validity has been verified both experimentally and through simulation.

Novel diagnostic method for a single phase pole-mount transformer using two-port measurement

Diagnosis and maintenance of a power transformer are important because it deals with high power in high voltage, and any failure of previous detection of the malfunction in transformer would cause a disaster in the household customers as well as in the industry. To diagnose a power transformer, Sweep Frequency Response Analyzer (SFRA) has been widely used and been studied for the past years. The SFRA measures the change of a transfer function characteristics of a transformer with some specific terminal conditions, and has been used to check the state of the transformer which could be caused due to aging or to any damage before and after moving, and so on. It, however, uses just one port of the transformer to check the impedance, so the information from the SFRA measurement is limited in principle. This paper suggests a novel way to measure two ports of a power transformer to get the inside information of a transformer. To prove the validity of the proposed method, two-port S-parameters were measured using Vector Network Analyzer (VNA), and the measured S-parameters were converted into the transfer function using proper equations for the comparison of the two measurement data. The comparison of two showed good matching in the range of 20Hz to 2MHz. It suggests that the proposed method could be used to effectively diagnose the power transformers.

Electrical/Mechanical Diagnosis of Local Deterioration in 600V Shielded Twist Pair Cable in a Nuclear Power Plant

In this paper, we propose a electrical/mechanical method to effectively diagnose the local deterioration of a 10m long power shielded twist pair cable defined by the American Wire Gauge (AWG) 14 specification using electrical/mechanical methods. The rapid deterioration of the cable proceeded by using the heating furnace, which is based on the Arrhenius equations proceeds from 0 to 35 years with the deteriorated equivalent model. In this paper, we introduce a method to diagnose the characteristics of locally deteriorated cable by using S21 phase and frequency change rate measured by vector network analyzer which is the electrical diagnostic method. The measured S21 phase and rate of change of frequency show a constant correlation with the number of years of locally deteriorated cable, thus it can be useful for diagnosing deteriorated cables. The change of modulus due to deterioration was measured by a modulus measuring device, which is defined by the ratio of deformation from the force externally applied to the cable, and the rate of modulus change also shows a constant correlation with the number of years of locally deteriorated cable. Finally, By combining the advantages of electrical/ mechanical diagnostic methods, we can efficiently diagnose the local deterioration in the power shielded cable.

Theory, Simulation, and Experiment on Extended Mixed-Mode S-Parameters in Three-Conductor Lines

This paper proposes novel mixed-mode <italic>S</italic>-parameters, which are dubbed as “extended mixed-mode <italic>S</italic>-parameters.” The extended mixed-mode <italic>S</italic>-parameters were applied to three-conductor transmission lines, resulting in the independent differential and common modes using the current division factor of three-conductor transmission lines. By contrast to the conventional mixed-mode <italic>S</italic> -parameters, there are no cross-mode <italic>S</italic>-parameters in the extended mixed-mode <italic>S</italic> -parameters, even in the asymmetrical conductor transmission lines. In addition, two new mode conversion matrices, which contain the current division factor, are also proposed to convert the extended mixed-mode <italic>S</italic> -parameters to the standard <italic>S</italic>-parameters. The validity of the proposed extended mixed-mode <italic>S </italic>-parameters and the mode conversion method were confirmed by comparing the <italic>S</italic>-parameters from the theory, EM-simulation, and experiment as well.

A Study on the Deterioration Diagnosis of 600V Shielded Twisted Pair Control/Measurement Cable using Resonance Frequency

Recent major domestic facilities, such as nuclear power plants, many control cables are installed and are degraded by long-term use, but research on deterioration diagnosis is lacking. In the event of a fault in the cable due to deterioration can be developed into a major accident such as the main plant is stopped, so the deterioration diagnostic techniques of high reliability for the cable is required. In this paper, proposes a methodology using a cable resonance that can effectively diagnose the deterioration of the cable. Prior to the test, we developed a setup for stable measuring the characteristics of the cable and it verified the suitable of the measurement set-up in terms of interactivity and reliability, also measured S-parameters applying verified measurement set-up to the cables that deterioration degree is different. Then, we had amplified the difference in resonance frequency between the healthy state and the deteriorated state using connection in a series of measured S-parameters. In a result from the method, we have verified that the more deteriorate the cables is, the more decrease the resonance frequency is. Measured results are justified by inducing the resonance frequency calculation of the cable from the S- parameters represented by the hyperbolic function formula. VNA(Vector Network Analyzer) for S-parameter measurements used in this study is Agilent E5061B and shielded twisted-pair cables was used for deterioration diagnostic test.

The Response to Impulse Signal on Three Phase Transformer using Vector Network Analyzer

Abstract Transformer is widely used element on power system and industrial area. Especially the transformers installed at power system are exposed to an environment of arbitrary changed. Thus the prediction of degradation and the analysis of response to impulse are important. To conduct those works, the electrical characteristics of system should be analyzed, effectively. But the analysis of electrical characteristic in electric machine level such as pole and pad-mounted transformer is almost no, thus commercial VNA (Vector Network Analyzer) is used to getting the response in wide frequency range. However, the output power of VNA is usually under 10mW, so verification for effectiveness of measuring electrically large component should be conducted, firstly. Next, after getting total S-parameter of transformer, predicting impulse response can be performed in time-domain with circuit simulator. In this paper, it is introduced that verification effectiveness of VNA using transfer function from SFRA (Sweep Frequency Response Analyzer), firstly. Next, total S-parameter, six by six matix form, was built using measured 2 port S-parameter from vector network analyzer. To get the response to impulse which is defined by IEC 60060-1, time-domain simulation is conducted to ADS (Advenced Design System) circuit simulator.