Kun-A Lee

Propagation Model of High-Power Electromagnetic Pulse by Using a Serial–Parallel Resistors Circuit

The risk of high power electromagnetic (HPEM) pulse is dramatically increasing as the output of HPEM pulse increases and the affected electronic devices becomes smaller [1], [2]. There are largely two ways of coupling HPEM pulse: 1) front door coupling, which is through antennas and sensors to receive signals and 2) back-door coupling, which is through an unintended way, such as punctures and slots. In this paper, we modeled the loss phenomenon of HPEM pulse which happens when HPEM pulse radiated from HPEM system propagates to the receiving antenna. The loss circuit consists of serial-parallel resistors, each value of resistor is formularized as distance. Our modeling consists of two parts: 1) one-stage model, which means initial value for various applications and 2) nth-stage model, which means additional distances. Therefore, we could figure out the effect of HPEM on antenna as the propagation distance changes. After the due simulations, we confirm our hypothesis as the HPEM pulse which reaches to receiving antenna is consistent with the existing theory. This circuit modeling is very remarkable in that it understands two different HPEM system and propagation/receiving antenna as one whole system.

Electrical Circuit Modeling for Efficiency Improvement of Axial Virtual Cathode Oscillator

The virtual cathode oscillator (vircator), which is one of the microwave sources, has been widely studied for about 40 years, since it has advantages, such as its simple structure and high-power radiation. To implement the behavior of the vircator, a simulation model of the axial vircator using circuit elements is studied in this paper. There are two steps in simulation of this paper: 1) obtaining the optimized case in the fixed input power that has a maximum efficiency and 2) at the case, conducting the circuit modeling. Passive elements and switches are used to model the power losses, emission threshold, etc. This circuit analysis is simulated by the Electro Magnetic Transient Program. Through the simulation model of the axial vircator using circuit elements, the high-power electromagnetic system can be handled as an integrated system, which contains a prime power part, a pulsed power part, a microwave source part, etc. This means that the circuit analysis can be carried out from the prime power to the vircator.

Damage modeling on a radar affected by high power electromagnetic pulse

As the damage caused by high power electromagnetic (HPEM) is getting worse, it is necessary to analyze the damage and to study of shielding it. The coupling of HPEM to electronic devices is divided into two ways; (1) Front-door coupling and (2) Back-door coupling [1]. The former is inflow of HPEM pulse through an intended path and the latter is inflow through an unintended path. Since HPEM pulse flow in through an intended path in former case, HPEM pulse with higher power is induced and cause bigger damage to electronic devices. Because of these problems, it is necessary to study the damage and shield of RF systems affected by HPEM pulse. In this paper, damage modeling on the radar affected by HPEM pulse is shown. The damage of a radar falls into four types: (1) Deception, (2) Jamming, (3) Upset and (4) Burnout [2]. The process of damaged radar, which is sorted by each damage levels, is simulated by circuit elements. Particularly on this paper, it is examined the low noise amplifier (LNA) in a radar system. Because it operates in lower power level than HPEM pulse, LNA burns out even in the low input power circumstances. This circuit model is simulated by PSIM. Through the circuit models, which non-linear phenomena and damage of LNA, was expressed through the steps and it is expected to help studies which are to model the damage of a radar and to shield a radar affected by HPEM pulse.

In-line circuit modeling for damage analysis of RF front end system affected by high power electromagnetic pulse

Output of microwave have been increased with development of pulsed power system. The risk of RF front end system is dramatically increasing as the output of high power electromagnetic (HPEM) pulse increases. There are largely two ways of coupling HPEM pulse: (i) Front door coupling, which is through antennas and sensors to receive signals (ii) Back-door coupling, which is through unintended way such as punctures and slots. Compared to back-door coupling, front-door coupling is more risky and hazardous since it is coupled with intended parts. The simulation studies of this problem are conducted by numerical method. However it takes too many times in computation. In this paper, the in-line circuit modeling for damage analysis of the RF front end system affected by HPEM pulse is proposed. This integrated circuit modeling is simulated by the Electro Magnetic Transient Program (EMTP). It is simulated from the output of the HPEM system to the RF front end system. The target RF system of the study is the antenna. Passive circuit elements are used to model for antenna efficiency, propagation attenuation and etc.

Adjustable circuit model of vircator according to its characteristics

A virtual cathode oscillator (vircator) is one of the most important microwave generators, because it has advantages in simple structure, giga-watt level power and low impedance. Because of these advantages, it is widely used in high power electromagnetic (HPEM) pulse applications. The main disadvantage of the vircator is its low efficiency and it is complemented by simulation studies. Many of simulation studies are conducted by numerical method. Considering the connection to the pulse power part, a circuit modeling is needed. In this paper, the adjustable circuit model of the vircator according to its characteristics is proposed. Through the circuit model of the vircator, HPEM system can be handled as an integrated system, which contains a prime power part, a pulsed power part, a microwave source part, and others. This circuit analysis is simulated by the electromagnetic transient program (EMTP). Passive elements and switch are used to model for space-charge limitation, absorptions, oscillation and etc, which are derived from simulation condition (structure, input power). The vircator emission in the air is represented by the load. This study is helpful to efficiency researches because circuit elements are derived by the simulation conditions.

Circuit models for band pass filter of RF front-end system damaged by high power electromagnetic pulse

Summary form only given. In present days, the effect of high power electromagnetic(HPEM) threats become increased. This HPEM threats cause critical damaging to electronic equipment. There are two ways of electronic equipment damaged by HPEM pulse: front-door coupling and back-door coupling1. Since front-door coupling is intended to transmit and to receive the electromagnetic wave, a lot more power is induced to it than back-door coupling and it is difficult to shield perfectly due to its purpose, transmitting and receiving electromagnetic waves. Because of these problems, it is necessary to study the damage and shield of RF systems affected by HPEM pulse.

Analysis on Induced Surge Voltage of Electric Car Line affected by Lightning in Rapid-Transit Railway System

Lightning is one of hazards affecting the rapid-transit railway system. There are two effects, which are direct lightning surge to electric car line and induced lightning surge. Protection methods for the direct lightning surge are studied with various occasions, however, study of induced lightning surge is insufficient in spite of a large or small effects. In this paper, it is analysed the way that serge voltage is induced to electric car line by lightning strikes. By modeling the propagation process and the coupling phenomenon of electromagnetic wave produced by lightning strikes, it is achieved to make integrative circuit model combined with existing electric car model. The study is conducted into three different waveform of electromagnetic wave produced by lightning; rectangular wave, double exponential distribution wave, triangle wave. It is also simulated that the inducing serge is coupled to electric car line in an arbitrary location. The simulation results in that, when rapidly changing rectangular wave is supplied, maximum power is induced to electric car line.

PPPS-2013: Analysis on circuit-elements-composed-simulator of vircator for electromagnetic pulse emission

Vircator (Virtual Cathode Oscillator), which is one of the microwave sources, has been stuided widely for more than 20 years since it has such advantages as simple structure and high power radiation1. As electromagnetic pulse (EMP) emitted by vircator has been developing, the studies about hazard of the EMP on target have been also increasing2. In these applications it is difficult to build the whole system for EMP protection, because it is costly, dangerous and complex. For this reason, the vircator simulator to be composed circuit elements (R, L, C and etc.) is strongly needed. Numerically, vircator can be analyzed by PIC (Particle In Cell). However it takes too many times in computation. Therefore, the purpose of this paper is to build a vircator simulator via circuit elements, which could have its equivalent behavior with lower computation. In this paper, passive elements and switch are used to model for space-charge limitation, absorptions, oscillation and etc. The number of oscillation between the anode and the virtual cathode is limited. These circuit analysis is simulated by EMTP (Electro Magnetic Transient Program). Through the circuit-elements-composed-simulator, it can be handled with as the whole system for EMP protection. This means that circuit analysis can be carried out from the prime power to vircator. It is expected to help the improvement of EMP system with vircator efficiently.

PPPS-2013: Damage prediction of RF system affected by electromagnetic pulse

Summary form only given. RF system plays an important role in many applications such as military, telecommunication and etc. Especially an antenna used in the RF system is essential in modern society because it transmits and receives a variety of information by wireless. However it is susceptible to unwished microwaves such as noise and electromagnetic pulse (EMP). Compared to the conventional microwave, EMP can reach up to 100 MW in peak power and span within the range of frequencies between 1 and 300 GHz, which could destroy the electronic equipment1. Therefore it is important to analyze the damage of the RF system affected by EMP. The damage of RF system falls into four types: (1) Deception, (2) Jamming, (3) Upset, (4) Burnout2. Among these, the burnout, which means physical damage to RF system, is fatal. There are two main coupling paths in microwave couplings. One is the front-door coupling which is through intentional receptors such as antennas and sensors and the other is the back-door coupling which is through apertures intended for other purposes or incidental coupling to the construction of the target system such as seams, cracks and etc. The former could strongly give affection the target. In this paper, we predict damages of the radar system by EMP. Main damage type considered is the burnout and only the front-door coupling is covered. It is simulated from EMP propagation to coupling the radar system via circuit modeling method. We modeled the equivalent circuit for antenna and sub-electronic equipment. The energy induced by EMP through antenna flows to weak parts of the radar system. The affected parts are analyzed by EMTP (Electro Magnetic Transient Program). Using the damage prediction, the protection plans can be established.

Damage prediction of RF system affected by electromagnetic pulse

RF system plays an important role in many applications such as military, telecommunication and etc. Especially an antenna used in the RF system is essential in modern society because it transmits and receives a variety of information by wireless. However it is susceptible to unwished microwaves such as noise and electromagnetic shock wave. Compared to the conventional microwave, electromagnetic shock wave can reach up to 100 MW in peak power and span within the range of frequencies between 1 and 300 GHz, which could destroy the electronic equipment. Therefore it is important to analyze the damage of the RF system affected by electromagnetic shock wave. The damage of RF system falls into four types: (1) Deception, (2) Jamming, (3) Upset, (4) Burnout. Among these, the burnout, which means physical damage to RF system, is fatal. There are two main coupling paths in microwave couplings. One is the front-door coupling which is through intentional receptors such as antennas and sensors and the other is the back-door coupling which is through apertures intended for other purposes or incidental coupling to the construction of the target system such as seams, cracks and etc. The former could strongly give affection the target. In this paper, we predict damages of the radar system by electromagnetic shock wave. Main damage type considered is the burnout and only the front-door coupling is covered. It is simulated from electromagnetic shock wave propagation to coupling the radar system via circuit modeling method. We modeled the equivalent circuit for antenna and sub-electronic equipment. The energy induced by electromagnetic shock wave through antenna flows to weak parts of the radar system. The affected parts are analyzed by EMTP (Electro Magnetic Transient Program). Using the damage prediction, the protection plans can be established.