TEM Antenna Research Articles

Verification of the electromagnetic deep-penetration effect in the real world

The deep penetration of electromagnetic waves into lossy media can be obtained by properly generating inhomogeneous waves. In this work, for the very first time, we demonstrate the physical implementation and the practical relevance of this phenomenon. A thorough numerical investigation of the deep-penetration effects has been performed by designing and comparing three distinct practical radiators, emitting either homogeneous or inhomogeneous waves. As concerns the latter kind, a typical Menzel microstrip antenna is first used to radiate improper leaky waves. Then, a completely new approach based on an optimized 3-D horn TEM antenna applied to a lossy prism is described, which may find applications even at optical frequencies. The effectiveness of the proposed radiators is measured using different algorithms to consider distinct aspects of the propagation in lossy media. We finally demonstrate that the deep penetration is possible, by extending the ideal and theoretical evidence to practical relevance, and discuss both achievements and limits obtained through numerical simulations on the designed antennas.

Arrays of combined antennas excited by high-voltage bipolar pulses

The main characteristics of the TEM antenna and the combined antenna (KA) with extended bandwidth are compared using numerical simulation. The influence of the high-voltage coaxial-strip junction on the KA characteristics is shown. The effective radiation potential is compared relative to the utmost one for high-power UWB radiation sources based on KA arrays, as well as single IRA, HIRA, TEM, and KA antennas.

절연재에 따른 TEM 안테나의 방사패턴 및 이득 변화

Abstract - TEM Horn antenna is typically used in HPEM area. It is necessary to apply a high voltage of the antenna for radiating HPEM. Then, it is necessary to insulate essentially of applying a high voltage to the antenna. At this time, radiation pattern and gain of the TEM Antenna is changed. For this reason, it is necessary to analyze changing characteristics by using simulation. In this paper, I analyzed the radiation pattern of the antenna in accordance with the lens and insulating material. As a result, it was observed that the value of the gain is changed in accordance with the frequency. The lens is used for the antenna, the gain characteristic is improved.Key Words : TEM horn antenna, TEM antenna insulation, Far-field pattern † Corresponding Author : Dept. of Electrical Engineering, INHA University, KoreaE-mail : cshuh@inha.ac.kr* Dept. of Electrical Engineering, INHA University, Korea** Agency for Defense Development***Korea Testing & Research Institute, (KTR)Received : December 10, 2013; Accepted : March 31, 2014

Generation of Ultrawide Band Electromagnetic Pulse from Blumlein Pulse Forming Line

A high voltage pulse generator was fabricated to radiate ultrawide band electromagnetic pulse. A coaxial type of Blumlein pulse forming line is employed to produce a pulse of high voltage (>300 kV) and short pulse duration (~5 ns). A helical strip/wire type of air-cored pulse transformer was used to charge the Blumlein pulse forming line up to more than 300 kV. A peaking switch is essential to make the pulse rise time as fast as possible. Typically, the rise time is ~500 ps. The output pulse of the generator is radiated into air through an exponentially tapered TEM horn antenna. The electric field intensity of a radiated pulse was measured as a function of the distance from the transmitting horn as well as the output voltage of the peaking switch. The peak-to-peak value of the electric field intensity at 10 m from the TEM antenna was~100 kV/m.

Analysis of a horn-lens TEM antenna

Matching and radiation characteristics of a horn-lens TEM antenna are studied theoretically and experimentally in an ultra-wide frequency band. Theoretical results are obtained by means of electromagnetic modeling on the basis of the finite-element method. Antennas with different geometries of the lens and different methods of excitation of the TEM horn are considered. Direct excitation by a coaxial line and excitation with the use of a smooth transition from a coaxial line to a stripline are studied. The results of calculations are compared with experimental results.

Generation of powerful, superbroad-band, subnanosecond electromagnetic pulses

The excitation of superbroad-band TEM antennas with a high-voltage subnanosecond modulator permitting a pulse-repetition frequency of up to 100 Hz is experimentally investigated. The modulator consists of a RADAN-303B nanosecond driver and a pulse amplifier based on gas discharges. The instrument generates unipolar and bipolar pulses of tunable length and amplitude. The amplitude and power of the pulses sent to the antenna reach 100 kV and 200 MW. Data are obtained on the stability of the parameters of the subnanosecond modulator pulses. Information is given on the electrical strength of the air insulation in the matching interval between the modulator and the antenna. The superbroad-band pulses emitted are recorded at distances of up to 25 m. The characteristics of the instrument permit the spatial resolution of reflections from conducting objects with a shape-inhomogeneity scale of no more than 25 cm. Emitters with increased directionality in the E or H (E and H) planes based on two (four) TEM antenna supplied with split modulator pulses are investigated. In-phase and antiphase antenna configurations are considered.

A determination of transient antenna impedance via a numerical solution of the electric-field integral equation

A numerical method for determining the broadband characteristic impedance of an antenna is described. The method is based on a solution of the electric field integral equation for the antenna surface subject to a strongly localized incident field, representative of a desired transient source voltage. A method is outlined for calculating, from the numerically simulated feed current, the frequency-dependent impedance spectrum of a finite antenna, subject to a sharp pulse. It is shown that this may be used to determine reliably the characteristic impedance of TEM antennas. Particular attention is paid to the problem of effectively modeling the feed region of the transient antenna. A general approach which ensures the stability and accuracy (to within a few percent) of solutions is described. It uses surface patches to model the antenna and obviates potential difficulties associated with thin wire models of the feed region.