Analysis of electromagnetic radiation from shaped-end radiators using the finite difference time domain method

Beggs, John H.; Luebbers, R.; Ruth, Brian G.

doi:10.1109/8.247761

Cited by 12 publications

(3 citation statements)

References 10 publications

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“…[ 1801 modeled frequency-dispersive microstrip antennas, while Wu et al [181] used the FDTD method to accurately measure the reflection coefficient of various microstrip-patch configurations. Uehara and Kagoshima [182] presented an analysis of the mutual coupling between two microstrip antennas, while Oonishi et al In 1993, Beggs et al [202] used the FDTD method to analyze the radiation from shaped-end radiators, while Maeshima et al…”

Section: Microstrip Antennasmentioning

confidence: 99%

A selective survey of the finite-difference time-domain literature

Shlager

Schneider²

1995

IEEE Antennas Propag. Mag.

188

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Section: Microstrip Antennasmentioning

confidence: 99%

A selective survey of the finite-difference time-domain literature

Shlager

Schneider²

1995

IEEE Antennas Propag. Mag.

188

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“…A "Vlasov" or shaped end radiator [10] was used as an antenna. This antenna has been characterized previously and provides a reasonable antenna pattern to measure.…”

mentioning

confidence: 99%

Extraction of 1 GW of rf Power from an Injection Locked Relativistic Klystron Oscillator

Kj¹,

et al. 1996

Phys. Rev. Lett.

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Initial results of extracted power from a moderately modulated intense relativistic electron beam are reported. The modulation circuit is operated as a relativistic klystron oscillator frequency locked to an external oscillator. A 40% modulated electron beam has yielded more than 1 GW of rms power to a vacuum load and also radiated through an antenna. The ratio of the rf power to the intense electron beam power is approximately 20%.PACS numbers: 84.40.Fe, 07.57.Hm, 41.60.-m A common milestone for all researchers working on high power microwave (HPM) sources has been to extract and radiate rf powers of the order of 1 GW [1][2][3][4][5][6][7]. Many projects also work on providing a long pulse, of order 1 msec, to provide both high power and high energy [1-3]. Many of these efforts have made use of moderate to high voltages (1 MV) at relatively high diode impedances (100 V to 1 kV).We report on an effort to operate at lower impedance and voltage, but with high power and high energy. This has led to complications due to the intense space charge depression of the beam kinetic energy. We began with a Friedman relativistic klystron amplifier (RKA) and converted the system to an injection locked oscillator due to limited power of the external oscillator drive power.This Letter begins with a discussion of the experimental geometry, followed by a discussion of the beam modulation results, and concludes with a brief discussion of extracting and radiating the rf wave.

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“…Other antenna designs like the Vlasov [4] and the shaped end radiator [5], [6] antennas, have been considered to radiate azimuthally symmetric aperture distributions, but they typically radiate a low-gain pattern with an off-boresight peak that changes direction as a function of the frequency (for high-power sources, the frequency tends to shift about a nominal center frequency during the output duty cycle). Consequently, the nature in which the microwave energy is pointed becomes an issue for some high-power applications.…”

Section: Introductionmentioning

confidence: 99%

The coaxial beam-rotating antenna (COBRA): theory of operation and measured performance

Courtney

Baum

2000

IEEE Trans. Antennas Propagat.

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Many microwave generators, especially high-power sources, utilize an azimuthally symmetric output mode such as the TM 01 circular waveguide or the coaxial TEM mode. If such a mode is projected into an antenna aperture and radiated directly, then a doughnut-shaped radiation pattern with a boresight null will result. Antenna designs to directly accommodate an azimuthally symmetric output mode and the high electric fields of high-power sources have been considered, but they tend to be low gain, do not radiate a boresight peak along the axis of the source, and the pattern peak direction changes with frequency. Mode conversion techniques to alter the aperture field distribution (i.e., TM 01 to TE 11 in circular waveguide) have also been explored, but losses and weight, size and cost additions impact negatively on total system design. This paper describes a novel antenna we call the coaxial beam-rotating antenna (COBRA) that mitigates many of the problems normally associated with the azimuthally symmetric output modes of high-power microwave sources. The COBRA accepts directly (without the need for mode conversion) an azimuthally symmetric guided mode of a microwave source and radiates a high-gain pattern with a boresight peak. In addition, the COBRA operates with a wide bandwidth, is compatible with the intense electric fields associated with high-power microwave sources, and the geometry of the antenna can be easily configured to produce an arbitrarily (elliptically) polarized boresight field. This paper presents the fundamental theory of operation, derives pertinent design and performance equations, and gives the measured operating characteristics of a COBRA prototype.

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Analysis of electromagnetic radiation from shaped-end radiators using the finite difference time domain method

Cited by 12 publications

References 10 publications

A selective survey of the finite-difference time-domain literature

A selective survey of the finite-difference time-domain literature

Extraction of 1 GW of rf Power from an Injection Locked Relativistic Klystron Oscillator

The coaxial beam-rotating antenna (COBRA): theory of operation and measured performance

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