An incident field sensor for EMP measurements

Farr, Everett G.; Hofstra, J.S.

doi:10.1109/15.78347

Cited by 12 publications

(5 citation statements)

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“…As discussed in [11], [15], [16] there is an important case of dipoles, which might be called a combined dipole. This is characterized by principal radition direction (center of beam) (6.1) Considerations to date have been for time invariant polarization, but (and ) can in principle vary as a function of time.…”

Section: Combined Dipolesmentioning

confidence: 99%

“…As discussed for transmission (MEDIUS) [15] or as a sensor (or receiver, designated BTW [16]), this type of antenna is a length of specially designed TEM transmission line, terminated in its characteristic impedance (hence BTW (balanced transmission-line wave)). As indicated in Fig.…”

Section: Combined Dipolesmentioning

confidence: 99%

“…As discussed in [15], [16] the dipole moments for each incremental length of transmission line are balanced as in (6.1) with vector orientation as indicated in Fig. 2.…”

Section: Combined Dipolesmentioning

confidence: 99%

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General properties of antennas

Baum

2002

IEEE Trans. Electromagn. Compat.

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In antenna design there are some fundamental relationships based on reciprocity. The equivalence of antenna pattern in transmission and reception is well known. Less well known is the time-derivative relationship going from reception to transmission. These relationships are derived here and expressed in various useful forms. Electric and magnetic dipoles are given special consideration, and the combined form constructed as a terminated TEM transmission line (the BTW antenna) is discussed for its transmission and reception properties.

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Section: Combined Dipolesmentioning

confidence: 99%

Section: Combined Dipolesmentioning

confidence: 99%

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General properties of antennas

Baum

2002

IEEE Trans. Electromagn. Compat.

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“…By now there exists a considerable body of literature concerning the design of IRA's [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] . There are two fundamental types of IRA, the reflector IRA and the lens IRA (Figure 1.1).…”

Section: Review Of Ira Designmentioning

confidence: 99%

Impulse Radiating Antennas, Part II

Farr

Baum²,

Buchenauer³

1995

Ultra-Wideband, Short-Pulse Electromagnetics 2

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In this continuation of our paper in the last conference proceedings 1 , we consider further developments in the area of Impulse Radiating Antennas (IRAs). First, we consider definitions of gain in the time domain, which are important for optimizing the performance of IRAs. A reasonable definition of gain must be equally valid in transmission as in reception. Such a definition leads naturally to a transient radar equation, which we discuss. Next, we consider how to optimize the feed impedance in a reflector IRA. If we use our simple model of IRA performance, the gain of an IRA is always better at lower impedances. But this implies larger feeds with more aperture blockage. To resolve this, we refine our simple model to account for feed blockage. We also consider the radiation pattern of IRAs, and we provide simple calculations. Finally, we provide a sample experiment which confirms our theory of IRA operation. I. REVIEW OF IRA DESIGNBy now there exists a considerable body of literature concerning the design of IRA's 1-17 . There are two fundamental types of IRA, the reflector IRA and the lens IRA (Figure 1.1). The reflector IRA consists of a paraboloidal reflector fed by a conical TEM feed and terminated in an impedance that maintains a cardioid pattern at low frequencies. The lens IRA consists of a simple TEM horn with a lens in the aperture for focusing 25,26 . Either design is fed by a voltage source that is ideally shaped like a step function, but is in practice shaped like a fast-risetime impulse with a slower decay. In addition, either design normally has a dielectric lens at the apex to maintain voltage standoff 26,27 . Although there is some feed blockage associated with the reflector design, there is a considerable penalty in weight associated with the lens design. Thus, until lightweight dielectrics (real or artificial) with appropriate loss and dispersion properties are found, lens IRAs will likely be confined to applications with small apertures.The step response of a reflector IRA on boresight consists, to first order, of a prepulse followed by an impulse. The magnitude of the prepulse is determined by transmission line techniques 1,8 , and it lasts for the round-trip transit time of the feed, 2F/c, where F is the focal length of the reflector, and c is the speed of light. The magnitude of the impulse is found by aperture integration 1,5 . The total response iswhere D is the diameter of the reflector, f g = Z feed / Z o , Z o is the impedance of free space, V o is the magnitude of the driving voltage step launched onto the feed, r is the distance away from the antenna on boresight, and u(t) is the Heaviside step function. Furthermore, δ a (t) is the approximate Dirac delta function 3 , which approaches a true Dirac delta function as r approaches infinity. This is a high-impedance approximation based on the aperture integration described by Baum 5 . Later, we provide a correction for lower impedances. Note that the above equation can be expressed in terms of an arbitrary driving voltage as

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“…For example, modified versions of conventional TEM horn antennas were developed with improved radiation efficiencies [9]- [11] in the low-frequency range. Combined electric and magnetic dipole antennas for electromagnetic pulse sensing applications were reported in [12], [13]. Low-profile wide loop antennas were demonstrated to have the maximum gain higher than that of a uniform line source of the same size over a wide frequency band [14].…”

Section: Introductionmentioning

confidence: 98%

Radiation $Q$ and Gain of TM and TE Sources in Phase-Delayed Rotated Configurations

Kwon

2008

IEEE Trans. Antennas Propagat.

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The radiation quality factor and gain of antennas are compared for two source configurations between TM/TE-only spherical mode radiation and combined TM + TE mode radiation. It is shown that the change to the combined TM+TE mode radiation can reduce the quality factor by up to 50% and increase the gain by maximum 3 dB simultaneously. The condition for maximum gain increase provides a guideline for antenna designs for successfully achieving wide bandwidths and small sizes at the same time.Index Terms-Antenna gain, antenna miniaturization, directive antennas, radiation quality factor.

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An incident field sensor for EMP measurements

Cited by 12 publications

References 0 publications

General properties of antennas

General properties of antennas

Impulse Radiating Antennas, Part II

Radiation $Q$ and Gain of TM and TE Sources in Phase-Delayed Rotated Configurations

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