Unusual features of the pseudo non-diffracting microwave vortex

Speciale, R.A.

doi:10.1109/aps.2007.4396427

Cited by 3 publications

(2 citation statements)

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“…In shifting from light to radio wavelengths, it is necessary to shift focus away from momentum to classical electric and magnetic field descriptions of waves and their phase and velocity behaviors rather than momentum and force. R.A. Speciale [1]- [2] examined a field solution that was a superposition of TE and TM Bessel modes, but did not obtain a complete modal description, which is supplied here.…”

Section: Introductionmentioning

confidence: 97%

More unusual features of the microwave vortex

Stearns

2012

Proceedings of the 2012 IEEE International Symposium on Antennas and Propagation

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The electromagnetic vortex was reported by R.A. Speciale [1]-[2]. The solution of the vector wave equation for the free space propagation of unguided, collimated Bessel beams is reexamined and new features are described. First, the set of modes is doubly indexed, nondenumerable, and overcomplete. Second, the phenomenon of mode cutoff frequency is absent. Third, axial phase velocity is superluminal, i.e. exceeds c, while energy or group velocity is subluminal, i.e. less than c. Yet unlike waveguide modes, the geometric mean of the phase and group velocities does not equal c. Einstein's constant c loses significance as "the" speed of light, and instead is an upper bound on the speed of light in free space. To the two known methods for slowing light -media and guiding structures -must be added a third, orbital angular momentum (OAM). In view of these results, certain statements in classical books on electromagnetics require emendation.

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Section: Introductionmentioning

confidence: 97%

More unusual features of the microwave vortex

Stearns

2012

Proceedings of the 2012 IEEE International Symposium on Antennas and Propagation

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“…For comparison, we define the concept of OAM-based radar cross section (ORCS) for OAM-based radar, in this paper. Currently, several open articles have discussed the unique features of the vortex EM waves, [20][21][22] e.g., the phase velocity in free space is greater than c and the energy velocity is less than c (c is the light speed in the vacuum). The properties of the EM scattering of a Bessel vortex beam by the water sphere were analyzed in Ref.…”

Section: -3226/2018/8(2)/025002/13mentioning

confidence: 99%

Target scattering characteristics for OAM-based radar

Liu

Gao

et al. 2018

AIP Advances

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The target scattering characteristics are crucial for radar systems. However, there is very little study conducted for the recently developed orbital angular momentum (OAM) based radar system. To illustrate the role of OAM-based radar cross section (ORCS), conventional radar equation is modified by taking characteristics of the OAM waves into account. Subsequently, the ORCS is defined in analogy to classical radar cross section (RCS). The unique features of the incident OAM-carrying field are analyzed. The scattered field is derived, and the analytical expressions of ORCSs for metal plate and cylinder targets are obtained. Furthermore, the ORCS and RCS are compared to illustrate the influences of OAM mode number, target size and signal frequency on the ORCS. Analytical studies demonstrate that the mirror-reflection phenomenon disappears and peak values of ORCS are in the non-specular direction. Finally, the ORCS features are summarized to show its advantages in radar target detection. This work can provide theoretical guidance to the design of OAM-based radar as well as the target detection and identification applications.

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