On the inapplicability of a negative‐phase‐velocity condition as a negative‐refraction condition for active materials

Abstract

STACKED APERTURE-COUPLED INTRODUCTIONSince its introduction in 1985 [1], Aperture-coupled microstrip antenna has proved to be very useful for several applications; simply, this kind of antenna overcome a lot of disadvantages of the regular patch antennas fed by coaxial probe or microstrip line [2], however, the big amount of back radiation and narrow bandwidth, which cause malfunction to the associated electronic devices, are the main disadvantages for that kind of antenna, to overcome limited bandwidth and bad front to back ratio of such kind of antenna, stacked patches were used to achieve wide bandwidth and good front to back ratio [3][4][5].In this article, a new technique is presented to achieve wide bandwidth, reasonable back radiation level, high radiation efficiency, and high gain. ANTENNA DESIGN AND SIMULATIONThe geometry of the stacked aperture-coupled coplanar patch are given below with respect to the notation of Figure 1 as follows: H 1 ϭ 1.27 mm, (Er 1 ϭ Er 2 ϭ Er 3 -duriod5880 ϭ 2.2), W f ϭ 3.34, L s ϭ 2.5 mm, (Er f -duriod6006 ϭ 6.15), Hr f ϭ 1.9 mm, W a ϭ 1 mm, L a ϭ 12 mm, H 2 ϭ 1.574 mm, W 1 ϭ 9 mm, L 1 ϭ 11 mm, H 3 ϭ 1.578 mm, W 2 ϭ 7 mm, L 2 ϭ 9 mm, S 1 ϭ 2 mm, S 2 ϭ 2.5 mm, S 1 ϭ 2 mm.In this antenna, an additional ground plane is added below substrate 1 to block the back radiation resulting from the aperture which radiates on both sides of the ground plane 2, besides that the aperture resonance (Fig. 2) does not contribute to the operating bandwidth to further eliminate the back radiation, coplanar patches were used as radiating patches based on the study done in Ref. 6 and shows that coplanar patch antenna has some advantages over the classical patch as low radiation loss, less dispersion, and uniplanar configuration, the radiating patches are of different sizes to have two overlapped resonance frequencies which form wide bandwidth antenna.The simulation has been done using Ansoft HFSS software [7]. The simulated bandwidth is ranging between 7.72 and 9.55 GHz which is about 22% (Fig. 3), although larger bandwidth has been achieved in Ref. 4, but it still has high back radiation, the 180-front to back ratio shown there is about 10 dB in H-plane, which is less than what achieved in the shown antenna (Fig. 4), the front to back ratio is about 13 dB, the simulated radiation efficiency is about 97% CONCLUSIONSA stacked aperture-coupled coplanar patch antenna has been studied, the simulation results indicate that the antenna has large bandwidth, good front to back ratio, less dispersion, and high efficiency; this type of antenna is useful for some miscellaneous radars which operates in X-band such as precision approach radar and X-band weather radar besides it could be used as an element in arrays that require large bandwidth and low back radiation. (1996), 1941-1942. 4 Depine and Lakhtakia (Microwave Opt Technol Lett 41 (2004) [315][316][317] for isotropic, homogeneous, passive, dielectric-magnetic materials is inapplicable as a negativerefraction condition for active materials.

A plethora of negative-refraction phenomenons in relativistic and non-relativistic scenarios

“…In the case of uniform plane waves propagating in passive isotropic dielectric-magnetic materials, negative refraction is synonymous with negative phase velocity. However, the correspondence between negative refraction and negative phase velocity breaks down if the materials are active [9], or if nonuniform plane waves are considered [7], or if anisotropic or bianisotropic materials are involved [7].…”

Erratum: Wireless network based on radio-over-fiber with optical carrier reuse by fiber grating

“…In a recent Letter [1], we pointed out that a condition-much used to indicate negative phase velocity (NPV) in passive linear isotropic dielectric-magnetic materials [2] -should not be used to predict negative refraction in active materials. In a recent Comment [3] on our Letter [2], it was pointed out that the derivation of the NPV condition [2] holds for active materials.…”

“…True! However, NPV and negative refraction are distinct phenomenons for linear isotropic dielectric-magnetic materials, active [1] or passive [4]. Therefore, satisfaction of the NPV condition [2]-reproduced as inequality (1) in Ref.…”

Response to “Comment on: On the inapplicability of a negative-phase-velocity condition as a negative-refraction condition for active materials”

“…In a recent Letter [1], we pointed out that a condition-much used to indicate negative phase velocity (NPV) in passive linear isotropic dielectric-magnetic materials [2] -should not be used to predict negative refraction in active materials. In a recent Comment [3] on our Letter [2], it was pointed out that the derivation of the NPV condition [2] holds for active materials.…”

“…However, NPV and negative refraction are distinct phenomenons for linear isotropic dielectric-magnetic materials, active [1] or passive [4]. Therefore, satisfaction of the NPV condition [2]-reproduced as inequality (1) in Ref. 3-does not necessarily imply negative refraction.…”