Scattered field improvement of tapered slot antenna using a parabolic-shaped slot

Abstract

and a coplanar microstrip feed has been studied. Good agreement between the simulated results and experimental ones confirms the cavity-model theoretical analysis. The results also demonstrate that this proposed antenna achieves high isolation (better than Ϫ41 dB) for two polarizations in the entire operating bandwidth (8.5-9.5 GHz) and a low cross-polarization level of less than Ϫ30 dB. . For the same substrate, length, and aperture size, the beamwidth of the LTSA appears to be narrower than the Vivaldi aerial's beamwidth. It has been noticed that the directivity of an LTSA spreads between 11 and 17 dB. A variant of the LTSA, the constant-width slot antenna (CWSA), has been used in an imaging array [3]. In general, the CWSA is more directive than the LTSA, with a counterpart of higher side lobes. The side-lobe levels of TSAs are different in the E-and H-planes (the planes are depicted in Fig. 1). This unwanted characteristic is overcome by using another special slot shape, corresponding to the Fermi function [4]. One of the major drawbacks of TSAs is their level of cross polarisation in the D-plane. It is reported that the lowest levels are achieved with the Vivaldi antenna (Ϫ15 dB in [5]). Unfortunately, this TSA exhibits poor directivity. As a trade-off, the broken tapered-slot antenna (BLTSA) was developed [6]. The latter has a gain of 13 to 14 dB for a cross-polarisation level of Ϫ11 dB, which is Ϫ2-dB less than its equivalent LTSA.From this brief introduction, we notice that TSA characteristics are very sensitive to slot shape. Herein, we attempt to present a new TSA that has a high directivity and a low cross-polarisation level based on a parabolic tapered slot (yielding the PTSA). The choice of this shape is inspired by qualitative principles obtained from various experimental contributions. On the other hand, the slot dimensions are obtained using numerical methods [7, 8]. ANTENNA DESIGNFirst, we determine the outer dimensions of the antenna. It is well known [3] that the directivity of a TSA is linear with respect to its length L (Fig. 1). The upper limit is fixed by the mechanical strength of the dielectric substrate because, without a ground plane, a too-long antenna bends under the effect of its weight. Given this consideration, we used an average length of L ϭ 5.5 0 . The choice of the width H (Fig. 1) is dictated by Janaswamy's experimental work [9], wherein it is said that TSAs exhibit interesting behaviour when they are made to be narrow. We retained H ϭ 1.5 0 . The chosen dielectric substrate has permittivity r ϭ 2.95 and thickness d ϭ 1.524 mm.Gibson [1] states that the directivity of a TSA antenna is proportional to the rate at which the electromagnetic energy is delivered. This basic idea is proven when studying the directivity versus the flare angle of the LTSA. This basic statement helps to explain the poor directivity of Vivaldi antennas. Indeed, the smooth exponentially shaped taper delivers its energy very slowly. Thus, optimising the directivity of TSAs is equivalent to finding the shap...

Compact shape of vivaldi antenna for water detection using ground pentrating radar

“…The exponential transition is utilized to connect to a suitable coaxial cable, which is the microstrip transmission feeder and is designed to have the characteristic impedance, Z o of 50 Ω, and is calculated using the following equations . The width of the strip on the bottom side is linearly increased to yield the ground plane for a microstrip feeder.…”

Ultrawideband doubly tapered slot antenna (DTSA) with integrated balun as a feed for time‐domain target detection

“…Considering all these limitation a planar Vivaldi antenna is good choice for this work as it can provide better bandwidth, gain and readily compatible with planar technology. The Vivaldi antenna or the exponentially tapered slot antenna (ETSA) which was first introduced by Gibson 7 is in the category of tapered slot antenna (TSA) which consists of many variations like exponentially tapered slot antenna (ETSA), logarithmic tapered slot antenna (LTSA), parabolic tapered slot antenna (PTSA) [8][9][10][11][12][13][14] etc. These types of antennas require a balance feeding network in order to work more efficiently.…”

Particle swarm optimization of the tapered slot antenna for wideband scanning E-plane linear array

“…It contains the radiating slot with an exponential taper profile and orthogonally feeding microstrip line with an open ended radial stub etched on the opposite sides of the substrate. Described geometry allows to achieve satisfactory reflection characteristics of a standalone TSA not only with exponential but also with linear [2], parabolic [3], constant width [2] and some other taper profiles of radiating slots if both length and width of antenna can exceed at least one wavelength for the lower working frequency.…”