Band‐notched ultra‐wideband square slot antenna

Abstract

Since the imaginary part of the propagation constant and its second derivative are involved, without knowing the unperturbed results, one cannot use Eq. (14) to calculate wavelength shift. However, the equations are useful for qualitative analysis of SPR sensor. At the resonance wavelength, the attenuation reaches to a maximum (␤ i reaches to a minimum), so the second derivative Ѩ 2 ␤ i /Ѩ 2 is positive. Equation (14) predicts that when the sensed medium index change ⌬ Ͼ 0 (⌬ Ͻ 0), the resonance wavelength will shift to longer (shorter) wavelength direction. The conclusion agrees with experimental results from all kinds of fiber/waveguide SPR sensor. The shape of attenuation dip in transmitted spectra reflects ␤ i and Ѩ 2 ␤ i /Ѩ 2 . Usually, the change of this shape is small in relatively broad wavelength range. This means that the index sensitivity roughly remains at a constant value. Although the factor I r is increasing as the sensed medium thickness t increases, due to the decay of the modified Bessel function, only the dielectric perturbation within the penetration depth makes real contribution. In the case of uniform index perturbation, the wavelength shift is proportional to ⌬. To obtain a good sensitivity, one should match the penetration depth of the electric field with the thickness of the sensed dielectric film. If the dielectric perturbation is not uniform, the wavelength shift must be determined by integrating Eq. (13a). In this case, it is impossible to distinguish dielectric perturbation effect from sensed medium thickness change by resonance wavelength shift. The effect of the thickness of the metallic thin film is partially included in the factor I r . The surface plasma mode cannot be developed if the thickness d is too small [10]. On the other hand, when the metallic film is too thick, the field ⌽(r,) almost vanishes in region r Ͼ a ϩ d, thereby I r Ϸ 0. This implies that there is an optimal metallic film thickness for SPR sensing. APPENDIXFrom Eq. (5a) we haveNote that the derivative is taken at resonance wavelength, we omit the terms that contain Ѩ␤ i /Ѩ in Eq. (A1). Substituting the relation (A2)into Eq. (A1), we obtain Eq. (9). Let ␤ r ϭ k 0 n r . In fiber SPR sensor, usually k 0 a ϾϾ 1, the mode index n r approaches a constant. ThereforeEquation (10a) and (10b) can be rewritten asClearly, it can be seen that C r Ͻ 0 and C m Ͻ 0. . In this paper, an alternative square slot antenna with an offset rectangular stub and an U-like slot is proposed for achieving the band-notched UWB operation. The proposed square slot antenna is simple in structure and easy to construct. The offset rectangular stub is first employed for achieving UWB operation. Then, a quarter-wavelength U-like slot is inserted into the rectangular stub and a notched frequency band at 5 GHz can thus be created. Details of the antenna design are described, and experimental results of the proposed antenna are presented and discussed. BAND-NOTCHED ULTRA-WIDEBAND SQUARE SLOT ANTENNA ANTENNA DESIGNThe geometry of the proposed band-no...

A compact ultra‐wideband slot antenna with multiple notch frequency bands

“…However, there is a tradeoff between the size of the antenna and the number of SRRs. Note that although the size of the antenna may increase with the increase of the number of SRRs, compared with previous reports [6,15] where a slot of about a quarter wavelength was cut from the antenna to obtain the desired notch frequency band, the average diameter of SRR can be designed as small as about one-tenth of the resonant wavelength, so that the total size of the proposed antenna is still relatively compact. In this article, we use two SRRs as a practical example to fabricate the prototype.…”

“…Compared with conventional UWB antennas etched with a quarter-wavelength slot for generating notch frequency bands [6,15], the average diameter of SRRs are much smaller, as about one-tenth of the resonant wavelength. Thus though multiple SRRs etched in the UWB antenna, the proposed antenna still keeps a compact dimension.…”

“…In the published literature, there have been some reports on UWB antennas with band notched characteristics [3][4][5][6]. However, each of these antennas is either complicated in design procedure [3,4], or with a bulky structure [5][6][7]. Moreover, most of the antennas [3][4][5][6][7] were designed to generate only one notch frequency band so that just one narrow band of disturbance can be eliminated.…”

“…Thus, it is desirable to design a UWB antenna with multiple band-notched characteristics to avoid the potential interference. In the published literature, there have been some reports on UWB antennas with band notched characteristics [3][4][5][6]. However, each of these antennas is either complicated in design procedure [3,4], or with a bulky structure [5][6][7].…”

Spline-based geometry for printed monopole antennas

“…Introduction: Geometries of recent UWB antennas are based on simple geometric elements, such as rectangles [1], circles [2] or ellipses [3], or a combination of these [4,5]. This Letter proposes a geometry based on quadratic Bézier curves (splines).…”