Normally, single element DRA acts as a low gain antenna, but it has a broad radiation pattern. In some applications, high gain antennas are the major requirement for efficient long distance communication. Like conventional low gain antennas, DRA gain can also be enhanced by placing it in an array configuration. Several different shapes of DRAs have been proposed in the literatures i.e., cylindrical , rectangular  and triangular . Among these shapes, cylindricaldielectricresonator antenna (CDRA) is widely used, due to its simple field structure as compared to rectangular DRA , and it is directional as compared to the rectangular and circular DRAs (i.e., rectangular and circular DRAs are bidirectional) . The CDRA is characterized by its height h, radius a and permittivity ε r as shown in Figure 1(a).
A dual- and triple-band cylindricaldielectricresonator antenna (CDRA) using varying permittivity in azimuth-direction fed by coaxial probe is proposed in this paper. The proposed structure is constructed using diﬀerent materials having diﬀerent permittivites in azimuth direction in cylindricaldielectricresonator (DR). The operating band can be scaled up or down by adjusting the design parameters. Dual-band and triple-band with equal segment CDRA have been fabricated using commercially available microwave laminates to validate the simulation results. In terms of radiation pattern, dual-band CDRA shows less cross-polar inﬂuence around 40 dB down in the direction of maximum radiation in yz-plane.
Engineering, Universiti Sains Malaysia, Penang 14300, Malaysia Abstract—A 1 × 3 element linear array using cylindricaldielectricresonator antennas (CDRAs) is designed and presented for 802.11a WLAN system applications. The top and bottom elements of CDRA array are excited through the rectangular coupling slots etched on the ground plane, while the slots themselves are excited through the microstrip transmission line. The third element (i.e., central CDRA) is excited through the mutual coupling of two radiating elements by its sides. This mechanism enhances the bandwidth (96.1%) and gain (14.3%) as compared to aperture coupled technique. It is also observed that the side lobe levels are reduced over the designed frequency band. Using CST microwave studio, directivity of 10.5 dBi has been achieved for operating frequency of 5.6 GHz. Designed antenna array is fabricated and tested. Simulated and measured results are in good agreement. The equivalent lumped element circuit is also designed and presented using Advanced design system (ADS) for this proposed array.
This article presents tuning of the operating frequency of an aperture coupled cylindricaldielectricresonator antenna (CDRA) by using a varactor diode. The aperture-coupled source is mostly used for DRAs because of its possibility of combination with monolithic microwave integrated circuits (MMICs). The varactor is used as a load to alter the resonant frequency of the antenna. Varactor diode has better switching speed, reliability and lowers applied voltage. It oﬀers a capacitance that can be continually tuned by varying the diode bias voltage. Hence the eﬀective electric length changes leading to the shift of antenna resonance to the higher frequencies.
Abstract—An ultra-wideband (UWB) planar monopole antenna integrated with a narrow-band (NB) cylindricaldielectricresonator antenna (DRA) is presented. The proposed antenna consists of a UWB monopole excited by a coplanar waveguide (CPW) transmission line, acting as a ground for a DRA excited by a slot. The mode HEM 11δ is excited in the NB DRA. To validate the concept of integration, an antenna is fabricated and measured. The measured results demonstrate that the UWB antenna provides a 2 : 1 voltage standing wave ratio (VSWR) bandwidth for 3.05–11 GHz, integrated with a dual-band NB antenna. Moreover, the two ports have the same polarization and a reasonable isolation (less than −10 dB) between each other. This is a promising candidate for applications in cognitive radio, where the UWB antenna can be used for spectrum sensing and the NB antenna for communication operation.
Abstract—This paper presents a novel compact Koch snowﬂake fractal ring based DielectricResonator Antenna (DRA) for ultra wideband application. Firstly, Koch snowﬂake fractal geometry is implemented on the conventional CylindricalDielectricResonator Antenna (CDRA). Further, the performance of the DRA is enhanced by fractal ring created on the snowﬂake geometry. With the application of the fractal and the fractal ring geometry, the Q-factor of DRA is reduced, thus the bandwidth of DRA is increased. The proposed antenna oﬀers a wide impedance bandwidth of 90% ranging from 4.7 GHz–12.4 GHz. The eﬀect of the fractal geometry enhances the gain of DRA. The proposed antenna achieves radiation eﬃciency more than 78%, throughout the bandwidth. Interestingly, the proposed conﬁguration reduces the DRA volume by 76.63% with reduced volume of 7.91 cm 3 . The experimental veriﬁcation of the proposed structure shows good agreement between simulated and measured results.
which include a removed-air-volume from a cylindricaldielectricresonator , a modified cylindricaldielectricresonator excited with a slot [2–4] and microstrip-fed line [5, 6], a quarter-wave monopole loaded with an annular dielectricresonator [7, 8], and also using hybrid dielectric resonators excited by a simple monopole antenna [9, 10]. A hemispherical dielectricresonator (HDR) antenna excited with a thick slot at the short circuited end of waveguide is recently analyzed in  using the Green’s function approach and the method of moments (MOM). Another MOM numerical study of split cylindricaldielectricresonator antennas on a conducting ground plane excited by a coaxial probe with a bandwidth of 35% is previously presented in . In addition, the other analytical simulations on the various DRAs were presented in [13, 14]. In these studies, not only, the analyses on the DRA with multiband operation have been not done, but also, the majority of the used dielectrics have low permittivity which simplifies the design.
A new broadband cylindricaldielectricresonator antenna is realized using drilling off Sierpinski carpet fractal shaped holes in the original cylindricaldielectric resona- tor. By shifting the feed position from the circumference to an inset position it is seen that matching over a wide- band covering the entire X-band becomes uniform. In this design, impedance bandwidth of 50% is obtained. In addition, the antenna cost is very low as an attempt has been made to realize DRA using low dielectric permitti- vity material like Teflon. With these features, this design Figure 8. Return loss plot of inset fed Sierpinski carpet
Abstract—Finite-Diﬀerence Time Domain (FDTD) is used to calculate the input impedance of the cylindricaldielectricresonator (DRA) antenna withdiﬀerent dimensions. A lumped- element circuit model for the input impedance calculation is proposed. The genetic algorithm is used to calculate the elements of the equivalent circuit. The Model-Based Parameter Estimation (MBPE) technique is used to ﬁnd the variation of each element in the equivalent circuit with varying the physical dimensions of the antenna. The use of this method reduces the time required for calculating the input impedance of the cylindrical DRA in eachvariation of the antenna dimension.
Abstract—In this paper dual segment half CylindricalDielectricResonator Antennas (DS h-CDRA), deploying homogenous elements, are designed and analyzed for wide-band applications. At ﬁrst a single element is analyzed followed by two element DS h-CDRA. Further, Radar Cross Section (RCS) analysis is performed for diﬀerent angles and frequencies. The proposed antennas are excited from the center of the ground plane using a coaxial probe feed, which results in TM 01δ as a mode of excitation in cylindrical DRA. The input impedance and radiation characteristics are determined and compared with measured results, which shows good agreement. The proposed DS h-CDRA provides measured wide bandwidth ( ≈ 98%) from 5.0 GHz to 11.5 GHz with gain of 4.85 dBi, and it is found constant throughout the operational band (with omnidirectional radiation pattern). The designed antennas performance has also been compared with two element h-CDRA and found even better for the same volume and eﬀective radiation area. The RCS analysis has been performed for monostatic and bistatic mode at diﬀerent frequencies and angles. The proposed antenna has been found suitable for 5.0 GHz WLAN and WiMAX wireless application.
generated in CDRA due to its low quality factor. These modes are not advantageous in the case of antenna because it aﬀects the radiation characteristics of other fundamental modes. Similarly, it is not easy to generate higher order modes (which is useful in the case of antenna) with the help of a simple feed structure [5, 6]. In order to avoid these diﬃculties, the concept of hybrid DRA comes into existence, which represents combination of DRA with other resonating structures [7, 8]. Similarly, Khalily et al. presented a hybrid CDRA (split half CDRA with fork shape monopole) for multiband applications . Cylindrical DRA along with parasitic slots on ground plane was proposed by Sharma and Gangwar . Recently, dual-polarized antennas are the most favorable topic of the researchers due to their several advantages such as orientation insensitive, getting more information by radar from targets, etc. In order to achieve dual polarizations along with multiband characteristics, some of the studies have been carried out by diﬀerent researchers such as aperture fed grooved modiﬁed RDRA (Rectangular Dielectricresonator antenna), probe-fed semi eccentricannular shaped DRA and metal covered CDRA [11–13].
∼ 28 . 3% and 9.5% in conjunction with a high gain of up to 13.9 dBic, which could have not been achieved at the absence of the outer dielectric coat. Increasing the impedance bandwidth by coating the antenna with a layer of lower permittivity is expected and have been reported in the literature. However, gain enhancement, wider axial ratio bandwidth, and improved fabrication tolerance have not been demonstrated earlier for a layered cylindrical DRA. Furthermore, two prototypes with outer layer thicknesses of δ a = 7 . 5 mm and 17 mm have been considered. The ﬁrst demonstrates a design with practical dimensions for the X-band frequency range. On the other hand, the potential of the second design could be exploited further at higher frequencies, for example at 60 GHz where the outer layer radius will be reduced to 4 mm.
The configuration of the proposed DRA is shown in Figure 1. It is prototyped on Rogers RO4350 substrate with dielectric permittivity of 3.66 and thickness of 0.762 mm. The feeding mechanism adopts a narrow slot (7.6×0.6 mm) centrally etched on a copper metallic ground with a size of 120 × 120 mm. The 50 Ω feeding microstrip line (width W = 1.7 mm) is etched at the center of the slot and terminated with an open stub of length L stub = 3.6 mm.
the simulated resonant frequency. Besides that, both return losses have almost the same matching level and lower than − 25 dB that showed good matching level. Both curves are in good agreement. As discusses earlier in the Section 2.2, the predicted resonant frequency by using dielectric waveguide model is 8.83 GHz. By comparing with the simulated and measured results, the frequency is nearly the same. The diﬀerence between theory and experiment resonant frequency is only 90 MHz or around 1%. Simulated bandwidth at − 10 dB return loss is 116 MHz whereas the measured bandwidth is lower with only 18 MHz. The measured result has a narrower bandwidth as compared to the measured one. This is due to the bad surface ﬁnishing of the rectangular dielectricresonator which tends to chip at the edge of the rectangular surface. Consequently, it aﬀects the dielectric properties of DRA and S-parameter value.
The dielectricresonator antennas (DRAs) have attracted wide attentions in various applications, as armored filters or oscillators [1,2], They offer several advantages in terms of high radiation efficiency and Q factor. Indeed, when a resonator is placed in a cavity, it presents a high quality factor, which allows the realization of a highly selective filter.
Abstract—Conical and cylindricaldielectricresonator elements are vertically stacked and excited by a simple coaxial monopole. Compared to all earlier conﬁgurations, the proposed geometry signiﬁcantly improves the impedance bandwidth. The ultrawideband response is enhanced due to the multiple resonances occurring by the suggested hybrid antenna. The footprint area of the antenna is only 63.6 mm 2 or 25 . 44 × 10 − 3 λ 2 o at the lowest operating frequency. The performance of the antenna is veriﬁed experimentally and numerically. Presented results show that the proposed hybrid monopole-DRA has a measured impedance bandwidth up to 148.6% ( S 11 < − 10 dB) along with consistent monopole-like
Abstract: This paper presents a stacked cylindricaldielectricresonator antenna with wide circular polarization (CP) bandwidth (axial ratio < 3dB) of 16.0%. This wide CP bandwidth is achieved by stacking low permittivity dielectric (9.2) resonator on high permittivity dielectric (9.8) resonator to obtain improved impedance and axial ratio bandwidths as compared to conventional DRA. It is also shown that the asymmetrical structure used in the geometry results in a very high impedance bandwidth (more than 100%) in the frequency range of 2.1 GHz-12.0 GHz but at the expense of distorted CP operation on the off-broadside. This essentially covers the FCC band of operation (3.1GHz to10.6 GHz).
Abstract: In Today’s wireless era, need of a highly optimized antenna having compact size, low cost, high efficiency, larger bandwidth is must. This increases demand of designing antennas having such benefits. This research study is a short description carried out in the past few years and latest progression of DielectricResonator Antenna for different uses. Special character of DielectricResonator Antenna provides compactness, high gain, and negligible metallic and surface losses. It also gives wider bandwidth. In modern communication, DielectricResonator Antenna is utilized for many implications as radar technology, nano-technology, wireless communication and satellite communication. This paper represents a study of simulation of a DielectricResonator based on its cylindrical shape for wireless application. Various technique of cylindricalDielectricResonator Antenna is described in this paper.
Abstract—In this paper, the radiation characteristics of the single- element cylindricaldielectricresonator antenna mounted on the surface of a metallic hollow circular cylindrical structure is investigated. The effect of the radius of curvature on the return loss, input impedance, standing wave ratio, and radiation pattern is explored. Mutual coupling between two identical cylindricaldielectricresonator antennas on a cylindrical structure in different configurations is determined. To reduce the mutual coupling between the two antennas, the surface of the cylinderical ground plane is defected by cutting slots, or inserting quarter wavelength grooves between the two antennas. The finite element method and the finite integration technique are used to calculate the radiation characteristics of the antenna.
By removing the shielding and with proper feeding schemes, these DRs are found to be functioning as efficient radiators. In fact, the theoretical investigations on the radiation characteris- tics of DRs were carried out long ago in the 1960s as a sideline and practically suppressed for the prevailing application of oscillators and filters until 1983 , . In this year, S. Long et al. published a paper on the cylindricaldielectricresonator antenna (DRA) which studied and examined at length the radiation performances of DRs as antennas . After that, they continued with the research on this subject to explore DRAs in other shapes: rectangle  and hemisphere . All their serial work laid the foundation for future extensive investigations on various aspects of DRAs in various forms , .