Modelling of probe‐fed cylindrical dielectric resonator antennas

Probe‐fed cylindrical dielectric resonator antennas (CDRAs), with dielectric constant ϵ_r=37 and supported by an infinite ground plane, are simulated using the finite element method. From this, closed form expressions are obtained for the resonant frequency, directivity, and unloaded Q‐factor, applicable to a wide range of antenna dimensions. The effects of (a) the finite circular ground plane, (b) the air gap between the CDRA and the ground plane, (c) the air gap between the CDRA and the feed probe, and (d) the length of the probe on these parameters are studied for a particular CDRA and appropriate correction factors are derived. The simulated results are compared with those obtained experimentally for various ground planes, probe lengths, and probe spacings. The closed form expressions provide good agreement with the experiments in resonant frequency, unloaded Q‐factor, and impedance bandwidth, but less accurate prediction in antenna directivity for the specified range of parameters. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 2–13, 1999     

Complementary meander‐line‐inspired dielectric resonator multiple‐input‐multiple‐output antenna for dual‐band applications

The communication presents a simple dielectric resonator (DR) multiple‐input‐multiple‐output (MIMO) dual‐band antenna. It utilizes two “I”‐shaped DR elements to construct an “I”‐shaped DR array antenna (IDRAA) for MIMO applications. The ground plane of the antenna is defected by two spiral complementary meander lines and two circular ground slots. In the configuration, two “I”‐shaped DR elements are placed with a separation of 0.098λ. The antenna covers dual‐band frequency spectra from 3.46 to 5.37 GHz (43.26%) and from 5.89 to 6.49 GHz (9.7%). It ensures the C‐band downlink (3.7‐4.2 GHz), uplink (5.925‐6.425 GHz), and WiMAX (5.15‐5.35 GHz) frequency bands. Each DR element is excited with a 50‐Ω microstrip line feed with aperture‐coupling mechanism. The antenna offers very high port isolation of around 18.5 and 20 dB in the lower band and upper band, respectively. The proposed structure is suitable to operate in the MIMO system because of its very nominal envelope correlation coefficient (<0.015) and high diversity gain (>9.8). The MIMO antenna provides very good mean effective gain value (±0.35 dB) and low channel capacity loss (<0.35 bit/s/Hz) throughout the entire operating bands. Simulated and measured results are in good agreement and they approve the suitability of the proposed IDRAA for C‐band uplink and downlink applications and WiMAX band applications.     

Wideband circularly polarized dielectric resonator antenna coupled with meandered‐line inductor for ISM/WLAN applications

A new meandered‐line inductor fed wideband circularly polarized rectangular dielectric resonator antenna (DRA) with partial ground plane has been developed in this work. Meandered‐line inductor feed and partial ground plane are used for generation of orthogonal modes, hence circular polarization (CP) in DRA. By controlling the length of meandered‐line inductor, three different CP DRA have been designed for different wireless applications such as Wi‐MAX and WLAN/ISM 2400 band. Distribution of electric field inside rectangular DRA shows that all three antenna having TE_11δ mode. Finally, a lower frequency band application at 2.4 GHz (ISM) called here as Proposed Antenna, has been considered for fabrication. This designed antenna shows measured ?10 dB input impedance bandwidth of 20.67% and 3‐dB axial ratio bandwidth of 27.95% in broadside direction. All these three CP antennas (Antenna‐1 to Proposed Antenna) are showing stable gain and right hand circular polarization in broadside direction.     

Design of a 16‐beam pattern‐reconfigurable antenna for vehicular environment

This article presents the design of a multipattern antenna with pattern switching for vehicular communications. The proposed antenna has four triangular patches integrated onto a split square ring (SR) resonator to operate at two distinct frequencies, viz. 2.4 and 3.5 GHz. The proposed antenna is designed with a view to enhancing the link reliability of Wireless Local Area Network (WLAN), WiMax, and vehicle to vehicle communication frequencies. Each triangular patch is separately excited using a microstrip line feed to enable beam steering. The ground plane of the antenna is embedded with two SR slots to improve the bandwidth and radiation performance. Further gain enhancement is achieved by loading the antenna with a plane reflector located at a distance of 20 mm from the antenna's ground surface. In reality, this reflector is realized using the vehicle's roof which provides gain enhancement up to 5.2 dBi at 2.4 GHz and 4 dBi at 3.5 GHz. By exciting single to multiple ports sequentially 16 different radiation patterns are obtained, which provides high‐gain omnidirectional coverage. The prototype antenna is fabricated and the simulation results are verified using experimental measurements. From the results, it is evident that the proposed antenna is suitable for vehicular communication applications.     

A thin‐layer dielectric and metamaterial unit‐cell stack loaded miniaturized SRR‐based antenna for triple narrow band 4G‐LTE applications

This article presents the design of a miniaturized dual‐band antenna for long‐term evolution (LTE) application is presented. In the basic antenna design, split ring resonator was loaded in the radiating plane of the patch and frequency of resonance was further modified with the help of E‐shaped stub. The antenna has been fabricated using FR‐4 substrate and the measured dual bands at 2.11 and 2.665 GHz are found in a close match with the simulated data. By placing a thin dielectric resonator of permittivity ε _r = 10.2 and thickness of 1.27 mm, two closely spaced narrow bands are obtained at 2.217 and 2.28 GHz. A novel metamaterial unit‐cell having near‐zero refractive index is designed and mounted above the dielectric resonator. This stack configuration generates triple narrow frequency band in the LTE 2 GHz spectrum range. The overall size of the proposed antenna is 20 × 25 mm².     

Input impedance of microstrip-slot-coupled dielectric resonator antennas mounted on thin dielectric layers

An efficient numerical technique based upon a surface integral equation formulation for the coupling of bodies of revolution (BORs) to non-BOR geometries for the design of practical microstrip-slot-aperture-coupled dielectric resonator antennas is presented. The moment method matrix fill time and memory requirements are significantly reduced by utilizing Fourier mode basis functions on the BOR together with the spectral domain Green's function for the printed circuit board. Two practical antennas are designed and fabricated. Antenna input impedances predicted by this technique are in good agreement with those of the actual devices. © 1996 John Wiley & Sons, Inc.     

A compact printed ultra‐wideband multiple‐input multiple‐output prototype with band‐notch ability for WiMAX,LTEband43, and WLAN systems

A compact ultra‐wideband multiple‐input multiple‐output (UWB‐MIMO) antenna with good isolation and multiple band‐notch abilities is developed in this work. It consists of two quadrant shaped monopole antennas backed by ground stubs. A good isolation is achieved due to the two proposed extended curved ground stubs. The frequency rejection for the WLAN system is realized by loading a capacitive loaded loop resonator adjacent to the feed line. The band rejection for the WiMAX and LTE band43 system is achieved by embedding a quadrant shaped CSRR on each radiator's surface. The measured bandwidth of the antenna is 3.06 GHz‐11 GHz (|S₁₁| < ?10 dB and |S₂₁| < ?18 dB) with a band rejection from 3.5 GHz‐4 GHz to 5.1 GHz‐5.85 GHz, respectively. Time domain performances are investigated in terms of group and phase delay characteristics. Diversity characteristics are evaluated in terms of the envelope correlation coefficient, mean effective gain, and channel capacity loss.     

A robust method for the computation of new closed‐form Green's functions for microstrip structures

A robust approach for the computation of new closed‐form Green's functions is considered to calculate the symmetrical microstrip Green's functions. In this method, the surface‐wave poles are first extracted using a recursive contour integration method. Then, the remainder is approximated by a series of complex exponentials using the Prony's method or the generalized pencil‐of‐function method (GPOF) along the extended rooftop shaped path in k_ρ‐plane. Subsequently, an analytical identity is employed to obtain the new spatial‐domain Green's functions. It is observed that this method can evaluate the spatial‐domain Green's functions accurately and efficiently for both near and far fields. In addition, there is no erroneous results in the near‐field region when z ≠ z′ and ρ → 0. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Stacked rectangular dielectric resonator antenna with different volumes for wideband circular polarization coupled with step‐shaped conformal strip

This paper presents a wideband circularly polarized broadside radiation characteristics by using stacked rectangular dielectric resonator antenna (DRA) with different volumes. In this designed antenna, the wide input impedance‐ and axial ratio (AR)‐bandwidths come from three factors: stacked rectangular DR with different volumes, stepped‐shaped conformal strip associated with microstrip line as a feed and different type of partial ground plane. Here, the orthogonal TE^x_δ11 and TE^y_1δ1 modes have been responsible for the generation of CP radiation in stacked rectangular DRA. Measured results show that the proposed stacked rectangular DRA with different volumes achieves input impedance bandwidth of 54.84% while AR bandwidth has been found to be 11.53%. The proposed antenna provides broadside right‐handed CP radiation pattern with gain ranges from 2.27–5.80 dBic and offers an average radiation efficiency of 89.48%, across the entire working bandwidth, respectively. Therefore, this antenna is very much useful for the ISM 2400 band applications.     

Investigation of higher order modes excitation through F‐shaped slot in rectangular dielectric resonator antenna for wideband circular polarization with broadside radiation characteristics

In this article, a wideband circularly polarized rectangular dielectric resonator antenna (RDRA) with broadside radiation characteristics has been proposed. By using modified ground plane having an F‐shaped slot, the proposed structure able to generates three sets of modes i.e., fundamental as well as higher order modes. To obtained circular polarization, an orthogonal mode (TE₁₁₃) in the RDRA has been generated by using the F‐shaped slot on the modified ground plane. The resonance frequency of fundamental mode (TE₁₁₁) in the rectangular dielectric resonator (DR) has been calculated by using dielectric waveguide model method. The same has been confirmed through E‐field distribution in RDRA. Here, wide axial ratio (AR) bandwidth of the proposed antenna is due to the generation of and modes. It is observed that input impedance bandwidth has been broadening with a pair of excited modes ( and modes) in the proposed antenna structure. All these modes have been excited and merged to form a wide input impedance bandwidth and wide AR bandwidth of the designed antenna. The proposed antenna shows measured input reflection coefficient (S₁₁ < ?10 dB) of 50.55% and measured AR bandwidth (AR < 3 dB) of 14.28%. The designed antenna shows left‐handed circular polarization in broadside direction and offering an average gain and radiation efficiency of 4.29 dBic and 92.22% respectively.     

Optically transparent broadband water antenna

In this article, we investigate an optically transparent broadband water antenna, which is composed of a cross‐shaped slot feeding structure and a thin layer of water supported by a transparent dielectric slab. This water antenna can be analyzed as an embedded stacked dielectric resonator (DR) antenna (DRA) mounted on a ground plane. Two distinct resonator modes—namely, DRA mode and dielectric‐loaded slot (DLS) mode—are excited to achieve a good impendence matching over a very wide frequency range. A prototype antenna is designed, fabricated, and measured. Measured results demonstrate that the designed water antenna exhibits a broad impedance bandwidth of about 37% from 1.07 to 1.56 GHz with antenna efficiency better than 65% and broadside radiation characteristics with low cross‐polarizations.     

Low profile four‐port super‐wideband multiple‐input‐multiple‐output antenna with triple band rejection characteristics

A quad‐port planar multiple‐input‐multiple‐output (MIMO) antenna possessing super‐wideband (SWB) operational features and triple‐band rejection characteristics is designed. The proposed MIMO configuration consists of four modified‐elliptical‐self‐complementary‐antenna (MESCA) elements, which are excited by tapered co‐planar waveguide (TCPW) feed lines. A radiator‐matched complementary slot is present in the ground conductor patch of each MESCA element. The proposed MIMO antenna exhibits a bandwidth ratio of 36:1 (|S₁₁| < ?10 dB; 0.97‐35 GHz). Further, a step‐like slit‐resonator is etched in the radiator to eliminate interferences at 3.5 GHz. A hexagonal shaped complementary split ring resonator (CSRR) is also loaded on the MESCA radiator to remove interferences at 5.5 and 8.5 GHz. The MIMO antenna is fabricated on FR‐4 substrate of size 63 × 63 mm² and experimental results are found in good agreement with the simulated results. The MIMO antenna exhibits inter‐element isolation >17 dB and envelope correlation coefficient (ECC) <0.01 at all the four ports.     

Circularly polarized rectangular DRA coupled through orthogonal slot excited with microstrip circular ring feeding structure for Wi‐MAX applications

In this article, a wideband circularly polarized rectangular dielectric resonator antenna (RDRA) coupled through orthogonal slots and excited with a new microstrip circular ring has been investigated. Circular polarization has been achieved by using plus shaped (+) slot on the ground plane and excited through a new microstrip circular ring feed. TE_11δ mode has been excited in the RDRA which has been confirmed through the distribution of E ‐field and dielectric waveguide model (DWM) method of RDRA. Circularly polarized (CP) RDRA offering measured ?10 dB input impedance bandwidth of 20.79% (centered at 3.27 GHz) and 3 dB axial ratio bandwidth in broadside direction of 12.09% (centered at 3.39 GHz), respectively. From the CP radiation pattern, proposed design confirms that right ‐ handed CP (RHCP) in broadside direction. The difference between RHCP field and left ‐ handed CP (LHCP) field are above ?26 dB in operational band. In addition, the proposed CP antenna offers stable gain and radiation efficiency in working bands and it is suitable for IEEE 802.16e/d Wi‐MAX (3.3‐3.7 GHz) band.     

A computer‐aided approach for designing dielectric‐covered planar array antennas consisting of longitudinal slots

A straightforward design approach is proposed to design arrays of longitudinal slots covered with dielectric slabs. The design of the arrays is accomplished via linking the slotted array antennas fed by the waveguides to a corresponding array of the loaded slots cut in an infinite ground plane and covered with dielectric slab. In this regard, the Elliott's design equations are modified for the dielectric‐covered longitudinal slotted array antennas. The introduced design equations are employed to find the final dimensions of the slot antennas while the updated mutual admittances of the corresponding array of the loaded slots are used iteratively in the design equations. Employing the introduced design equations, a two by three slotted array antenna was designed, simulated and tested. The proposed design approach is verified by the simulation and the measurement results.     

CSRR‐loaded T‐shaped MIMO antenna for 5G cellular networks and vehicular communications

This article proposes a multiple input multiple output (MIMO) antenna for 5G‐based vehicular communication applications. The designed MIMO antenna consist of two element iterated T‐shape antenna with defected ground structure (DGS) and split ring resonator. The antenna providing reflection coefficient S₁₁ s₁₁ ≤10 dB and bandwidth of 6.3 and 3.96 GHz over the frequency range of 26.83 to 33.13 GHz and 34.17 to 38.13 GHz, respectively. For the suitable future vehicular millimetric wave communications, this antenna achieved resonant frequencies at 28, 33, and 37 GHz. The designed antenna has achieved peak gain of 7.11 dB in operating band. It is fabricated on 12 x 25.4 x 0.8 mm³ Rogers RT duroid 5880 substrate with dielectric constant (ε_r) of 2.2. The antenna is placed on vehicle in virtual environmental using ANSYS SAVANT tool and the simulated results are showing good matching with the measured results of proposed MIMO antenna.     

Isolation enhanced circularly polarized patch antenna array using modified electric‐field‐coupled resonator

A modified electric‐field‐coupled (MELC) resonator featuring negative permittivity is proposed to enhance the inter‐element isolation of a circularly polarized (CP) patch antenna array operated at Chinese compass navigation satellite system (CNSS) downlink band. The resonator comprises two capacitive gaps and a common inductive strip connected to the ground plane by two metal vias. A suspended microstrip line excitation is employed to efficiently design and investigate the MELC resonator whose constitutive parameters are subsequently extracted. A dual‐element CNSS antenna array has been prototyped and measured. The experimental results demonstrate that under the assistance of the proposed MELC resonator, a mutual coupling reduction of 15 dB has been achieved while maintaining good impedance matching and CP radiation performance. Details of the design considerations along with simulation and measurement results are presented and discussed.     

Miniaturized dual‐band dielectric resonator antenna for IEEE 802.16d fixed WiMAX applications

A miniaturized dual‐band C‐shaped dielectric resonator antenna (DRA) with partial ground plane is presented for IEEE 802.16d fixed WiMAX applications at 3.5 and 5.8 GHz. The design starts with dimensioning a single band cylindrical DRA, which has been transferred to get a dual‐band ring‐shaped DRA. One portion of the ring‐shaped DRA is removed for forming a C‐shaped DRA to get a more compact antenna. For easy fabrication, the compact DRA dimensioned as 60 × 50 × 6.6 mm³ is excited by a microstrip line feeding. The design parameters are inner and outer radii of the C‐shaped antenna and air gap (between DR and ground) to control both the resonating frequency and the quality factor. The result shows peak gain around 3.26 and 5.55 dBi at 3.5 and 5.8 GHz, respectively. The obtained results indicate very good agreement between the simulated and measured results. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 22: 682–689, 2012.     

Quad notch UWB antenna using combination of slots and split‐ring resonator

A novel coplanar waveguide fed UWB antenna with quad notch band characteristics has been proposed in this work. The antenna layout is designed based on a combination of well‐known geometrical shapes: a half ellipse patch, rectangle, and triangle. The shape of the ground plane is partially tapered rectangular. The overall dimension of the antenna is 41.5 × 32 mm. The antenna uses three U‐shaped slots at the top surface to create three notched band characteristics. A split‐ring resonator is then introduced at the bottom surface of the antenna. With the integration of split‐ring resonator at the bottom surface, an additional notch band at 7.25 to 7.75 (6.7%) GHz is created in the antenna. The designed antenna has an operating impedance bandwidth (VSWR ≤2) ranges from 3.03 to 12.34 GHz except in quad frequency stop bands of 3.3 to 3.7 (11.4%), 5.15 to 5.35 (3.8%), 5.725 to 5.825 (1.7%), and 7.25 to 7.75 (6.7%) GHz. The proposed antennas are successfully designed, prototyped, and measured. The simulated and measured results are extensively studied and discussed. Correlation between the time‐domain transmitting antenna input signal and the received antenna output signal is calculated in order to ensure that the proposed antenna can be used in pulse‐communication systems. This antenna finds applications in medical imaging, military radar systems, and other common UWB applications.     

Design of Miniature UWB-Based Antenna by Employing a Tri-Sectional SIR Feeder

A novel ultra-wideband (UWB)-based microstrip antenna is presented in this work by using a slotted patch resonator, a tri-sectional stepped impedance resonator (SIR) feeder, as well as a reduced ground plane. The whole structure was realized on an FR4 substrate. The impact of incorporating several cases of ground planes on the input reflection has been thoroughly investigated under the same tri-sectional SIR feeder and by employing a slotted patch radiator. Since the complete ground plane presents an inadequate frequency response, by reducing the ground plane, the induced UWB responses are apparent while the antenna exhibits higher impedance bandwidth. The impact of both the uniform impedance resonator (UIR) as well as the SIR feeder on the input reflection has also been examined by following the same adopted reduced ground technique and using a slotted patch radiator. As a result, the UIR feeder exhibits a dual-band frequency response, when a wide notched band is incorporated in the range from 4.5–6.5 GHz. The dual-band response of the bi-sectional SIR feeder is still apparent with a narrower notched band in the frequency range from 4–5 GHz. As far as the tri-sectional SIR feeder is concerned, the UWB response is discernible without recording the existence of a notched band. Additionally, the antenna displays a higher impedance bandwidth compared with the previously reported steps. Our proposed antenna configuration is designed with highly compact dimensions and an overall size of 14 × 27.2 mm². Moreover, it operates under the impedance bandwidth of 2.86–10.31 GHz that can be leveraged for numerous applications where wireless systems are used. Our approach presents several advantages compared with the other reported UWB-based antennas in the literature, whereas the measured S₁₁ pattern is in good agreement with the simulated one.     

A vertex‐fed hexa‐band frequency reconfigurable antenna for wireless applications

Present article embodies the design and analysis of an octagonal shaped split ring resonator based multiband antenna fed at vertex for wireless applications with frequency‐band reconfigurable characteristics. The proposed antenna is printed on FR4 substrate with electrical dimension of 0.4884 λ × 0.4329 λ × 0.0178 λ (44 × 39 × 1.6 mm³), at lower frequency of 3.33 GHz. The antenna consists of SRR based vertex fed octagonal ring as the radiation element and switchable reclined L‐shaped slotted ground plane. Antenna achieves six bands for wireless standards viz: upper WLAN (5.0/5.8 GHz), lower WiMAX (3.3 GHz), super extended C‐band (6.6 GHz), middle X band (9.9 GHz—for space communication), and lower K_U band (15.9 GHz—for satellite communication systems operating band). Stable radiation patterns are observed for the operating bands with low cross polarization. The proposed design achieves hexa band characteristics during switching ON state of PIN diode located at reclined L‐shaped slot in the ground plane. Experimental characteristic of antenna shows close agreement with those obtained by simulation of the proposed antenna.