Conformal Strip Research Articles

A Self-Decoupling Method for MIMO Linear and Planar Dielectric Resonator Antenna Arrays Based on Transmission Characteristics of Feeding Structure

In this paper, a novel self-decoupling method for the multi-input multi-output (MIMO) dielectric resonator antenna (DRA) arrays is investigated. This method is based on the transmission characteristics of the conformal strip that feeds the DRA. It is found that when the strip-fed DRA operates in the higher-order mode, e.g., TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">113</sub> mode, the E-field coupled to the metal strip of the adjacent passive DRA presents a standing wave distribution. By appropriately adjusting the dimensions of the feeding strip, the E-field can form a node with zero amplitude at its bottom where a coaxial probe is connected, preventing the energy from getting into the receiving port and hence achieving a high isolation level without requiring any extra decoupling structure. This self-decoupling method is applicable not only to one-dimensional (1-D) H- and E-plane coupled MIMO linear arrays but also to two-dimensional (2-D) MIMO planar array. To verify its feasibility, a prototype of 2 × 2 MIMO planar DRA array is simulated, processed, and tested. The results show that a usable bandwidth (|S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ii</sub> | < -10 dB and |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ij</sub> | < -20 dB) of 10.8% is achieved, and the maximum isolation is over 40 dB within the passband.

Conformal strip fed circularly polarized defected dielectric resonator antenna (CPDDRA) for 6G applications

In this paper, a broadband circularly polarized (CP) dielectric resonator antenna (DRA) is proposed for terahertz (THz) applications. It consists of a silicon-based defected rectangular dielectric resonator (DR), excited by an asymmetric conformal strip feeding and a defective metallic ground plane. Multiple orthogonal modes are excited using a defective dielectric resonator antenna (DRA) and asymmetric conformal metallic strip to generate circular polarization. The proposed antenna has a fractional bandwidth of 89.5% (2.87–7.52 THz) and an axial ratio bandwidth of 79.2% (2.73–6.31 THz). The proposed antenna provides RHCP radiation pattern in the +z-direction and LHCP in the −z-direction. A peak gain of 6 dB is achieved at 6.9 THz with a compact antenna dimension of 50 × 40 μm2. An equivalent circuit with lumped elements is also presented for the proposed antenna in this paper. The simulated results of the proposed structure are in good agreement with those of equivalent circuit model. The proposed antenna structure fulfils all the requirements of a 6G antenna by operating over a wide terahertz frequency spectrum with circular polarization characteristics, an average peak gain, stable radiation patterns and compact dimensions.

Circular Dielectric Rod With Conformal Strip of Graphene as Tunable Terahertz Antenna: Interplay of Inverse Electromagnetic Jet, Whispering Gallery and Plasmon Effects

In this article, we consider the radiation characteristics of a THz antenna made of a circular dielectric rod decorated with conformal graphene strip and illuminated by the field of a line magnetic current. The strip has arbitrary angular size and location and its surface impedance is characterized with Kubo theory. Our mathematically accurate analysis uses a dedicated hypersingular integral equation for the current induced on the strip. Discretization of this equation is carried out by the Nystrom-type method, which has a guaranteed convergence. We study the dependences of the powers radiated and absorbed in this configuration and also the directivity of antenna emission, in wide frequency range from 0 to 10 THz. They show very interesting interplay between the broadband inverse photonic-jet effect of lens-like dielectric rod and two types of resonances: on the moderate-Q plasmon modes of graphene strip and on the extremely high-Q whispering-gallery modes of the circular rod.

An ultra wideband “ OM ” shaped DRA with a defected ground structure and dual polarization properties for 4G / 5G wireless communications

This research article reports a new Dielectric Resonator Antenna (DRA) with its Dielectric resonator (DR) modified to an “OM” shape for UWB (3.1-11.1 GHz), to support high data rate multimedia applications for 4G/5G communications. The proposed DRA reports a peak gain of 7.68 dB and a dual polarization behavior for a frequency band from 6 to 11.1 GHz. It has overall antenna dimensions of 50 × 40 × 4.87 mm3 and is fabricated on a commercially available Rogers RT 5880 substrate (with εr = 2.2), which is fed using a microstrip feedline with a P-type transformer that offers an input impedance of 50 Ω to the DR. A conformal strip between the feedline and the OM shaped DR improves the impedance matching at the UWB frequency response of the DRA. This UWB frequency response is mainly because of its optimized “OM” shaped DR structure that excites a TE111 mode at 4.9 GHz and two higher order modes TE211 and TE221 at resonant frequencies of 7.2 and 8.35 GHz, respectively. Additionally the proposed OM shaped DR also generates orthogonal modes of TE211x and TE211y at 6.5 and 7.2 GHz and TE221x and TE221y at 8.35 and 10 GHz, respectively. The proposed DRA therefore exhibits an elliptically polarized behavior with axial ratio bandwidth of 5.1 GHz (≤10 dB) from 6 to 11.1 GHz. A measured impedance bandwidth of 5.25 GHz from 3.8 to 9.05 GHz and 1.5 GHz from 10 to 11.5 GHz and a peak-measured gain of 7.68 dB at 10.5 GHz (with an average gain of 4.6 dB) has been reported for the proposed DRA. An UWB performance, with good gain properties and an elliptically polarized behavior allows the proposed “OM” shaped DRA to be suitable for short range 4G/5G UWB wireless communications for future multimedia rich WPAN (wireless personal area networks), WLAN, Wi-MAX, INSAT applications, satellite applications, and X band RADAR (for defense communication) applications.

A compact multiband dielectric resonator antenna for wireless communications

AbstractA compact multiband rectangular dielectric resonator antenna (RDRA) is proposed in this study for worldwide interoperability for microwave access, wireless local area network, and fifth‐generation applications. The dielectric resonator antenna is fed by a 2‐slot etched coplanar waveguide with a conformal strip feed, a dielectric resonator with a dielectric constant of 37 is used and embedded into the substrate, and a foam substrate is used as a holder. The RDRA exhibits multiband and omnidirectional radiation patterns by generating a monopole mode as well as the typical and modes, which provides impedance bandwidths (|S11| &lt; −10 dB) of 29.0% at the first band, 15.1% at the second band, and 6.2% at the third band. Additionally, the RDRA achieves a maximum total efficiency of 94.4% at 4.8 GHz and an overall total efficiency of 70% at the desired frequency bands.

Dielectric resonator based multiport antenna system with multi-diversity and built-in decoupling mechanism

In this article, an eight-element, sixteen port dielectric resonator (DR) based double sided multi-port antenna is presented, which supports the unique dual-directional pattern diversity feature. The orientation of the double-sided dielectric resonator antenna (DRA) is one of the novel features of the proposed antenna. Four cylindrical dielectric resonator antennas (cDRAs) are placed at the top of the substrate, and each top cDRA is excited with the help of two orthogonally placed coplanar waveguide (CPW) fed conformal microstrip lines. In the same manner, the other four cDRAs are placed at the bottom of the substrate, and each cDRA is fed via conformal strip lines. The proposed antenna works in between 5.4 GHz and 6.0 GHz. Several isolation techniques (polarization diversity, pattern diversity, and separation between the antenna elements) within the antenna elements are approached to improve the antenna performance. As a result, without using any isolation improvement technique, the proposed structure achieves 17 dB of isolation between the ports, which makes the proposed radiator unique. The similarity in simulated and experimental outcomes confirms that the designed 16-port multi-port antenna system is suitable for Wireless LAN applications.

The design of a turtle-shaped dielectric resonator antenna for ultrawide-band applications

A novel type of turtle-shaped dielectric resonator antenna is proposed for use in ultrawide-band applications. Nine layers of different shapes of slabs are integrated and excited through a conformal strip. This staired-pyramid-type structure provides a large surface area for higher radiation efficiency. The integrated antenna is built on a defected ground structure to enhance the bandwidth of the antenna. The simulations and measured results for a fabricated prototype antenna for use in ultra-wideband applications are found to be in good agreement. The proposed antenna operates from 3.0 to 10.9 GHz (bandwidth 7.9 GHz), providing an impedance bandwidth of 114%. The ultrawide bandwidth is achieved by proper mixing of lower and higher modes generated through the slabs.

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 TExδ11 and TEy1δ1 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.

Compact Single-/Dual-Polarized Filtering Dielectric Resonator Antennas

A compact single-polarized filtering dielectric resonator (DR) antenna (DRA) with high selectivity is investigated. The DRA is fed by hybrid microstrip line/conformal strip, excited in its fundamental TE $_{1\delta 1}^{y} $ mode. Owing to different loading effects of the microstrip stub and conformal strip, the resonance frequency of TE $_{1\delta 1}^{y}$ mode excited by the two feed lines is slightly different. Such stepping resonances yield a wide bandwidth of 21.9% and a very flat gain of 5.1 dBi. The hybrid-feeding scheme also establishes a cross-coupled structure in the DRA, which introduces two radiation nulls right near the band edges. A compact wideband filtering DRA (FDRA) with quasi-elliptic bandpass response is, therefore, obtained without requiring any specific filtering circuit. This single-polarized design is also modified to realize a dual-polarized FDRA by adding another orthogonal port with the same feeding scheme. To reduce mutual coupling between the two ports, the microstrip stubs are folded to L shape, and four additional metal posts are inserted into the DR. As a result, the isolation is improved by 14 dB, from 7.2 to 21.2 dB.

Compact back‐to‐back DRA‐based four‐port MIMO antenna system with bi‐directional diversity

This Letter presents a dielectric resonator (DR)-based multiple-input-multiple-output (MIMO) antenna with bi-directional pattern diversity. The back-to-back arrangement of cylindrical DR antennas DRAs (cDRAs) is one of the unique features of the proposed design. The cDRAs are placed on an FR4 substrate with a common ground plane. Each cDRA element is excited by two ports to establish a four-port MIMO antenna system. At ports 1 and 2, the top cDRA is excited via co-planar waveguide (CPW) fed conformal strip lines. In case of ports 3 and 4, the bottom cDRA is excited by microstrip line fed conformal strip lines. Isolation between all ports is improved (better than 18 dB) by generating orthogonal modes in the cDRAs and use of opposite excitations. Measured results confirm that the proposed four-port MIMO antenna system is useful for the frequency ranges between 5.4 and 6.0 GHz for WLAN applications.

A-shaped wideband dielectric resonator antenna for wireless communication systems and its MIMO implementation

In this article, a new A-shaped dielectric resonator antenna (DRA) excited by a conformal strip is proposed for wideband applications. The wide bandwidth is achieved by combining two adjacent modes that is, TM101 and TM103. The experimental results demonstrate that the proposed DRA offers an impedance bandwidth (for S11−10 dB) of 59.7% (3.24-6.0 GHz), covering IEEE 802.11 and U-NII bands. The antenna provides a fairly stable radiation pattern with the gain ranging from 5.29 to 7 dBi across the operating bandwidth. A dual-element multiple-input multiple-output (MIMO) system is also realized using the proposed wideband DRA. The impedance bandwidth of the dual-element MIMO antenna is 59.2% and 60.9% for Port1 and Port2, respectively and the isolation between the ports is better than 20 dB across the bandwidth. For Port1, the gain of the MIMO antenna ranging from 6.03 to 7.45 dBi is obtained across the bandwidth. Furthermore, the diversity performance of the MIMO antenna is found to be good with envelope correlation coefficient below 0.003 over the operating band. The proposed antenna could be the potential candidate for worldwide interoperability for microwave access (WiMAX), wireless local area network (WLAN) and lower European UWB frequency band (3.4-5.0 GHz) applications.

Investigation of an asymmetrical E‐shaped dielectric resonator antenna with wideband characteristics

A novel low profile dielectric resonator antenna (DRA) is presented in this study for broadband applications. An asymmetric E-shaped dielectric resonator is analysed and optimised numerically as a wideband radiator. The fundamental mode is excited along with three nearest higher modes inside the DRA. A detailed impedance transformation is discussed to merge these modes collectively resulting in a single wideband operation. A microstrip fed conformal strip is used to stimulate the DRA. The proposed DRA is fabricated and tested. For |S11| ≤ −10 dB, the DRA offers a frequency band of 6.0–10.2 GHz with an impedance bandwidth of 52%. The measured and calculated results are compared and found in good match. The DRA's radiation characteristics are measured at different frequencies. A stable radiation pattern is observed throughout the band of operation. The measured gain of the wideband antenna is ranging from 4.5 to 8.1 dBi.

A wideband circularly polarized dielectric resonator antenna excited with conformal‐strip and inverted L‐shaped microstrip‐feed‐line for WLAN/WI‐MAX applications

ABSTRACTA new wideband circularly polarized dielectric resonator antenna (DRA) has been developed and presented in this article. The proposed antenna consisting rectangular and cubical‐shaped dielectric resonator (DR) with optimum gap excited by using combination of conformal‐strip and inverted L‐shaped microstrip‐feed‐line. The combinations of two different feeds (i.e., conformal‐strip and microstrip‐fed‐line) excite orthogonal modes in two DRs to generate circular polarization. The gap between these DRs and conformal strip offers wideband of impedance and axial ratio bandwidth. Designed antenna offers measured −10 dB impedance bandwidth of 27.36% (at center frequency 5.78 GHz) and measured 3‐dB axial ratio bandwidth has been achieved in broadside direction of 23.00% (at center frequency 5.65 GHz). It has been confirmed from the radiation pattern that the antenna having right hand circular polarization (RHCP). Proposed antenna can be used for wireless communication systems such as WLAN/Wi‐MAX applications. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2525–2531, 2016

Design, Fabrication, and Measurement of Dual-Segment Rectangular Dielectric Resonator Antenna Array Excited with Conformal Strip for S-Band Application

ABSTRACTA conformal strip connected to a microstrip line is proposed to excite the professed dielectric resonator antenna array to achieve the critical coupling for material having lower dielectric constants of less than 10. Fabrication of two-element dual-segment linear broadside rectangular dielectric resonator antenna array with copper plates on one side has been successfully presented for the first time. The combination of high gain and wide bandwidth with low cross-polarization is always a challenge for researchers. The gain of a two-element array has been increased by a factor of 2.0 compared with the gain of a single dielectric resonator antenna, and there is also a 6.14% increase in bandwidth of the proposed array compared to the single element rather than a decrement in bandwidth as reported in previous studies. Although the gain and bandwidth are not very high for the two-element case, the proposed fabrication technique can be applied for a large number of elements for higher gain application, and the structure can be modified for other desired bands of operation. The proposed array can be used as a medium-gain wideband antenna or can form a sub-array in a large low-profile structure for high-gain applications.

Conformal VHF Log-Periodic Balloon Antenna

A conformal log-periodic balloon antenna operating at a very high-frequency (VHF) band is presented in this communication. The antenna consists of eight conformal bowtie-dipole elements cross-fed by a parallel-strip transmission line and is then attached to the surface of a cylindrical balloon. After a detailed comparative analysis of the radiation performance of conformal strip dipole and bowtie dipole, a conformal log-periodic bowtie-dipole balloon antenna is designed. Simulated results show that its operating bandwidth ranges from 60 to 233 MHz with the voltage standing wave ratio (VSWR) less than 2 and a good end-fire radiation pattern of 5-dBi average gain. Measured results of a full-scale prototype fabricated with aluminum foils and a polyvinyl chloride balloon are in good agreement with simulated ones, which demonstrates the balloon antenna’s potential applications in VHF communication systems.

Wideband circularly polarized conformal strip fed three layer hemispherical dielectric resonator antenna with parasitic patch

ABSTRACTIn this work, a circularly polarized conformal strip fed three‐layer hemispherical dielectric resonator antenna (HDRA) with parasitic patch is analyzed theoretically and experimentally. The effect of position of conformal strip and parasitic patch at first and third dielectric layer interfaces of three‐layer HDRA is investigated for impedance and axial ratio (AR) bandwidths. The optimized permittivities of the layers and conformal strip and patch locations are found for three‐layer HDRA to realize wide impedance and AR bandwidths. The antenna structure is analyzed using Green's function and method of moments approach. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:72–77, 2014

Transparent Dielectric Resonator Antennas for Optical Applications

The transparent dielectric resonator antenna (DRA) for optical applications is proposed for the first time. For demonstration, a dual function transparent hemispherical DRA made of Borosilicate Crown glass (Pyrex) is investigated. The dual function DRA simultaneously works as an antenna and a focusing lens for an underlaid solar cell. The system is very compact because no extra footprint is needed for the solar cell. A conformal strip is used to excite the hemispherical DRA in its fundamental broadside TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">111</sub> mode. Due to the focusing effect of the DRA, higher voltage and current outputs of the solar cell can be obtained. In this paper, the transparent rectangular DRA was also studied, and it was found that the rectangular DRA does not provide the focusing function. It was also found that the proposed transparent DRAs can provide a higher gain ( ~ 4 dBi) than for the state-of-the-art transparent microstrip antennas ( ~ -5 dBi to 0 dBi). The reflection coefficients, input impedances, antenna gains, and radiation patterns of the two transparent DRAs are studied, and reasonable agreement between the simulated and measured results was observed. The proposed configurations can potentially be used for applications that need a self-sustaining power.

Small‐size surface‐mountable circularly polarized ceramic‐chip antenna for GPS application

AbstractA small‐size circularly polarized ceramic‐chip antenna suitable for surface mounting on a system circuit board is presented. The antenna mainly comprises a square radiating patch with a cross slot on the top surface, a square ground plane on the bottom surface, and a side‐feed conformal strip on the side surface. For obtaining circular polarization (CP) radiation for global positioning system (GPS) operation at 1575 MHz, a prototype is constructed using a square‐disk ceramic chip of dimensions 12 × 12 × 4 mm3 and having relative permittivity of 90, and the experimental results are presented. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 300–302, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11360

Excitation of low‐profile equilateral‐triangular dielectric resonator antenna using a conducting conformal strip

A new configuration that employs a conducting conformal strip to excite the low-profile equilaterial-triangular dielectric resonator antenna (DRA) of very high permittivity is proposed. As compared with the previous aperture-coupling configuration, the new configuration has a wider impedance bandwidth (∼5.5%) and a higher front-to-back radiation ratio. The return loss, radiation patterns, and antenna gain are measured and discussed. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 29: 317–319, 2001.

Excitation of low‐profile equilateral‐triangular dielectric resonator antenna using a conducting conformal strip

AbstractA new configuration that employs a conducting conformal strip to excite the low‐profile equilaterial‐triangular dielectric resonator antenna (DRA) of very high permittivity is proposed. As compared with the previous aperture‐coupling configuration, the new configuration has a wider impedance bandwidth (∼5.5%) and a higher front‐to‐back radiation ratio. The return loss, radiation patterns, and antenna gain are measured and discussed. © 2001 John Wiley &amp; Sons, Inc. Microwave Opt Technol Lett 29: 317–319, 2001.