In this paper, mutual coupling reduction between elements of UWB MIMO antenna using small size uniplanar EBG is presented. Proposed UWB antenna geometry consists of two circular shaped monopole radiator swith a slot in ground plane for proper impedance matching. A UC-EBG (Uniplanar Electromagnetic Band Gap) cell of size 6.8 mm × 6.8 mm is inserted between the antenna elements in 4 × 1 array configuration to improve the isolation. Bandgap of the UCEBG is determined using dispersion diagram and suspended stripline method. The proposed antenna is fabricated on 1.6 mm thick, low cost FR4 substrate, possessing an overall size of 27.2 mm × 46 mm. The antenna has been fabricated and experimentally verified. The antenna shows simulated and measured −10 dB impedance bandwidths of 14.6 GHz (3–17.6 GHz) and14.8 GHz (3.6–17.9 GHz) respectively. UCEBG structure exhibits multiple stop bands and suppresses E-plane coupling over these bands. Isolation better than −18 dB is achieved over the complete impedance bandwidth. Radiation efficiency and peak gain of the antenna varies from 78% to 96.7% and 1.4 dB to 4 dB respectively. MIMO parameters, i.e. error correlation coefficient (ECC) better than0.018 and Total active reflection coefficient (TARC) better than −26 dB is achieved over the impedance bandwidth.

Mutual coupling reduction between elements of UWB MIMO antenna using small size uniplanar EBG exhibiting multiple stop bands

A state‐of‐art review on performance improvement of dielectric resonator antennas

In this article, a simple string of H-shaped defected ground structure (DGS) is used to reduce the mutual coupling and cross-polarization of a MIMO antenna. A MIMO antenna has been designed using two identical square patches to operate at the frequency of 2.4 GHz. The proposed DGS decreases the direct coupling path among the closely spaced (edge to edge gap 0.038 λ0) patches and thereby reduces the mutual coupling and cross-polarization by 46 dB and 11 dB respectively. To study the amount of mutual coupling is decoupled; a new term namely, coupling to decoupling ratio (CDR) has been defined. A mathematical model is developed using multiple polynomial regression analysis techniques to observe the dependency of CDR as a function of frequency and inter-element spacing. Also, an equivalent circuit of the DGS is constructed and validated. Diversity performance of this MIMO antenna is presented through Envelope Correlation Coefficient (ECC) and Mean Effective Gain (MEG) ratio and well acceptable values of 0.0002 and 0.03 dB are obtained respectively. A prototype is fabricated and measured. The experimental results show good agreement with that of the simulated results. Maximum peak gain of 2dBi and radiation efficiency of 74% also proves the practicality of this design.

Reduction of mutual coupling and cross-polarization of a MIMO/diversity antenna using a string of H-shaped DGS

We investigated a dielectric resonator ceramic microstrip
patch antenna The antenna was formed using barium strontium
titanate (BST), which had a dielectric constant of 15 A new approach,ie, the use of a high temperature dielectric probe kit, was used to determine the dielectric constant of BST A computer simulation technology (CST) microwave studio was used to simulate the BST array antennas, taking into consideration the dielectric constant We also measured the gain of the antennas loaded with two-, four, and six-element arrays of the BST antenna and found that the
gain of a six-element BST array antenna was enhanced by a gain of about 16 dB over the four-element BST array antenna at 23 GHz The impedance bandwidths of these BST array antennas for voltage standing wave ratio (VSWR) < 2 were in the application ranges,ie, 230 to 250 GHz, established for Worldwide Interoperability for Microwave Access (WiMAX) and Wireless Local Area Network
(WLAN) Compared with the conventional array antenna with the same aperture size, the performance of the antenna obviously was improved, and the design is suitable for array applications, including base stations, for example

Investigation of the characteristics ofbarium strontium titanate (bst) dielectricresonator ceramic loaded on array antennas

The electromagnetic band gaps (EBGs) have been considered for the array antenna to reduce the mutual coupling. In this paper, we have developed a novel fractal shape of the EBG for reducing the mutual coupling for wireless application between microstrip patch arrays at 5.9 GHz. We have focused on developing the EBG unit cell based on the conventional mushroom EBG and studying the dispersion diagram for minimizing the unit cell. Here, the modeled miniaturized by increasing the unit cell capacitance and inductance based on fractal structure. The studies show that the initial frequency of the band gap reduced. The S21 has reduced more than 30 dB while the EBG cells placed in 2 × 5 arrangement with the total size of 36 mm × 68 mm × 1.6 mm. We show that the couple current ratio value is reduced drastically to 0.3% by the shielding while for the basic model it is around 18%. The gain reducing is the unsolved drawbacks in this structure. The simulation of the unit cell and structure has done by HFSS as full-wave software. The experimental results have confirmed the simulation. We have presented a full comparison between current and previous models, which were suggested for this application.

Fractal EBG structure for shielding and reducing the mutual coupling in microstrip patch antenna array

In this paper, a novel parasitic configuration to reduce the mutual coupling between two adjacent microstrip patch antennas is presented. It is shown that mutual coupling between the antenna elements can be reduced significantly by two simple slots structure on the ground plane and several shorted simple conducting strips between patch antennas. The structure has been constructed and tested. Both simulated and measured results are presented. The results are shown that more than 7 dB reduction within operational frequency bandwidth with the maximum 41 dB mutual coupling at center frequency can be achieved. The measurement results prove the high efficiency of this configuration in multi antenna systems.

High mutual coupling reduction between microstrip patch antennas using novel structure

In this paper, two circularly polarized rectangular dielectric resonator antennas (RDRAs) are proposed for wideband applications. One common method for achieving the orthogonal modes for circular polarization is used by coupler. In this configuration, a 45° rotated branch-line coupler which is located under the hollow RDRA with two tapered excitation strips are connected to sidewall of RDRA to excite two degenerate TE111 modes is used. For the second antenna, a pair of tapered stubs and metallic vias is added to structure to increase bandwidth, and antenna gain. These antennas exhibit better results in comparison with similar conventional DRA with similar feeding technique. The major differences of the proposed antenna compared to the prior arts were using a few simple techniques simultaneously to improve impedance and axial ratio (AR) bandwidths, gain, and cost of structure. These techniques consist of using wideband branch-line coupler, hollow RDRA, placing the coupler under DR with 45° rotation, tapered excitation strip, FR4 substrate, and tapered stubs and metal vias in the second antenna. Both simulated and measured results are presented. These first and the second antennas offer an impedance bandwidth (S11 < −10 dB) of 69.4% and 96.3%, and axial ratio bandwidth (AR < 3 dB) of 52.45% and 57%, respectively.

Circularly polarized rectangular dielectric resonator antennas with branch-line coupler for wideband applications

A cross slot coupled cylindrical dielectric resonator antenna (CDRA) operating in the X-band (8GHz -12GHz) frequency range is studied. The proposed CP designs are achieved by implementing a suitable cross slot on the ground plane (in the case of aperture coupled feed method), which results in excitation of two near degenerate orthogonal modes of near equal amplitudes and 90 ° phase difference. Attempts are made to change the geometry of slots ends to introduce a novel structure in order to achieve a better impedance bandwidth with an improved 3dB axial ratio (AR) bandwidth. It is found that the hourglass of cross slot has a great effect on the strength of coupling between the feed line and the dielectric resonator antenna. In simulation an impedance bandwidth of 46.15% and axial ratio bandwidth of 22% has been achieved with the above geometry. An improvement of 12% in impedance bandwidth and 11.2% in Axial ratio bandwidth is obtained over conventional rectangular cross slot. DOI: http://dx.doi.org/10.11591/ijece.v4i6.6484

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Circularly Polarized Cylindrical Dielectric Resonator Antenna with Different Shapes Cross Slot

This article presents the design of a novel structure to increase bandwidth of single layer dual-polarized microstrip patch antenna using metallic cone on top of the patch antenna. The antenna is fed by two orthogonal 50Ω microstrip feedlines using λg/4 transformers. Tunable stubs are employed along the quarter-wavelength transformer to optimize the antenna's impedance match. Results confirm the parasitic cone mounting provides significant bandwidth enhancement. The antenna was fabricated, and a good agreement is achieved between measurement and simulation. The measured results show that the antenna achieves a −10 dB impedance bandwidth of 29% and isolation of >22 dB between the two input ports across its operating bandwidth (4.8–6.44 GHz) with low cross polarization level of <20 dB. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1599–1602, 2016

Design of a wideband dual‐polarized microstrip patch antenna with novel structure for WLAN application

This paper presents a novel phase shifter working two-way at two different frequencies in order to obtain equal phase shift. The proposed phase shifter consists of two grounded coplanar waveguide (GCPW) lines and high dielectric constant slab over the GCPW lines. In realization of equal phase shift at two different frequencies, the length of two GCPW lines should be have inverse portion of frequency. Also, the length of BLT assumes to be equal to the length of two GCPW Lines. The simulated results show equal phase shift at 20GHz and 30GHz which is highly desired for many applications such as full duplex array, interleaved array, and multiband array.

Zahra Rahimian

Papers

High mutual coupling reduction between microstrip patch antennas using novel structure

Circularly polarized rectangular dielectric resonator antennas with branch-line coupler for wideband applications

Circularly Polarized Cylindrical Dielectric Resonator Antenna with Different Shapes Cross Slot

Design of a wideband dual‐polarized microstrip patch antenna with novel structure for WLAN application

Two-Way Phase Shifter with Equal Phase Shift