J. Vijayakrishnan

Bio: J. Vijayakrishnan is an academic researcher from VIT University. The author has contributed to research in topics: Coupling & Patch antenna. The author has an hindex of 2, co-authored 2 publications receiving 32 citations.

Compact S-Shaped EBG Structures for Reduction of Mutual Coupling

Abstract: In this article, two new shapes of EBG structures are presented for reducing mutual coupling between patch antenna MIMO arrays. The first structure is contained an S-shape patch with a via at center of it and the second one is a multilayer structure that is based on the S-shape formation. The patch antennas are operating at 5.35 GHz, which is defined for wireless application. Here an array of 2×5 EBG structures is implemented to reduce mutual coupling to more than 13.5dB and 20.5 dB respectively for first and second structures. The total size of antenna is 36mm×68mm×1.6mm. All the simulations have been carried out with HFSS for full wave simulation. The surface current density is reduced dramatically more than 84% and 92% for first and second structures respectively. In addition the effect of the change in unit cells distance on mutual coupling are studied for the second structure. The results are compared with some previous researches.

Mutual coupling reduction and gain enhancement in patch array antenna using a planar compact electromagnetic bandgap structure

Abstract: This research work presents a planar compact electromagnetic bandgap (EBG) structure with the potential to reduce the mutual coupling between the elements of a microstrip antenna array The proposed structure is investigated at 559 GHz, which is the centre frequency of the wireless local area network band To achieve the highest radiation performance for microstrip antenna arrays, with minimal inter-element spacing and mutual coupling, different unit cell arrangements were considered along with two adjacent patch elements The simulations and measurement results for the proposed arrangements indicate that the mutual coupling tends to diminish significantly For instance, when adjacent patches are spaced by 04 λ , the mutual coupling improves by ~25 dB For the particular spacing of 04 λ , it is favourably observed that the proposed EBG cells can also improve the antenna gain by ~25 dB Such improvements can be attributed to the compactness of the cells (~ λ /8 × λ /10) and their remarkable ability to suppress the surface waves

Mutual coupling reduction in microstrip array antenna by employing cut side patches and EBG structures

Abstract: This paper presents the simultaneous application of Minkowski fractal geometry and EBG structures for mutual coupling reduction in microstrip array antennas for the first time. In this approach, a modified version of Minkowski fractal geometry is applied on the patch elements, and at the same time 1D electromagnetic bandgap (EBG) structures, composed of 4 EBG elements, are placed between the array elements in a very close distance. Unlike many other coupling reduction methods, which have at least one of the issues of gain reduction or complex fabrication, the proposed method does need any via or double-sided etching and slightly increases the gain of the antenna, while an excellent reduction level of 22.7 dB has been achieved. To verify the concept, 2 array antennas with the spacing of λ0 and λ0/3 were fabricated and tested, showing very good agreement between predicted and measured results.

Reconfigurable microwave SIW sensor based on PBG structure for high accuracy permittivity characterization of industrial liquids

Abstract: In this paper, we present a novel tunable microwave sensor for permittivity determination of industrial liquids. The proposed sensor is cavity based which is developed on a Substrate Integrated Waveguide (SIW). To enhance the characterization accuracy, the reconfigurable sensor is equipped with a Photonic Band Gap method and variable capacitors. Moreover, we employ the cavity perturbation technique in order to calculate the permittivity. In the characterization process, we obtain the permittivity of an unknown material by considering a resonant frequency shift. In fact, a capacitance is the main parameter for controlling the sensor resonance. We herein change this capacitance via reconfigurable SIW cavity and applying different materials. The proposed tunable architecture lets us study the material characteristic in the wider frequency range. The structure is designed in 5–6 GHz in order to determine the electromagnetic behavior of a brand new and used transformer oil samples. The results present a highly accurate permittivity of these oil samples. Hence, the proposed method and setup is not only suitable for oil ageing programs, but also applicable for other industrial liquid applications.

Coupling Reduction for a Wideband Circularly Polarized Conformal Array Antenna With a Single-Negative Structure

Abstract: Decoupling of a wideband circularly polarized (CP) conformal array is studied by a single-negative (SNG) metamaterial (MTM) isolator. The conformal array consists of two wideband CP antennas, which are assembled on an arched carrier, and a wideband SNG structure is placed between the antenna elements for coupling reduction. The SNG structure consists of four wheel-shaped units concentrically. The SNG structure is bianisotropic, and its constitutive parameters are tailored to form a wide isolation band. By using the proposed wideband SNG structure, the mutual coupling between the conformal antenna elements is reduced up to 25 dB at 4.5 GHz, and the mutual coupling is improved in the 3.9–5.05 GHz band. In addition, the loading of the SNG structure has little effect on the axial-ratio bandwidth. Besides, the gain and radiation patterns are improved. This research provides some basis in the decoupling of the conformal array.

Design and Parametric Analysis of Hexagonal Shaped MIMO Patch Antenna for S-Band, WLAN, UWB and X-Band Applications

Abstract: In this paper, a hexagonal-shaped multiple-input multiple-output (MIMO) patch antenna is presented. It covers the S band (2–4 GHz), WLAN (2400–2480 MHz & 5150–5350/5725–5875 MHz), UWB (3.1–10.6 GHz), and X band (8–12 GHz) applications. The proposed structure is simulated and fabricated on an FR4 substrate with overall dimensions of 0.186λ0 × 0.373λ0 and separation of two patches with a distance of 0.053λ0 (where λ0 is the wavelength at 2GHz). The single UWB patch is antenna derived from the triangular-shaped edge cuttings in the bottom of the rectangular patch antenna with a partial and defected ground. The proposed MIMO structure produces simulated results from 2GHz to 13.3 GHz and measured results from 2.1 GHz to 12.9 GHz, with good agreement. The proposed structure resonates at 3.4 GHz, 5.8 GHz, 10.2 GHz, and 11.8 GHz. The isolation is improved to above 20 dB by placing an E-shaped tree structure and parasitic element in most of the band. The radiation efficiency and peak gain values are 78–94% and 1.4–6.6 dB, respectively. Diversity performance of the proposed structure is verified with low envelope correlation coefficient (ECC < 0.04), high diversity gain (DG > 9.985), and acceptable total active reflection coefficient (TARC < −10 dB) values.