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A single-layer, four-element multiple-input-multiple-output (MIMO) antenna for 5 GHz (5150–5850 MHz) band WLAN application is proposed. Each unit element consists of three sections and this behaves as a travelling wave antenna, which enables frequency scanning feature. The combination of orthogonal feeds and placement of elements introduce dual-polarisation, and pattern diversity respectively. Thus, the proposed MIMO antenna offers a higher degree of freedom (pattern diversity, frequency scanning and dual polarisation), which makes it exceptional. The proposed MIMO antenna has a maximum impedance bandwidth of 17% (4.93–5.87 GHz) corresponding to port 4 and isolation of 17.5 dB, which is achieved without additional decoupling/isolation enhancement circuits. The envelope correlation coefficient of 0.25, capacity loss less than 0.4 bits/sec/Hz, and the mean effective gain (MEG) ratio of 0 dB in the desired frequency band quantifies the diversity performance for WLAN applications. The proposed MIMO has gain from 2 to 5.5 dB and occupies a compact volume of 1.3 λ × 1.3 λ × 0.02 λ mm3, which may be one of the most miniaturised electrical configurations. © 2022 Informa UK Limited, trading as Taylor & Francis Group.

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(SoE) School of Engineering

International Journal of Electronics

Travelling Wave Antenna Based MIMO for 5GHz WLAN Band Application With Pattern Diversity

A rectangular patch antenna with π shaped slot is proposed as a miniaturized antenna element with a gain of 5.83 dB for WLAN (5.2 GHz) application. This compact π shaped slot antenna is used as a radiating element for the design of a 2 × 1 MIMO system for WLAN application. A near field passive parasitic element is used in the proposed MIMO antenna to improve the isolation. The MIMO system has a surface area of 0.29λ2 with a measured gain of 6 dBi and impedance bandwidth of 110 MHz. The diversity characteristics of MIMO are quantified with envelop correlation coefficient of 0.004, capacity loss of 0.35 bits/s/Hz, mean effective gain ratio (less than 1), mutual coupling around −20 dB, and TARC is −14.5 dB. The measured results are in good agreement with the simulation results and validate the proposed design. © 2021 IETE.

IETE Journal of Research

A Pi-Shaped Slot Antenna for 5.2 GHz WLANMIMO Application

<p>This paper proposes a dual-polarized and high gain, four-element based compact multiple-input-multiple-output (MIMO) antenna operating at 5.2 GHz. First, a hammer-shaped antenna has been designed with a gain of 5.3 dBi, impedance bandwidth of 400 MHz, and broadside radiation. A mathematical analysis for radiated electric field and an equivalent circuit model of the hammer-shaped antenna are developed. Using the hammer-shaped antenna as an element, four element MIMO design with shorting walls is proposed. The shorting walls near non-radiating edges improve isolation between the elements by changing the direction of the major lobe. The proposed MIMO design has an envelope correlation coefficient (ECC) &lt; 0.15, measured gain of 5.5 dBi, and mean effective gain (MEG) ∼−3dB. This design has a low profile and single layer planar structure of area 65 mm × 65 mm, which makes it a good contender for portable devices or low-profile hand-held applications in WLAN band. © 2021, Electromagnetics Academy. All rights reserved.</p>

Progress in Electromagnetics Research Letters

Hammer-shaped element-based compact mimo antenna for wlan application

In this paper a dual band butterfly shaped planar antenna is proposed. The structure consist of two trapezoid located symmetrically to the y axis. An inductive stub is used for impedance matching. The measured antenna resonates at 2.9GHz and 5.32 GHz with impedance bandwidth of 63.6 MHz, 188.7MHz respectively. The measured gain of the proposed antenna is 2.5dBi at 2.9 GHz and 5.5dBi at 5.32GHz. © 2019 IEEE.

2019 6th International Conference on Signal Processing and Integrated Networks, SPIN 2019

Dual Band Butterfly Planar Antenna for WLAN Applications

A MIMO antenna using dual - band planar antenna with rectangular slothas been proposed. The edge cleaving reduces the width of patch in comparison with conventional rectangular patch antenna designed at the same frequency, while its gain and radiating efficiency is noticeably improved. Measured results of the proposed antenna exhibits resonant frequency at 3.6GHz and 5.48GHz with an impedance bandwidth of 100MHz and 130MHz respectively. Further, the antenna is used as a radiating element for the design of 2-Element MIMO system. © 2019 IEEE.

Dual Band Slot Antenna for MIMO Applications

In this paper a wide band planar antenna is proposed. Two dumbbell shape antennas are designed using with and without slots. Each element resonates at 5.2GHz and radiates in broadside direction. The return loss of type-l antenna is 17dB with impedance bandwidth of 458MHz and return loss of type-2 antenna is 29dB with impedance bandwidth of 395MHz. This wide bandwidth is achieved by using staggered tuning, resulting from antenna element spacing and low impedance microstrip line for connecting the elements. © 2018 IEEE.

2018 3rd International Conference for Convergence in Technology, I2CT 2018

Dumbbell Shape Antenna for MIMO Applications

In this paper a novel planar antenna is proposed for 5.2GHz band application. The area of designed antenna has been reduced by 52\% in comparison to a conventional rectangular microstrip patch antenna. The antenna has three vertical stripes and one horizontal stripe. The length and width of these stripes are varied to tune the antenna for a certain operating frequency. The antenna is fed by using a 50 ohm microstrip line connected at the center of horizontal stripe. The fabricated antenna has return loss of 22dB at 5.27GHz and impedance bandwidth of 120MHz. A parametric study has been carried out to analyze and to find the design sensitive parameters. © 2017 IEEE.

2017 International Symposium on Antennas and Propagation, ISAP 2017

Step shape antenna for MIMO applications

The present work focusses on the design and simulation of a thin film bulk acoustic resonator (TFBAR) and a polyimide based TFBAR (PI-TFBAR) and compares the radio frequency (RF) bandpass filter response designed from these resonators. The Polyimide layer in the PI-TFBAR acts as an acoustic wave reflector along with providing mechanical strength to the device. The designed third order bandpass filter has a ladder topology. The insertion loss of the TFBAR filter is 1.69 dB and the return loss is 39.60 dB whereas the insertion loss and return loss are 1.71 and 23.7 dB respectively for the PI-TFBAR filter. The bandwidth of the TFBAR filter is 68.0 MHz and for PI-TFBAR it is 25 MHz. The proposed filter designs, with further optimization, may have application in the 2.6 GHz band, which has been identified by the International Telecommunication Union as a global band for International Mobile Telecommunications and is one of the core bands of LTE-Advanced technology. © 2017, Springer-Verlag Berlin Heidelberg.

Microsystem Technologies

A comparative study on the design and simulation of TFBAR and polyimide-TFBAR based RF bandpass filters

Radio Frequency (RF) Microelectromechanical system (MEMS) switches are becoming more and more popular in the electronics industry. The main concern in using RF MEMS switch is its high actuation voltage. Thus the main focus in this paper is to obtain low actuation voltage. This paper presents the simulation and analysis of RF MEMS cantilever beam and Fixed - Fixed beam switches. RF MEMS switches simulated in this paper use electrostatic actuation method. Simulations were done using finite element modeling. Different designs and parameters such as gap between electrodes, beam thickness, beam length, and relative permittivity values of medium between electrodes were chosen for analyzing the deflection of beams for various actuation voltages. Perforations of different dimensions were made on both type of beams and the resulted deflections were studied. The simulation results show that the Cantilever and Fixed - Fixed beams follow approximately similar deflection pattern with Cantilever beam deflecting more for applied actuation voltage in all the studies. © 2016 IEEE.

Proceedings - 2016 International Conference on Micro-Electronics and Telecommunication Engineering, ICMETE 2016

Simulation and analysis of actuation voltage of electrostatically actuated RF MEMS cantilever and fixed - Fixed switches with variable beam parameters

This work presents the design and simulation of a zinc oxide based thin film bulk acoustic resonator (TFBAR) bandpass filter for 2.6 GHz band applications. Third and fifth-order filters in ladder topology are designed and compared. The third-order filter has an insertion loss of 1.62 dB and return loss of 18.97 dB with a bandwidth of 80 MHz whereas the fifth-order filter has insertion loss, return loss, and bandwidth of 2.85 dB, 25.28 dB, and 60 MHz, respectively. With a central frequency of 2.67 GHz, the designed filter has applications in the 2.6 GHz (2500-2690 MHz) band, which has been identified by the International Telecommunication Union as a global frequency band for mobile broadband services. © 2016 IETE.

Design and Simulation of a Zinc Oxide Thin Film Bulk Acoustic Resonator Filter for 2.6 GHz Band Applications

In the present work, we report preparation and characterization of silicon carbide (SiC) films obtained by RF magnetron sputtering using a SiC ceramic target. The films were deposited in Ar ambient without external substrate heating. The residual stress of the films was measured as a function of sputtering parameters. The stress of the as-deposited films was observed to be compressive for the entire range of sputtering parameters used in the present work. Postdeposition annealing at 400 °C in N 2ambient was useful in reducing the stress in the films. On sequentially annealing the films at higher temperatures (600 and 800 °C), the nature of the stress changed from low compressive to high tensile. A superhard SiC film with low residual compressive stress (58.7 MPa) was obtained with hardness and Young's modulus values of 49.86 GPa and 363.75 GPa respectively. The x-ray diffraction pattern revealed that the films were either amorphous or nano-crystalline, depending on the deposition parameters and postdeposition annealing temperature. Atomic force microscopy roughness results confirmed good chemical stability of the films in potassium hydroxide and buffered hydrofluoric acid solutions. Several types of micro-structures were fabricated to demonstrate the feasibility and compatibility of these films in MEMS fabrication. © 2012 IOP Publishing Ltd.

Journal of Micromechanics and Microengineering

Mechanical and structural properties of RF magnetron sputter-deposited silicon carbide films for MEMS applications

We report structural and optical properties of aluminum nitride (AlN) thin films prepared by RF magnetron sputtering. A ceramic AlN target was used to sputter deposit AlN films without external substrate heating in Ar-N 2 (1:1) ambient. The X-ray diffraction and high resolution transmission electron microscopy results revealed that the films were preferentially oriented along c-axis. Cross-sectional imaging revealed columnar growth perpendicular to the substrate. The secondary ion mass spectroscopy analysis confirmed that aluminum and nitrogen distribution was uniform within the thickness of the film. The optical band gap of 5.3 eV was evaluated by UV-vis spectroscopy. Photo-luminescence broad band was observed in the range of 420-600 nm with two maxima, centered at 433 nm and 466 nm wavelengths related to the energy states originated during the film growth. A structural property correlation has been carried out to explore the possible application of such important well oriented nano-structured two-dimensional semiconducting objects. © 2011 Elsevier B.V. All rights reserved.

Applied Surface Science

Structural and optical properties of RF magnetron sputtered aluminum nitride films without external substrate heating

Aluminum nitride (AlN) films were deposited on a variety of substrates (glass, Si, oxidized Si, Al-SiO2-Si, Cr-SiO2-Si, and Au-Cr-SiO2-Si) by radio frequency (RF) magnetron sputtering using an AlN target. The films were deposited without external substrate heating. The effect of RF power, ambient gas (Ar and Ar-N2) and sputtering pressure on deposition rate and crystallinity were investigated. The structure and morphology of the films were studied by X-ray diffraction, scanning electron microscopy and atomic force microscopy techniques. These investigations revealed that the AlN films prepared in mixed gas ambient (Ar-N2) were highly c-axis oriented with moderate surface roughness on all the substrate. A strong IR absorption band was observed around 670 cm- 1 which confirms the presence of Al-N bond in the film. The dc resistivity of the films was measured to be in the range of 1011 to 1012 Ω-cm at moderate electric fields. The application of these films in piezoelectric based micro-electro-mechanical systems is discussed. © 2011 Elsevier B.V. All rights reserved.

Thin Solid Films

Deposition and characterization of c-axis oriented aluminum nitride films by radio frequency magnetron sputtering without external substrate heating

In the present work we report design, simulation, fabrication and characterization of thin film bulk acoustic resonator (FBAR). The FBAR has been modeled as a single port device with two terminals. The FBAR has been fabricated using Si-SiO2-Al-ZnO-Al structure. Zinc Oxide (ZnO) films were deposited by RF magnetron sputtering using Ceramic ZnO target in Ar-O 2 (1:1) ambient without external substrate heating. The XRD result confirms the preferred C-axis orientation of the films required for good piezoelectric properties. These ZnO films have been used to fabricate air gap type resonator. A four mask process sequence was used for this purpose. Lift-off process was used to pattern Al top electrode. In order to create the air cavity under the active device area, the bulk Si was etched in 40 % KOH at 80 °C. A specially designed mechanical jig was used to protect the front side of the device during anisotropic etching. Vector network analyzer was used to measure the reflection coefficient (S11: Return Loss) of the device. The resonant frequency of the resonator was measured to be 2.89 GHz as compare to the simulated frequency of 2.85 GHz with a return loss of 14.51 dB. © (2011) Trans Tech Publications, Switzerland.

Advanced Materials Research

Design, fabrication and characterization of ZnO based thin film bulk acoustic resonators

In the present work, silicon carbide (SiC) films were deposited by RF magnetron sputtering process on Si (100) substrates for micro-cantilever fabrication. The films were deposited without external substrate heating using a ceramic SiC target at 10 mTorr sputtering pressure, 200 W power and 50 mm target-to-substrate spacing. X-ray diffraction pattern shows that the films were amorphous in nature. In order to investigate the chemical inertness, the SiC coated Si substrates were dipped in buffered HF (BHF) at room temperature and in 40% KOH solution at 80 °C for varying length of time. Atomic force microscope was used to investigate surface roughness and morphology of the films before and after chemical processing. Micro-cantilever beams of the SiC film were fabricated by a single mask process. The SiC film was patterned using reactive ion etching (RIE) in SF6-O2 plasma. Thermally evaporated Al film was used as a mask during RIE process. This process also resulted in the formation of convex corners which were exploited for anisotropic etching of Si under the SiC film. The SiC cantilever beams were released by anisotropic etching of Si in KOH at 80 °C without using additional masking material. Scanning electron microscopy was used to observe the fabricated SiC micro-cantilever beams. The morphology of the SiC film after prolonged exposure to KOH was observed to be similar to that of the as-deposited film. The RF magnetron sputtered SiC films were found to be highly inert in KOH and BHF solutions. Due to difficulty in micromachining of bulk SiC material and its high cost, the RF sputtered SiC films on Si can provide a low cost structural material in MEMS. © (2011) Trans Tech Publications, Switzerland.