Design of High Directive Inset Feed Microstrip Triangular Patch Antenna with Dielectric Superstrate

The subject of enhancing microstrip patch antennas directivity, using either a frequency selective surface (FSS) or a double-negative (DNG) metamaterial slab, has been investigated by a number of researchers in recent years. The purpose of this paper is to show that we can also achieve the same goal by using a much simpler design for the superstrate, namely a dielectric slab. In this paper, we study the influence of dielectric superstrate on the performances of inset feed triangular patch antenna. This dielectric layer is disposed above the patch and both are separated by the air. The return loss, radiation pattern, directivity and VSWR are studied using HFSS software. The simulation results show that the gain, directivity and S11 parameter of the antenna with dielectric superstrate are increased significantly at X band (8-12GHz). Compared with the conventional patch antenna with the same size but without superstrate, the performance of the proposed antenna is improved obviously

Metasurface based MIMO microstrip antenna with reduced mutual coupling.

Masters Degree. University of KwaZulu- Natal, Durban.In this thesis, a negative permeability (μ) metasurface is used to reduce the mutual coupling of a 2-port Multiple-Input Multiple-Output (MIMO) rectangular inset fed microstrip antenna. That was designed using the transmission model of analysis, simulated and optimized using CST microwave studio. The microstrip antenna that operates at the (5.9-6.1) GHz band is designed for 5G applications, at the extended 6 GHz band (5.925-7.125) GHz. The extended band was chosen because of its new additional spectrum, which results in less noise interference. Three metasurface wall based antenna designs and two metasurface superstrate based antenna designs are conducted. The metasurface wall based antenna designs are formulated by placing a metasurface wall vertically between the two radiating antenna elements. The metasurface superstrate based antenna designs are formulated by suspending a metasurface superstrate above the 2-port microstrip antenna. Both the metasurface wall and superstrate are made up metasurface unit cells, which are formulated by periodic split ring resonators printed on a FR-4 dielectric substrate. The metasurface cells are responsible for introducing a negative permeability medium, which converts the electromagnetic propagating waves into evanescent hence rejecting mutual coupling. In the first metasurface based antenna design, a single metasurface wall is vertically placed between the two microstrip antenna elements. A slight increase of 0.5 dB in mutual coupling is observed. In the second design, a double metasurface wall is vertically placed between the two antenna elements. A mutual coupling reduction of 11 dB is achieved. In the third design a triple metasurface wall is also placed between the two antenna elements, a mutual coupling reduction of 25 dB and up to 17 % bandwidth enhancement is achieved. In the fourth design a single metasurface superstrate is suspended above the 2-port microstrip antenna. A mutual coupling reduction of 32 dB is achieved. Lastly, in the fifth design a metasurface superstrate is also suspended above the 2-port microstrip antenna. A mutual coupling reduction of 22 dB, a 38% bandwidth enhancement and a 2.09 dB gain enhancement is achieved

Design and analysis of metamaterial based microstrip patch antennas for wireless applications.

Doctoral Degree. University of KwaZulu-Natal, Durban.Due to the tremendous growth of wireless communication applications, there is an enormous demand for more compact antennas with high speed, wider coverage, high gain, and multi-band properties. The microstrip patch antennas (MPAs) and multiple-input multiple-output (MIMO) antennas with high gain and multi-band properties are suitable to fulfil these requirements. MPAs have been found to possess unique qualities such as light weight, low profile, easy fabrication, and integration. However, the low gain, narrow bandwidth, and mutual coupling in the MIMO antennas limit the performance of MIMO systems. Several techniques have been studied and implemented over the years, but they are not without limitations. The utilization of artificial materials such as metamaterials has proven to be efficient in overcoming the limitations of MPAs. Due to the advancement in modern technology, it is necessary to study and use recently developed metamaterial structures. Metamaterials (MeTMs) are artificially engineered materials with electromagnetic properties that are not found in nature. MeTMs are used due to their electric and magnetic properties. The goal of this thesis is to design and investigate a novel metamaterial structure which can be integrated into the microstrip patch antennas for improving their performance. The design, simulation, and measurement of the metamaterial is carried out on the Computer Simulation Technology (CST) studio suite, Advance Design Systems (ADS) software, MATLAB, and the Rohde and Schwarz network analyzer etc. In this thesis, a novel I-shaped metamaterial (ISMeTM) structure is proposed, designed, and investigated. The proposed novel ISMeTM unit cell structure in this work has a characteristic shape that distinguishes it from earlier multi-band MeTMs in the literature. The structure's unit cell is designed to have an overall compact size of 10 mm × 10 mm. The structure generates transmission coefficients at 6.31 GHz, 7.79 GHz, 9.98 GHz, 10.82 GHz, 11.86 GHz, 13.36 GHz, and 15. 5 GHz. These frequency bands are ideal for multi-band satellite communication systems, C, X, and Ku-bands, and radar applications etc. The performance of the MPA is improved in this work, by integrating a novel square split ring resonator (SSRR) metamaterial. The performance of the proposed antenna is investigated and analyzed. The SSRR is designed to have a dimension of 25 x 21.4 x 1.6 mm2 which is the same dimension as the radiating patch of the MPA. The SSRR is etched over the antenna, and it operates at single operating frequency of 5.8 GHz with improved gain from 4.04 to 5.3 dBi. Further, the MPA with improved parameters for multiband wireless systems is designed, analyzed, fabricated, and measured. The proposed design utilizes the ISMeTM array as superstrate with the area of 70 x 70 mm2. The superstrate is etched over a rectangular MPA exhibiting multi-band properties. This antenna resonates at 6.31, 9.65, 11.45 GHz with increased bandwidth at 240 MHz, 850 MHz, and 1010 MHz. The overall gain of the antenna increases by 74.18%. The antenna is fabricated and measured. The simulated results and the measured results are found to be in good agreement. The mutual coupling and low gain problems in MIMO patch antennas is also addressed in this thesis. A 3 x 5-unit cell array of the ISMeTM is used as a superstrate over a two port MIMO patch antenna. The two port MIMO antenna with the superstrate provides triple-band operation and operates over three resonance frequencies at 6.31, 9.09, and 11.41 GHz. A mutual coupling reduction of 26 dB, 33 dB, and 22 dB for the first band, second band and third band, respectively is attained. In this thesis, a novel I-shaped metamaterial structure is introduced, which produces multiband operation. The presented metamaterial is suitable for various multiband wireless communication applications. The integration of a square split ring resonator metamaterial enhances the performance of the antenna. Using the I-shaped metamaterial a high gain multiband microstrip antenna is designed. The I-shaped metamaterial array is utilized to improve the performance of the MIMO antenna. Various antenna parameters confirm that the presented MIMO antenna is suitable for multiband wireless communications

Planar beam-forming antenna array for 60-GHz broadband communication

The 60-GHz frequency band can be employed to realise the next-generation wireless high-speed communication that is capable of handling data rates of multiple gigabits per second. Advances in silicon technology allow the realisation of low-cost radio frequency (RF) front-end solutions. Still, to obtain the link-budget that is required for wireless gigabit-per-second communication, antenna arrays are needed that have sufficient gain and that support beam-forming. This requires the realisation of antenna arrays that maintain a high radiation efficiency while operating at millimeter-wave frequencies. Moreover, the antenna array and the RF front-end should be integrated into a single low-cost package that can be realised in a standard production process. In this thesis, antenna solutions have been presented that meet these requirements. This work covers the complete development cycle, viz modelling, design, optimisation, manufacturing, measurement and verification for three antenna prototype generations. An in-depth view of each development step is provided, while the combined work provides an overview of millimeter-wave antenna development. Modelling is a crucial step in the development cycle and has been discussed in Chapter 2. The production processes that are used for antenna design and packaging realise planar multi-layered structures. Therefore, the modelling of electromagnetic (EM) structures in stratified media has been considered. First, the Green’s function for stratified media has been derived. Second, a MoM-based approach has been proposed that provides an accurate analysis of the physical behaviour of these structures. Special attention has been given to the analysis of surface waves that propagate in the planar geometry, because they can significantly affect the radiation efficiency of planar antennas. The resulting model provides a computationally efficient tool (Spark) for the analysis and design of a wide range of planar antenna topologies. The first prototype is the balanced-fed aperture-coupled patch (BFACP) antenna element, that employs a unique topology and therefore exhibits excellent performance regarding bandwidth and radiation efficiency. The modelling and design of this antenna has been discussed in Chapter 3. It has been shown that the use of two coupling slots improves the bandwidth of the antenna as well as the radiation efficiency. Simultaneously, the back radiation is significantly reduced by employing a reflector element. The resulting antenna design has a measured bandwidth of 15% in combination with a radiation efficiency that is larger than 80% and an accompanying measured gain of 5.6 dBi. In Chapter 3, an extension of the BFACP antenna element has been presented that supports dual polarisation and/or circular polarisation as well. The proposed BFACP antenna designs can be employed both as single-element antenna and as a building block for antenna arrays. Obviously, the accurate measurement of the manufactured antenna prototypes is of importance for verification of both the modelling methods and the antenna designs. For this purpose, specific measurement setups have been designed. In Chapter 4 these setups have been introduced, motivated and explained. To obtain a reliable interconnection between the measurement equipment and the antenna under test, RF probes have been employed. Additional transitions (coplanar waveguide to microstrip transition, balun) have been designed to convert the single-ended signal of the measurement equipment to the balanced signal that is required by the antenna under test. Moreover, a far-field radiation pattern measurement setup has been developed from scratch which is completely tailored for the measurement of millimeter-wave antennas and beam-forming antenna arrays. It has been shown that these setups provide reliable measurement data that is in good agreement with the results obtained from the derived models. To maximise the performance of the antenna, an optimisation algorithm has been presented in Chapter 5 that gives the designer the flexibility to obtain the best antenna design for the considered application. This algorithm extends the derived EM model of the BFACP antenna (Chapter 3) to include sensitivity information about design parameters. The sensitivity has been employed to jointly optimise the bandwidth and the radiation efficiency of the antenna element. In Chapter 6, the optimised antenna element is used in the design of antenna arrays. Here, the modelling of beam-forming antenna arrays is discussed and the performance of several array configurations is compared. It has been concluded that a 6-element circular array shows best performance in terms of gain and radiation efficiency. Moreover, the mutual coupling between the elements of this array is low such that the active reflection coefficient remains well below -10 dB throughout the entire scan range. A second prototype has been designed that demonstrates beam-forming. For this prototype, 6-element circular arrays have been designed in combination with fixed feed networks that provide each antenna element with an RF signal that has the appropriate phase for beam-forming to a specific angle. The performance of these antenna arrays has been investigated in terms of radiation efficiency, bandwidth and gain. The prototype has a maximum measured gain of 11.8 dBi for broadside scan and it has been shown that these antenna arrays can be readily employed for the realisation of adaptive beam-forming at millimeter-wave frequencies. Chapter 7 discusses the packaging of the transceiver. First, the package requirements are listed and several package topologies are discussed. For example, the performance of superstrate topologies is analysed. Additionally, a package is proposed that embeds the BFACP antenna. This package combines ceramic-based layers and teflon-based layers. The ceramic-based layers provide the package with stiffness and are used to realise the RF feed network, whereas the teflon-based layers are employed to allow an antenna design that has a high radiation efficiency. For a high-performance package design, it is important that the electrical properties of the materials used is welldefined. Therefore, special efforts have been undertaken to characterise the electrical material properties of the materials used at millimeter-wave frequencies. For this purpose, ring resonators have been designed. Measurement results indicate that the electrical properties at higher frequencies can differ significantly from the values that are specified by the manufacturer for an operating frequency of 10 GHz. To demonstrate the performance of the BFACP antenna in a package configuration, a third prototype has been developed, in which the BFACP antenna is packaged in combination with active electronics. This prototype demonstrates that the antenna can be embedded in a package that contains not only the antenna, but also the RF electronics, RF feed network and control circuitry. In the prototype, the BFACP antenna has been connected to a power amplifier that has been realised in CMOS technology. The PA has been connected to the RF feed through a flip-chip interconnection process. It has been demonstrated that the proposed packaging topology results in an efficient transmitter. In conclusion, three antenna prototype generations have been presented and it is demonstrated that the presented concepts can be readily used for the design of a transceiver package that embeds a beam-forming antenna array and that supports gigabit-per-second communication

Design and fabrication of multi-fingered lines and antenna

Master'sMASTER OF ENGINEERIN

Performance Improvement of Dense Dielectric Patch Antenna using Partially Reflective Surfaces

Recently, millimeter-wave (MMW) band is being considered as the spectrum for future wireless communication systems. Several advantages are achieved by utilizing the millimeter-wave range, including high gain with large available bandwidth, compact size, and high security. Nevertheless, attenuation loss may restrict wireless communication systems’ transmission range. Meanwhile, printed antenna technology has gained the attention of antenna designers’ due to its low profile and ease of fabrication. High-gain antennas are very desirable as a critical part of MMW systems. Designing millimeter wave antennas with high gain characteristics would be a significant advantage due to their high sensitivity to atmospheric absorption losses. Moreover, planar configurations are required in many applications, such as for wireless communication. The main goal of this thesis is to design and propose state of the art designs of Fabry Pérot Cavity antenna (FPCA) designs with several types of superstrates to achieve high gain, wide bandwidth, and high efficiency to satisfy the requirements of today’s advanced wireless communication systems. A dense dielectric patch (DD) antenna is used as the main radiator and designed to operate at 28 GHz. The thesis presents several contributions related to the design and analysis of FPC antennas using several types of superstrates. The first research theme of this thesis has two parts. The first part presents a holey dielectric superstrate applied over a 2×2 dense dielectric square patch antenna array to enhance the gain, improve the bandwidth and efficiency, as well as to reduce the side lobe levels (SLLs). A dense dielectric patch replaces the metallic patch and is used as a radiated element. The measured results show a high gain of 16 dBi, with radiation efficiency of about 93 %, wide bandwidth of 15.3 %, and a reduced SLL. The second part focusses on a partially reflective surface (PRS) unit cell composed of two thin perforated dielectric slabs. The effect of the thicknesses of the unit cell dielectric slabs is discussed in detail. An array of the proposed PRS unit cell is applied over a dense dielectric square patch antenna array to broaden the bandwidth and to enhance the gain as well. The measured results exhibit a 3 dB gain bandwidth of 27 % with a high gain of 16.8 dBi. The second research theme presents an effective method to design a tapered superstrate of an FPC antenna with a DD patch element. This type of superstrate is designed to correct the phase above the superstrate to be almost uniform. The proposed single-layer perforated tapered superstrate is constructed by tapering the relative permittivity to be high in the center of the superstrate slab and then decrease gradually as it moves towards the edges. This tapered relative permittivity is then applied over a single DD patch antenna. The proposed antenna exhibits good performance in terms of the antenna gain and bandwidth. The antenna gain becomes flat and as high as 17.6 dBi. The antenna bandwidth is about 16 %, and the side lobe level of the antenna is very promising. A third theme presents the implementation and design of a high gain dense dielectric patch antenna integrated with a frequency-selective surface (FSS) superstrate. A 7×7-unit cell is used to build the superstrate layer, and applied above the high DD patch antenna. A modified unit cell is proposed to generate a positive reflection phase with high reflection magnitude within the frequency design in order to broaden the antenna bandwidth. A bandwidth of 15.3 % with a high gain of 16 dBi is obtained. Finally, a high gain linearly polarized (LP) substrate integrated waveguide (SIW) cavity antenna based on a high-order mode is implemented, fabricated, and tested. A TE440 mode is excited at 28 GHz. In this design, 4×4 slots are cut into the top metal of the cavity, where each slot is placed above each standing wave peak. These slot cuts contributed to a high gain of 16.4 dBi and radiation efficiency of about 96 %. The LP SIW cavity antenna was then integrated with a linear-to-circular polarization converter developed as a high gain circularly polarized (CP) SIW cavity antenna with high gain and high radiation efficiency of 16 dBi and 96 %, respectively