A comprehensive survey on 'circular polarized antennas' for existing and emerging wireless communication technologies

Circular polarized (CP) antennas are well suited for long-distance transmission attainment. In order to be adaptable for beyond 5G communication, a detailed and systematic investigation of their important conventional features is required for expected enhancements. The existing designs employing millimeter wave, microwave, and ultra-wideband (UWB) frequencies form the elementary platform for future studies. The 3.4-3.8 GHz frequency band has been identified as a worthy candidate for 5G communications because of spectrum availability. This band comes under UWB frequencies (3.1-10.6 GHz). In this survey, a review of CP antennas in the selected areas to improve the understanding of early-stage researchers specially experienced antenna designers has presented for the first time as best of our knowledge. Design implementations involving size, axial ratio, efficiency, and gain improvements are covered in detail. Besides that, various design approaches to realize CP antennas including (a) printed CP antennas based on parasitic or slotted elements, (b) dielectric resonator CP antennas, (c) reconfigurable CP antennas, (d) substrate integrated waveguide CP antennas, (e) fractal CP antennas, (f) hybrid techniques CP antennas, and (g) 3D printing CP antennas with single and multiple feeding structures have investigated and analyzed. The aim of this work is to provide necessary guidance for the selection of CP antenna geometries in terms of the required dimensions, available bandwidth, gain, and useful materials for the integration and realization in future communication systems

Advanced Circularly Polarised Microstrip Patch Antennas

The thesis describes outcomes of research on advanced circularly polarised antennas. The proposed designs are intended for integration into small mobile devices, therefore low profile and easy manufacturability are key parameters, along with good CP radiation properties. The designs were validated by simulation and measurement, and are also backed by theory and design guidelines. The primary focus is on the development of planar omnidirectional circularly polarised antennas, which are fabricated using multilayer PCB techniques and thus are lightweight and cost-efficient. Unlike in classical microstrip patch antenna designs, the groundplane of the proposed antenna was substantially reduced. This helps to achieve an omnidirectional circular polarisation pattern and miniaturize the antenna, however at the cost of increased feed circuit complexity. The basic design, its advantages and disadvantages are discussed in Section 3. In the next step, the omnidirectional circularly polarised antenna was extended with additional, advanced features. A miniaturized version is investigated, which offers a 20% footprint reduction by folding parts of the patch underneath itself. Further miniaturization is possible by increasing the dielectric constant of the substrate. A method to adjust the omnidirectional circularly polarised antenna performance by trimming four lumped capacitors is also investigated. Manufacturing inaccuracy in large scale production may cause some of the units to radiate outside of the desired frequencies. By integrating four trimmed capacitors into the antenna it can be precisely tuned to the desired band. Simulated results demonstrate this property by trimming the antenna between GPS L1 band (centre frequency at 1.575 GHz) and Galileo/Beidou-2 E2 band (1.561 GHz). Furthermore, a dual-band omnidirectional circularly polarised antenna is presented, which employs slots and capacitor loading to steer the current path of the first and second resonant mode. The design offers a small frequency ratio of 1.182. The methods to obtain a planar omnidirectional circularly polarised antenna have been further advanced to propose a reconfigurable antenna. The beam reconfiguration is capable of rotating it dipole-like radiation pattern around an axis, thus allowing reception or transmission from any spherical angle. The switching method is simple and does not require any semiconductor devices. Finally, a dual circularly polarised antenna is presented, which achieves dual-polarisation by employing even and odd modes in a coplanar waveguide. This technique allows greater flexibility and size reduction of the feed network, as two signals can be transmitted by a single multi-mode transmission line. Simulated results demonstrate this property by trimming the antenna between GPS L1 band (centre frequency at 1.575 GHz) and Galileo/Beidou-2 E2 band (1.561 GHz). Furthermore, a dual-band omnidirectional circularly polarised antenna is presented, which employs slots and capacitor loading to steer the current path of the first and second resonant mode. The design offers a small frequency ratio of 1.182. The methods to obtain a planar omnidirectional circularly polarised antenna have been further advanced to propose a reconfigurable antenna. The beam reconfiguration is capable of rotating it dipole-like radiation pattern around an axis, thus allowing reception or transmission from any spherical angle. The switching method is simple and does not require any semiconductor devices. Finally, a dual circularly polarised antenna is presented, which achieves dual-polarisation by employing even and odd modes in a coplanar waveguide. This technique allows greater flexibility and size reduction of the feed network, as two signals can be transmitted by a single multi-mode transmission line

Reconfigurable Antennas

In this new book, we present a collection of the advanced developments in reconfigurable antennas and metasurfaces. It begins with a review of reconfigurability technologies, and proceeds to the presentation of a series of reconfigurable antennas, UWB MIMO antennas and reconfigurable arrays. Then, reconfigurable metasurfaces are introduced and the latest advances are presented and discussed

Design and characterization of antennas for wireless communications systems

In this PhD thesis the author has dealt with the design and characterization of novel antenna layouts for modern communication systems. Specific attention has been devoted to cost-effective and compact solutions; also, some of the proposed antenna layouts have been designed facing with severe integration constraints. A novel slot-coupling feeding technique for dual-polarized patch antennas is presented in Chapter I. A square patch is fed through a square ring slot excited by two non-overlapping feed lines printed on the same side of a single-layer substrate. This technique was used to implement a wideband dual-polarized 2x1 microstrip stacked patch array working in the GSM band (1710 – 1910 MHz), UMTS band (1920 - 2170 MHz), ISM band (2400 - 2484 MHz) and UMTS 3G expansion band (2500 - 2690 MHz) or, alternatively, WIMAX™ band (2300 – 2700 MHz), with a resulting 45% percentage bandwidth. Moreover a circularly polarized 2x2 microstrip array, where each array element is fed through two microstrip lines which are excited 90° out-of-phase, has been realized for the WiMAX (3300 - 3800 MHz) band, resulting in excellent Axial Ratio performance. In Chapter II, a compact dual-band Planar Inverted-F Antenna (PIFA) working in both the DVB-T (Digital Video Broadcasting-Terrestrial) and the WLAN (Wireless Local Area Network) IEEE 802.11b,g frequency bands is presented. It has been designed to be integrated in a monitor-equipped device, exhibiting reduced electrical size with respect to similar PIFA solutions, also in a L-shape configuration. In the context of compact wideband antenna design, Chapter III presents a numerical analysis of a novel wideband two-arm Archimedean spiral antenna whose arms are made of vertical metallic strips. An advantage of this spiral is that the input impedance and polarization purity can be effectively controlled by varying the strip width and turn thickness. Also, when the antenna is embedded in a dielectric block, miniaturization is more effective than in conventional planar Archimedean spirals. In Chapter IV, two configurations of slot antennas suitable for integration into a class of commercial large photovoltaic (PV) panels are presented. The basic idea is to exploit the room available between adjacent PV cells, also taking advantage of the presence of the cover glass layer that gives a valuable miniaturization effect. As test cases, two antenna designs are presented for stand-alone communication systems operating in the GSM/UMTS (1710-2170 MHz) and WIMAX (3300-3800 MHz) frequency bands. Finally, a top-loaded vertical monopole antenna was designed to be integrated in a wireless sensor of a car park monitoring system operating at 433MHz, and it is described in Chapter V. The final design came out from a careful analysis of the effects on the antenna input impedance of nearby elements (photovoltaic cells, battery, sensor cover, ultrasonic transducer). A performance comparison between the proposed vertically polarized antenna and a commercial ceramic antenna has been carried out, showing an average increase of the received power level at the reader of about 2.2dB, when measurements are performed on a distance range of 10-60m between the sensor and the reader antenna of the car park monitoring system

Design, Modelling, and Characterisation of Millimetre-Wave Antennas for 5G Wireless Applications

PhDFuture 5G systems and beyond are expected to implement compact and versatile antennas in highly densifi ed millimetre-wave (MMW) wireless networks. This research emphasises on the realisation of 5G antennas provided with wide bandwidth, high gain, adaptable performance, preferably conformal implementation, and feasible bulk fabrication. Ka{band (26.5{40 GHz) is selected based on recent 5G standardisation, and novel antenna geometries are developed in this work on both rigid and flexible substrates by implementing advanced techniques of frequency reconfi guration, multiple-input-multiple- output (MIMO) assembly, as well as wideband and multiband antennas and arrays. Nove lMMW wideband antennas are presented for 5G and spatial diversity at the antenna front-ends is substantially improved by deploying wideband antennas in a MIMO topology for simultaneous multiple-channel communication. However, wideband operation is often associated with efficiency degradation, which demands a more versatile approach that allows the adaptable antenna to select the operating frequency. In this research, high performance recon figurable antennas are designed for frequency selection over Ka- {band. Also, an efficient and conformal antenna front-end solution is developed, which integrates both frequency recon guration and MIMO technology. Gain of the antenna is critically important for 5G systems to mitigate high propagation losses. Antenna design with both high gain and bandwidth is challenging as wideband antennas are traditionally gain-limited, while antenna arrays deliver high gain over a narrow bandwidth. An Enhanced Franklin array model is proposed in this thesis, which aggregates multiband response with high gain performance. Furthermore, novel flexible monopole antenna and array con gurations are realised to attain high gain profi le over the complete Ka{band. These proposed 5G antennas are anticipated as potential contribution in the progress towards the realisation of future wireless networks.EECS Fees Waiver Award and National University of Sciences and Technolog

Antenna Designs for 5G/IoT and Space Applications

This book is intended to shed some light on recent advances in antenna design for these new emerging applications and identify further research areas in this exciting field of communications technologies. Considering the specificity of the operational environment, e.g., huge distance, moving support (satellite), huge temperature drift, small dimension with respect to the distance, etc, antennas, are the fundamental device allowing to maintain a constant interoperability between ground station and satellite, or different satellites. High gain, stable (in temperature, and time) performances, long lifecycle are some of the requirements that necessitates special attention with respect to standard designs. The chapters of this book discuss various aspects of the above-mentioned list presenting the view of the authors. Some of the contributors are working strictly in the field (space), so they have a very targeted view on the subjects, while others with a more academic background, proposes futuristic solutions. We hope that interested reader, will find a fertile source of information, that combined with their interest/background will allow efficiently exploiting the combination of these two perspectives

Balanced antennas for mobile handset applications. Simulation and Measurement of Balanced Antennas for Mobile Handsets, investigating Specific Absorption Rate when operated near the human body, and a Coplanar Waveguide alternative to the Balanced Feed.

The main objectives of this research are to investigate and design low profile antennas for mobile handsets applications using the balanced concept. These antennas are considered to cover a wide range of wireless standards such as: DCS (1710¿1880 MHz), PCS (1850¿1990 MHz), UMTS (1920¿2170 MHz), WLAN (2400¿2500 MHz and 5000 ¿ 5800 MHz) and UWB frequency bands. Various antennas are implemented based on built-in planar dipole with a folded arm structure. The performance of several designed antennas in terms of input return loss, radiation patterns, radiation efficiency and power gain are presented and several remarkable results are obtained. The measurements confirm the theoretical design concept and show reasonable agreement with computations. The stability performance of the proposed antenna is also evaluated by analysing the current distribution on the mobile phone ground plane. The specific absorption rate (SAR) performance of the antenna is also studied experimentally by measuring antenna near field exposure. The measurement results are correlated with the calculated ones. A new dual-band balanced antenna using coplanar waveguide structure is also proposed, discussed and tested; this is intended to eliminate the balanced feed network. The predicted and measured results show good agreement, confirming good impedance bandwidth characteristics and excellent dual-band performance. In addition, a hybrid method to model the human body interaction with a dual band balanced antenna structure covering the 2.4 GHz and 5.2 GHz bands is presented. Results for several test cases of antenna locations on the body are presented and discussed. The near and far fields were incorporated to provide a full understanding of the impact on human tissue. The cumulative distribution function of the radiation efficiency and absorbed power are also evaluated.UK Engineering and Physical Sciences Research Council (EPSRC

Design and synthesis of non-uniform high impedance surface-based wearable antennas

This thesis is concerned with the design and fabrication of flexible textile wearable antennas integrated with the newly introduced artificial materials known as high impedance surfaces (HIS). With the rapid growth and use of wireless communication systems more and more people are taking advantage of portable computing systems on daily basis. Also with the advancement in electronic industry new and sophisticated wireless devices have been introduced which are being used closed to human body. For user convenience there is an increasing need for integrating antennas on or in the clothing. The conventional antennas being rigid and obtrusive to user movements have limitations. There is a need of antennas made of flexible textile materials that can be part of user clothing defined as wearable antennas. Also with the miniaturisation trend in electronic industry, antenna designers are facing a challenge to come up with a compact, low profile,multi function efficient antenna designs occupying a small physical space. By integrating antennas in user clothing this limited space problem can also be resolved. With the easy availability of electro textile materials it is now possible to manufacture complete fabric antennas. The entire design cycle of wearable fabric antennas starting from material selection to prototype fabrication and antenna testing was carried out in this thesis. A novel technique for antenna fabrication using electro textile material is proposed that will have major implications on wearable computing industry. The use of HIS for antenna performance enhancement is growing at a rapid pace. In this thesis a modified wearable form of HIS defined as non uniform HIS is presented and successfully integrated with antenna for improved performance under low profile limitation. The HIS was also integrated with normal patch antenna to reduce its size and improve its gain and impedance bandwidth. These wearable antennas were then tested under real operating conditions. The measured results validated the design idea and showed that there are many possibilities for these unique artificial materials to be exploited for future wearable on body communication antennas