A Triangular-shaped Quarter-mode Substrate Integrated Waveguide based Antenna for WBAN Applications

In this study, a compact quarter-mode substrate integrated waveguide (QMSIW) based dual-band antenna is proposed for wireless body area network applications. A QMSIW resonator is realised by splitting the full-mode substrate integrated waveguide cavity along the perfect magnetic conductor walls. The proposed antenna preserves the fundamental mode TE110 and the third order mode TE220 of the square SIW cavity. The proposed antenna is linearly polarised in the lower band at 2.45 GHz and circularly polarised in the higher frequency band at 5.8 GHz. The on-body performance of the antenna is validated on a piece of pork muscle tissue and it has been found to be stable with respect to surroundings. The proposed antenna covers the ISM bands 44 MHz (2.445 GHz - 2.489 GHz) and 225 MHz (5.730 GHz - 5.955 GHz) at 2.45 GHz and 5.8 GHz, respectively. The measured gain of the antenna on pork tissue is 1.87 dBi and 5.5 dBi at two bands. In addition, the specific absorption rate is obtained of 0.65 mW/g and 1.51 mW/g at two bands (wext = 2 mm), averaged over 1 g of muscle with 100mW input power. Moreover, the simulated and experimental results demonstrate a good agreement

Wearable, small, and robust: the circular quarter-mode textile antenna

A miniaturized wearable antenna, entirely implemented in textile materials, is proposed that relies on a quarter-mode substrate integrated waveguide topology. The design combines compact dimensions with high body-antenna isolation, making it excellently suited for off-body communication in wearable electronics/smart textile applications. The fabricated antenna achieves stable on-body performance. A measured on-body impedance matching bandwidth of 5.1% is obtained, versus 4.8% in free space. The antenna gain equals 3.8 dBi in the on-body and 4.2 dBi for the free-space scenario. High radiation efficiency, measured to be 81% in free space, is combined with a low calculated specific absorption rate of 0.45 mW/g, averaged over 1 g of tissue, with 500 mW input power

Circularly-polarised cavity-backed wearable antenna in SIW technology

This study presents a circularly-polarised substrate-integrated waveguide (SIW) antenna implemented using a textile substrate and operating at 2.45GHz, in the industrial, scientific, and medical frequency band. The antenna topology is based on a folded cavity with an annular ring as a radiating element, and it permits to obtain compact size and low sensitivity to the environment, without deteriorating the radiating performance. These characteristics, together with the choice of adopting a textile substrate, make the SIW antenna suitable for the integration in wearable systems for body-centric applications. The electromagnetic performance of the proposed antenna achieved in simulations was verified through the measurement of the device in an anechoic chamber. The circularly-polarised antenna exhibits a maximum gain of 6.5dBi, a radiation efficiency of 73% and a very high front-to-back ratio

Microstrip Patch Antennas Fed by Substrate Integrated Waveguide

Dizertační práce je zaměřena na výzkum mikropáskových flíčkových antén a anténních řad napájených vlnovodem integrovaným do substrátu (SIW). Využitím vlnovodu integrovaného do substrátu pro napájení mikropáskové flíčkové antény dochází ke kombinaci výhodných vlastností obou struktur. Výsledkem je kompaktní anténní struktura, jejíž napájecí vedení neprodukuje parazitní záření a neovlivňuje tak vyzařovací charakteristiku antény. Práci lze z věcného hlediska rozdělit do dvou částí. První část práce (kapitola 2) je zaměřena na návrh flíčkových antén a jejich navázání na vlnovod integrovaný do substrátu. První dvě navržené flíčkové antény využívají vlnovod integrovaný do substrátu a štěrbinu nebo koaxiální sondu pro buzení lineárně polarizované vlny. Napájení koaxiální sondou je dále použito pro buzení kruhově polarizované flíčkové antény. Za účelem získání širšího pásma osového poměru je navrženo napájení flíčkové antény ve dvou bodech. Funkčnost všech anténních struktur je popsána pomocí parametrických simulací a ověřena realizací a měřením vyrobených prototypů antén. Prezentované napájecí metody představují nový způsob napájení pro mikropáskové antény využívající technologii SIW. Ve druhé části práce (kapitola 3) je pojednáno o implementaci štěrbinou napájené mikropáskové anténní struktury do malých anténních polí o velikosti 2x2 a 1x4. V případě lineární řady je uvažováno amplitudové rozložení pro optimální potlačení postranních laloků. Obě navržené anténní řady jsou ověřeny měřením a v porovnání s podobnými anténními řadami dostupnými v literatuře dosahují širšího pracovního pásma kmitočtů a vyššího zisku.The thesis deals with the research of microstrip patch antennas and antenna arrays fed by a substrate integrated waveguide (SIW). Exploiting an SIW structure for microstrip patch antenna feeding combines the benefits of both structures. The result is a compact antenna structure retaining advantageous properties of microstrip patch antennas and having a radiation characteristic non-effected by spurious radiation which is usually produced by a conventional feeding line. The thesis consists of two factual parts. The first one (Chapter 2) deals with the design of microstrip patch antennas and exploiting a substrate integrated waveguide for their feeding. The first two microstrip patch antennas exploit an SIW and a slot or a coaxial probe in order to excite a linearly-polarized wave. SIW-based probe feeding is further utilized for exciting a single- and dual-fed circularly-polarized microstrip patch. The functionality of the proposed antenna structures is described using parametric analyses and verified by measuring of fabricated prototypes. The proposed feeding methods represent a novel feeding approach for microstrip patch antennas exploiting SIW technology. The second part of the thesis (Chapter 3) deals with implementing the linearly-polarized aperture-coupled microstrip patch antenna structure fed by SIW into two small antenna arrays consisting of 2x2 and 1x4 radiators. An amplitude distribution is considered in the case of the linear antenna array for optimum suppression of side lobes. Both proposed antenna arrays are verified by measurements. Compared to similar antenna arrays available in the literature, they reach a wider operating frequency band and a higher gain.

The bolometric focal plane array of the Polarbear CMB experiment

The Polarbear Cosmic Microwave Background (CMB) polarization experiment is currently observing from the Atacama Desert in Northern Chile. It will characterize the expected B-mode polarization due to gravitational lensing of the CMB, and search for the possible B-mode signature of inflationary gravitational waves. Its 250 mK focal plane detector array consists of 1,274 polarization-sensitive antenna-coupled bolometers, each with an associated lithographed band-defining filter. Each detector's planar antenna structure is coupled to the telescope's optical system through a contacting dielectric lenslet, an architecture unique in current CMB experiments. We present the initial characterization of this focal plane

Wearable flexible lightweight modular RFID tag with integrated energy harvester

A novel wearable radio frequency identification (RFID) tag with sensing, processing, and decision-taking capability is presented for operation in the 2.45-GHz RFID superhigh frequency (SHF) band. The tag is powered by an integrated light harvester, with a flexible battery serving as an energy buffer. The proposed active tag features excellent wearability, very high read range, enhanced functionality, flexible interfacing with diverse low-power sensors, and extended system autonomy through an innovative holistic microwave system design paradigm that takes antenna design into consideration from the very early stages. Specifically, a dedicated textile shorted circular patch antenna with monopolar radiation pattern is designed and optimized for highly efficient and stable operation within the frequency band of operation. In this process, the textile antenna's functionality is augmented by reusing its surface as an integration platform for light-energy-harvesting, sensing, processing, and transceiver hardware, without sacrificing antenna performance or the wearer's comfort. The RFID tag is validated by measuring its stand-alone and on-body characteristics in free-space conditions. Moreover, measurements in a real-world scenario demonstrate an indoor read range up to 23 m in nonline-of-sight indoor propagation conditions, enabling interrogation by a reader situated in another room. In addition, the RFID platform only consumes 168.3 mu W, when sensing and processing are performed every 60 s

Advanced Technologies for SIW Passive Microwave Components

The rapid growth of wireless networks and technologies of the last few decades has imposed new requirements on the performance of microwave components. There is a demand for wireless devices and sensors with high performance, high miniaturization and low production cost. Given this framework, the aim of this work is to provide a useful contribution through the study of existing techniques and the proposal of new ones. This is done by pursuing two specific lines of research: the study and analysis of compact Substrate Integrated Waveguide (SIW) resonators and filters, and the development of particularly simple and inexpensive reconfigurable antenna arrays based on an innovative amplitude beam-steering technique. Resonators are used as the basis for many different microwave devices. The achievable performance of said devices is limited by the losses of their resonators. The SIW is a planar transmission line technology which is a promising candidate for a wide array of applications. Compared to other planar technologies, the SIW offers particularly low losses and high electromagnetic performance, with an increase in the size of the components as a trade-off. In order to increase the miniaturization of SIW devices, the Half-Mode technique has been proposed, resulting in the Half-Mode Substrate Integrated Waveguide (HMSIW) topology. The Half-Mode technique can be applied multiple times to the classic square SIW resonator. With every iteration, the miniaturization factor is increased. The topologies that can be obtained are the Half-Mode resonator, the Quarter-Mode resonator and the Eighth-Mode resonator. While the SIW topology is completely closed and electromagnetically shielded, HMSIW and derived structures are partly open. For this reason, the performance of HMSIW devices suffer from the introduction of leakage and radiation losses. This work offers a study on the performance of the size reduction technique by the systematic analysis of these topologies. In a practical application, the results of this analysis are used to find which compact topology may be more convenient to employ depending on the design constraints such as frequency or kind of substrate to use. In order to mitigate the problem of losses, a few modified topologies which offer a substantial increase in the Quality Factor for only a modest increase in the size of the resonators have been proposed. An antenna array is defined as a group of antenna elements which operate concurrently. By acting on the relative phase of the signal of each radiator, it is possible to control the shape and orientation of the radiation pattern of the entire array. A phased array provides a high level of flexibility on the shape of the radiation pattern, but it is usually a complex system which requires a high amount of control elements. This work proposes an alternative technique that can be used to synthesise arrays with beam-steering properties without the use of phase shifters. The array is divided in two sub-arrays with the same amount of elements. Each sub-array is designed with a fixed phase profile and direction of maximum radiation. The pointing direction of the overall radiation beam can be controlled by adjusting the ratio of signal power being distributed between the two sub-arrays. The proposed technique manages to minimize the amount of control elements required to obtain beam-steering, since only a single power divider is needed. Fixed sub-array cells are simple to design and implement. The result is a large reduction in the complexity of the system. This work presents in detail the advantages, limits and drawbacks of the proposed amplitude-based beam steering technique. This technique is then used to design two different antenna arrays for 5G applications.The rapid growth of wireless networks and technologies of the last few decades has imposed new requirements on the performance of microwave components. There is a demand for wireless devices and sensors with high performance, high miniaturization and low production cost. Given this framework, the aim of this work is to provide a useful contribution through the study of existing techniques and the proposal of new ones. This is done by pursuing two specific lines of research: the study and analysis of compact Substrate Integrated Waveguide (SIW) resonators and filters, and the development of particularly simple and inexpensive reconfigurable antenna arrays based on an innovative amplitude beam-steering technique. Resonators are used as the basis for many different microwave devices. The achievable performance of said devices is limited by the losses of their resonators. The SIW is a planar transmission line technology which is a promising candidate for a wide array of applications. Compared to other planar technologies, the SIW offers particularly low losses and high electromagnetic performance, with an increase in the size of the components as a trade-off. In order to increase the miniaturization of SIW devices, the Half-Mode technique has been proposed, resulting in the Half-Mode Substrate Integrated Waveguide (HMSIW) topology. The Half-Mode technique can be applied multiple times to the classic square SIW resonator. With every iteration, the miniaturization factor is increased. The topologies that can be obtained are the Half-Mode resonator, the Quarter-Mode resonator and the Eighth-Mode resonator. While the SIW topology is completely closed and electromagnetically shielded, HMSIW and derived structures are partly open. For this reason, the performance of HMSIW devices suffer from the introduction of leakage and radiation losses. This work offers a study on the performance of the size reduction technique by the systematic analysis of these topologies. In a practical application, the results of this analysis are used to find which compact topology may be more convenient to employ depending on the design constraints such as frequency or kind of substrate to use. In order to mitigate the problem of losses, a few modified topologies which offer a substantial increase in the Quality Factor for only a modest increase in the size of the resonators have been proposed. An antenna array is defined as a group of antenna elements which operate concurrently. By acting on the relative phase of the signal of each radiator, it is possible to control the shape and orientation of the radiation pattern of the entire array. A phased array provides a high level of flexibility on the shape of the radiation pattern, but it is usually a complex system which requires a high amount of control elements. This work proposes an alternative technique that can be used to synthesise arrays with beam-steering properties without the use of phase shifters. The array is divided in two sub-arrays with the same amount of elements. Each sub-array is designed with a fixed phase profile and direction of maximum radiation. The pointing direction of the overall radiation beam can be controlled by adjusting the ratio of signal power being distributed between the two sub-arrays. The proposed technique manages to minimize the amount of control elements required to obtain beam-steering, since only a single power divider is needed. Fixed sub-array cells are simple to design and implement. The result is a large reduction in the complexity of the system. This work presents in detail the advantages, limits and drawbacks of the proposed amplitude-based beam steering technique. This technique is then used to design two different antenna arrays for 5G applications