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Compact Multilayer Yagi-Uda Based Antenna for Iot/5G Sensors

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Compact Multilayer Yagi-Uda Based Antenna for Iot/5G Sensors sensors Article Compact Multilayer Yagi-Uda Based Antenna for IoT/5G Sensors Amélia Ramos 1,2,*, Tiago Varum 2 ID and João N. Matos 1,2 ID 1 Universidade de Aveiro, Campus Universitário de Santiago, 3810-135 Aveiro, Portugal; [email protected] 2 Instituto de Telecomunicações, Campus Universitário de Santiago, 3810-135 Aveiro, Portugal; [email protected] * Correspondence: [email protected]; Tel.: +351-234-377-900 Received: 27 July 2018; Accepted: 30 August 2018; Published: 2 September 2018 Abstract: To increase the capacity and performance of communication systems, the new generation of mobile communications (5G) will use frequency bands in the mmWave region, where new challenges arise. These challenges can be partially overcome by using higher gain antennas, Multiple-Input Multiple-Output (MIMO), or beamforming techniques. Yagi-Uda antennas combine high gain with low cost and reduced size, and might result in compact and efficient antennas to be used in Internet of Thins (IoT) sensors. The design of a compact multilayer Yagi for IoT sensors is presented, operating at 24 GHz, and a comparative analysis with a planar printed version is shown. The stacked prototype reveals an improvement of the antenna’s main properties, achieving 10.9 dBi, 2 dBi more than the planar structure. In addition, the multilayer antenna shows larger bandwidth than the planar; 6.9 GHz compared with 4.42 GHz. The analysis conducted acknowledges the huge potential of these stacked structures for IoT applications, as an alternative to planar implementations. Keywords: Yagi-Uda; multilayered antenna; millimeter-waves; IoT 1. Introduction People’s interconnection was improved by 4G, making the communication more efficient, fluent, and natural. Nowadays, 5G intends to continue that demand and take it to a higher level. In this framework, 5G aims to guarantee people’s interaction, devices interconnection, as well as the connection among people and devices. A network composed of users, daily gadgets, traffic information, personal health conditions, or the status of all the home electronic devices is only a small example of a possible scheme, shown in Figure1, within many 5G scenarios that are not yet discovered. For now, it is known that 5G services will be divided in three categories; namely, enhanced mobile broadband, mission-critical control, and massive Internet of Things (IoT) [1]. Probably the most effective method to fulfil some demands for 5G cellular services, which are expected to be commercially available in 2020, is to increase the bandwidth [2]; hence, the migration to higher frequencies (in the mmWaves) is mandatory, mainly to support the required gigabit data rate service [3]. On the other hand, as a disadvantage, the frequency ranges of mmWaves present higher path-loss resulting in fragile link, due to weak diffractions at these frequency bands. To overcome these issues, high gain antennas and highly directive antenna arrays using several elements, as well as the application of beamforming techniques, can be used, in order to transmit the wave in the right direction. Yagi-Uda antennas present several characteristics that make them suitable for application in sensors or in larger antenna arrays. Sensors 2018, 18, 2914; doi:10.3390/s18092914 www.mdpi.com/journal/sensors Sensors 2018, 18, 2914 2 of 13 Sensors 2018, 18, x 2 of 14 FigureF 1.igureExample 1. Example of 5G of communications5G communications andand a a massive massive Internet Internet of Things of Things (IoT) (IoT)scenario scenario.. Structurally Yagi-Uda antennas are well known. 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With the emergence of printed circuits, several Yagi-like antennas proposed for different frequencies of operation and a wide number of applications [Error! Reference have beensource proposed not found. for,Error! different Reference frequencies source not of found. operation]. and a wide number of applications [6,7]. In InternetIn Internet of Things of Things (IoT) (IoT) scenarios, scenarios, antennas antennas are are to to be be implemented implemented in every in every small smallgadget gadgetor or wearablewearable gadget, gadget mainly, mainly to assure to assure the the interaction interaction between sensors sensors placed placed in the in most the mostvarious various devices devices and people.and people. Because Because of theirof their widespread widespread us use,e, it is it highly is highly recommended recommended that antennas that antennasare small and are small and compact.compact. Over the years, some effort has been made to find antenna miniaturization techniques that allow Over the years, some effort has been made to find antenna miniaturization techniques that allow reducing antenna size, maintaining or improving its main characteristics. Some of these methods are reducingdescribed antenna in size, the literature maintaining [Error! or Reference improving source its main not characteristics.found.], presented Some in different of these classes, methods are describedincluding in the techniques literature such [8], as presented fractals, metamaterials, in different high classes, dielectric including constant techniques substrates, slow such wave asfractals, metamaterials,structures high, or engineered dielectric ground constant planes. substrates, A miniaturization slow wave technique structures, described or engineered in the literature ground that planes. 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