Novi rezultati u projektiranju i mjerenju antena za osobne pokretne komunikacije

Mobile communications are taking more and more importance in everyday life, creating the need for smaller and lighter mobile terminals. Unlike the electronic circuits, the size of an antenna is not technology related, but imposed by the wavelength of a given application. This makes antenna miniaturization to an art of compromise between size and radiation performances. In this presentations we will first state the limitations of antenna miniaturization, by reminding of the well known laws linking gain, bandwidth and antenna size. Then some well known ways to reduce antennas sizes will be reviewed and illustrated on a practical example designed and realized in our laboratory. Finally, we will deal with the non trivial problem of small antenna measurement: the problems encountered when measuring small antenna will be presented and some clues on how to proceed correctly will be given.Pokretne komunikacije postaju sve važnije u svakodnevnom životu, a time se povećava potreba za što manjim i lakšim pokretnim komunikacijskim uređajima. Za razliku od elektroničkih sklopova, veličina antene nije određena stupnjem tehnološkog razvoja već je zadana frekvencijskim područjem koje se koristi za određenu primjenu. Zato je minijaturizacija antena umjetnost kompromisa između malih izmjera i dobrih osobina zračenja. U ovom su radu ograničenja minijaturizacije antena prikazana kroz povezanost dobitaka, širine pojasa i izmjera antene. Zatim su opisani neki uobičajeni postupci za smanjivanje izmjera antena. Njihova je primjena prikazana na praktičnoj izvedbi koja je projektirana i izrađena u našem laboratoriju. Konačno se razmatraju problemi pri mjerenjima malih antena: izneseni su problemi koji su uočeni pri mjerenju malih antena kao i naputci za njihovo prevladavanje

A novel, low-profile, vertically-polarized UWB antenna for WBAN

This paper proposes a novel, low-profile UWB antenna for wireless body area network (WBAN) applications. The antenna has a polarization perpendicular to the body-free-space interface, which is interesting in order to minimize the coupling into the body. Its structure comprises a modified mono-cone with a top-cross-plate and is coaxially fed through the ground plane. The higher frequency band |S11| performance is due to the mono-cone while the top-cross-plate is responsible for the lower frequency band. This plate also leads to a height reduction when compared to conventional mono-cone antennas. A comprehensive parametric study is done to provide design guidelines. Both frequency- and time-domain results have been measured and presented to validate the design. Results show that the antenna operates from 3.06 to beyond 12 GHz based on |S11| ≤ -10 dB, radiates omni-directionally in the H-plane, and has a radiation efficiency over 95%. The system-fidelity factor for UWB signals is adequate for pulse transmission. Finally, the influence of the human proximity on the antenna matching was tested. Results show that its impedance is nearly unchanged as compared to free-space

RoSe: A sub-GHz wireless sensor platform with housing integrated overmolded antenna

A wireless sensor platform for use in ultralow-power wireless sensor networks (WSNs) is presented. The proposed round sensor (RoSe) node is physically robust, is resistant to humidity, and has a housing that can be in direct contact with food. These characteristics are achieved via injection molding technology which is investigated at both the component and the system levels. The results of injection molding tests on the node's electronic components are reported, while a housing-integrated overmolded antenna is conceived and realized. The radiator, operating in the subgigahertz industrial, scientific, and medical (ISM) band (ISM 868 or 915 MHz), has been characterized, and a good correspondence with theoretical predictions is observed. The proposed system enables industrialized mass production and results in a generic platform for wireless monitoring applications. In this paper, we present the RoSe node with a temperature sensor for use in food cold chain management, i.e., for use at temperatures down to -30 °C and in frequent contact with water due to condensation or cleaning. Its ultralow-power characteristics are demonstrated by the analysis of the charge consumption when the node performs specific tasks both in a test case and operating in a WSN. Long-term battery lifetime results while running a demo WSN are also presented

A New Power Divider Architecture for Suspended Strip Line

In this paper the authors present a novel power divider architecture intended to be used with the Suspended Strip Line (SSL) transmission line. The new antenna array systems, that are designed to work in the millimetre wave ranges, are suffering from the losses in their beam forming networks. In order to mitigate the losses one can use special types of transmission lines. One of them is the so-called Suspended Strip Line (SSL). In this paper the authors present a novel RF power divider intended to be used with the SSL. It uses the properties of the suspended stripline geometry in order to give the designer an increased number of degrees of freedom to achieve the desired power division ratio and a good input match. The advantages of the proposed geometry are compactness, good power handling, no need of any soldering or introducing lumped elements and the sole use of standard 50 Ohm lines