Roberto Vallauri

Switched Beam Antenna Employing Metamaterial-Inspired Radiators

We present a novel switched beam antenna (SBA) consisting of four identical metamaterial-inspired electrically short printed monopoles, vertically placed at the corners of a grounded square board. The antenna is designed to operate in the frequency range 1600-2700 MHz, with global dimensions 120 mm × 120 mm × 30 mm. The SBA has been first numerically simulated and optimized and, then, fabricated and tested. Numerical and experimental results show a good agreement. The obtained switched beam capabilities, the achieved realized gain levels, and the synthesized radiation pattern shapes on the horizontal plane, make the proposed SBA a good candidate as a radiating element of a receiving module for wireless telecommunication systems (DCS, UMTS, Wi-Fi, LTE) in areas with reduced signal coverage and/or high interference levels.

A Fraunhofer-Based Approach for the Assessment of the Field Radiated in the Fresnel Region of an Antenna

The letter focuses on a simplified and conservative method for the assessment of the electromagnetic exposure in proximity of a radiator. The method allows the use of the Fraunhofer antenna pattern to estimate the electromagnetic field radiated in the Fresnel region of base transceiver station (BTS) antennas. The proposed approach is introduced from a theoretical point of view and validated with simulations and measurements on linear and planar array systems. For its application, a specific description of the boundaries of the Fresnel region for a generic antenna of parallelepipedal shape, which takes into account the dependency from the direction of observation, is introduced. The method provides a rapid and simple solution of assessment issues in relation to the electromagnetic fields exposure limits.

Electromagnetic Field Zones Around an Antenna for Human Exposure Assessment: Evaluation of the human exposure to EMFs.

The regulatory framework on human exposure to electromagnetic fields (EMFs) is a crucial task that the telecommunication operators and the authorities have to face. Some procedures have been introduced in standards, based on both computations and measurements, for the assessment of the compliance of the radio transmitters to the given EMF limits. The procedures could vary depending on the position of the observation point around the transmitting antennas. In this article, the definitions of EMF zones and the zones boundaries around an antenna are revised and tailored for the evaluation of human exposure to the EMFs. The space around the antenna is sectioned into three regions: reactive, radiating near field, and far field. The analytical and numerical results are used to support the proposed regions boundaries. Some examples of region boundaries are given for a few antenna types.

Simplified numerical field assessment in the Fresnel region of BTS antennas

Numerical field assessment is a topical point of interest for a preliminary estimation of human exposure to upcoming radio stations. In many practical situations, the electromagnetic field must be calculated far from the antenna, into the Fraunhofer region of the radiator, and analysis techniques can be satisfactory based on far-field simulations. If obstacles and buildings are present, the simulation can be integrated by use of ray-tracing techniques [1]. All these methods do not require the knowledge of geometrical and electrical design data, since in the Fraunhofer region, the electromagnetic field depends only on the radiation pattern that is typically provided by antenna manufacturers or can be alternatively measured directly by the end-user. If the points of interest belong to regions closer to the radiator, the angular representation of the radiation diagram is not unique. Hence, the radiation pattern concept is not valid and the field must be calculated by means of a full-wave solution of the electromagnetic problem. As an alternative to the use of standard full-wave numerical techniques, some authors propose dedicated solutions [2], in some cases adopting simplified approaches [3].

Active antenna system testing and trials in Telecom Italia

Active Antenna Systems embed into one equipment only everything between Base Band processing and signals radiated over the air. It is a new technology for the mobile communications market whose testing requires well-known measurement techniques to be revisited, new ones to be invented and trials are worth being done. Current paper summarizes Telecom Italia experience in that field, after having worked on it for a few years.