M. Gallo

Antennas and propagation for on-body communication systems

On-body communication channels are of increasing interest for a number of applications, such as medical-sensor networks, emergency-service workers, and personal communications. This paper describes investigations into channel characterization and antenna performance at 2.45 GHz. It is shown that significant channel fading occurs during normal activity, due primarily to the dynamic nature of the human body, but also due to multipath around the body and from scattering by the environment. This fading can be mitigated by the use of antenna diversity, and gains of up to 10 dB are obtained. Separation of the antennas performance from the channel characteristics is difficult, but results show that for many channels, an antenna polarized normal to the bodys surface gives the best path gain. Simulation and modeling present many challenges, particularly in terms of the problems scale, and the need for accurate modeling of the body and its movement.

A Broadband Pattern Diversity Annular Slot Antenna

An annular slot antenna suitable for pattern diversity in wideband applications is presented. Pattern diversity is obtained by feeding the antenna simultaneously with two microstrip lines printed on the back of the substrate, which generate orthogonal radiation patterns. Two shorts placed at 45 degrees between the microstrip lines and in the opposite direction ensure an isolation above 15 dB according to measurements. The antenna operates in the range of frequencies from 3 GHz to 12 GHz (1:4 bandwidth) and covers many different standards (Wireless-LAN, HIPERLAN2, WIMAX, UWB). Simulations and measurements for return loss, isolation and radiation patterns are presented. Furthermore, measurements have been carried out in a real multipath environment in order to evaluate pattern diversity performance. Results of measurements of the correlation coefficient and diversity gain over the entire operating bandwidth show that the antenna is suitable for antenna diversity systems.

Use of Animation Software in Simulation of On-Body Communications Channels at 2.45 GHz

As wearable electronic devices become increasingly popular, there is a growing interest in the design of body area networks (BAN). The propagation characteristics of such channels are of interest to assist in proper design of BAN systems. It has been shown that body movement is a primary factor in channel fading and hence channel modelling must include the effect of movement. In this letter, results are presented for a walking phantom created using animation software. Simulations of a walking avatar for three different channels at a frequency of 2.45 GHz are shown and compared to measurements made on a human body in an anechoic chamber. It is shown that such a phantom can give good prediction of mean and standard deviation of the propagation channel of a walking subject.

Compact Wideband Vivaldi Monopole for LTE Mobile Communications

A novel compact broadband monopole antenna inspired by a Vivaldi antenna is presented. In order to get a compact solution, the profile of a slot Vivaldi antenna has been modified and a wideband antenna covering LTE700, GSM850, GSM900, DCS1800, PCS1900, WCDMA2100, Bluetooth, WiMAX2350, WLAN2400, and LTE2600 standards has been obtained, with a size reduction length of 30% over conventional λ/4 monopole antennas. In contrast to traditional designs using Vivaldi antennas, a compact design with omnidirectional radiation pattern is proposed. Simulated and measured results are provided, which verify the broadband behavior of the antenna. In addition, the proposed design is perpendicularly mounted to a ground plane, being then suitable for mobile communications in vehicular applications.

Novel ultra-wideband antenna for diversity applications

It is a well-known fact that wireless communications systems suffer from channel fading caused by multipath environment. However, the performance of a wireless link can be significantly improved using spatial, polarization or pattern diversity techniques [1]. Nowadays the trend for mobile terminals is to increase the number of operating frequency bands, in order to cover different applications. Therefore, a wideband diversity antenna seems to be an attractive solution to include in a multi-standard device. In recent years, some diversity antennas with large operating bandwidth have been proposed for different applications [2]-[4]. In this paper, a compact diversity antenna with a bandwidth increase is presented.

Design and experimental validation of a windscreen patch array for C2C communications

In this paper the design and experimental validation of a 2×1 linearly polarized patch array for Car-to-Car communications is presented. The antenna operates in the 5.850-5.950 GHz frequency band and has been designed to be integrated in a car windscreen. Thanks to the presence of the glass superstrate, a valuable miniaturization effect has been obtained. On the other hand, surface waves excited into the glass superstrate reduce antenna gain, and surface wave diffraction injures radiation pattern too. In order to limit above phenomena, a square copper ring film has been printed on the same plane of the radiating elements. To compensate for the windscreen inclination respect to the ground, a proper phase shift between the currents of the two radiating elements has been considered.

Modal analysis of a MIMO antenna for sensor networks

Multiple antennas have emerged as an important technology for increasing the efficiency of wireless communication systems. multiple-input multiple-output (MIMO) systems, offering significant capacity gain, can be used to maximise the transmission channel throughput or to decrease the channel fading. However, multiple antennas are not easily integrated in mobile devices or sensors, because the space available is usually limited. Moreover, in order to lead high performances, good isolation and decoupling between antennas are required. Another drawback is that multiple antennas require multiple RF devices for signal processing that are very expensive. To suppress mutual coupling several methods were proposed in the available literature. In [1] the distance between MIMO antennas array was increased mounting them at the corner of a PDA. In [2] several parasitic elements were employed between MIMO antenna array, while in [3] band-notch slots on a ground plane were etched. In this paper we propose a new MIMO antenna that consists in a metallic ring fed at four ports with alternate phase. The alternate phase of the feeding leads to the excitation of orthogonal modes and allows the implementation of the MIMO antenna. The antenna has been analysed using the Theory of Characteristic Modes [4], which is really appropriate to design multimode antennas because of the physical insight it provides.

Design of a dielectric applicator for microwave heating.

In this paper the design of a handheld light applicator for microwave heating is presented. The applicator is made of an array of resonant longitudinal slots cut on a broad wall of a rectangular waveguide, and it is covered by a cylindrical lens made of Plexiglas with a permittivity of 2.53. The geometrical optics approach is used as initial approximation to establish the lens profile. It allows for the shaping of the slotted waveguide’s radiation pattern into a desired output pattern in the transversal plane. Three-dimensional simulation results show that the applicator performance can be improved at 2.45 GHz by using a homogeneous dielectric lens.

A compact 3D antenna for automotive LTE MIMO applications

A low-profile and compact 3D antenna operating at LTE, GSM and UMTS frequency bands (790–2690 MHz) is proposed for a vehicular 2×2 MIMO system. The performance of the single 3D radiating element is here analyzed. Then, the two-antenna system performance is analyzed in terms of impedance matching, isolation and envelope correlation coefficient, highlighting the effect of some geometrical parameters such as inter-element distance and reciprocal orientation. Preliminary measured results are presented.

A novel 3D antenna for LTE MIMO systems

Two low-profile and compact 3D antennas operating at LTE, GSM and UMTS frequency bands (790-2690 MHz) are here numerically analyzed for a vehicular MIMO system. After an analysis of the single element performance, two identical 3D antennas are considered. A preliminary numerical analysis on the effect of geometrical parameters such as inter-element distance and reciprocal orientation have been discussed to improve the two-antenna system performance in terms of impedance matching, isolation and envelope correlation coefficient.