A. Giacomini

Wide-band dual polarized probes for near field antenna measurements

Wide-band, dual polarized probes based on an innovative self-balanced feeding scheme has been developed for high accuracy near field measurements. The innovative self-balanced feeding gives a reduction in cost and complexity while maintaining high performance standards. The overall simplicity makes the new technology attractive for probe designs in the L to Ka band range.

Miniaturized Array Antenna Using Artificial Magnetic Materials for Satellite-Based AIS System

The ground-based automatic identification system (AIS) is a coastal tracking and messaging system used by vessels for maritime traffic monitoring. The European SAT-AIS initiative aims at providing a space-based complementary system to extend the range of the existing AIS to high seas via very high frequency (VHF) satellite constellation. The AIS Miniaturized Antenna (AISMAN) activity concentrates on the development of a VHF array antenna for minisatellite platforms in low Earth orbit. Array element volume minimization and mass reduction are considered performance drivers due to the in-orbit array deployment and satellite mass requirements. Artificial magnetic materials (AMMs) have been chosen as design concept of the baseline array element due to the significant size reduction they can offer. Further technical solutions, such as slotted ground plane, combined with AMM, have allowed for an outstanding profile reduction, while preserving high radiation efficiency and low back radiation. Innovative testing methodologies have been specifically developed to handle truncation errors and echo signals while performing radiation pattern measurement of the array on a full-scale mockup platform in a hemispherical automotive near field (NF) range. This paper discusses the design of array elements, from breadboard to engineering model (TRL4), manufacturing and validation campaigns at single element and array level.

High accuracy field probes in circular polarisation

The development, manufacturing and test of dual circular polarized probes with up to 1:2 bandwidth has been discussed. Preliminary measurements with “ideal” BFN show that the design is compliant with the specification.

Miniaturized dual polarized VHF array element for AIS space application

An important satellite based application at VHF band is the Automatic Identification System (AIS). The system is devised to receive messages sent by vessels for maritime safety and security purposes. The intended platform is a mini-satellite in Low Earth Orbit (LEO). Due to the in-orbit deployment of the array and overall mass requirements for the satellite, the array element minimization and mass reduction are considered performance drivers. The important size reduction properties of Artificial Magnetic Materials (AMM) / Meta Materials (MM) made this approach a natural choice as baseline array element technology. This paper presents the preliminary study of the array element including the manufacturing of an elegant bread-board and verification by measurement.

Measurement of low gain VHF array element in hemispherical NF antenna test range

Accurate measurements on low gain antennas at VHF frequencies are very demanding due to the limited dimensions of available test ranges. This paper presents the findings and post processing issues involved in the verification measurement on a low gain VHF antenna array element with minimized mass and dimensions developed for space application and suitable for an Automatic Identification System (AIS). The testing has been performed in a hemispherical spherical near field antenna test range of Renault in Aubevoye, France.

Wideband dual polarized probe with interchangeable apertures for advanced antenna measurement applications

Dual polarized probes for modern high precision measurement systems have strict requirements in terms of pattern shape, polarization purity, return loss and port-to-port isolation. A desired feature of a good probe is that the useable bandwidth should exceed that of the antenna under test so that probe mounting and alignment is performed only once during a measurement campaign [1]. As a consequence, the probe selection/design is a trade-off between performance requirements and the usable bandwidth of the probe. Recently, a new orthomode junction (OMJ) and probe technology has been developed capable of achieving as much as 1:4 bandwidth while maintaining the high performance standards of traditional probe designs [2–9]. An example of a field probe based on this technology is shown in Figure 1. The development, test and performance details of these probes has been reported in [7]. At the lower frequencies the aperture diameter of these probes is about 0.7λ making them highly useful for any measurement application. However, the aperture diameter in terms of wavelengths increases with frequency and becomes close to 3λ on a 1:4 frequency range.

Design and testing of a miniaturized dual polarized VHF array element for AIS space application

The space-based Automatic Identification System (SAT-AIS) is devised to provide identification and position information to vessels for maritime safety and security purposes. The system is intended to operate at VHF through mini-satellite platforms in Low Earth Orbit (LEO). Due to the in-orbit deployment of the antenna array and overall mass requirements for the satellite, the array element minimization and mass reduction are considered performance design drivers. The important size reduction properties of Artificial Magnetic Materials (AMM) / Meta Materials (MM) made this approach a natural choice as baseline array element technology. The following antenna array verification represents a challenging task due to the low-gain and overall DUT dimensions at VHF band. This paper presents the preliminary study of the array element including the manufacturing of an elegant bread-board and testing in a hemispherical near-field antenna test range together with post-processing issues involved.

Analysis of measurement probe spherical higher order modes based on equivalent currents

Probe correction in Spherical Near Field (SNF) measurements is typically performed during the NF/FF transformation assuming a probe with limited |μ|=1 spectrum [1]-[2]. This requirement leads to challenging probe designs, especially if the required bandwidth is wide. For this reason, in many practical cases, higher order spherical modes could be radiated. In this paper, the source of higher order spherical modes of the MVI SP1100 probe is investigated using INSIGHT software [3] which reconstructs equivalent currents starting from the measured NF. The equivalent currents associated to higher order modes have been computed on a conformal geometry encompassing the probe. In this way, the origin of such higher order modes has been evidenced. Knowledge of these sources are useful to improve future probe designs.

Evaluation of antenna coupling based on measurements and numerical simulations

Integration of antenna measurements in numerical simulations, based on the equivalent current technique, has been validated in previous activities [1-8]. A link, enabling the export of an accurate numerical model, derived from the measured antenna pattern, to a number of commercial Computational Electromagnetic (CEM) solvers has been created and validated [9-14]. The equivalent current processing and the link have been implemented in the commercial INSIGHT software [4]. This tool has recently been applied to antenna placement problems to investigate the antenna radiation pattern in embedded conditions [1-3]. This paper discuss an extension of the link between measurements and simulations in antenna placement scenarios applied to the evaluation of antenna coupling problems.