Abstract—Measurement of the radiation properties of low gain antennas at VHF frequency is in many cases a challenging task. Measurements performed in shielded anechoic chambers are usually preferred to outdoor ranges because they are not subject to the electromagnetic pollution and less affected by the scattering of the environment.
Recent use of measured data as near field sources in Computational Electro Magnetic (CEM) tools has opened the possibility to represent antennas in numerical simulations, even when the antenna characteristics and geometry are unknown and therefore cannot be included in a full wave model [1-4].
This article gives an overview of the activities of the company Microwave Vision, formerly Satimo, oriented to health-related applications. The existing products in terms of Specific Absorption Rate (SAR) measurement and RF safety are described in detail. The progress of the development of a new imaging modality for breast pathology detection using microwaves is shortly reported.
Accurate spherical Near-Field antenna measurements are typically performed compensating for the probe pattern during the Near-Field to Far-Field transformation. Depending on the complexity of the probe modal content and on the required accuracy, different Probe Correction (PC) techniques can be applied.
This paper presents a compact X-band antenna with an isoflux radiation pattern and circular polarization. It consists of a miniaturized helix antenna connected to a stripline circuit that provides a sequential rotation feeding. The antenna is arranged over a vertically corrugated ground plane and it has been optimized for a CubeSat 3U nanosatellite platform.
In spherical Near Field (NF) measurements postprocessing techniques based on spatial filtering have been presented as promising tools for the mitigation of echoes or stray signals deriving from the surrounding environment. The spatial filtering is very efficient in measurement scenarios with a stationary Antenna Under Test (AUT).
In this paper, a wide-band numerical model of the measured antenna is presented, improving the accuracy of the coupling assessment. The finding are supported by radiated and conducted measurement on the single element and the array configuration.
Probe correction in standard spherical near field measurements are typically limited to probes with |μ|=1 spherical wave spectrum when performing spherical wave expansion. The design of such probes is often a trade-off between achievable performance, modal purity and bandwidth. Compensation techniques for probes with higher or full order modal spectrum have recently been proposed.
This paper presents a near-field antenna test procedure providing single or double main plane patterns including the gain. The procedure is applicable to antennas, with separable excitation in the two main planes. The test set-up is based on an azimuth positioner and near to far-field transformation based on expansion in cylindrical modes.
In this paper, the QZ cross-polar reduction properties of the CXR feed is measured in a standard corner-fed CATR in both orthogonal polarization over the full 1.6:1 bandwidth. The advantages of the CXR in general measurement scenarios are investigated by measurement of an antenna with low cross-polarization level at different QZ positions and frequencies.
Dual polarized wideband probes are convenient for accurate and time efficient Planar Near Field (PNF) antenna testing -. Traditional probe designs are often bandwidth limited and electrically large leading to high scattering - in PNF measurements with short probe-AUT distances.
We have developed a 60 GHz chip antenna designed for use as a gain and pattern verification tool in the calibration process of a millimeter wave antenna test chamber. The antenna is designed to interface with ground-signal-ground (GSG) micro-probes that have a probe pitch of 150 um to 250 um.
This paper will outline design requirements and present test results of 60 GHz Chip Reference antennas. Several dozen antennas have been tested. The related uncertainties in the micro-probed antenna measurements will be evaluated with particular emphasis on the gain calibration uncertainty.
An innovative spherical NF/FF transformation algorithm for offset measurements based on a Translated Spherical Wave Expansion (TSWE) has been recently proposed. In this paper we investigate by experiment the echo reduction properties of offset AUT measurements using TSWE.
Probe correction in Spherical Near Field (SNF) measurements is typically performed during the NF/FF transformation. 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 can be radiated.
The polarization purity of an antenna system is an important performance parameter, particularly in dual-polarized systems, where depolarization can prevent operating objectives from being achieved. Accurate polarisation testing requires a significantly higher polarisation purity of the test system than of the test object.
Integration of antenna measurements in numerical simulations, based on the equivalent current technique, has been validated in previous activities. 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.
Accurate numerical models of a given antenna can be derived from measurements using the inverse source technique. Using this technique, measured antenna patterns can currently be imported and used as numerical sources in a number of commercial Computational Electromagnetic (CEM) solvers.
Electromagnetic simulation allows engineers to investigate the performance of antennas in a wide range of different environments which may be inaccessible or infeasible to measure. However, it is often the case that a suitable model of the antenna is not available for the simulation, especially for off-the-shelf antennas with geometries that are protected by intellectual property.