Temperature changes cause thermal expansion of antenna materials and will have an important impact on antenna performances. In some applications, it is sufficient to calculate the antenna deformation by mechanical analysis and determine the RF impact by EM analysis tools.
V-band (50-75GHz) applications such as 5G and myriad others are the catalyst for high performance near-field antenna measurement systems. For Spherical Near-Field (SNF), the traditional approaches at millimeter wave frequencies collect two full spheres of data in the near-field where each sphere samples one of two linear and orthogonal fields of the antenna under test (AUT).
Antennas installed in modern cars are often highly integrated. In such cases, the entire vehicle is contributing to the radiated field, in particular at lower frequencies such as VHF. The complete characterization of the full vehicle is thus typically required.
Automotive antenna measurements are increasingly demanding. Modern cars are equipped with a large number of integrated antennas, spanning a wide frequency range for a large number of applications. Integrated antennas are strongly coupled with the structure, final testing are thus performed on the vehicle to accurately determine the performance.
The measured source or Huygens box antenna representation has become an increasing popular solution to create accurate computational models of measured source antennas for the numerical analysis of antenna placement on complex platforms such as satellites.
The accurate characterization of low-gain antennas at VHF frequencies is challenging. Such antennas can be tested outdoors for convenience or in very large and thus expensive indoor Far-Field (FF) ranges. Indoor Near-Field (NF) systems are often considered a better cost compromise for such measurements, mainly due to the relaxed requirements on chamber size.
Current techniques for testing of aircraft radomes are time consuming, not as precise as desired, and requires dedicated far field test range, compact test range, or anechoic chamber, or other specific systems for measuring one or other of the parameters.
Comparison activities in which a number of measurement facilities compare their measurements of the same antenna in a standard configuration have become important for documentation and validation of laboratory expertise and competence. It is also mandatory to have regular participation in such activities to obtain and maintain accreditations like ISO 17025.
Dual-polarized probes with wide-bandwidth operational capabilities are highly desirable for time-efficient Planar Near-Field (PNF) measurements -. However, sometimes the performance tradeoffs necessary to achieve the desired operating bandwidth make such probes impractical for many applications.
This paper addresses the problem of how to accurately calibrate Massive MIMO systems using time-division duplexing (TDD). In practical MIMO array implementations the transmission and reception path are different and hence a calibration mechanism, linking optimum receive array coefficients to optimum transmit coefficients is needed.
The adoption of millimeter wave phased arrays for a variety of applications has led to an increased need for on-chip antenna measurements. The antenna elements are tested via micro-probe connections due to their tiny dimensions. For typical wireless applications (e.g. 5G/NR or IEEE 802.11.ad) these phased arrays, are expected to provide near omni-directional coverage.
Recent publications have reported on an innovative technique in which measured antennas are represented as numerical sources in the accurate computation of antennas in complex environments [1-5]. The measured antenna is accurately characterized as a Huygens box in a format compatible with different Computational Electro-Magnetic (CEM) solvers.
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.