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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. The numerical representation of the measured antenna is...
This paper address the problem on how to accurately calibrate Massive MIMO system 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. We propose an Over-the-Air OTA calibration technique based on post-processing...
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. However, different source of errors, such as truncation of the scanning surface...
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]. The near field source consists of an equivalent current representation of the antenna, which is prepared...
In spherical Near Field (NF) measurements post-processing 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). Whenever the AUT is rotating, in order to increase the effectiveness...
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. It is common practice to distinguish between first order PC, where only |μ|=1 spherical modes of...
The inverse source technique is an accurate post processing and diagnostics method for antenna measurements [1-3]. Indeed, this technique has proven useful to suppress and filter disturbances in measurement scenarios such as presence of the feeding cable and mounting support [4-6]. Performing accurate measurements of on-chip antennas at millimeter wave frequencies is difficult in particular due to...
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). These two orthogonal polarizations...
Dual-polarized probes with wide-bandwidth operational capabilities are highly desirable for time-efficient Planar Near-Field (PNF) measurements [1]-[3]. However, sometimes the performance tradeoffs necessary to achieve the desired operating bandwidth make such probes impractical for many applications. Traditional probes are often bandwidth limited, and their electrical size can be an undesired source...
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. The main goal of the facility comparison...
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 [1]. Indoor Near-Field (NF) systems are often considered a better cost compromise for such measurements, mainly due to the relaxed requirements on chamber size. However, reflectivity issues and other...
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. However, if the environmental conditions of the final antenna are stringent and considered critical as in the case of military...
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. For frequencies down to 70 MHz, a widely accepted and cost effective solution is a multi-probe spherical Near Field (NF) system in which the...
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 physical and electrical size of typical cars, impose...
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 equivalent representation of the measured antenna is obtained through the equivalent current (EQC) or inverse source technique, which is a...
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...
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...
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. Accurace polarisation testing, requires a significantly higher polarisation purity of the test system than the test object. The Compact Antenna Test Range (CATR) is widely used for antenna system testing...
Accurate numerical models of a given antenna can be derived from measurements using the inverse source technique [1–3]. Using this technique, measured antenna patterns can currently be imported and used as numerical sources in a number of commercial Computational Electromagnetic (CEM) solvers [4–9]. This method has been validated experimentally and the achievable accuracy investigated for both stand-alone...
The application of large antenna arrays for space missions in VHF band is hindered by the dimension and weight of the single radiating element from a conventional design approach. Satellites used for this kind of applications are typically micro/mini platforms and cannot accommodate large antennas. To this purpose, element volume minimization and mass reduction are considered performance drivers,...
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