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The integration of directive elements into a circular switched parasitic array at 868 MHz is presented. The typical usage of reflective parasitic monopoles is supplemented with additional, shorter monopole elements which are positioned closer to the central active monopole to induce directive behaviour. This allows for more degrees of freedom with the steering of the antennas beam and to increase the gain of the antenna. This leads to a greater flexibility of the system and enables power reduction of the amplifiers for enhanced battery life time. The design and configuration of a circular switched parasitic array with directive elements is shown and a prototype is built for validation., Bundesministerium für Bildung und Forschung (BMBF)

Canonical objects with known radar cross section (RCS), for example, the trihedral corner reflector (TCR), play a crucial role in the calibration of automotive radar sensors. Moreover, these canonical objects are also used in the validation of simulated RCS obtained using asymptotic methods, such as hybrid geometric optics (GO) and the physical optics (PO) based methods. However, accurate RCS prediction with asymptotic methods is highly dependent on the individual scattering mechanisms considered in a simulation, for example reflection and diffraction from the TCR surfaces and edges, respectively. Reliable measurements are therefore required to evaluate if a particular interaction mechanism can be neglected to reduce computation complexity without adversely affecting the accuracy of the predicted RCS. In this letter, the monostatic scattering characteristics of three metallic TCRs are investigated with varying geometrical sizes in the E-band, that is, from 60 GHz to 90 GHz. The ultra-wideband (UWB) measurements, which offer a high delay resolution, can enable the identification of the individual scattering mechanisms. Diffraction from the TCR edges is experimentally demonstrated to contribute to a non-negligible scattered power in this frequency band.

To accurately determine radio coverage, it is necessary to have an omnidirectional antenna pattern. Our measurement results show that this is not the case for an antenna mounted on a vehicle. We present two improved antenna solutions with an additional ground plane in the form of a disk and a corrugated cone. The peak-to-peak variation in the horizontal plane is then reduced from 5 to 2.5 dB and 1.7 dB, respectively. Although our results are limited to a medium-size vehicle and frequencies around 2 GHz, we believe that they are of interest for all measurements where high accuracy is desired., QC 20120615

Great social concern has risen about the potential health hazard of living near a cellular telephony base-station antenna, and certain technical questions have been posed on the appropriate way to measure exposure in its vicinity. In this paper, standard spherical near–near field transformation is proposed to obtain the electromagnetic field close to the antenna in free space conditions. The field obtained in this way allows to define an exclusion zone from the exposure compliance point of view, but also makes possible to bound the error committed by standard field measurement procedures. Furthermore, the visualization of the electromagnetic field in the proximity of the antenna in free space conditions, allows to define clearance templates that have to be met in the siting of the antenna in complex environments in order not to obstruct its main beam., Peer Reviewed

An evaluation of two-branch antenna diversity on mobile telephones is performed in the presence of head and hand phantoms to model the influence of the user. Two mobile telephone prototypes for the 1800-MHz band are considered. The evaluation is done by measuring the three-dimensional (3-D) complex radiation patterns from each antenna with the prototypes positioned near the phantom head and hand (i.e., in talk position) and calculating the diversity performance for three different scenarios of the incoming field. The two-branch antenna setups on both prototypes produce a calculated diversity gain of about 9 dB for selection diversity at the 99% reliability level., QC 20180119

Electromagnetic fields close to radiant structures can be measured quickly using an infrared camera. Examples of induced fields by wire antennas over a detection screen at distances shorter than one wavelength are presented. The measured thermograms agree with simulations that take into account heat propagation on the detection screen., Peer Reviewed

Electromagnetic fields close to radiant structures can be measured quickly using an infrared camera. Examples of induced fields by wire antennas over a detection screen at distances shorter than one wavelength are presented. The measured thermograms agree with simulations that take into account heat propagation on the detection screen, Peer Reviewed, Postprint (published version)

A novel dual-polarized antenna array designed for a spatial division multiple access (SDMA) system working in the 1850-1990-MHz band is designed and built. The antenna is designed to have similar element patterns, and measurements of S-parameters and radiation patterns are presented. The array signal processing performance of the array using all elements and with no compensation for mutual coupling or differences in element patterns is studied through direction-of-arrival (DOA) estimation using total least squares estimation of signal parameters via rotational invariance techniques (TLS-ESPRIT). The results show that the accuracy of the DOA estimates is quite acceptable for wireless communication applications., QC 20180119

Cellular radio systems have been in operation since the early 1970s and are experiencing tremendous growth. However, a major problem for cellular systems is the multipath, or short-term fading. One way to combat multipath fading on the uplink is to implement a diversity scheme at the base station. Until recently this was done by using two separate antennas positioned some distance apart from each other. The disadvantage with this method, however, is that the antennas have to be separated by several wavelengths to receive "independently fading" signals. Thus the antenna systems become large. With polarization diversity two antennas are also used but there is no need for any physical separation between them. Instead the two antennas are polarized in two orthogonal polarizations, e.g., horizontal/vertical or /spl plusmn/45 degrees slanted. In a study by Lotse et al. (see IEEE VTS 46th Vehicular Technology Conference Proceedings, vol.3, p.1643-46, 1996) it was found that space diversity yields typically about 1 dB better "diversity gain" than polarization diversity. However, how different antenna parameters affect the results has to our knowledge never been studied. The authors aim to fill this void., QCR 20180207

An equivalent magnetic current (EMC) approach has been proposed as an alternative method to the classical modal formulation for computing the far-field pattern of a radiating antenna from planar near-field measurements. The attractiveness of this EMC approach includes the possibility of producing the correct far-field pattern in all regions in front of a planar antenna under test (AUT), a drawback of the classical modal formulation due to its dependence on the Fourier transform and assumptions which must be made about the field outside of the measurement zone, and its adaptability to both irregularly sampled and non-canonical near-field measurement surfaces. A drawback of the EMC approach, however, is its significantly larger computational requirements. A comparison of the EMC and classical modal approaches for near-field to far-field transformation is examined in terms of the resultant far-field patterns. Measurement results for a waveguide-fed slot array using the UCLA bi-polar planar near-field measurement scanner are presented. An implementation of the EMC approach for the bi-polar geometry is described and results obtained using different subsets of the measured bi-polar near-field data are presented and compared to that obtained using the classical modal approach., Peer Reviewed, Postprint (published version)

A very simple approximate expression for the process gain (PG) for the cylindrical case is derived. The different approximations and assumptions required to obtain this expression are shown. This expression might be useful for most practical cylindrical near-field measurements, providing a very simple mean to assess the near-field dynamic range requirements to obtain a desired far-field signal-to-noise ratio (SNR)., Peer Reviewed