New EBG solutions for mutual coupling reduction

Electromagnetic Band Gap (EBG) based on Frequency Selective Surfaces (FSS) [1] are one type of metamaterials [2] with electrical properties [3]. This EBG are used in mutual coupling reduction, back lobe radiation reduction, etc. In this work not only new shapes for the mushroom-type are presented, but also multilayered configurations were studied in order to reduce the patch size and the necessary number of elements.

Study of an electronic steering antenna with a staggered phase shifter configuration

This paper presents a study of three possible solutions that can be taken into account to control the phase shift between elements in an antenna array. Because commercial digital phase shifters have become a strategic element by U.S. Government, these elements have increased their price. For this reason, it is necessary to adopt some solutions that allow us to deal with the design and construction of antenna arrays.

Surface Impedance Characterization for UTD Based Solution with IBC for Surface Fields on a Dielectric-Coated PEC Circular Cylinder

A novel formulation for the surface impedance characterization is introduced for the canonical problem of surface fields on a perfect electric conductor (PEC) circular cylinder with a dielectric coating due to a electric current source using the Uniform Theory of Diffraction (UTD) with an Impedance Boundary Condition (IBC). The approach is based on a TE/TM assumption of the surface fields from the original problem. Where this surface impedance fails, an optimization is performed to minimize the error in the SD Green?s function between the original problem and the equivalent one with the IBC. This new approach requires small changes in the available UTD based solution with IBC to include the geodesic ray angle and length dependence in the surface impedance formulas. This asymptotic method, accurate for large separations between source and observer points, in combination with spectral domain (SD) Green?s functions for multidielectric coatings leads to a new hybrid SD-UTD with IBC to calculate mutual coupling among microstrip patches on a multilayer dielectric-coated PEC circular cylinder. Results are compared with the eigenfunction solution in SD, where a very good agreement is met.

Surface Impedance Characterization for Mutual Coupling Calculation of Patches on a Dielectric-Coated PEC Circular Cylinder

A novel formulation for the surface impedance characterization is introduced for the canonical problem of surface fields on a perfect electric conductor (PEC) circular cylinder with a dielectric coating due to a electric current source using the Uniform Theory of Diffraction (UTD) with an Impedance Boundary Condition (IBC). The approach is based on a TE/TM assumption of the surface fields from the original problem. Where this surface impedance fails, an optimization is performed to minimize the error in the SD Green?s function between the original problem and the equivalent one with the IBC. This asymptotic method, accurate for large separations between source and observer points, in combination with spectral domain (SD) Green?s functions for multidielectric coatings leads to a new hybrid SD-UTD with IBC to calculate mutual coupling among microstrip patches on a multilayer dielectric-coated PEC circular cylinder. Results are compared with the eigenfunction solution in SD, where a very good agreement is met.

Study of a new 4×3 beam forming network for triangular arrays of three radiating elements

An innovative dissipative multi-beam network for triangular arrays of three radiating elements is proposed. This novel network provides three orthogonal beams in θ0 elevation angle and a fourth one in the broadside steering direction. The network is composed of 90º hybrid couplers and fixed phase shifters. In this paper, a relation between network components, radiating element distance and beam steering directions will be shown. Application of the proposed dissipative network to the triangular cells of three radiating elements that integrate the intelligent antenna GEODA will be exhibited. This system works at 1.7 GHz, it has a 60º single radiating element beamwidth and a distance between array elements of 0.57λ. Both beam patterns, theoretical and simulated, obtained with the network will be depicted. Moreover, the whole system, dissipative network built with GEODA cell array, has been measured in the anechoic chamber of the Radiation Group of Technical University of Madrid, demonstrating expected performance

Research activities of Spanish antenna groups

When we look at the history of electricity and electromagnetism in Spain we discover that the most important Spanish researchers are generally out of the official institutions or stable research groups until the 20th century [1] [2]. In the 20th century most of the scientific research is done in stable research institutions and universities and the most important electromagnetism research centres in Spain are located in the Faculty of Physics of the most important universities, the National Scientific Research Council (CSIC) and the School for Telecommunication Engineering created in 1923. But the greatest impulse of research in the antenna and radiowave propagation field is done after 1960 reaching the first national URSI conference in 1980. After that year, the relation between groups and the number of research groups is continuously growing and the relation to industry is also increasing. When Spain joins the European research organizations (COST, ERC...) and the European Union in 1985 the research support experience a fast growing and the participation in the European research structures. In the antenna design field, there exist some specializations although most of the groups have dome specific projects in almost all the antenna analysis and design fields. Here, we have selected the most important and characteristic area related to each of the research groups and institutions. The easiest way to classify the research work in antennas is the selection between antenna analysis, design and measurement. After that the selected frequency bands technology, the type of antennas and the related circuits can be a good criterion to describe the variety of research work and specialization between groups.

Application of postprocessing techniques methods for noise reduction in cylindrical near field antenna measurements

Three different methods to reduce the noise power in the far-field pattern of an antenna when it is measured in a cylindrical near field system are presented and compared. The first one is based on a modal filtering while the other two are based on spatial filtering, either on an antenna plane or either on a cylinder of smaller radius. Simulated and measured results will be presented.

Estimation of atmospheric attenuation at 99 GHz using a total power radiometer

A total power radiometer operating at 99 GHz was implemented for a propagation experiment aimed to estimate attenuation along a slant path, in Madrid. Valuable data was collected during a measurement campaign in mid-april of 2012. The retrieved time series of radiometric attenuation allow the use of this technique at this frequency to be validated, under clear sky and cloudy conditions, using a low cost instrument calibrated with simple procedures. In spite of some hardware limitations, this experiment shows an interesting application of radiometric technique in order to study atmospheric propagation at 99 GHz.

Bifocal reflector antenna system for radar imaging at 300 GHz

A 300 GHz radar imaging system is presented, including descriptions of the radar sensor and antenna subsystems. The antenna consists of a Bifocal Ellipsoidal Gregorian Reflector whose beam is scanned by a combination of the rotation and vertical tilting of a flat small secondary mirror. A prototype is being mounted and its characterization will be presented.

Man-pack antenna at X-band

In this paper a low cost man-pack antenna for satellite communications at X band is presented. The antenna has dual circular polarization in Tx and Rx.

On the design of a planar phased array radar antenna architecture for space debris situational awareness

The Space Situational Awareness (SSA) program from the European Space Agency (ESA) protects Europe's citizens and their satellite-based services by detecting space hazards. ESA Ground Systems (GS) division is currently designing a phased array radar composed of thousands of radiating elements for future stages of the SSA program [1]. The radar shall guarantee the detection of most of the Low Earth Orbit (LEO) space debris, providing a general map of space junk. While range accuracy is mainly dictated by the radar waveform, the detection and tracking of small objects in LEO regimes is highly dependent on the angular accuracy achieved by the smart phased array antenna, demonstrating the important of the performance of this architecture.

GEODA-SARAS: Multi-Phased array planar antenna for satellite communications

Nowadays, earth stations have as a common feature the use of large reflector antenna for downloading data from satellites. Large reflectors have impairments such as mechanical complexity, low flexibility and high cost. Thus, the feasibility of other antenna technologies must be evaluated, such as conformal adaptive antennas based on multiple planar active arrays. In the scenery under study, the capability to track several satellites simultaneously, higher flexibility, lower production and maintenance cost, modularity and a more efficient use of the spectrum; are the most important advantage to boost up active antenna arrays over large dishes.

Surface impedance for scattered field on a dielectric-coated circular cylinder

In the scattering analysis of a circular cylindrical structure, the impedance boundary condition (IBC) can approximate and simplify the perfect electric conductor (PEC) boundary condition. The circular cylinder problem can be solved with modal methods but they require a large number of terms when the cylinder radius is large in terms of the wave length. The uniform theory of diffraction (UTD) [1] is commonly used to overcome this issue. The two-dimensional problem of scattering on a circular cylinder covered by a dielectric layer has been analyzed by [2]–[5], but their solutions either do not consider oblique incidence, fail on the transition region or use a constant surface impedance.

Surface impedance for electromagnetic fields over a dielectric-coated circular cylinder

For small or medium size conformal array antennas in terms of the wave length, modal solutions in spectral domain for mutual coupling analysis are convenient for canonical shapes such as circular cylinder [1] or sphere [2], but as the antenna dimensions increase a large number of terms are necessary. For large structures the uniform theory of diffraction (UTD) is commonly used to solve this problem for canonical and arbitrarily convex shaped perfect electric conductor (PEC) surfaces [3]. A UTD solution for mutual coupling on an impedance cylinder has been introduced in [4], [5] but using a constant surface impedance.

A reflection suppression technique for far field antenna measurements

This paper presents a reflection suppression technique for far field antenna measurements. The technique is based on a source reconstruction over a surface greater than the antenna itself. To be able to perform the reflection construction the next steps are required: the complete far field antenna pattern is obtained through interpolation of the acquired cuts, the currents are obtained through a holographic technique, the field out of the antenna area is filtered, and the pattern is reconstructed. The algorithm is used with measurements in the LEHA-UPM antenna measurement facilities and in the outdoor far field facility of LIT INPE in Brazil.