Patrick Dumon

Phase Center Study of the Electromagnetic Band Gap Antenna: Application to Reflector Antennas

Recent studies have shown that the electromagnetic band gap (EBG) antenna can be used to feed a reflector, especially to realize multibeam coverage with geostationary satellite. However, it is necessary to evaluate its performances in terms of aperture efficiency to compare this solution to the classical ones. Among all the parameters which contribute to the aperture efficiency, one of the most important is the phase center, which has never been determined for EBG antennas. This is the aim of this letter. After defining a simple method to calculate the phase center of the EBG antennas, the position and the frequency evolution of this parameter will be studied. Then, the performances of such a feed associated with a Side Fed Offset Cassegrain Antenna (SFOCA) will be evaluated and compared with a classical feed for reflector, a Potter horn

EBG Focal Feed Improvements for Ka-Band Multibeam Space Applications

This letter presents the enhancement of an electromagnetic band-gap (EBG) antenna that is used to feed a reflector antenna for a space multibeam application in Ka band. One of the main difficulties in a typical focal feed cluster design is to obtain high illumination performances with neighbored and close radiating elements. The new structure presented in this letter tackles this difficulty by using a two-level EBG antenna as a multibeam focal feed. This last one is designed to illuminate a side-fed offset cassegrain antenna (SFOCA) working in Ka band and dedicated to a multibeam telecommunication coverage over Europe. A prototype has been measured, and the reflector antenna performances have been evaluated in order to show the good results obtained with this new multibeam focal feed.

EBG Focal Feed Design Optimization

Recent works have shown that the electromagnetic bandgap (EBG) antenna can be used as a reflector focal feed. The design of such feeds needs to take into account several parameters to obtain both high illumination performances and low reflector antenna side-lobe level. Among these EBG antenna parameters, the quality factor, the excitation probe used and the phase center location constitutes key elements to obtain high performances. This article presents useful design curves to conceive an efficient EBG focal feed. These curves have been used to realize a 30-GHz single-feed EBG device illuminating a side-fed offset Cassegrain antenna (SFOCA). Results show good performances in terms of aperture efficiency and radiation patterns of the reflector antenna compared to the Potter horn previously used with the same reflector.

Reflector focal array based on multi-feed EBG antenna for Ka-band space applications

The demand for multimedia communications via satellite systems have increased considerably in the last years. Normally, the satellite coverage is composed of a hexagonal lattice of many small beams. An example of an experimental satellite coverage named “Agora” is composed of 40 0.65°-diameter spots, using 4 frequency channels in a 4x reuse scheme with the same circular polarization. A first solution which meets the requirements of such a mission (C/I, efficiency, roll-off) is the use of 4 Rx/Tx parabolic reflectors on the same satellite, providing each a family of spots at the same frequency. This solution has the drawback of heavy weight and the challenging accommodation of 4 reflectors on the platform. These 4 reflectors could be replaced by only one, when using a focal array which is capable of generating a specific illumination law (overlapped beams). This focal array could be composed of an active BFN which is, unfortunately, expensive and has moderate RF efficiency. Several studies have shown that overlapped beams could be obtained by using multi-feed EBG antennas [1, 2]. The major problem of these structures is the mutual coupling between different feeds. It was demonstrated recently that suitable filter designs could be connected to each feed [3, 4] in order to ensure the isolation between different channels and also to reconstruct properly the radiation patterns which are otherwise disturbed by the coupling. In [4] and [5] it is shown that the use of a matched multi-feed EBG antenna with 2 linear polarizations and 2 frequency channels provides a 4x reuse scheme that simplifies the system architecture. In fact, the use of a matched antenna relaxes the need for the filters to provide matching inside the operating band; they just need to act like a short circuit with the appropriate phase outside their operating band, in order to reconstruct properly the radiation patterns. On the other hand the use of 2 frequency channels reduces the number of required filters (2 filters instead of 4). Finally, linear polarizations are considered in order to prevent the design of bulky filters for circular polarization (6 poles filters with 6 cavities are needed to ensure the transmission of circularly polarized wave and isolation between channels). In this paper, a metallic multi-feed EBG antenna operating in Ka band [29.5–30] GHz is presented, and its performances before and after connecting the filters will be shown. Finally, this antenna is used to illuminate a reflector and the coverage characteristics (C/I) will be given.

Phase center study of the Electromagnetic Band Gap antenna

This paper is dedicated to the phase centre study of the Electromagnetic Band Gap (EBG) antennas. Such antennas can be used to feed a reflector and they represent a new passive technology to realize multi beam coverage at an attractive cost compared to usual systems with beam forming networks. This work aims at determining the relative position of the EBG antenna phase centre and the parameters which affect it. A performance study is also made to show that these devices reach good performances compared to classical feed like horns.