Cyril Mangenot

Sunflower Array Antenna with Adjustable Density Taper

A deterministic procedure to design a nonperiodic planar array radiating a rotationally symmetric pencil beam pattern with an adjustable sidelobe level is proposed. The elements positions are derived by modifying the peculiar locations of the sunflower seeds in such a way that the corresponding spatial density fits a Taylor amplitude tapering law which guarantees the pattern requirements in terms of beamwidth and sidelobe level. Different configurations, based on a Voronoi cell spatial tessellation of the radiative aperture, are presented, having as a benchmark the requirements for a typical multibeam satellite antenna.

High-Performance Electrically Thin Dual-Band Polarizing Reflective Surface for Broadband Satellite Applications

This paper describes an anisotropic impedance surface that provides dual-band linear-to-circular polarization conversion in reflection with the peculiar property that a same linear polarization is converted into a given circular polarization handedness over the first frequency band and into the orthogonal one over the second frequency band. This property is of interest for multiple beam satellite communication systems, as the transmit and receive signals are commonly operating in orthogonal polarizations. This paper demonstrates that a simple, electrically thin polarizer design can provide high-performance conversion over the extended frequency bands used for broadband satellite applications. Some insight on the operation of the proposed polarizer is provided, supported by equivalent circuit models and analytical formulas, and compared with full-wave simulation results. The proposed design achieves an axial ratio better than 0.2 dB in simulation at normal incidence. A further iteration of the design and breadboard, taking into account measurement and practical implementation errors, provides an axial ratio better than 0.5 dB in measurement over the full transmit and receive frequency bands allocated to broadband satellite applications within the K/Ka bands.

GA optimized thinned hexagonal arrays for aatellite applications

In this paper the optimization of a transmitting array for satellite applications has been considered. Resorting to GA more than 30% of the initial elements can be switched off satisfying the technical requirements. The optimized configuration permits to drastically reduce the cost of the array and to improve the C/I level with respect to the initial fully populated array. Having all the active elements fed with the same amplitude, the HPA can be used in the most efficient way. Further improvements can be achieved by refining the cost function, and optimizing the element factor.

Dual band hard horn for use in cluster-fed multi-beam antennas in Ka-band

A hard hom for dual band operation is designed. Emphasis has been put on low cross-polar performance over both the Rx and Tx bands in the Ka-band multimedia application. The horn has also been designed with manufacturability in mind, with direct transition from the metal section to the corrugated section, and, with a corrugated section which is slightly conical with constant number of corrugations. The horn operates with high efficiency at the lower band (17.7-20.2 GHz) and medium efficiency at the higher band (27.5-30.0 GHz), and it has a maximum cross-polar level within the main beam which is low over both bands. The return-loss is below -35 dB over both bands.

Spaceborne P-band SAR for BIOMASS mission

In the frame of the BIOMASS mission promoted by ESA for evaluating and monitoring Earth biomass, the expected performance of a P-band SAR instrument based on very large Direct Radiating Array antenna is addressed, as well as its architecture and the accommodation challenge on a platform.

Theoretical study of the corrugated hard horn used as feed in multi-beam antennas for dual band operation at 20/30 GHz

We have demonstrated that in a cluster-fed reflector, a normal single-tuned hard horn can satisfy the usual -25 dB system requirements for the cross polarization over a large frequency band, but it cannot completely satisfy the requirements for the copolar level in the neighboring beam We have also tried larger reflector diameters than those presented here. In those cases, the beam isolation becomes better, but the 30 GHz footprint gets a dip in the center The reason for the dip is that the sidelobe of the feed is illuminating the reflector at 30 GHz. This may be improved for finite lengths of the horn, for which phase of the aperture field at the horn causes a beam broadening mainly at 30 GHz.

Impact of new technologies on future space-borne radar design

In the 1990s radar instruments for Earth observation started to generate continuous streams of high quality data for scientific and commercial applications alike. Now that these instrument concepts have been proven and the demand for their data has become apparent, the next generation must provide even better quality with increased temporal and spatial coverage but, as ever, at a reduced price. Fortunately advances in new technology developments have continued apace and these are set to transform space-borne radar design, increasing capabilities whilst at the same time reducing unit costs.