N. J. G. Fonseca

Design of a waveguide dual-mode three-way power divider for dual-polarization beam forming networks at Ka-band

This paper presents the design and performance of a dual-mode 3-way power divider optimized for dual-polarization operation at Ka-band. Similar performance are obtained for the TE10 and TE01 modes with a well-balanced power division over the three output ports and input matching better than -23 dB over the frequency range 27.5-30.0 GHz. In combination with dual-mode directional couplers, this three-way power divider is of great interest for the design of dual-polarization beam forming networks.

An improved design method for two-dimensional Rotman lenses with reduced phase-aberrations

This paper introduces an improved design method supported by analytical formulas defining the focal curve of a Rotman lens with reduced worst-case phase-aberrations. The benefit of this design approach is illustrated through a specific numerical example and compared to the standard design method.

Miniaturized dual polarized VHF array element for AIS space application

An important satellite based application at VHF band is the Automatic Identification System (AIS). The system is devised to receive messages sent by vessels for maritime safety and security purposes. The intended platform is a mini-satellite in Low Earth Orbit (LEO). Due to the in-orbit deployment of the array and overall mass requirements for the satellite, the array element minimization and mass reduction are considered performance drivers. The important size reduction properties of Artificial Magnetic Materials (AMM) / Meta Materials (MM) made this approach a natural choice as baseline array element technology. This paper presents the preliminary study of the array element including the manufacturing of an elegant bread-board and verification by measurement.

Measurement of low gain VHF array element in hemispherical NF antenna test range

Accurate measurements on low gain antennas at VHF frequencies are very demanding due to the limited dimensions of available test ranges. This paper presents the findings and post processing issues involved in the verification measurement on a low gain VHF antenna array element with minimized mass and dimensions developed for space application and suitable for an Automatic Identification System (AIS). The testing has been performed in a hemispherical spherical near field antenna test range of Renault in Aubevoye, France.

Design and testing of a miniaturized dual polarized VHF array element for AIS space application

The space-based Automatic Identification System (SAT-AIS) is devised to provide identification and position information to vessels for maritime safety and security purposes. The system is intended to operate at VHF through mini-satellite platforms in Low Earth Orbit (LEO). Due to the in-orbit deployment of the antenna array and overall mass requirements for the satellite, the array element minimization and mass reduction are considered performance design drivers. The important size reduction properties of Artificial Magnetic Materials (AMM) / Meta Materials (MM) made this approach a natural choice as baseline array element technology. The following antenna array verification represents a challenging task due to the low-gain and overall DUT dimensions at VHF band. This paper presents the preliminary study of the array element including the manufacturing of an elegant bread-board and testing in a hemispherical near-field antenna test range together with post-processing issues involved.

Irregular superstrate array for the reduction of the side lobe level in satcom user terminal antennas

We present here the irregular superstrate array, a novel technique to control the side lobe level (SLL) of an antenna array using an isophoric excitation. In this work, the radiation pattern of the array is tailored by properly adjusting the directivity of the single elements without resorting to complicated feeding networks. The proposed array is fed with a uniform excitation and an irregular superstrate is used to change the directivity of each element. Numerical results obatined with a linear array of 20 elements demonstrate the relevance of the proposed concept.