Marc Hélier

Multiarms Multiports Externally Fed Spiral Antenna

This letter deals with an externally fed spiral antenna. This design is a slot antenna that exhibits a behavior similar to that of the center-fed Archimedean spiral antenna with an improvement in terms of polarization. The antenna radiates a circular polarization over a wide frequency band within a wide angular range. Moreover, the polarization radiated can be right/left circular or linear vertical/horizontal. A prototype has been manufactured and compared to the modeled antenna. Good agreement is shown between measurement and simulation results.

Prediction of Sky and Surface Wave Radiation of a Wideband HF Antenna

In this letter, the prediction of the radiation of wideband HF antennas is investigated. The ground upon which they are placed mainly influences the sky wave and the surface wave mode radiated by these antennas. Classical methods of simulation or measurement applied to microwave radiating structures are not suitable for this kind of antenna. Thus, this letter proposes a method to perform a near field to far field transformation, adapted to the problem of interest, and based on a power criterion. This criterion requires both the electric and magnetic near fields, but by using an appropriate approximation, it is possible to assert that only the measurement of the electric near field is required. Far field radiation has been computed at two different frequencies within a bandwidth of 1.3:1 (28.5%).

Kriging method to perform scintillation maps based on measurement and GISM model

This paper presents an ionosphere scintillation mapping algorithm. The technique used is a Kriging technique, well known in geostatistics. It is an interpolation method applied to a set of random data, namely, in this application, to the intensity scintillation (S4) index. The paper focuses on the importance of the regression model used in the algorithm. The one-dimensional and then the two-dimensional problems have been investigated. One example of results combining measurement data recorded by two different networks in Peru is presented. The accuracy of the results has been verified using a cross-validation technique, which consists in removing part of the known data set and comparing the interpolated results to it.

Multipolar modelization of EMC emission tests setup for automotive vehicle

Electromagnetic interferences due to on board-devices may differ from what can be expected after unitary on-bench tests. This work deals with the extension to the multipolar case of a previous approach, aiming at ensuring that the on-board device performances will be satisfactory. It is based on the computation of new limits for on-bench tests obtained through a global optimization process.

Simulation of indirect effects of lightning on an aircraft engine

This paper presents a new approach for simulating the indirect effects of a lightning impact on an aircraft engine. Based on macro modeling, it performs a model reduction of the lightning current on a geometric support called a “patch”. The associated macro finite element space allows for reliable and sufficiently fast resolution so that parameter analysis can be carried out.

A precise technique for ground wave radiation and propagation over an irregular surface

This paper deals with the problem of HF surface wave radar. The goal is to integrate in a unique tool the antenna radiation and the propagation calculations in order to make the analysis consistent.

Prediction of HF wave propagation for “over the horizon” radar application

This paper deals with the problem of HF surface wave radar. The goal is to integrate in a unique tool the antenna radiation and the propagation calculations in order to make the analysis consistent. Only the antenna problem is presented here. However the way the propagation problem will be further considered is presented. Cross check of the tool validity and robustness were insured by developing concurrently several techniques, mixing measurements and theoretical techniques.