HF radio direction finding operating on a heterogeneous array: Principles and experimental validation

Abstract

[1] Array processing usually operates on identical sensors. In this paper an investigation is made to apply the direction finding algorithm MUSIC to an antenna array with nonidentical elements (heterogeneous array). This original solution is polarizationsensitive though it resorts to only one sensor at each point of the spatial sampling. As a major consequence of its structure, the computation of the MUSIC algorithm is based on an expression of the steering vector that integrates the spatial response of each sensor. This concept is then validated in the special context of HF radio direction finding, for which a deterministic model of the polarization at the exit of the ionospheric channel is derived. A multichannel radio receiving system has been developed and experimented using transmitters located more than 1000 km from the receiving site.

High data rate radio communications through the ionospheric channel

“…The second is the angle, evaluated in the plane of the wave front, between the main axis and the local horizontal. Considering the location of the receiver and for a given radio link configuration, it has been shown [5] that these two parameters can be expressed as functions of the DOA characterized by the azimuth and elevation angles = (Az, El).…”

“…where F ( ) is named spatial response of the antenna [5,7]. F ( ) is generally complex due to the structure of the electrical field.…”

“…Each of them is classically characterized by its direction of arrival (DOA), group delay, differential frequency Doppler shift and, in addition, by the structure of the incoming polarization. Actually, the Appleton-Hartree magnetoionic theory [1][2][3] associated with the Budden's conditions [4] shows that the waves emerging from the ionospheric layers present a transverse and elliptical shaped polarization, the parameters of which are DOA dependent: for a given receiver location, they can be computed in a deterministic way using a database relative to the Earth's geomagnetic field [5].…”

Direction of Arrival Estimation Based on Heterogeneous Array

“…Thus, the searching in polarization space can be avoided, and a(ϑ, ϕ) is given by formula (3). Different from [8], our method does not need to know the polarization state of incoming wave beforehand. Because the module of manifold of heterogeneous array is not unit (see in Equation (4)), the normalization operation of the manifold is required.…”

“…These DF systems require at least two channels for each space sampling point, and the system equipments are complex, which require good isolation between the dipole pairs [7]. Heterogeneous array with only one element at each point of the spatial sampling is proposed in [8]. The DOAs are estimated for two known polarized waves (ordinary wave and extraordinary wave) in HF using active loop antennas with eight different polarized states.…”