Abstract
The vortex electromagnetic (EM) wave carrying orbital angular momentum (OAM) has been introduced in radar imaging to take full advantage of its special phase front. It has been demonstrated that the azimuthal and range resolution are decided by the number of OAM mode and frequency bandwidth respectively. In this paper, theelevation resolution of the vortex wave transmitted by a uniform circular array is derived for the first time through the calculation of correlation function of two closely adjacent points. Since large number of OAM modes should be applied to achieve high-resolution image, which is difficult to realize in practice, the sparse Bayesian learning (SBL) is introduced to reconstruct the targets for 2-D EM vortex imaging. Simulation results show that the targets located at different elevation angle can be reconstructed correctly and higher resolution can be achieved based on the SBL reconstruction algorithm.
Highlights
The electromagnetic wave carrying orbital angular momentum has attracted much attention for its particular helical phase front in recent years
Since Allen et al [1] found that the light beams could carry orbital angular momentum as well as spin angular momentum in 1992, and Thidé et al [2] pointed out that low-frequency radio wave carrying OAM has a similar phase structure as that in optics, much research have been done to the generation and application of OAM in radio wave
In this paper, elevation resolution of the electromagnetic vortex wave based imaging is derived for the first time, demonstrating the ability of 2D imaging for single frequency
Summary
The electromagnetic wave carrying orbital angular momentum has attracted much attention for its particular helical phase front in recent years. The electromagnetic vortex wave has the potential to image the radar target in 2013 [9], and Liu et al [16], [18] validated the ability of azimuthal resolution using OAM modulation, and pointed out that range resolution is correlated to the bandwidth, and it has been realized based on UCA through the method of FFT. Equation (12) indicates that the elevation resolution is closely related to the aperture of UCA and the elevation angle of the target, the normalized correlation function of the echo from two adjacent scattering points is computed in the following. The radius of the UCA used to generate EM vortex wave is 0.15m and the frequency is 10 GHz. A reference scattering point is set as θ = 10, 30, 50 degree, φ = 0 degree separately, and the adjacent point is at θ + θ, φ = 0 degree.
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