Forming the Radio Image with Multiple Antennas
In the preceding chapter, we discussed image-formation options at radio wavelengths, and we committed ourselves to an array of directional antennas, a “compound eye” architecture. We have seen that the directional sensitivity of individual sensors is essential, and that their fields must be somewhat overlapped. We have also seen (in Sect. 2.2) that every distant radio source produces sensors’ outputs that lie on a lobe shape pointing toward that source; we refer to this shape as the rotated lobe.
The crux of radiolocating the sources lies in accurately determining the direction of the rotated lobe, on the basis of somewhat sparse data points, which are the antenna signals. Optimizing the fit between the antenna signals and the rotated lobe synthesizes the “image” of the source, i.e., its direction, and we see that the overlap and directional sensitivity of the individual sensors are essential for that synthesis. We entrusted the optimization to a straightforward iterative minimization algorithm, and while this approach was successfully implemented and proved reliable in a networking device, we explore in this chapter an alternative method of image synthesis.
KeywordsDiscrete Fourier Transform Spherical Harmonic Input Function Image Spectrum Directional Sensitivity
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