VERTICAL BEAM SCANNING FOR THINNING CYLINDRICAL ARRAYS

By analyzing the principle of a grating lobe forming of the three-dimensional cylindrical arrays, the relationship between the limit wavelength of the vertical beam scanning and other parameters of the arrays is derived, and the directivity functions are shown complex. In order to eliminate vertical grating lobes of a cylindrical array and expand beam scanning region, the nullr are interposed in the directivity patterns of the ring arrays by means of the sub-arrays phase shift.
The optimum values of the phase shift parameter β are found. In general, it is better to take Kβ≈0.5. As an example, numerical values are calculated for two different partial cylindrical arrays, the results show that the limit wavelength derived for full cylindrical arrays can also be applied to partial cylindrical arrays. Compared with the arrays without phase shift under the same conditions, vertical beam scanning region is expanded to a extent that the beam can scan ±20° when d≈5λ, or the number of elements is decreased 2 to 4 times; and the directivity index is increased 1.7 to 5.5 dB when the grating lobes present in the directivity patterns of the arrays without phase shift.