By Igor V. Minin, Oleg V. Minin
The short effortless fundamentals of antenna arrays -- Lens applicants to antenna array -- FZP lens array -- a few fields of lens array functions
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Extra resources for Basic Principles of Fresnel Antenna Arrays
The metal subzones of the FZPL antenna are replaced with sub-zones that allow the radiation to pass through and also introduce the required 180° phase shift with respect to the adjacent zone. These sub-zones are thus made by cutting circular grooves, with a fixed depth, s, into a slab of dielectric material at the appropriate Fresnel radii. The groove depth is important since when chosen correctly, it will cause the radiation passing through the groove to undergo an 180° phase shift. In this way, the radiation that hits the grooves will be corrected and will be in phase with the radiation that exits in the adjacent zone.
By redistributing the structure of zones on the surface of the diffractive element, the synchronization condition for boundary waves in a certain prescribed region can be changed by choosing the value of R0. This makes it possible to considerably suppress the spurious central maximum even for a binary diffractive element and to increase field intensity in the ring itself through spatial redistribution of energy. Similarly, it is possible to correct the shape of the focusing region. For instance, the problem posed by focusing radiation onto a ring with maximum intensity at a point Rk was solved in this manner, that is, through optimization of the type: I ∼ min ⎪U(Rk,0,B)U*(Rk,0,B)⎪.
9 shows the focusing gain, G, as a function of the base thickness, t, for the two zone plates: F/ λ =15 (solid line) and F/ λ =20 (dashed line). 629 , or 0 ≤ t / λd ≤ 1 . 1λ . 3λ , however, would reverse the result, and the zone plate with F/ λ =15 would outperform the zone plate with F/ λ =20 by more than 1 dB. 5 t/λ Fig. 9 Focusing gain, G, as the base thickness t is varied for two similar quarterwave zone plates. The solid line shows G for a zone plate with F/ λ = 15 and the dashed line for a zone plate with F/ λ =20.