Design of reflectarray antennas to achieve an optimum near‐field radiation for RFID applications via the implementation of SDM procedure

Abstract

This paper presents the design of reflectarray antennas to radiate an optimum near-field distribution by using the procedure of steepest decent method to synthesize the impressed phases of reflectarray elements. In particular, the closed-form formulations used in the electromagnetic modeling were developed for an efficient design. The design was further implemented to realize a reflectarray of microstrip patch elements, which is illuminated by the radiation of a feed antenna at the 2.4 GHz band in the radio frequency identification applications. Numerical investigations as well as experimental measurements over a prototype are presented to validate the feasibility of the developed models and the implemented antenna structure.

Near-Field Focused Reflectarray Antenna and Reconfigurable Intelligent Surfaces: The Potential of Wave Propagation Control for Smart Radio Environment

“…The complexity of this model and other models [18,27] commonly have the same number of floatingpoint operations (FLOPs) for an equal number of reflectarray antenna elements and the number of UE locations N . It usually costs O(MN ) FLOP, where FLOP refers to a single complex floating point operation, e.g., addition and multiplication.…”

“…The model discussed in [27] involves a division operation on each new UE location x, and it costs O(M (n ) log(n )), where OM (n ) refers to the complexity of the multiplication algorithm, and log(n ) refers to the complexity per digit numbers n . It is obvious that the developed channel gain model is characterized as low complexity due to the reduction in computing the scattered fields by searching the Fresnel tables instead of performing cumbersome integration operations.…”

“…By subsisting Equation ( 30) into Equation (27), this approximately gives J(η). The PEB(η) is then calculated from the resulting J(η) and is expressed as in [29]…”

“…The RIS consists of a reflectarray antenna of M = 144 unit cells, extending from [−0.4, −0.4] to [0.4, 0.4] m in x-y plane with an interelement spacings Δx = Δy = 6.25 cm in both the x and y coordinates. The reflectarray antenna unit cells dimensions are tabulated in [27]. The unit cells of the reflectarray antenna are realized by using microstrip patches.…”

Technologies for Near-Field Focused Microwave Antennas

“…A dual-band reflectarray as that in [43] has been designed and prototyped in [44], by using concentric square rings as reflecting elements at both 915 MHz and 2.4 GHz. An optimization procedure based on the steepest descent method (SDM) [28] has been applied in [45] to derive the phase correction required for each reflectarray element, as an alternative to the conventional conjugate-phase profile. At higher frequencies, a NFF reflectarray operating at 8 GHz has been designed and prototyped to show its effectiveness for H3N2 virus sanitization [46].…”