Abstract
A two-dimensional (2-D) metasurface design for backward leaky wave suppression in microwave regime is proposed based on the theory of holography. The so-called Rabbit’s ears phenomenon describes that the backward mode in the reference wave plays the destructive role and makes the holography principle to behave properly mainly in an only narrow frequency interval. Here, we explore the utilization of the surface wave reflectors to suppress the backward mode to achieve wide-band holograms. Therefore, the reference wave form is manipulated by the choice of various reflector shapes and some providing forward mode dominant reference wave are analyzed and simulated. The less backward mode participates in the reference wave; the wider operation frequency range is obtained. With the canceled Rabbit’s ears phenomenon, variations in the reference wave frequency cause elevation angle scan. The results provide general insights into relation of the Rabbit’s ears phenomenon and the object wave accuracy in frequencies except the design frequency. The idea is also applied to multiple object wave holograms. The concept is verified using both electromagnetic full-wave simulations and experimental measurements.
Highlights
Surface wave leakage manipulation is one of the important applications of the metasurfaces
The recorded interference of reference and object waves called interferogram can project the object wave while it is excited by the reference wave[19,20]
We proposed reflector-enabled holograms to suppress the backward mode and refine the surface wave distribution in a more constructive manner
Summary
A two-dimensional (2-D) metasurface design for backward leaky wave suppression in microwave regime is proposed based on the theory of holography. We explore the utilization of the surface wave reflectors to suppress the backward mode to achieve wide-band holograms. Lack of acceptable radiation directivity and bandwidth in center-fed hologram is caused due to a destructive effect called Rabbit’s ear phenomenon[17]. By placing a reflector on the hologram, backward mode distribution can be changed to eliminate the Rabbit’s ear phenomenon. The surface impedance distribution and the corresponding reference wave must be modified to scatter the desired object wave after placing the reflector. We propose the surface wave confinement on holographic metasurfaces using surface scatterers which can cancel out the Rabbit’s ears phenomenon in a more beneficial way than the previous reflector-free works. As the following explorations prove, surface wave confinement on hologram causes considerable improved radiation bandwidth and scannability for single and multi-beam holograms. The proposed reflector-enabled hologram can achieve single-beam frequency scanning between 13–19 GHz (representing 37.5% fractional bandwidth) and multi-beam frequency scanning between 14–18 GHz (25% fractional bandwidth)
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