Shaping Electromagnetic Waves with Flexible and Continuous Control of the Beam Directions Using Holography and Convolution Theorem

Abstract

In this article, several versatile electromagnetic (EM) waves are presented with predefined shapes and directions based on the holography and convolution theorem. Inspiring the holography theory, a reflective interferogram is characterized by interfering the near field distributions of the object and reference waves. In this regard, the interference pattern on the hologram could be viewed as the inverse Fourier transform of the object and reference waves. Therefore, the capability of steering the EM shaped beam is realized using the convolution theorem (as an interesting property of the Fourier transform), which makes a link between the hologram impedance-pattern and far-field pattern domains. The main advantage of incorporating the holography concept and convolution theorem is realizing arbitrary shaped-beam EM waves with the possibility of flexible manipulation of the beam directions without employing any optimization algorithm and mathematical computation. It is demonstrated that the method could implement a combination of simple beams (such as collimated beams) and complex beams (such as cosecant squared, flat top, isoflux beams, etc.) with each beam possessing arbitrary direction by the same design topology. To experimentally verify the concept, a prototype of the hologram with three separate beams including two tilted cosecant squared shaped beam and one broadside pencil beam is fabricated and measured. The measured results show a significant agreement between theoretical findings.

Holographic transmitarray antenna with linear polarization in X band

“…In other words, the sheet starts changing its reaction to the electromagnetic waves from reflection to transmission at 360 ohms. This is a critical difference between RA unit cells and TA unit cells, which necessitates applying a method different from what has been proposed in [2][3][4][5]. For more clarification, a lossless transmission unit cell is examined.…”

“…It achieves 19.23% 1-dB gain bandwidth and 45.8% aperture efficiency. In 5 , a holographic reflectarray with the capability of producing shaped electromagnetic waves is proposed. The antenna can produce multiple beams with arbitrary shapes.…”

“…Z(x, y)|Y (x, y) = j X + Mℜ ψ ob j ψ * re f (5) where X and M are arbitrary average impedance (admittance) value and arbitrary modulation depth, respectively. These values must be assigned so that the impedance (admittance) distribution of the hologram can be correctly implemented by the unit cell.…”

High-efficiency dual-polarized broadband reflecting metasurface using continuous polarization conversion technique and element with multi degree of freedom

“…This is why it benefits from the advantages of reflector and classic array structures 3 . In general, a reflecting metasurface manipulates the phase of the wave impinging from the feed and reflects it with the desired characteristic such as direction, shape, polarization, and beamwidth 4 – 7 . This is performed by introducing a given progressive phase shift over the reflected wave by designing a proper phase-shifting surface or making an artificial impedance surface to engineer the reflected waves 8 .…”

High-Efficiency Dual-Polarized Broadband Reflecting Metasurface Using Continuous Polarization Conversion Technique and Element with Multi Degree of Freedom

“…This is why it benefits from the advantages of reflector and classic array structures 1 . In general, a reflecting metasurface manipulates the phase of the wave impinging from the feed and reflects it with the desired characteristic such as direction, shape, polarization, and beamwidth [2][3][4][5] . This is done by introducing a given progressive phase shift over the reflected wave by designing a proper phase shifting surface or making an artificial impedance surface to engineer the reflected waves 6 .…”