| Holographic technology, originating from physical optics, is an imaging technique that can fully record and reconstruct the 3D image of the object. Based on holographic impedance modulation, artificial tensor impedance surface antennas can stimulate leaky-wave radiation by exploiting the surface wave that travels along it, which can be accomplished without complex feeding networks while the antenna gain maintains relatively high and the polarization flexible. Due to the light weight and low profile, antennas of this kind also have great conformal capabilities. Therefore, not only do holographically-modulated tensor impedance surface antennas have significant theoretic value, but also extensive prospects in practical applications.To focus on holographically-modulated tensor impedance surface antennas, the development background and research trends of holographic impedance modulated surface antennas are firstly introduced, followed by the basic theoretic analysis of their radiation by introducing and analyzing conventional leaky-wave antennas and optical holography. Both the principles and simulation setups of the surface impedance exaction are explained in detail then, including a simplified curve-fitting rule in tensor case that greatly reduces the required data-quantity and increases the design-efficiency, after which the formulas involving scalar/tensor holographic impedance modulation are explicitly derived. Finally, several antenna models are simulated base on the exacted impedance data, fitted curves and the proposed impedance modulation formulas. Both linear-polarized scalar cases and circularly-polarized tensor cases are included, among which a tensor prototype is also manufactured and measured. The simulated and measured results show good electric performance and agreement, validating the correctness and reliability of the extraction, curve-fitting, holographic modulation of surface impedance and the whole antenna design strategy. |
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