Abstract
Generation of arbitrarily shaped transient electric fields in a prescribed bounded region, especially with high precision and low sidelobes, is a challenging fundamental issue with applications ranging from electromagnetic (EM) switch, microwave chemotherapy to wireless power transfer. In this work, we study for the first time the transmission of the EM field excited by point current sources (PCSs) in time reversal cavity (TRC) or time reversal mirror (TRM) from the view of EM radiation. We first decompose the predefined area into a number of spatial grids, those are all utilized as PCSs here. When the electric field of one PCS is calculated, other PCSs are treated as secondary sources. We can get the whole electric field distribution by calculating these grids one by one. Based on this theory, we choose the closed TRC/TRM as excitation transmitters to construct arbitrarily shaped electric field inside TRC/TRM, whose excitation can be synthesized after all the TRC/TRM elements capture their responses to the known probing signals emitted from probe antennas situated at all grids. Thanks to the spatial and temporal focusing property of time reversal (TR), a set of the TR focusing field is produced simultaneously with their focal spots spaced by grids. We successfully and dynamically demonstrate the simple generation method for different desired transient electric fields, and observe the electric distribution during the process of getting desired shaped electric field with time under different limited given regions.
Highlights
With the scope of electromagnetic (EM) wave application unceasingly expanding, EM field shaping in space and time domain with specific geometry is badly needed, especially in tumor microwave therapy, breeding, catalysis, localized wireless power transfer, regional confidential communication, etc
In the simulations, we observe the specific field shaping in a circular time reversal cavity (TRC), since circular arrays are widely used in practial engineering fields
The radius of TRC can be obtained by 4.0816 ns ×c = 10λ, therein, λ = 122 mm is the wavelength corresponding to 2.45 GHz, and c = 3 × 108 m/s is the velocity of light
Summary
Significant breakthroughs have been made in the random generation of acoustic and water wave field. Point, planar and spherical surface fields have already. More complex acoustic fields are achieved physically to control the movement of suspended particlesas [4]. Some water wave fields with a variety of geometries are generated in an artificial basin [5], [6]. More complex water wave fields, such as wash wave, are shaped arbitrarily by numerical experiments [7], [8]. There are some achievements in optics [9]–[11], such as spatial light modulators [10] and phase conjugation [11], which are proved to be a powerful means for light control. Taking advantage of electronically tunable micromirrors/microstructured light resonators/liquid crystal cells, both amplitude and phase of light can be freely controlled in an active way [12], combined with interative
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