Planar array near-field multipoint focusing system and method based on time reversal

Abstract

The invention discloses a planar array near-field multipoint focusing system and method based on time reversal, and relates to the field of electromagnetic wave regulation and control. The planar array near-field multipoint focusing system comprises a signal generator for generating a channel detection signal, a transmitting module which is used for receiving the detection signal and transmittinga TRM return signal, a control module which is used for regulating and controlling the return signal, and a focusing module which transmits a detection signal. According to the planar array near-fieldmultipoint focusing system, SVD decomposition is utilized to represent a focusing field receiving signal as linear superposition of a plurality of orthogonal sub-signals so as to avoid redundancy caused by superposition of non-orthogonal signals; through threshold discrimination, a part of sub-channels are discarded, and the number of optimization variables is reduced, and the optimization speedis increased; a power fluctuation threshold is set to improve the transmission efficiency; and the energy ratio of each focus point is regulated and controlled by changing the power distribution ratio. Multi-point focusing can be generated in a near field with extremely uneven electromagnetic field intensity distribution according to a preset energy ratio, and the problems of microwave thermal therapy and multi-target selective wireless energy transmission can be effectively solved.

Description

technical field [0001] The invention belongs to the field of space propagation and control of electromagnetic waves, and in particular relates to a planar array near-field multi-point focusing system and method based on time inversion. Background technique [0002] With the continuous expansion of the application range of electromagnetic waves, for example, microwave hyperthermia, biological effect research, wireless energy transmission, encrypted communication, microwave cutting, etc., these applications all require the ability to precisely focus electromagnetic waves at a fixed position for Act on a specific object. In the field of electromagnetism, there are a lot of researches on the propagation and regulation of electromagnetic waves. [0003] Among them, beamforming is to make the radiation pattern of the far-field area of ​​the antenna array into a specific beam by rationally designing the excitation amplitude and phase of each array element of the antenna array, the...

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Problems solved by technology

In 2014, an application for an invention patent with the patent number 201410440116.7 disclosed a space electromagnetic field shaping method based on time-reversed electromagnetic wave transmission. With the help of the space-time focusing principle of time-reversed electromagnetic waves, the electromagnetic wave is generated in the space area. Energy is concentrated in a specific shape range. Although this is the regulation of electromagnetic waves in the near field, its research cannot precisely focus energy on a target point; in 2018, an application for an invention patent with patent number 201810580750.9, A multi-target selective wireless energy transmission method and device based on focused waves is disclosed, and an optimization algorithm for realizing multi-point energy distribution is mentioned. The transmission excitation signal is linearly superimposed according to the specified weighting coefficient, so that the wireless energy is concentrated at the specified focus point according to the required ratio. This method works well in the cavity environment, but it does not consider the propagation of electromagnetic waves in free space with severe attenuation. How to improve space efficiency does not consider the correlation between superimposed signals. The superposition of non-orthogonal signals leads to redundant calculation variables, and the optimization rate is low, which cannot meet the high-efficiency requirements in engineering applications.

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