Analysis of time reversal cavity characteristics based on multipath channel model

Abstract

The electromagnetic wave time reversal technology using time reversal cavity (TRC) has potential applications in many areas, such as pulse compression, power synthesis, perturbation detection, beamforming, etc. Microwave chaotic cavity with multi-path transmission characteristics is usually used in TRC. Based on diffraction theory, it can prove that this kind of cavity has spatiotemporal focusing characteristics and can be used for compressing pulses, but it cannot be used to analyze the reversal performance of the cavity. In order to obtain a suitable analysis method and guide the design of TRC, in this work, the scattering, diffusion and attenuation characteristics of electromagnetic wave propagation are analyzed and a multipath channel model of TRC is built by the channel theory. Moreover, the crosstalk characteristics between paths are studied, and the generation mechanism of time sidelobe, time sidelobe shift and interference are also investigated. In addition, under the assumption of random plane wave, the distribution characteristics of spatial focal spot are analyzed, which is consistent with the diffraction theory. Moreover, the actual focal spot size is not only limited by the diffraction limit, but also related to the initial focal spot size. The theoretical analysis results are basically consistent with the experimental and numerical simulation results.

A novel power-combination method using a time-reversal pulse-compression technique

“…As a result, the attenuation coefficient and correlation index of the path can be considered as a constant. Based on the multichannel model, [2] the autocorrelation function and the reversal reconstructed signal can be expressed as…”

“…According to the path crosstalk, [2] the crosstalk among the channels mainly occurs in the channels with the same input port, such as between Port 1-TRC-Port 0 and Port 1-TRC-Port 2. For two channels with the same input port, the crosscorrelation function κ i, j , which describes the channel crosstalk properties, can be expressed as…”

“…The time-reversal (TR) method refers to when the response signal of a system is turned into a reversal signal and then input into the system, and the original waveform is reconstructed at the initial position. [1,2] TR has the characteristics of spatiotemporal focusing, which can be used in various fields such as pulse compression, [3][4][5] secret communication, [6,7] reversal imaging, [8,9] beam forming, [10][11][12][13] positioning, [14,15] perturbation detection, [16,17] etc. The first electromagnetic reversal system consisted of a single transmitting and receiving antenna and a reverberation chamber with a high Q value.…”

“…[18,19] Specific to the TR characteristics of the TRC, a multipath channel mode with attenuation and crosstalk has been established, and the side lobe time shift and spatial focusing characteristics have been studied. [2] To expand the applications of TRCs, the influence of parameters such as TRC loss and shape structure upon the reversal performance have also been studied. [20,21] The influence of the original signal upon the reversal performance has been studied by both theoretical and experimental methods.…”