Research On Key Technologies Of Time-Reversal Based Wireless Communication Systems With Densely Spaced Multiple Channels

Time reversal(TR) technology can effectively compensate the multipath propagation delay and collect multipath energy. According to the time delay compensation, the multipath components can be adaptived convergence synchronously, then we can build new electromagnetic application systems. For the TR based electromagnetic communication with densely spaced multiple channels, the key techonologies include time reversal super-resolution focus theory, time reversal channel model, the analog signal time reversal, subwavelength antenna arrays, time reversal electromagnetic communication principle experiments, etc. In the case that the basic theory, processing algorithm and system architecture of traditional TR communications are becoming mature. This article will research the communication system which combined TR and orthogonal frequency division multiplexing(OFDM), and the two-dimensional planar compact multi-port antenna applied to the multi-antenna TR-OFDM system based on multipath delay compensation, space focus and other advantages of TR. Finally, we will construct a prototype experimental system of the TR-based electromagnetic communication.OFDM is different from the general scheme for dividing the sub-channels, its sub-carrier spectrum overlap each other, and maintain orthogonal relationship in a integral cycle. However, the channel phase fading will influence the OFDM system performance significantly, phase fading can cause intercarrier interference and intersymbol interference. Meanwhile, for large-scale multi-antenna system, the limited space size for the array arrangement and complex decodeing will affect the its further application. The OFDM and multi-antenna system based on the TR have unique advantages in overcoming multipath delay, reducing the spatial size arrangement of antenna, etc. The main work of this paper is as follows.First, the design scheme of the combination of OFDM and TR at transmit side is proposed, and the TR-OFDM system performance will be analyse in different scattering environments, and different modulation. The sub-carrier frequency domain magnitude equalization(SFME) TR-OFDM system is proposed for the limitation of TR technology. Then the multiple antenna TR-OFDM system performance is analysed.After that, a two-dimensional planar multi-port antenna with compact structure is proposed for the practical application of multiple antenna TR-OFDM system. This antenna provide a reliable plane antenna to construct a compact three-dimensional array.Finally, The implementation of TR module is given based on PicoSDR software defined radio platform. And the performance of the prototype experimental system of TR-OFDM communication is verified by experiments.