Super-resolution Characteristics Of Time-Reversed Electromagnetic Wave And Its Application

Time-reversed (TR) electromagnetic wave not only has the property of spatial and temporal focusing in common circumstance, but also has spatial super-resolution focusing characteristics in some special circumstances. Therefore, the investigation of key factors of super-resolution focusing of TR electromagnetic wave, together with the research of design for sub-wavelength array with element distance far less than half wavelength, the integration of sub-wavelength array into wireless MIMO system and the evaluation of its communication performance, would provide guidance for the design of compact wireless terminal system with multiple antennas.In Chapter 1, the research background of this dissertation is presented. The property of spatial and temporal focusing characteristics and super-resolution characteristics of time-reversed electromagnetic wave are introduced. And then the development and recent advancements of the super-resolution characteristics of time-reversed electromagnetic wave are reviewed. Finally, the arrangement and focus of this dissertation are described.In Chapter 2, a TR sub-wavelength array prototype has been set up and simulations are carried out for three different circumstances respectively: sub-wavelength array without metal wires and metal cavity, array with metal cavity but without metal wires, and array with metal wires but without metal cavity. The focusing characteristics under these three different circumstances are compared, and then the key factors of super-resolution focusing are revealed.Chapter 3 takes research of the ultra-wideband and super-resolution (UWB-SR) characteristic of TR electromagnetic wave. The initial prototype consists of coaxial probes and a cluster of non-uniform distribution thin metal wires around the probes. With proper length and location of the metal wires, this prototype could achieve UWB-SR characteristic for TR electromagnetic wave. Improvement is then made on the elements of the microstructured array. Metal strips are placed in a non-uniform arrangement around a planar dipole array, and the array can also demonstrate UWB-SR characteristic for TR electromagnetic wave. This provides references for exploring other types of UWB-SR arrays.In Chapter 4, several sub-wavelength arrays are presented. Test results show that all these arrays could demonstrate the 1/20 wavelength super-resolution focusing characteristic with TR electromagnetic wave. As the elements in the arrays are fabricated with printed circuit board, the array structure is easy for fabrication. Therefore, it provides an advanced design solution to build up wireless communication with multiple independent channels for space-limited wireless terminals.Chapter 5 takes TR-UWB multiple-input-multiple-output (TR-UWB-MIMO) as an example, and constructs one TR-UWB-MIMO wireless communication system with a high data-rate to verify the communication quality improvement with sub-wavelength array. In this system, the sub-wavelength array consists of 3 face-to-face elements at the distance of 1/20 wavelength between each other. Each element of this array could process data independently at the rate of 500Mb/s, so the overall data-rate of the array could amount to 1.5 Gb/S. Moreover,one advanced TR technique with better focusing performance is proposed. This improved TR technique could increase the spatial resolution of target antenna, and restrain signal received by nearby monitoring antennaChapter 6 summarizes the research work in this dissertation. Unsolved problems and future research areas are given.