Research On The Environmental Adaptive Leaky Waveguide Structures

With the rapid development of communication technology, higher communication quality, more stable signal and especially broader signal coverage are required for many application scenarios like tunnel, mine and metro. However, multiple reflections of electromagnetic waves in these scenarios results in a strong multipath effect, which makes the electromagnetic wave attenuates rapidly. Therefore, conventional antennas cannot provide satisfied signal coverage in these communication systems. On the other hand, leaky waveguide structure can be used to solve the problem by improving signal coverage. As wave propagates forward within the waveguide, energies also radiate through the slots along the waveguide structure, and these energies are limited within a certain range with low interference with environment. In most of current applications, power distribution of radiated field is designed to be uniform around the waveguide and therefore, wave attenuates rapidly along the waveguide and yields strong multipath effect. Focus on this problem; this dissertation aims to design leaky waveguide structures which can make the radiated energy remains at one side of the waveguide. Since this kind of structure improve signal coverage while reducing the multipath interference.Main points of the work in this dissertation can be concluded as follows:1. Considering relatively low directivity in conventional leaky coaxial cables, flat reflector and circular arc reflector were proposed. We analyze the two models created using the EM simulation software, and optimize the waveguide structure with higher direction. By comparing these two kinds of improved leaky cable with traditional leaky cable on intensity of radiation field and radiation gain, we can find that they can both significantly improve the leaky cable’s direction of radiation, and the gain in the main radiation direction was also promoted, and backward radiation was suppressed well.2. Reflector-backed leaky waveguide structure was proposed and analyzed with full-wave method, and the structure was simulated with full wave method. According to the radiation distance in reality, extract the intensity of radiation field33cm above the slot to analyze. By optimizing the structure and comparing the leaky cable which has reflector with the traditional leaky cable which has no reflector on the intensity of radiation field at the same height, the flat reflector’s structure parameters were finally determined. The results show that the intensity of radiation field33cm above the slots on rectangular leaky waveguide can be improved significantly by adding flat reflector, which can reduce the transmission loss caused by the backward environment.3. Measurements are conducted for the fabricated leaky waveguide with specific test protocols. By contrast, the simulation results basically agrees well with the measured results. The data shows that the simulation results are consistent with the measured results, which proves the effectiveness of the rectangular leaky waveguide structure with flat reflector.