| Coal-mine underground tunnel and working face can be regarded as narrow long heterogeneous limited communication space. Therefore, multipath fading of wireless signal is obvious in the process of transmission, resulting in poor communication quality. Nowadays, multiple standards, multiband and multiple communication methods coexist in coal-mine wireless communication systems. The radio frequency front-end microwave power divider and antenna are integral parts and play a critical role to ensure the communication quality. Hence, the research of power divider and antenna which contains a variety of communication requirements, frequencies and communication standards is of high theoretical value and realistic significance. The topic in this doctoral dissertation mainly focuses on the power dividers with the functions of large frequency ratios, high power applications, impedance matching and multiband to improve the quality of coal-mine wireless communication systems. Antenna is located at the terminal position of wireless communication systems and plays a significant role in transmitting and receiving signals. So research of circular polarization microstrip antenna which is suitable for coal-mine wireless communication systems scan is also an important direction of this topic.This work is mainly supported by the National Natural Science Foundation Project of Monitoring Technology of Mine Moving-Targets and Current Intelligent Control Platform and Equipment based on the Io T Security Control Technology(2013BAK06B05) and the main researches are as follows:(1) In order to meet the requirements of large frequency ratios for coal-mine wireless communication systems, by adopting cascaded coupled lines and shifted output, three kinds of dual-band Wilkinson power divider with impedance transformation are put forward. Three power dividers are based on two open stubs at the input port, input port extension, and two isolation resistances respectively. The theoretical analysis and simulation show that the frequency ratios of three kinds of Wilkinson power divider are 2.7-6.8, 1.5-6.1 and 3.1-6.2 respectively.(2) In order to meet the requirements of high power for coal-mine wireless communication systems, the methods of three(four) sections of cascaded coupled lines and one open stub are adopted to design two kinds of dual-band Gysel power divider suitable for high power applications. Compared with the first kind, the second has one more pair of coupled line; therefore it has more flexible impedance transformation and extends the frequency ratios correspondingly. At last, the theory correctness is verified by one experiment.(3) For the sake of the requirements of dual-band or multi-band multi-way for coal-mine wireless communication systems, the method of replacing all the microstrip lines in the modified Bagley power divider with four pairs of U-type coupled lines is adopted to design one compact dual-band multi-way Bagley power divider. By adopting the method of replacing the microstrip lines between the input port and output ports in the modified coupled-line Bagley power divider with three pairs of cascaded coupled lines, one three-band planar multi-way Bagley power divider is put forward. The theoretical analysis and experiments validate the correctness of the theory.(4) With the purpose of improving the receiving and dispatching efficiency of antenna signals, a kind of circular polarized microstrip antenna based on coupled-line power divider feed network, coupled patch and rotating short-circuit radiation patch is proposed for the signal transceiver in wide-angle range and it has wider half power beam and wider frequency range. The second antenna based on T-type power divider and 16 square corner cut radiation patch is put forward for the transceiver of signal in long distance and high directivity and it has higher front-to-rear ratios. These two circular polarized microstrip antennas are all suitable for the applications of RFID communication systems in the coal mine.The research results greatly extend the applications of power dividers with large frequency ratios, high power, impedance match and multiband. In addition it expands the power divider applications in antenna feed networks in coal-mine RFID systems. |
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