Design Of Leaky Coaxial Cable With Circular Polarization Property

Leaky coaxial cable(LCX) is achieved by curving a series of regular slots on the out conductor of radio frequency cable. Not only transmitting energy, leaky coaxial cable can radiate uniform and steady signal. It is widely used in subway, coal mine as well as highrise office buildings. The main polarization pattern of the LCX is linear polarization and circular polarization. At present the linear polarization LCX has been widely used, and the circular polarization LCX can be applied to multi-terminal antenna system with different polarization mode, therefore the research of circular polarization LCX has important significance.This thesis especially focused on two new kinds of leaky coaxial cable, which achieved ultra wide band and circular polarization character. The main work of this paper are as follows:First the basic theory of LCX is expounded, and basic structure of leaky coaxial cable as well as its index are introduced such as coupling loss, frequency band range, transmitting loss. Then the radiation characteristic of the slots on the cable is analyzed, and the single-mode radiation and resonant point theory is discussed.Second the way to restrain resonant point as well as expanding frequency band is discussed. By virtue of simulations of tilt slotted and vertical slotted LCX, the way to expand frequency band is verified. On that basis a ultra wide band leaky coaxial cable is introduced which achieved80MHz to2600MHz available to communication. Combined with LCX and circular polarization theory, a new type of circular polarization leaky coaxial cable is introduced.Based on the topic "research on the wireless transmission of monitored gas data and communication protocol", and according to the simulation, the ultra wide band LCX is fabricated by relative manufacturers. The indexes of the ultra wide band LCX such as voltage stand wave ratio(VSWR),transmitting loss, coupling loss are tested using the test instruments such as vector network analyzer, signal generator, spectrum analyzer, standard dipole antenna, power meter and the error analysis is implemented, the test result indicates that the designed LCX meets the requirements of practical engineering.