The Research On Terrestrial Digital Television Transmitting Antenna And Feeding System

With the rapid development of the global terrestrial digital TV career, China’s terrestrial digital TV has been entering a stage of vigorous development. During this revolution of technology, it is to promote the further development of the terrestrial digital TV career that research and design the high performance of transmitting antenna and duplexer.According to the relevant provisions of our country as well as the practice of construction, ensuring the transmitting antenna performance, it is better to reduce the antenna size, increase the impedance bandwidth and power capacity, select the reasonable polarization and raise the gain as much as possible. With the high demand of the terrestrial digital TV transmission system requiring the performance of duplexer, duplexer with small size, low insert loss, high out-of-band suppression, and large power capacity is more and more popular.Based on the project cooperated with Liaoning Putian digital Company, this paper designs a wide band vertical polarization antenna array for the terrestrial digital TV transmission system applications. This antenna mainly consists of two stacked antenna units. From the top to bottom layer board of the antenna unit are upper layer, lower layer and ground layer. Feeding network is located between the bottom layer and lower layer, with the shape of asymmetry S shape. The outer of the probe is fixed on the ground layer, and the inner penetrates the ground layer directly connecting to the feeding network. Vertical polarization is used. This antenna with wide impedance bandwidth, low VSWR level, and large power capacity, is very suitable for terrestrial digital TV transmission system applications.This paper also designs a duplexer with excellent performance, which consists of two band-pass filters and3dB couplers. Based on the filter theory, this paper firstly develops software for filter designing to get the used dates. A device has been firstly put forward in this paper that makes input/output continuously tuning, which reduces the difficulty of tuning filter in practice. This combined device with small insertion loss, high out-of-band suppression, and large power capacity, is suitable for the terrestrial digital TV transmission system applications.