The Design Of High-performance LNB For DBS Reception

With the improvement of people's living standard, there are more and more people travel extensively. Watching a live program, keeping in touch with immediate news or the sports event on the trip have become a desirable life experience, which can be solved well by the direct broadcasting. This needs to have a series of the equipment and technology which can match with this system. And, the low noise block (LNB) is a significant module in it. It has a higher request and more superior performance compared to the general direct broadcasting satellite. This paper first overall introduced the work principle and technical specification of the LNB, divided into five modules according to its performance, low noise amplifier (LNA), image-reject filter, dielectric resonator oscillator (DRO), mixer and IF amplifier. Then take a detailed explanation and design on each module. Then, the principle, technical parameters and the design method of each module are presented in detail, and all the modules are simulated by the ADS. At last, the paper introduces the design of Biasing circuit, and the PCB is designed by Protel. Then the LNB is manufactured, and the gain and the noise figure are measured by noise meter. The best scheme is determined with testing and modifying again and again. The result of measurement shows that the noise figure of the LNB is below 0.6dB between 950MHz and 1450NHz, while the gain above 65dB. The LNB is passed the thermocycling test, and it has high performance and high reliability.The main research content of this paper can be divided into the following several aspects:The first chapter elaborated the research background and the significance of the vehicle carries satellite TV receiving antenna LNB, introduced the concept, structure, principle and the domestic and foreign development present situation. Systematically introduced the Specific function of each module.The second to the fourth chapter analyze each module separately, explains their principle, structure and technical parameter in detail. Carries on the simulation and optimization by ADS, finally obtains the most superior result. The fifth chapter combines every module LNB in turn according to the principle request, designing the good biasing circuit, manufacturing the PCB, processing and debugs many times, finally has conformed to the performance requirement LNB.Overall, this paper designed a LNB which use in vehicle carrying satellite TV receiving antenna. The simulation and the test result indicated that its high performance, usable, meets the design requirements completely. What's more, the design method and the step of radio frequency modules introduced in this paper can serve as a guideline for the microwave module designer.