The Design Of 3.4-4.2GHz Low Noise Amplifier For DBS Reception

In December 1993, the Hughes Company in United States launched the world's first direct broadcast satellite (DBS) providing compact digital TV signal. For the first time, it is possible for the satellite to provide business service to common consumers. Because of encryption, conditional access and paid watching became possible. Since then the industry of satellite broadcast digital TV in the world developed rapidly. Now, more than 30 countries and regions in North America, South America, Europe, Asia, Oceania, and Africa have developed the satellite direct broadcasting business. Among these countries, the United States, Britain and Japan are the countries which provide the best services of satellite direct broadcasting digital TV. It not only brings enormous economic benefits for these countries, stimulates the development of related technology and industry, but also promotes trade competition level effectively.Amplifier is one of the most common radio frequency (RF) circuits. However, as the front-level power amplifier of DBS ground receiving RF device LNB (Low Noise Converter), it must be with minimum noise figure, so as to guarantee the ability to receive weak signals (i.e. high sensitivity). Consequently, the conception of LNA (Low Noise Amplifier) is presented. LNA is generally composed of one or two-level low noise amplification circuit and power driver circuit, which is constructed by low noise figure components.The main content and innovations in this thesis:First, this thesis introduces the forms and characteristics of DBS television, as well as its domestic and overseas development process and the status, so as to introduce the LNB, which is used to receive DBS TV signals outdoors. Second, this thesis focuses on the analysis of the basic circuit characteristics of LNA (the core circuit of LNB), and describes the theoretical basis and methods for the LNA circuit design. Last, this thesis records the design process of LNA, which can receive C-band direct broadcast satellite television signals.The innovations of this design lies in the expanded full-band frequency 800MHz (3.4-4.2GHz), and LNA circuits can ensure the absolute stability of circuit, with meeting the ultra-low noise figure (0.6dB). It is introduced how to use the equal noise figure circle and equal power-gain circle jointly for designing, so as to meet the gain and noise figure indicators. At the same time, it is also described how to add a negative feedback to increase the stability of circuit. All of the design is simulated, completed and optimized by using the most popular RF & MW design software ADS. Furthermore, the final PCB diagram of LNA circuit is presented for practical application in LNB, and this is the process from theory method to practical application.