| The satellite navigation system can provide high precision all-weather time and space information for land, aviation, maritime and other fields. An independent satellite navigation system can bring us huge economic benefits and social benefits. Our independent development of the Beidou satellite navigation system is one of the four global satellite navigation systems. Since the satellite receiver’s low power, easy to receive interference from all sides, the interference has become a mustperformance for satellite navigation receiver. RF receiver channel is at the forefront of the whole anti-jamming module, the main role is to amplify the received signal from antenna and downconvert to a lower frequency, signal reception performance directly determines the overall system functionality.In various application situations of satellite navigation equipment, it’s important to ensure the accuracy, also hoped that the device is small and light. Because of the small size, light weight, easy integration, easy in getting all kinds of forms of polarization and other characteristics, the microstrip antenna is widely used in satellite navigation system. Circularly polarized antenna polarization mismatch resistant, anti-multipath effects and other features, make it the preferred polarization in the form of a navigation system. The main function of the radio frequency receiving channel at the most front end of an anti-jamming navigation system receiver is to filter and amplify the signal received by the antenna. In this paper, we mainly study the circular polarized microstrip antenna and radio frequency receiving channel used in the Beidou satellite navigation system. This paper is carried out in the following parts:1. This paper introduces the basic theory of microstrip antenna, and discusses the realization of circular polarization antenna, and discussed in detail for small, wideband, wide-beam microstrip antenna.2. According to the main trend of the development of microstrip antenna, two kinds of dual band circularly polarized microstrip antennas are designed. One kind of the methods is realized by means of unit form, the other is array form. Through the use of stacked structure and Wilkinson power dividers, a CP antenna is designed working on BD-B3 band and the GPS-L1 band. The design has small size, low profile, and good CP radiation performance in the working band. Size of the unit structure is 55mm×55mm×6.654 mm, the overall size of the array structure 60mm×160mm×4.114 mm.3. This paper uses RF circuit theory to guide the RF front-end design, discusses the basic structure of the RF front-end, the core technical indicators. The main idea of the design is from top to bottom: The superheterodyne structure is determined after comparing multiple receiving structures. Then selecting each chip according to the indicator from a modular point of view, and through software simulation to validate the design is reasonable. Designing local oscillator module to generate a fixed frequency and use it to realize the downconversion by mixing with RF signal.4. According to the theory of the RF front-end, schematic and PCB documents are designed combined with the specific requirements for the size. After adjusting and testing the designed receiving channel, the results basically meet the target. The phase locked loop output LO signal stable at 1.222 GHz and receiving channel total gain is 47 d B. Finally, we analyze the parameters which did not meet the index and propose further improvement program. |
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