Design And Implementation Of The GNSS Anti-jamming Receiver Front-end

Global satellite navigation systems have been increasingly widely used in civil and military fields. However, the problem that the signal of satellite navigation is so weak that it is vulnerable to unintentional or intentional electromagnetic interference also urgently needs to be addressed. Antenna array and RF channel circuit are located in the front-end of anti-jamming receiver, which have a large extent effect on the performance of the anti-jamming algorithm. In this dissertation, the performance of various kinds of antenna arrays are simulated as the theoretical direction for the hardware system design at the same time the RF channel circuit is designed and realized.The research status of the satellite navigation anti-jamming technology at home and abroad is summarized firstly, as to clearly define the application background and research direction of this design. The principles,the advantages and disadvantages of the GNSS frequency domain anti-jamming technique, space domain anti-jamming technique and space-time anti-jamming technology are analyzed. It is derived which kind of adaptive rule should be chosen for the GNSS space domain anti-jamming technique in the dissertation. The principle of the power inversion algorithm in space domain is researched and the anti-jamming receiver system framework is designed.In terms of array antenna design, the commonly used array antenna receiving models is established firstly. Based on the power inversion algorithm, how the space and number of the array antenna element have influence on the performance of anti-jamming algorithm is researched through the theoretical derivation and the software simulation. According to research for the space of array element, it is concluded that the antenna array which element is uniformly distributed with half a wavelength has optimal performance. Through simulating the performance of uniform line array, uniform circular array and plane circular array, the plane circular array of the center existing array element is chosen as the receiver array antenna layout. By comparing the performance of a few types of commonly used antenna, the microstrip antenna is selected as the element of array antenna.In the aspect of RF channel circuit design, low IF architecture is adopted through analyzing and comparing the performance, complexity, costs and power consumptions of different RF front-end structures. The detailed analysis of the key index for the RF channel circuit such as the channel gain, system dynamic range and system noise index is given in the dissertation. Based on the above study,low noise amplifier circuit, frequency synthesizer circuit, mixer circuit and so on in the RF front-end are designed in detail. The two-stage low noise amplifier is designed to provide adequate gain and suppress noise figure at the same time ensures that does not produce saturation distortion and third-order intermodulation distortion. The automatic gain control module with large dynamic range is applied to ensure that low IF output signals meets the requirements of the sensitivity of digital signal processing and avoids producing saturation distortion. Considering the possible signal integrity problems, some impedance matching circuit and filter circuit is added in the RF front-end circuit and the key points that need to be noticed in the design of the hardware are summarized.Finally, the each part of the system has carried on the detailed test and the test result is analyzed. The test results show that the design of the hardware meet the needs of the anti-jamming receiver front-end.