Anti-saturation And Adaptive Anti-jamming Techniques Research

The increasingly complex electromagnetic environment in the space makes the equipment receivers vulnerable to the influence of interference signals including both intentional and unintentional interference, resulting in the emergence of analysis error; some part of receivers even suffer from saturation problems and cannot work properly. Those navigation receivers with high sensitivity of weak signals, such as GPS or Compass receivers, are more likely to be influenced by the strong interference and the saturation leading incapacity to locate and navigate; Also the interferences with high power near the base station are great hampers to figure out what the users' demand are in this region. As a result, it causes interruption and loss of communication between the client user and the base station. The transmitter working in the saturation would produce the interference beyond the working band, due to the nonlinear effect of power amplifier. Avoiding the nonlinear effect can be regarded as anti-saturation for transmitter. Therefore, it is highly significant to do research about anti-saturation for both receiver and transmitter and anti-jamming for receiver.The categories of interference, as well as the research states of anti-jamming and anti-saturation technology are presented first in the first part of paper. The second part, starting from the principles of spatial filtering, detailed beamforming techniques and convergence criterion before the introduction of advanced space-time adaptive anti-jamming technology. For direction of arrival(DOA) known and unknown, there are respective methods to solve the jamming problem, while the DOA must be gained before the application of the techniques under the circumstance of a Signal to Interference and Noise Ratio(SINR) that is not pretty low. The high DOA resolution multiple signal classification algorithm(MUSIC) was illustrated in Chapter 3, followed with series of simulation experiments. To increase the resolution and reduce complexity of hardware design, a simple vector array was raised to estimate the DOA. Further, method by rotating the array was used to solve the ambiguity of DOA estimation.After demonstrating the traditional nonlinear model of the power amplifier, a model based on some sparse delays was proposed to decrease the numerical calculation, as well as the pre-distortion methodology. Then, a brief description of the principle and categories of the Automatic Gain Control(AGC)was given. Both two ways can avoid the saturation, however, with a great sacrifice of the gain of useful signal. To overcome that problem, amplitude and phase weighting RF-fonts were designed as an anti-saturation module to suppress strong interference while ensuring the gain of useful signal. Furthermore, two-level equivalent array was put forward to anti saturation and interference as well.In the last part, the macrocosmic scenario was designed to overcome the jamming and saturation problem existing in the GPS receivers. And relevant algorithms were realized through the FPGA platform before a test in anechoic chamber to verify its feasibility.