Research And Implementation Of Digital Interferometer

Interferometer has been a common method for direction finding. It has many advantagessuch as high performance and simple structure. It uses the difference phase between the antennasfor the azimuth estimation. This paper focuses on several aspects related to the interferometer.Studies phase interferometer and the ambiguity of the phase. The paper proposes somemethods for solving ambiguity. It highlights the mixed baseline interferometer. The algorithm forsolving the ambiguity of the mixed baseline was proposed. The interferometer using mixedbaseline method can cover a wide frequency range, while the antenna lineup relatively free. Thepaper gives two mixed unambiguous baseline condition. A non-ambiguity baseline system wasconstructed under the two conditions.Frequency is important for interferometer. The paper gives two different methods forfrequency estimation. One method is called instantaneous frequency estimation. Another is basedon DFT algorithm. Rife algorithm is introduced as a classical methods based on DFT. M-Rifewas proposed for improving the inadequate of the Rife method. Also proposed a complexfrequency spectrum estimation method based on interpolation. The simulation results of varietymethods were shown.To improve the probability of intercept, interferometer needs to work in a wide-bandwidth.The high sampling rate increased the cost of the system. Phase measurement and the samplinghas proved irrelevant. And the paper gives a frequency estimation method with the sub-Nyquistsampling rate. The system was simulated.The frequency estimation algorithm was implemented in FPGA. At the same time thealgorithm for solving the ambiguity was implemented using C language.