Research On Digital Frequency Measurement Of Multiple Signal With Sub-sampling

The war in the future is the information warfare, so the major task of Electronic Reconnaissance Facility is how to quickly acquire the useful information of the enemy to the utmost extent. Carrier frequency is one of the most important parameters. Measuring frequency precision determines the probability of sorting and identifying signals to the same radiation source. As the developing of digital signal processing and the mature of digital devices, digital receiver is a trend. Digital frequency measurement is getting more and more important. The signal reconnaissance receiver dealing with is of large bandwidth, if designing the system in Nyquist sampling rate, the digital signal processing part behind can’t satisfy a rate so high, or the cost is large and leads to the problem of data quantity, a sub-sampling concept is put forward,but it results in frequency aliasing, it needs ambiguity resolution algorithm to recovery the correct frequency.Firstly,this paper analyzes digital channelization technique based on STFT, the filtering characteristics of windowed DFT and the principle STFT algorithm implementing digital channelization technique is analyzed,a model of the algorithm is given. A case study of single-carrier frequency signal and linear frequency modulation signal, procedure of the algorithm is simulated,parameter estimation method in time domain and frequency domain is given.Secondly, Some questions of the algorithm are discussed in detail, so as to improve the working efficient on the premise of satisfying the quantity of system, including detection threshold, window width and so on. The influence of these parameters is analyzed. The modulation of Radar signals with STFT is Talked about. A principle on sorting signals is given. Three kind of algorithm following STFT are discussed, the performance of each algorithm is simulated. The impact of the strong signal on the weak signal is analyzed, The effect of the window function and how to choose the suitable window are talked about.At last, the reason of frequency aliasing caused by sub-sampling is discussed. Four kind of structure to solve ambiguity is given. The procedure and principle are simulated and analyzed. The advantages and disadvantages of each structure is pointed. A method combining digital channelization technique with sub-sampling technology is put forward. A case study of double rate solving ambiguity, the feasibility of this method is simulated and verified. Points for attention of the method is given,provides reference for the related hardware implementation.