Research On Reconstruction Of Wideband Radar Signal

In the field of radar technology, hardware-in-the-loop simulation in the laboratory is very important for the development of various radar systems. Based on simulated radar signal model, radar signal simulator can nimbly reconstruct radar target signal, interference signal and environment signal, which meet the need of new radar system design and test. For hardware-in-the-loop simulation, it refers to the real-time reconstructing architecture of wideband radar signal. In this paper, related reconstructing methods are discussed and researched thoroughly, and certain improvement is estimable for applications of radar system.Generally, the frequency-domain statistical property of radar signal which is a kind of random signal can be derived easily in the laboratory. A signal reconstructing algorithm applied in the project extensively is mainly studied in this paper, which includes conversion from power spectrum to magnitude spectrum, randomization of phase to obtain vector spectrum, inverse Fourier transform, randomization of series of finite time-domain sequences, interpolation of the infinite sequence, digital quadrature modulation for frequency up conversion, D/A conversion, and lowpass filtering.The reconstructing algorithm of wideband radar signal must be characteristic of real time and high resolution. Because of the restriction, the emphasis of this paper includes two parts: randomization of series of finite time-domain sequences and interpolation of the infinite sequence, which affect the simulated signal's characteristics greatly. Considered different frequency spectrum properties of several windows in the time-domain randomization, a new randomizing method is proposed, which includes addition of hanning window, overlap, and amplitude amending process. The interpolation ofbaseband signal which raises the sample rate is implemented by a new kind of multistage architecture combined multiphase filter with Lagrange polynomial filter. The polynomial interpolating filter has a little computation in real-time digital signal processing, and the multistage structure can reduce the filters'design requirement and decrease the quantity of computation efficiently. Aiming at different defects of multiphase filter and polynomial filter in practical design, certain improvement has been made accordingly. Finally, a method of wideband signal digital quadrature modulation based on DSP and FPGA is proposed. The parts of interpolation and lowpass filtering with large quantity of computation are carried on by FPGA device, and the hardware design structure of digital interpolating filter is discussed deeply.