Research On Multi-parameter Estimation Of FM/PM Radar Signals

In the real world, many signals whose frequency contents evolve with time are statistically nonstationary. The traditional methods in array signal processing, based on the narrowband and stationary assumptions, may fail to treat with these nonstationary signals. The theme of this dissertation is to estimate spatial and time-frequency/modulation parameters of some nonstationary radar signals, with a novel approach that combines nonstationary signal processing with array signal processing. And in the dissertation, we focus on a few aspects of nonstationary signal array processing, such as array signal modeling, signal's property analysis, multi-parameter estimation and array error calibration. The main contributions of the dissertation are summarized as follows:1. The spectral redundancy (also called cylcostationary) property of phase-coded signals(PCSs) is first introduced, then an effective method is proposed for cylic-frequency and DOA estimation of PCSs without a prior. Compared with some existing algorithms, the proposed method can perform signal selective DOA estimation well, and get signals' cylic-frequencies at little computational cost.2. Based on the PCSs' time-frequency structure analyzed by STFT, a novel algorithm is presented, not only to estimate 2-dimensional angle of arrive (2-D AOA) of PCSs, but also to obtain all basic modulation parameters (i.e. carrier frequency, symbol time and code sequence) estimation for multi-component PCSs with different modulation type.3. For the problem of direction finding of wideband chirp / wideband linear frequency modulation (WLFM) signals, a new method called FRFT-CSSM is achieved, by jointly exploiting the LFM signal's selectivity in FRFT domain and auto-focusing idea of the conventional CSSM. Except for the merit of accumulating the whole signal band's energy to improve the singal to noise ratio, the proposed algorithm is also insensitive to initial estimates and converges fast to the true DOA value.4. To reduce computational load of the time-frequency CSSM while handing coherent WLFM signals well, a novel method based on instantaneous beamspace array model is developed to estimate the modulation parameters and 2-D AOA of the WLFM signals, and without spatial smoothing or focusing, the proposed method can also process coherent WLFM signals effectively.5. The Jacobi-Anger series representation of sinusoidal frequency-modulated signals is first analyzed, then one new approach based on Jacobi-Anger series representation is derived to estimate the modulation parameters and 2-D AOA of the wideband sinusoidal frequency-modulated signals.6. The problem of array error calibration in nonstationary signal environment is discussed, and in direction-dependent sensor perturbation model, one novel method which can offer closed-form 2-D AOA estimation and model errors self-calibration, is proposed to estimate 2-D AOA of wideband chirp signals, by exploiting the algebraic structure of wideband chirp signal's time-varying manifold.