An ISAR Imaging Algorithm for Maneuvering Targets With Low SNR Based on Parameter Estimation of Multicomponent Quadratic FM Signals and Nonuniform FFT

An Efficient ISAR Imaging of Targets with Complex Motions Based on a Quasi-Time-Frequency Analysis Bilinear Coherent Algorithm

“…In practice, the coherent integration time is usually short, and therefore the target rotation angle during that time is small, i.e., $3–5^{\circ }$ [8,9]. From that, $sin \theta \left(t_m\right)$ and $cos \theta \left(t_m\right)$ are approximated by $\theta \left(t_m\right)$ and 1.…”

“…The $H_{\mathrm{Kernel}}\left(t_m,f_{{\tau }_m^2}\right)$ in (12) is a novel transform kernel function that is given by $H_{\mathrm{Kernel} }\left(t_m,f_{{\tau }_m^2}\right)=\exp \left[j8\pi \frac{\tan \left({\theta }_T\right)}{3}{t}_m^3-j2\pi f_{t_m}{t}_m\right]$ where $f_{t_m}$ is the frequency variable with respect to $t_m$. Note that in the case of zero cubic term, i.e., $b_3=0$, the proposed RCFT reduces to the coherent integrated CPF (CICPF) approach proposed in our previous work [9]. Moreover, when both the second- and three-order terms are zeros, i.e., $b_3=b_2=0$, the proposed RCFT becomes the FT, which indicates that FT is a special case of the RCFT.…”

“…Recently, a new ISAR strategy termed Range Instantaneous Doppler (RID) algorithm was proposed to produce ISAR image of a maneuvering target [7,8,9,10,11,12,13,14,15,16]. The RID algorithms are usually divided into two groups.…”

“…The RID algorithms are usually divided into two groups. The first group is the parametric approach, where the received signal in a range bin is modeled by a special signal [7,8,9], and based on that, the instantaneous Doppler frequency is estimated and the corresponding ISAR image is obtained by using the estimated Doppler frequency. However, those approaches require the estimation or extraction of each scatterer in each range cell, which is computationally demanding and inefficient.…”

“…However, those approaches require the estimation or extraction of each scatterer in each range cell, which is computationally demanding and inefficient. In addition, model mismatch issue is usually present, resulting in unfocused images [9]. The second group is the nonparametric method [10,11,12,13,14,15,16], in which time-frequency distribution (TFD) analysis tool as the substitution of FT in the azimuth focusing processing, is utilized.…”