Inverse synthetic aperture radar (ISAR) imaging for long range small/stealthy target plays an important role in the field of national defense surveillance. However

the performances of the traditional envelop-based range alignment method dramatically degrade due to low signal-to-noise ratio (SNR) of received echo signal

which leads to the inapplicability for the subsequent phase adjustment or azimuth focus. In this paper

a parametric-based approach is proposed to perform joint range alignment and phase adjustment. To that end

translational motion is modeled as multi-component polynomial phase signal (PPS)

and inspired by the fact that all the scatterers in the moving target experience the same translational range history

the phase difference (PD) operation and Keystone transform (KT) are utilized to transform the energy of all the scatterers into one range cell. Second

a coherently integrated cubic phase function (CICPF) is developed to focus the energy of all the scatterers onto a peak point

from which the polynomial coefficients can be obtained accurately to realize the translational motion compensation in low SNR environment. Finally

theoretical analysis and experimental results are also provided to validate the effectiveness of the proposed method.