The keystone transform: Practical limits and extension to second order corrections

This paper reports on analytical and simulation-based investigations of the Keystone transform (KT), which is used to remove range walk in radar systems. The KT modifies the cross ambiguity function to fix a radar target at its initial range, allowing longer integration times and higher SNRs. Limits on the useful length of integration time are explored, demonstrated, and found to depend on residual range migration caused by the acceleration of the target. A second order double-Keystone transform is then presented as an alternative that corrects for both velocity-based and acceleration-based range walk and enables chirp detection of an accelerating target.