The Doppler centroid frequency (azimuth) is computed as a second degree polynomial:

(D34) |

Where:

is read from the leader file.

In the

Xtrack_f_DC_constant (Hz, early edge): 117.3210000 Xtrack_f_DC_linear (Hz/s, early edge): 72338.0000000 Xtrack_f_DC_quadratic (Hz/s/s, early edge): -455000000.00000

This frequency is used in the azimuth filtering, and in the resampling. It should also be used if the complex SLC data is harmonically oversampled (as is done in the range filtering routine), but we did not implement this yet. But, for Hz this should not have any effect (assuming PRF-ABW=300Hz).

Since for a signal f(t) with Fourier transform F()

(D35) | |||

(D36) |

The azimuth spectrum of a SLC image processed on a certain Doppler frequency (spectrum shifted to this frequency) can be shifted back to zero by multiplication in the space domain by the term

(D37) |

(See also any signals and systems book, or e.g., [7].) The spectrum can be shifted back to the original doppler centroid frequency by multiplication by (after e.g., interpolation):

(D38) |

Proper care should be taken to get the correct line number in both situations.