Time-Frequency Distribution Series (TFDS), which achieves an effective balance between the time-frequency resolution
and the cross-term interference, can effectively reconstruct complicated maneuver targets' instantaneous ISAR images.
However, original algorithm is quite inefficient, and the approach to fast computation proposed in some literature cannot
be directly applied to engineering. In this correspondence, a straightforward realizable two-dimensional filter is derived.
Meanwhile, FTFDS, as the fast implementation of TFDS, is proposed based on the formula, and computational burden of
FTFDS is analyzed theoretically and experimentally in detail. The analysis of FTFDS indicates that FTFDS makes a
great advance of efficiency. As FTFDS fits parallel process, time-frequency analysis by FTFDS can be approximately
carried out in real-time. Simulated data processing has shown that FTFDS is practical and valid in fast reconstruction of
instantaneous ISAR imaging.