Figure 43 GMAP Algorithm Steps
Table 51 GMAP Algorithm Steps
GMAP Step Description
Step 1: Window and DFT First a Hamming window weighting function is applied to the IQ values and
a discrete Fourier transform (DFT) is then performed. This provides better
spectrum resolution than a fast Fourier Transform (FFT) which requires that
the number of IQ values be a power of 2.
Note that if the requested number of samples is exactly a power of 2, then
an FFT is used.
As mentioned in 7.3.2 Frequency Domain Processing- Doppler Power
Spectrum (page 185), when there is no or very little clutter, use of a
rectangular weighting function leads to the lowest- variance estimates of
intensity, mean velocity and spectrum width. When there is a very large
amount of clutter, then the aggressive Blackman window is required to
reduce the "spill-over" of power from the clutter target into the sidelobes of
the impulse response function. The Hamming window is used as the
first
guess. After the first pass GMAP analysis is complete, a decision is made to
either accept the Hamming results, or recalculate for either rectangular or
Blackman depending on the clutter-to-signal ratio (CSR) computed from
the Hamming analysis. The recalculated results are then checked to
determine whether to use these or the original Hamming result.
RVP900 User Guide M211322EN-J
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