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njit-etd2003-081 - New Jersey Institute of Technology

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59<br />

One can therefore recover the original signal from the Wigner distribution for a<br />

given resolution. The preceding relation can be used to determine whether a signal<br />

exists which will generate a given ρw(t,f).<br />

The Wigner distribution also satisfies the marginals properties. To prove these,<br />

one can use the constraint <strong>of</strong> the kernel for marginals properties, that is:<br />

By inspection, the kernel <strong>of</strong> the Wigner distribution g(v, r) = 1 satisfies both<br />

marginals. Thus, the Wigner distribution satisfies the total energy. Note the converse is<br />

not true [38]. For the first conditional moment at a fixed time, the Wigner distribution<br />

gives the instantaneous frequency and at a fixed frequency the first conditional moment<br />

would be the group delay.<br />

For a finite duration signal, the Winger distribution is zero before the signal<br />

starts and after the signal ends [38]. If one have a band limited signal, the Wigner<br />

distribution will be zero for all frequencies that are not included in that band. These<br />

properties are called the support properties <strong>of</strong> the Wigner distribution. In general the<br />

Wigner distribution is not zero when the signal is zero [40].<br />

Consider the multicomponent signal z(t):<br />

The Wigner distribution is:

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