Analytic signal generation-tips and traps

In this correspondence we discuss methods to produce the discrete analytic signal from a discrete real-valued signal. Such an analytic signal is complex and contains only positive frequencies. Its projection onto the real axis is the same as the original signal. Our use stems from instantaneous-frequency estimation and time-frequency signal analysis problems. For these problems the negative frequency component of real signals causes unwanted interference. The task of designing a filter to produce an approximation to the ideal analytic signal is not as simple as its formulation might suggest. Our result is that the direct methods of zeroing the negative frequencies, or using Hilbert transform filters, have undesirable defects. We present an alternative which is similar to the "quadrature" filters used in modem designs.<
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