Title:
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Some characteristics and applications of a general purpose optimum multichannel stacking filter
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An exclusive study of a general class of multichannel stacking
filters is made. They are designed in the time domain as optimum
multichannel Wiener filters for various models of random stationary processes
and include some known stacking filters as special cases. It is shown that
filters of this class may be specified as two- and three-dimensional velocity
filters, polarisation filters and stacking filters for the rejection or
enhancement of signals with differential normal moveout. The two- and
three-dimensional Fourier transforms are used as valuable tools for the
characterisation of velocity filters. Transforms for special differential
moveout filters are also given. The concept of a stacking filter transfer
function is defined and it is shown under which conditions it
can be obtained from the two- or three-dimensional Fourier transform of a
filter. It gives a deep insight into the filter characteristics.
A discussion of the given multichannel normal equations shows
how to select special time windows to obtain zero phase transfer functions.
Zero phase stacking filter components do not necessarily guarantee zero phase
transfer functions, while non-zero phase components may give phasefree
transfer functions.
Some rules for the characteristics of the class of filters
are presented. They are used in the design of special velocity filters,
which have superior properties over known velocity filters. A study of the
presented multichannel normal equations leads as well to the discovery of
the 'scaling effect'. This effect helps to reduce computer calculations
of filters. It also explains observations connected with their characterisation
and application. Because the filter design depends on a host of
design parameters, computational experiments were done to show in which way
important parameters influence filter characteristics. A short re-appraisal
of the basic theory of time series analysis is given. The theory of
continuous and discrete stacking filters is also reviewed.
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