Chapter 6 ______________________________________________________ Processing Algorithms
VAISALA______________________________________________________________________ 181
CHAPTER 6
PROCESSING ALGORITHMS
This chapter describes the processing algorithms implemented within the
RVP900 signal processor. The discussion is confined to the mathematical
description of these algorithms. Figure 36 on page 182 shows the overall
process by which the RVP900 converts the IF signal into corrected
reflectivity, velocity, and width. Table 9 on page 181 summarizes the
quantities that are measured and computed by the RVP900. The type of the
quantity (that is, real or complex) is also given. Subscripts are sometimes
used to denote successive samples in time from a given range bin. For
example, sn denotes the "I" and "Q" time series or "video" sample from the
n'th pulse from a given range bin. In cases where it is obvious, the
subscripts denoting the pulse (time) are dropped. The descriptions of all the
data processing algorithms are phrased in terms of the operations
performed on data from a single range bin- identical processing then being
applied to all of the selected ranges. Thus, there is no need to include a
range subscript in this data notation.
It is frequently convenient to combine two simultaneous samples of "I" and
"Q" into a single complex number (called a phaser) of the form:
s = I + jQ
where "j" is the square root of -1. Most of the algorithms presented in this
chapter are defined in terms of the operations performed on the "s"'s, rather
than the "I"'s and "Q"'s. The use of the complex terms leads to a more
concise mathematical expression of the signal processing techniques being
used. In actual operation, the complex arithmetic is simply broken down
into its real-valued component parts in order to be computed by the
RVP900 hardware. For example, the complex product:
NOTE
Optional dual polarization processing algorithms are described in IRIS
and RDA Dual Polarization User’s Manual.
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