Real time digital scan converter

A digital scan converter for use with a scanning system which supplies a sequence of n return signals having a one-to-one correspondence with n radially extending scanning paths that are angularly spaced apart from one another about the azimuthal axis of a polar coordinate system to define a sectorial surveillance region, each of said return signals representing signal reflection occurring along said corresponding scanning path, said digital scan converter for supplying output signal information representative of at least a portion of said sectorial surveillance region relative to a Cartesian coordinate system wherein the first axis thereof is substantially parallel to said azimuthal axis of said polar coordinate system and the second axis of said Cartesian coordinate system is perpendicular to the first axis thereof, said digital scan converter comprising:

• signal sampling means connected for receiving said sequence of n return signals, said signal sampling means including means for sampling each of said return signals at a rate proportional to the cosine of the angle between said corresponding scanning path and said azimuthal axis of said polar coordinate system to supply n ordered sets of signal values, the successive signal values of each said ordered set of signal values representing signal reflection occurring from incremental regions of said surveillance region that are located along said corresponding scanning path at equally spaced apart positions relative to said first axis of said Cartesian coordinate system;
• memory means connected for receiving and storing said n ordered sets of signal values, said memory means being addressable for accessing those ones of said signal values that are associated incremental regions of said surveillance region that lie along m equally spaced apart traces that are substantially parallel to said second axis of said Cartesian coordinate system to form m ordered sets of signal values in which successive signal values of each ordered set are associated with the successive scanning paths of said surveillance system;
• output processor means for sequentially receiving a first sequence of signal values that is formed from an associated one of said m ordered sets of signal values, and for supplying a second sequence of digital signals that represents signal reflection occurring at substantially equally spaced apart locations along that one of said m traces that is associated with the sequence being receiving by said output processor means;
• and
• mapping means for controlling said output processor means, said mapping means including addressing means for sequentially accessing the sets of said m ordered sets of signal values, means for sequentially accessing the n signal values within each of said m ordered sets and individually supplying the sequentially accessed n signal values to said output means as said first sequence of signal values, said mapping means further including means for operating said output processor means to establish a predetermined number of consecutive elements within said second sequence of digital signals equal to that one of said n signal values currently being supplied to said output processor means, the predetermined number associated with each of said stored signal values being determined on the basis of the location of the associated one of said m traces and the associated one of said n scanning paths.