Comb filter arrangement having delay time compensation and load matching in all circuit paths

DETAILED DESCRIPTION We claim: 1.
A comb filter arrangement in which signals A, B, and C of three picture lines, made simultaneously available by means of two successively arranged delay elements which have a delay time of two picture lines for PAL signals and one picture line for NTSC signals, are utilized for obtaining two comb filter functions, AB and BC and in which the signal having the middle instantaneous amplitude is constantly filtered out of the signals of the three picture lines and the two comb filter functions, characterized in that a one-stage median filter is provided in which the amplitudes of the simultaneously available signals of the three picture lines and the two comb filter functions are compared with each other in a comparator stage which supplies logical comparison signals to a selection logic in dependence upon the comparison results, said selection logic constantly determining that signal having the middle instantaneous amplitude of the signals applied to the comparator stage on the basis of the comparison signals and applying that signal to the median filter output.
2.
A comb filter arrangement as claimed in claim 1, characterized in that the comparator stage comprises five comparators each of which compares two signals with each other and supplies a logical output signal in dependence upon the comparison, three of said five comparators being used for comparing the simultaneously available signals of the three picture lines with one another, and two of said five comparators being used for comparing the signals of the comb filter functions with that signal of the three picture lines which is not utilized for forming the concerned comb filter function.
3.
A comb filter arrangement as claimed in claim 1, characterized in that five switching signals SWA, SWB, SWC, SWAB, and SWBC are generated in the selection logic, said five switching signals being respectively associated with the simultaneously available signals A, B and C of the three picture lines and with the two signals AB and BC of the comb filter functions, and being gained in accordance with the following logical operations: SWA=[(A>B) (C>A) (BC>A)] [(A>B) (C>A) (BC>A)] SWB=[(A>B) (B>C)] [(A>B) (B>C)] SWC=[(B>C) (C>A) (AB>C)] [(B>C) (C>A) (AB>C)] SWAB=[(B>C) (C>A) (AB>C)] [(B>C) (C>A) (AB>C)] SWBC=[(A>B) (C>A) (BC>A)] [(A>B) (C>A) (BC>A)]