Appeal No. 1997-0795
Application 08/087,362
The invention relates to circuitry for de-emphasizing high frequencies in a luminance
signal and for reemphasizing high frequency in a reproduced luminance signal, useful in a
system for transmitting a wide bandwidth luminance signal to a narrow bandwidth channel
in a backward compatible manner.
Independent claim 35 is reproduced as follows:
35. Apparatus for reversing the spectrum of a video signal descriptive of
the scanning of successive image frames supplied at a prescribed frame
rate, which scanning is done line-by-line at a prescribed scan line rate, said
apparatus comprising:
a source of said video signal having a lower video frequency portion
and an upper video frequency portion;
a generator of a carrier signal of a carrier frequency that is a multiple
of said prescribed scan line rate and above said upper video frequency
portion;
a multiplier having a multiplicand input terminal coupled to receive
one of said video and carrier signals and a multiplier input terminal coupled
to receive another of said video and carrier signals for generating, a product
signal having a first amplitude-modulation sideband that is lower in
frequency than said carrier frequency and having a second
amplitude-modulation sideband that is higher in frequency than said carrier
frequency; and
means for reversing at said prescribed scan line rate the
phase of the carrier signal received by said multiplier, each reversal
being at a respective instant between successive scan lines, thereby
enabling conversion of said product signal into a reversed-spectrum
video signal with line-to-line inversion of phase.
2
Page: Previous 1 2 3 4 5 6 7 8 9 Next
Last modified: November 3, 2007