Producing compatibility between NTSC and HDTV channels - using pre-filter for first indication signal to prevent aliasing, scanning converter, coder and RF modulator

摘要

A t.v. camera (11) provides a first display signal. A prefilter (13) filters the first signal to prevent aliasing. A first scunning converter (14) a first NTSC encoder (15), a first RF modulator (16), a delay unit (17), a first line rejector (18), a second probe transformer (19), an afterfilter (20), a second line rejector (21), a subtractor (22), a frequency shifter (23), a signal reconstructer (24), a second NTSC encoder (25) and a second RF modulator (26) are used in the circuitry. USE/ADVANTAGE - Image signal made up of more scan lines than HDTV for aspect ratio of NTSC format. For NTSC channel, send 525 line image and for HDTV channel rejects upper and lower lines before transmission.