CROSS-CHANNEL INTERMODULATION DISTORTION CORRECTION DEVICE FOR ADJACENT-CHANNEL NTSC/DTV TELEVISION BROADCAST TRANSMITTERS

摘要

When analog and digital television signals are amplified by the same highpower amplifier in a combined analog- and digital-format television transmitter, intermodulation distortion (IMD) is caused by a digital television (DTV) signal that occupies a channel that is immediately below and adjacent an analog-format (e.g., NTSC) television signal. This cross-channel IMD must be corrected. The IMD correction may be achieved by essentially pre-correcting for radio frequency (RF) IMD by processing corresponding DTV and NTSC television signals at intermediate frequency (IF). The precorrection is preferably achieved by tapping the DTV IF signal and using it to precompensate for the expected RF IMD that is inherent in the NTSC IF signal.