Method for rejecting NTSC interference and NTSC interference rejection filter circuit using 3-stage notch filter

摘要

A technique for rejecting NTSC co-channel interference uses 3-stage notch filters. In received I-channel data symbols 101 and data field sync reference patterns 102, frequency components causing NTSC co-channel interference, which are an NTSC visual carrier, an NTSC chrominance subcarrier and an NTSC aural carrier, are 3-stage notch filtered 120,130. A first energy of digital broadcasting signals 321, before being 3-stage notch filtered, is produced from a first error signal between received I-channel data symbols and data field sync reference patterns. A second energy of digital broadcasting signals 331, after being 3-stage notch filtered, is produced from a second error signal between received I-channel data symbols and data field sync reference patterns which are 3-stage notch filtered. After comparing the first energy with the second energy 400 for detecting NTSC co-channel interference, an output path 500 is controlled so that a signal having a lower NTSC co-channel interference energy out of the I-channel data symbols and the 3-stage notch filtered I-channel data symbols is selectively outputted. Consequently, a received digital TV signal which does not contain frequency components of the three carriers causing NTSC co-channel interference is outputted 530.