Design of a digital filter with variable characteristics for luminance signal processing of DTVs

A new luminance circuit is presented for a multistandard television, based on a noble filter with variable characteristics. The circuit consists of 3-stage filters with noise reduction and DC-gain control circuitry. The composite video signal is sampled and quantized by 4_sc at the first stage of the filter; the chrominance signal is trapped at the second stage; and two variable bandpass filters of the final stage control the overall characteristics of the circuit. One of the bandpass filter amplifies the center frequency of the luminance signal, and the other adjusts the aperture gain with respect to SECAM, PAL and NTSC signals reflecting the control factors of the transfer gain. The proposed circuit provides a gain attenuation greater than 40 dB at the chroma trap and about 14 dB aperture compensation for the 3.3 MHz bandwidth of the NTSC standards