A new SoC video ghost canceller
A video ghost canceller, which reduces the effect of multi-path signal echoes (ghosts), is described in this paper. An adaptive LMS algorithm was used to improve the received image quality of PAL or NTSC broadcasts. The internal 576-tap digital filter, which is comprised of a 144-tap FIR and a 430-tap IIR filter, cancels ghosts occurring from -6.15 muS before to +41.6 muS after the main signal. In order to reduce the chip area occupied by the filter, an algorithm that combines the error threshold and the error accumulation methods is applied for reducing the coefficients word-length. Also, a tap-decimated equalizer is proposed, which can greatly reduce the number of the multipliers in the adaptive filter. The system on chip (SoC) device performs all the functions required for ghost cancellation, eliminating the need for external DSP controllers, memory, sync detection, D/A converters, A/D converters, and user programming. From chip tests, the canceller can remove the ghost whose power is lower than -6 dB compared to that of the main signal and make ghost residue down to -40 dB. When operating at a rate of 14.318 MHz (4 Fsc), it dissipates 1.3 W from a 3.3 V power supply.