Ever since the early days of television, poor picture quality due to the ghosting effect has always been a source of bother for viewers. Ghosting in a broadcasting environment is caused by television signals being reflected by large objects and obstacles such as hills, large buildings and airplanes, before reaching their destination. This multi-path propagation above results in the signals transmitted along each path reaching a television receiver with varying delays and powers, resulting in duplicate images horizontally- shifted along the television screen.
Over the past two decades, there have been many attempts to implement ghost cancellation, but it has never been popular due to the cost of high performance signal processors. With the advanced technology available today, television ghost removal is becoming more realisable as the powerful integrated-circuits necessary are becoming more affordable.

The aim of this project is to implement a ghost canceller by using a digital signal processor to analyse the interference encountered through the broadcast channel. Once evaluated, the processor will be used to add suitably delayed, scaled and phase-shifted copies of the received video signal to remove the ghosting effect, restoring it to its intended picture quality.

In the near future, with the introduction of all-digital high-definition (HDTV) systems, the effects of multi-path propagation could become disastrous as it can prevent the compressed signals from being decoded properly or at all, resulting in more severe reception problems than merely ghosted images. Consequently, ghost cancellers will then be an essential component within every television.

Dr Lachlan Andrew, Ni Su, Sherman Mun Tat Lau, Andrew Payne