Ghost signal cancellation system using feedforward and feedback filters for television signals

摘要

Disclosed is a television ghost cancellation system based on digital filtering. A baseband video signal at the output of the demodulator is lowpass filtered before being digitized at an analog-to- digital converter. The signal is then processed in digital filters to remove the ghosts. The clean digital signal is then passed to a digital- to-analog converter and lowpass filter to become a clean baseband video signal. The digital filters consist of a feedforward section and a feedback section. The coefficients of the digital filters are calculated by digital signal processor, which processes the data stored in First-In- First-Out buffers (FIFOs). The FIFOs are used as outputs, while one FIFO is used as input to the feedback section. The FIFO stores the standard ghost canceler reference (GCR) signal. Switches are controlled by a synchronization separation circuitry. The coefficients of the feedforward section are estimated by processing data stored in the FIFO. The coefficients of the feedback filter are estimated by adapting a virtual finite impulse response (FIR) filter, which processes data stored in the FIFOs. A scheme is provided to optimize the adaptation process. The advantages of this system are stability and efficiency of the feedback section, fast cancellation and small residuals after convergence.