Television ghost cancellation system with phase-controlled remodulation

In a television receiver, including a source of desired video signals, said signals being subject to contamination by ghost signals, and a television signal ghost detector responsive to said video signals for determining the time interval between the occurrence of said video signals and their corresponding ghost signal components when a ghost signal is present;

• a television signal ghost cancellation system comprising:
• a variable delay line having an input coupled to receive said video signals, and an output, and coupled to said ghost detector for delaying said video signals applied to the input of said delay line by a time substantially equal to the time interval between the occurrence of said applied video signals and their corresponding ghost signal components when a ghost signal is present;
• a source of modulating carrier signals;
• a modulator having a first input coupled to the output of said delay line for receiving said delayed video signals, and a second input coupled to said source of modulating carrier signals, and an output at which modulated delayed video signals are developed;
• a variable phase shifter having a first input coupled to receive said modulating carrier signals, a control input, and an output;
• a demodulator having a first input coupled to the output of said modulator, a second input coupled to the output of said variable phase shifter, and an output at which demodulated delayed video signals are developed;
• means coupled to the output of said demodulator for developing pseudo-ghost signal components which are opposite in polarity, substantially equal in amplitude to, and aligned in time with said ghost signal components of said video signals from said source;
• phase comparison means having a first input coupled to receive said pseudo-ghost signal components, a second input coupled to receive said video signals from said source, and an output coupled to said control input of said variable phase shifter, for developing a control signal representative of the phase relationship between said ghost signal components and said pseudo-ghost signal components;
• and
• means having a first input coupled to receive said pseudo-ghost signal components and a second input coupled to receive said video signals from said source, for combining said signals to produce a deghosted video signal.

In a television receiver, including a source of desired video signals, said signals being subject to contamination by ghost signal components, and a television signal ghost detector responsive to said video signals for determining the time interval between the occurrence of said video signals and their corresponding ghost signal components when a ghost signal is present;

• a recursive television signal ghost cancellation system for producing processed video signals comprising:
• a variable delay line having an input coupled to receive said processed video signals, and an output, and coupled to said ghost detector for delaying said processed video signals by a time substantially equal to the time interval between the occurrence of said desired video signals and their corresponding ghost signal components when a ghost signal is present;
• a source of modulating carrier signals;
• a modulator having a first input coupled to the output of said delay line for receiving said delayed video signals, and a second input coupled to said source of modulating carrier signals, and an output at which modulated delayed video signals are developed;
• a variable phase shifter having a first input coupled to receive said modulating carrier signals, a control input, and an output;
• a demodulator having a first input coupled to the output of said modulator, a second input coupled to the output of said variable phase shifter, and an output at which demodulated delayed video signals are developed;
• means coupled to the output of said demodulator for developing pseudo-ghost signal components which are substantially equal in amplitude to, and aligned in time with said ghost signal components of said video signals from said source;
• means having a first input coupled to receive said pseudo-ghost signal components, and a second input coupled to receive said video signals from said source, for combining said signals to produce at an output said processed video signals;
• phase comparison means having a first input coupled to receive said pseudo-ghost signal components;
• a second input coupled to receive said video signals from said source, and an output coupled to said control input of said variable phase shifter, for developing a control signal representative of the phase relationship between the ghost signal components of said video signals and said pseudo-ghost signal components,
• wherein said processed video signals are processed to become substantially free of ghost signal components.