System and method for inserting data into a video signal.

摘要

A system and method for modulating a data signal uses a phase shifting transformer function to phase shift the lower and upper sidebands of the data signal so that the sidebands of the data signal have a 180 DEG phase shift with respect to each other (i.e., are complementary). The phase shifted sidebands are added to a standard video signal and then transmitted. A television or other video receiver demodulates the video signal with a simple demodulator circuit, which causes the upper and lower sidebands to be summed together. The data signal, with complementary sidebands, cancels out so that the data signal does not interfere with normal video operation. The upper and lower sidebands of the data signal are processed separately from the video processing circuitry of the television receiver. An inverse phase shifting circuit performs a second phase shift operation on the upper and lower sidebands of the data signal so that the data signal can be demodulated and the data signal recovered. <IMAGE>