Economical high-definition television using a modulated-signal

Abstract

A television (TV) system having a compatible high-definition signal receivable at conventional resolution by conventional TV receivers without auxiliary apparatus with carrier modulated high-definition luminance information being transmitted in a continuous spectrum spanning two conventional TV channels, carrier modulated quadrature amplitude modulated (QAM) high-frequency chrominance information being transmitted in the luminance spectrum and carrier modulated QAM low-frequency chrominance information being transmitted outside luminance spectrum. A decoder recovers the high-definition luminance information by demodulating the transmitted signal. The chrominance information is recovered from the transmitted signal by first notch filtering the transmitted high-definition signal to remove energy existing between the two sidebands of the QAM high-frequency chrominance information, and then, demodulating at the carrier frequency. The demodulating at the carrier frequency results in the QAM high- and low-frequency chrominance information forming a continuous spectrum that is then bandpass filtered. The high-definition I and Q chrominance signals are then recovered from the bandpass filtered chrominance information by a QAM demodulator. The QAM demodulation of the latter results in continuous high-definition I and Q chrominance signals.