Economical high-definition television using a modulated-signal combination

• US 4,641,179 A
• Filed: 12/21/1984
• Issued: 02/03/1987
• Est. Priority Date: 12/21/1984
• Status: Expired due to Term

• Current Assignee: Bell Telephone Laboratories, Inc. (Nokia Corporation)
• Original Assignee: AT&T, Inc.
• Inventors: Rzeszewski, Theodore S., Pazarci, Melih, LoCicero, Joseph L.
• Primary Examiner(s): Shepperd, John W.
• Application Number:
  US06/684,489
• Time in Patent Office: 774 Days
• Field of Search: 358/12, 358/15, 358/16
• US Class Current: 348/487
• CPC Class Codes: H04N 11/14 in which one signal, modulated in phase and amplitude, conveys colour information and a second signal conveys brightness information, e.g. NTSC-system
• CPC Class Codes: H04N 11/26 involving two-channel transmission

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.

Claims

1. A system for encoding high-definition luminance and chrominance information from a high-definition video source for transmission on a transmission media and said high-definition chrominance information having low-frequency and high-frequency chrominance components, said system comprises:

means for modulating said high-definition luminance information at a transmission carrier frequency;

means for band splitting said high-definition chrominance information into said low-frequency and high-frequency chrominance components;

means for quadrature amplitude modulating said low-frequency chrominance components at a subcarrier frequency;

means for modulating the quadrature amplitude modulated low-frequency chrominance components at said transmission carrier frequency;

means for filtering the carrier frequency modulated quadrature amplitude modulated low-frequency chrominance components to remove the lower sideband resulting from the carrier frequency modulation;

means for quadrature amplitude modulating said high-frequency chrominance components at said subcarrier frequency;

means for modulating the quadrature amplitude modulated high-frequency chrominance components at said transmission carrier frequency;

means for filtering the carrier frequency modulated quadrature amplitude modulated high-frequency chrominance components to remove the upper sideband resulting from the carrier frequency modulated; and

means for combining the carrier frequency modulated high-definition luminance information and the filtered carrier frequency modulated low-frequency chrominance components and the filtered carrier frequency modulated high-frequency chrominance components for transmission on said transmission media.

2. A system for decoding high-definition display information from a received high-definition video signal having carrier modulated high-definition luminance and carrier modulated low-frequency and high-frequency chrominance information having low-frequency and high-frequency chrominance components, said system comprises:

means for demodulating said modulated luminance information in response to the latter and a signal at the carrier frequency for display purposes; and

means for notch filtering said video signal to remove said modulated luminance information from between said high-frequency chrominance components;

means for demodulating the filtered video signal to insert said low-frequency chrominance components into the notch portion of said filtered video signal;

means for QAM demodulating the demodulated filtered video signal with a subcarrier frequency signal to recover said low- and high-frequency chrominance components for display purposes.

3. A system for encoding high-definition luminance and chrominance information from a high-definition video source for transmission on a transmission media and said high-definition chrominance information having low-frequency and high-frequency chrominance components, said system comprises:

means for modulating said high-definition luminance information at a transmission carrier frequency;

means for band splitting said high-definition chrominance information into said low-frequency and high-frequency chrominance components;

means for quadrature amplitude modulating said low-frequency chrominance components;

means for modulating the quadrature amplitude modulated low-frequency chrominance components at said transmission carrier frequency;

means for filtering the carrier frequency modulated quadrature amplitude modulated low-frequency chrominance components to remove the lower sideband resulting from the carrier frequency modulation;

means for quadrature amplitude modulating said high-frequency chrominance components;

means for modulating the quadrature amplitude modulated high-frequency chrominance components at said transmission carrier frequency;

means for filtering the carrier frequency modulation quadrature amplitude modulated high-frequency chrominance components to remove the upper sideband resulting from the carrier frequency modulation; and

means for combining the carrier frequency modulated high-definition luminance information and the filtered carrier frequency modulation low-frequency chrominance component and high-frequency chrominance component for transmission on said transmission media.

4. The system of claim 3 further comprises means for comb filtering said high-definition luminance information received from said video source before modulation by said luminance modulating means;

and

means for comb filtering said high-definition chrominance information received from said video source before the latter is band split into said high- and low-frequency chrominance components.

5. The system of claim 4 wherein said luminance modulating means comprises means for vestigially sideband filtering said carrier frequency modulated luminance information before transmission.

6. A system for decoding high-definition luminance and chrominance information from a transmitted signal having carrier modulated high-definition luminance information and carrier modulated quadrature amplitude modulated high-frequency chrominance information and quadrature amplitude modulated low-frequency chrominance information, said system comprises:

means for demodulating said modulated luminance information in response to said transmitted signal and a carrier frequency signal;

means for low pass filtering said demodulated luminance information;

means for comb filtering said bandpass limited luminance information for display purposes;

means responsive to said carrier modulated quadrature amplitude modulated high-frequency and low-frequency chrominance information for notch filtering the latter information;

means for demodulating said notch filtered high-frequency and low-frequency chrominance information;

means for bandpass filtering said demodulated high-frequency and low-frequency chrominance information; and

means for quadrature amplitude demodulating said band limited high-frequency and low-frequency chrominance information for display purposes.

7. The system of claim 6 wherein said luminance demodulating means further comprises means for vestigial sideband shaping said carrier modulated high-definition luminance information upon receiving the latter information.

8. The system of claim 7 further comprises means for recovering the carrier frequency from said transmitted signal;

and

said quadrature amplitude modulated demodulating means further comprises means for comb filtering the demodulated high-frequency and low-frequency chrominance information.

9. A system for encoding high-definition luminance and chrominance information from a high-definition video source for transmission on a transmission media and said video source having first and second chrominance components and said second chrominance component having high- and low-frequency segments, said system comprises:

means for band limiting said high-definition luminance information;

means for band limiting the high-frequency segment of said second chrominance component;

means for single sideband modulating said band limited high-frequency segment of said second chrominance component;

means for summing said single sideband modulated high-frequency segment of said second chrominance component and said low-pass limited luminance information;

means for double sideband modulating the summed information;

means responsive to said first chrominance component and said low-frequency segment of said second chrominance component for modulating the latter component and segment;

means responsive to the modulated first chrominance component and low-frequency segment of said second chrominance component for frequency translating the latter; and

means responsive to the frequency translated chrominance component and low-frequency segment of said second chrominance component and the summed information for combining the latter for transmission on said transmission media.

10. The system of claim 9 further comprising means for comb filtering said low-frequency and high-frequency segments of said second chrominance component upon reception from said video source.

11. The system of claim 10 wherein said double sideband modulating means comprises means for vestigially sideband filtering said double sideband modulated information.

12. A system for decoding high-definition luminance and chrominance information from a transmitted signal and said high-definition chrominance information comprising a first and second chrominance component and said second chrominance component comprises low- and high-frequency segments, said transmitted signal having carrier modulated high-definition luminance information with said high-frequency segment of said second chrominance component, and said low-frequency segment of said second chrominance component and said first chrominance component modulated and frequency translated to the carrier frequency, said system comprises:

means for detecting said carrier modulated high-definition luminance information with said high-frequency segment;

means responsive to said detected information for comb filtering the latter to obtain said high-definition luminance information for display purposes;

means responsive to said detected information for single sideband demodulating said information to obtain said high-frequency segment of said second chrominance component;

means for demodulating said first chrominance component for display purposes from said transmitted signal;

means for demodulating said low-frequency segment of said second chrominance component; and

means responsive to the demodulated low-frequency segment of said second chrominance component and the demodulated high-frequency segment of said second chrominance component for summing the latter for display purposes.

13. The system of claim 12 further comprises means for comb filtering said first chrominance component for display purposes;

and

said summing means comprises means for comb filtering the summed information for display purposes.