Direct digital encoding and radio frequency modulation for broadcast television application
View Patent ↗A digital audio encoder, digital video conditioner, and a digital modulator are described for producing a television broadcast signal at a desired channel frequency range. Left and right audio channel signals are digitized and encoded according to a stereo standard and then combined to form a stereo audio signal. A second audio programming channel signal may be included. A video input can be digitized and conditioned to form a digital video channel. The stereo audio signal can be placed directly at a desired channel frequency by frequency modulation without the need for using an intermediate frequency. The digital video channel can be placed at a desired frequency by amplitude modulation. The digital and audio channels can be digitally combined to create a television transmission signal at a desired frequency and according to a desired standard.
1. A system for producing a NTSC television broadcast signal, comprising:
a digital video conditioner configured to receive a digitized broadcast-compatible video signal and to produce a conditioned video signal and a pilot signal;
a digital stereo BTSC encoder configured to receive at least two digitized audio signals and the pilot signal and to produce a combined audio signal;
a digital modulator configured to receive the conditioned video signal and the combined audio signal, wherein the digital modulator is configured to (a) provide frequency modulation to the combined audio signal at a broadcast frequency without the need for use of an intermediate frequency signal, (b) provide amplitude modulation to the conditioned video signal, and (c) produce a complete digital television broadcast signal as a function of the combined audio signal and conditioned video signal;
an analog-to-digital stage operatively coupled to the digital video conditioner and configured to convert an analog broadcast-compatible video signal to the digitized broadcast-compatible video signal;
an analog-to-digital stage operatively coupled to the digital stereo encoder and configured to convert at least two analog audio signals to the at least two digitized audio signals; and
a digital-to-analog converter operatively coupled to the digital modulator and configured to receive the television broadcast signal, and convert the television broadcast signal to an analog NTSC format signal.
2. The system of claim 1 , wherein the digital stereo encoder is further configured to receive a SAP audio signal.
3. The system of claim 1 , wherein the digital stereo encoder is further configured to receive a professional channel audio signal.
4. The system of claim 1 , wherein the digital video conditioner is further configured to receive a video signal complying with a standard selected from one of the following: PAL, PAL I, PAL B, PAL G, PAL H, PAL M, PAL D, PAL N, SECAM, SECAM D, SECAM K, SECAM L, SECAM B, and SECAM G.
5. The system of claim 1 , wherein the digital stereo encoder is further configured to receive audio signals complying with a standard selected from one of the following: dual-FM, EIA-J, and NICAM.
6. A system for producing an analog NTSC television broadcast channel signal, the system comprising:
an audio digitizing stage configured to receive left, right, and SAP analog audio signals and convert the signals to a digital format;
an audio stereo encoder configured to receive the digital format audio signals and encode them according to the BTSC audio stereo standard so as to provide a digital combined audio signal;
a video digitizing stage configured to receive a broadcast-compatible video signals and convert the video signals to a digital format;
a video conditioning stage configured to (a) receive and combine the digital video signals, (b) produce a digital conditioned video signal, and (c) produce a pilot signal;
an audio FM modulator configured to receive the digital combined audio signal and directly place it at a broadcast audio channel frequency without resort to using an intermediate frequency, creating a modulated digital audio signal configured for broadcast, at the broadcast audio channel frequency;
a video AM modulator configured to receive the digital conditioned video signal and place it at a broadcast video channel frequency, creating a modulated digital video signal;
a summer configured to sum the modulated digital audio signal and the modulated digital video signal to create a complete digital television broadcast signal;
a DAC configured to receive the complete digital television broadcast signal and convert the complete digital television broadcast signal to an analog NTSC format signal; and
at least one anti-aliasing filter configured to receive the analog NTSC format signal.
7. The system of claim 6 , further comprising at least one line amplifier configured to receive the analog NTSC format signal.