Zenith Radio Corporation

Zenith Electronics Corporation

Carl G Eilers

Pieter Fockens

Richard W Citta

Ronald B Lee

Rudolf Turner

A system for minimizing co-channel interference into NTSC receivers from digitally transmitted ATV signals. The NTSC receiver subjective random noise sensitivity characteristic is utilized to shape the ATV transmitter power curve. A complementary filter incorporated in ATV receivers for compensating for the shaped ATV transmitter power curve. The shaped ATV power curve emphasizes signals at the frequencies where the NTSC subjective random noise sensitivity is low and deemphasizes signals at the frequencies where the NTSC subjective sensitivity is high.

ATV television system with reduced co-channel NTSC interference

A co-channel interference reduction system for digital high definition television includes a transmitter having a modulo 4 processing precode filter. A receiver includes a pair of selectable video processing modes. The first mode provides a comb filter for removing co-channel interference signals together with a modulo 4 interpreter for restoring the four level data signal despite the intersymbol interference signal introduced by the comb filter segment. In the alternate mode operable in the absence of co-channel interfering signals, a level slicer and postcoder are used to restore the precoded signal to the original four level data signal.

Co-channel interference reduction system for digital high definition

A CATV television system has the sync and color subcarrier reference information replaced in the horizontal blanking intervals with compressed digital audio data. The digital audio data is in the form of a modified duobinary signal having data sampling points selected to coincide with the zero crossings of a color reference subcarrier. A phase locked loop provides the master clock for the signal generator and the data sampler. A horizontal interval detector circuit recovers a 1.8 MHz CW signal of greater than one half line duration, followed by a white horizontal identification pulse of 4.7 microseconds width, that are supplied in place of the pre-equalizing, vertical sync and post equalizing pulses in the vertical interval. CODE 1TV60CATV

CATV scrambling system with compressed digital audio in synchronizing

A television signal audio transmission system comprises transmission means for developing first and second stereophonically related audio signals and means for developing a third audio signal. The transmission means further includes circuitry for developing a composite baseband signal having a first component comprising the sum of the first and second audio signals, a second component comprising a double sideband suppressed carrier signal formed by amplitude modulating a 2f.sub.H subcarrier with the difference between the first and second audio signals, a third component comprising a pilot signal having a frequency f.sub.H and a fourth component comprising a 4f.sub.H subcarrier signal frequency modulated according to the third audio signal, where f.sub.H represents the horizontal scanning line frequency. The composite baseband signal may include a fifth component comprising an approximately 5.5f.sub.H subcarrier signal frequency modulated in accordance with a first information signal and a sixth component comprising an approximately 6.5f.sub.H subcarrier signal frequency modulated in accordance with a second information signal. In an alternate embodiment, the fourth and fifth components are replaced by a 5f.sub.H subcarrier signal frequency modulated according to the third audio signal. The composite baseband signal is used to frequency modulate a transmitted main audio RF carrier, the transmitted signal being detected by receiving circuits for reproducing the stereophonic audio signals, the third audio signal and the first and second information signals.

TV Sound transmission system

A television signal audio transmission system comprises transmission means for developing first and second stereophonically related audio signals and means for developing a third audio signal. The transmission means further includes circuitry for developing a composite baseband signal having a first component comprising the sum of the first and second audio signals, a second component comprising a double sideband suppressed carrier signal formed by amplitude modulating a 2f.sub. H subcarrier with the difference between the first and second audio signals, a third component comprising a pilot signal having a frequency f.sub.H and a fourth component comprising a 4f.sub. H subcarrier signal frequency modulated according to the third audio signal, where f.sub.H represents the horizontal scanning line frequency. The composite baseband signal may include a fifth component comprising an approximately 5.5f.sub. H subcarrier signal frequency modulated in accordance with a first information signal and a sixth component comprising an approximately 6.5f.sub.f.sub.H subcarrier signal frequency modulated in accordance with a second information signal. The composite baseband signal is used to frequency modulate a transmitted main audio RF carrier, the transmitted signal being detected by receiving circuits for reproducing the stereophonic audio signals, the third audio signal and the first and second information signals.

TV Sound Transmission system

A transmitter or a receiver processes four-channel stereo frequency-modulation information. The information represents four audio signals A, B, C and D that correspond to sources respectively located at the left-front, right-front, left-rear and right-rear of a listening point. First and second sub-carrier signals .omega..sub.s and .omega..sub.s2 both have frequencies substantially higher than the highest audio signal component. In one disclosed embodiment all of the different signals are combined to develop a signal having a carrier signal frequency that is modulated by double-sideband amplitude-modulated suppressed-carrier sub-carrier signals as expressed by the modulation function

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River Forest, IL, United States of America

Carl G Eilers