Abstract: An apparatus for demodulating an AM data multiplexed modulated wave signal in which an analog modulated signal and digital modulated signals are multiplexed, in order to derive therefrom a baseband digital signal. The demodulation apparatus aims to derive the digital baseband signal from the AM data multiplexed modulated wave signal in which the analog modulated signal obtained by amplitude modulating a carrier having a frequency fc with an analog signal and the digital modulated signals at frequency position of (fc+f.alpha.) and (fc-f.alpha.) line-symmetrical with respect to a frequency axis of the frequency fc are multiplexed. A demodulation apparatus includes an AM type modulated wave signal eliminating circuit for removing an AM modulated wave signal from an input AM data multiplexed modulated wave signal, and a data demodulation circuit for receiving an output of the AM type modulated wave signal eliminating circuit and for deriving therefrom a baseband digital signal.

Abstract: An AM multiplexing broadcast apparatus multiplexes a digital modulated signal independent of an AM modulated signal, in the same frequency band as the AM modulated signal. A sum signal is amplified by a first amplifier. An inverse of the sum signal is obtained by an inverse calculator. A divider divides this inverse signal by a magnification factor of the first amplifier. An output of the divider and a digital modulated signal in the same frequency band as an AM modulated signal are multiplied by a first multiplier. A carrier generated by a carrier generator is phase-modulated by a phase modulator. Outputs of the phase modulator and first multiplier are synthesized and thereafter amplified by a second amplifier. Outputs of the first and second amplifiers are multiplied by a second multiplier and transmitted from an antenna.

Abstract: An AM data multiplexing modulation apparatus for multiplexing a digital signal to an AM modulation signal without adversely affecting an AM sync detection output even if AM sync detection is performed. An AM modulator AM modulates a carrier having a frequency fc by an input signal, an orthogonal modulator 3 orthogonally modulates a carrier having a frequency (fc+f.alpha.) by a QPSK baseband digital signal generated by a QPSK baseband digital signal generator 2, a sign inverter and a complex conjugate unit change the sign of a signal having the same phase as a reference carrier of vector shift and corresponding to a dibit formed by the QPSK baseband digital signal generated by the QPSK baseband digital signal generator, another orthogonal modulator orthogonally modulates a carrier having a frequency (fc-f.alpha.

Abstract: As to a differential code (DPCM) transmission system for an input signal as such as an audio signal, in case higher frequency components thereof are dominant, every another samples of the input signal are alternately into two groups, in each of which differential coding effected, so as to maintain a dynamic range in higher frequency range; in case no frequency components exceeding one fourth of the sampling frequency are contained in the input signal, successive 3 MSB's having a pattern "1, 0, 1" or "0, 1, 0" are corrected into "1, 1, 1" or "0, 0, 0" respectively; and in case 2 symbols of a tertiary code converted from 3 bits of a binary code are transmitted and restored, peripheral bit arrangement of a matrix having rows consisting of the first symbols of the converted tertiary codes and columns consisting of the second symbols thereof are allotted such as Gray codes are obtained, while an inner 2.times.2 matrix of a 4.times.

Abstract: A signal transmission system for high definition television that can handle a second television signal which is superior in quality to a first television signal such as an NTSC (National Television System Committee) television signal. The transmitting end of the system transmits a first television signal including a video signal, audio signals, etc., through a main transmission line, as well as a third television signal including a high definition components obtained as the difference between the second and the first television signal through an auxiliary transmission line. The receiving end of the system receives and synthesizes the first television signal transmitted through the main transmission line and the third television signal transmitted through the auxiliary transmission line to produce the second television signal.

Abstract: A differential code (DPCM) transmission system for an audio signal, in case higher frequency components thereof are dominant, every another samples of the input signal are alternately into two groups, in each of which differential coding effected, so as to maintain a dynamic range in higher frequency range; when a near instantaneously compressed DPCM signal is transmitted, coding errors caused by the compression are corrected by varying the difference between samples in response to the comparison between a locally decoded signal and the original signal; when the frequency components exceeding one fourth of the sampling frequency are contained in the input signal, successive 3 MSB's having a pattern "1, 0, 1" or "0, 1, 0" are corrected into "1, 1, 1" or "0, 0, 0" respectively; and in case 2 symbols of a tertiary code converted from 3 bits of a binary code are transmitted and restored, peripheral bit arrangement of a matrix having rows consisting of the first symbols of the converted tertiary codes and columns

Abstract: A method and system for multiplexing additional audio information in the form of pulse code modulation (PCM) audio signals onto a television signal. The PCM audio signal is time multiplexed into scanning retrace intervals of the video signal. At a receiver, the bit error rate of the decoded PCM audio signal is compared with a threshold so as to switch the audio output from the PCM audio signal to a conventional FM demodulated audio signal when the bit error rate exceeds the predetermined threshold. In this way, the benefits of both PCM audio and FM audio can be obtained by utilizing the higher immunity of FM signals in low signal-to-noise ratio environments, while the high fidelity PCM audio signal is utilized when the signal-to-noise ratio environment is relatively high.