This paper presents a Digitalized Modulator for FM Broadcasting including digital stereo modulator by using DDS(Direct Digital Synthesizer). This modulator employs "Over Nyquist sampling " for reducing the sampling frequency and "Time-variant coefficient FIR(Finite Impulse Response) filter" for using the internal sampling clock independent from the input sampling clock. This FM modulator displays signal-to-noise ratio of 73dB or better and total harmonic distortion of 0.2% (50Hz~15kHz).

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Digital transmission systems are required to introduce new services of CATV such as PPV and VOD. In this paper we describe the development of 64QAM transmission equipment . It has 30Mbps transmission capability with 6MHz bandwidth. We experiment hybrid optical transmission with a 64QAM signal and 60 VSB-AM signals of conventional CATV systems. We get sufficient 64QAM BER performance. We also measure phase noise of recovered IF carrier and estimate its effect on the QAM transmission performance.

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A multilevel weighted channel coding with coded modulation is proposed. This is developed for hierarchical transmission system. including terrestrial digital TV broadcasting. Using proposed channel coding the main portion of the FEC (Forward Error Correction) decoding of all transmission layers can be single. This paper shows some BER (Bit Error Rate) performance simulations and analyzes the error propagation which is characteristic of Viterbi decoding for multiplexed convolutional coding. A method which removes the error propagation is also described, and could be applicable to the European DAB (Digital Audio Broadcasting) system.

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MPEG-2 MP@ML Verification Tests were carried out by 10 organizations in Australia. Europe and Japan at January 1994. The assessment tests were organized according to ITU-R Rec.500-5 and used DSCQS. The results of the tests were processed by each organization and raw data were submitted to the MPEG Test Chairman. The outline of the results was reported in MPEG Paris meeting at March 1994. This paper describes the test procedure, test materials and the details of the test results.

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ISDB (Integrated Services Digital Broadcasting) has been studied for the future digital broadcasting system which will provide multi-program and multi-media services. To investigate into video coding system suitable for ISDB, an SDTV video codec and a variable bit rate program multiplexer have been developed. They conform to various services through a flexible service planning which ISDB makes possible. They also support low delay operation and error resilience, which are the necessary features for broadcasting. A variable bit rate control is very advantageous in efficient program multiplexing. Multi-program and multi-media transmission experiments, linked with ISDB system, have been successfully carried out to verify the expected functions and performance.

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PCM sound transmission system, that uses quadrature amplitude modulation of the video carrier is evaluated for use in 2nd generation EDTV (Enhanced TV) systems by BTA (Broadcasting Technology Association) Audio Working Group. This system features ISO/IEC 11172-3 Layer-II , BEST (Burst and random Error correction System for Teletext) error correcting code, dicode modulation and a low multiplexing level of -26dB. By theoretical analysis and experiments, we show that this PCM sound service area covers existing NTSC television service area.

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PCM Sound Transmission System using quadrature amplitude modulation of the video carrier is evaluated for use in 2nd generation EDTV(Enhanced TV) system by BTA (Broadcasting Technology Assosiation) Audio Working Group. This system utilizes quadrature ghost cancel reference signal(QGCR), compatible with conventional NTSC ghost cancel reference signal standardized by BTA in 1989. Waveform equalizer using the QGCR at receiver eliminates linear distortion caused by ghosts or adjacent channel notch filter.

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BTA(Broadcasting Technology Assosiation) audio working group performed indoor evaluation to the PCM sound transmission system for the second generation EDTV(Enhanced TV)system. First, This paper describes specifications of Channel Coding, such as error correction methods, data multiplex area, block formats and audio or data channel modes. Then, we show experimental results of BER(bit error rate with/without error correction) vs. picture S/N etc..

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PCM sound transmission system using quadrature amplitude modulation of the video carrier is evaluated to apply second generation EDTV(Enhanced TV) by BTA(Broadcasting Technology Association) audio working group. The system employs ISO/IEC 11172-3 Layer H for a source coding method. Besides the conventional two analog sound channels, four digital sound channels are available due to the sophisticated compression technique. Subjective tests to assess the impaired sound signal with transmission error was conducted. Acceptable quality of the impaired sound signal is clarified by the result.

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