Currently, the broadband FM is used for satellite broadcasting system in the 12 GHz band. For future 21 GHz band broadcasting systems, digital broadcasting will be expected because of the higher flexibility and compatibility with other digital media. The information bit rate will increase according to requirement of definition and channels. The 21 GHz band satellite broadcasting has degradation of performance due to rain. Therefore, we need to adopt modulation methods that has advantage to noise and efficiency of frequency bands. The convolutional coding and the Viterbi decoding is known to have advantage to Gaussian noise. Also, the trellis coded 8 PSK has advantage to efficiency of frequency bands. This paper describes consideration of these modulation and error correction methods for digital satellite broadcasting system in 21 GHz band.

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An improved strip element for strip line fed CP-PASS (Circularly Polarized Printed Antenna composed of Strip dipoles and Slots) is presented. The improved strip element consists of a strip dipole, a window and a probe (Short strip) which helps strip dipoles to be easily coupled to the feed line. A new-type element-set for CP-PASS is composed of the improved strip element and the comventional slot. Experiments were conducted in the 12 GHz band. A band width of axial ratio less than 2 dB was obtained over 9% for one element-set antenna. A maximum actual gain of 16.6 dBi (83 % in efficiency) was obtained for 9 element-set CP-PASS.

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The Multi-channel PCM sound broadcasting has been started in Japan since the summer of 1992 via two Communication Satellites (CS). Six stereo sound channels are delivered on a transponder, which are multiplexed and modulated using MSK on one carrier. We have developed a prototype receiver for this broadcasting service. A new MSK demodulator with an AFC using a carrier recovery error signal is employed to the receiver. It has a sufficient BER characteristics under ±4MHz frequency offset and a good stability at low C/N. This paper describes a configuration of the receiver and the results of the satellite transmission experiment.

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In Thailand, His Majesty King Bhumiphol has officially named the satellite "THAICOM" which Thailand's first national satellite system. The Thaicom satellite will carry 10 C-band and 2 Ku-band transponders. The Thaicom satellite is the earliest Ku-band satellite system in Southeast Asia. Rain attenuation is an important problem for Southeast Asia in using the Ku-band satellite system. There are anumber of unclarified points regarding rainfall intensity characteristics and rain attenuation in tropical zone. The present report therefore aims at presenting basic data on rainfall characteristics in Thailand.

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Cliff effect of digital transmission in its threshold is not favorable for terrestrial broadcasting, which is received under various conditions. AW-CDM transmission system has a soft threshold by dividing the hierarchical information into subchannels, each of which has a different priority and therefore a different threshold. In the present paper, as a hierarchical transmission system which is beneficial for terrestrial digital television broadcasting, AW-CDM system is proposed.

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In the case of VSB-AM cable transmission of the MUSE signal via satellites , two methods are easily available depending on the mode of the modulated MUSE signal : FM mode and AM mode. We have carried out subiective assessment to examine the DU ratio required to avoid the intereferences that are caused by discrete frequency, adjacent channel signal and ghost signal. The results show that the transmiSsion level of the MUSE signal must be raised in comparison with that of NTSC signal and that the tolerance of the transmission level of the FM mode is larger than that of the AM mode.

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