This paper presents a domestic satellite communication system accommodating numerous 30/20 GHz band small earth stations emphasizing the system outline, the use of multiple-access (MA) techniques. It also describes associated earth station configurations, equipment performance, and experimental results using the Japanese CS (medium capacity communications satellite for experimental purposes). Two kinds of earth stations are employed in this system, a small earth terminal (SET) and a master earth station (MES). The SET, which has an antenna about 2 m in diameter, is placed near a subscriber. The MES, which has an 11.5 m diameter antenna, is connected to the terrestrial telephone network through a satellite telephone switching center (STC). There are about 50 two-way channels with bit rates of 32 kbits/s which are achieved through the use of a 30/20 GHz band transponder whose EIRP is about 71.5 dBm, aG/Tof about 2.7 dB/K and an SET's antenna diameter of 1.8 m. This results in a system availability of 99.5 percent under typical Japanese statistical rain attenuation data. To enable a demand-assigned MA technique to be employed in this system, a single channel per carrier (SCPC) is selected, taking into consideration power efficiency of the SET, flexibility of system configurations, and the adaptability of the adaptive power control during rainy periods.

One modulation method called the frequency counting modulator (FCM), which can produce various constant envelope signals, is proposed. The FCM is materialized by only digital circuits and, therefore, is easily implemented in a large scale integrated circuit (LSI). From analytical study of the FCM, design formulas are derived for MSK-type modulation, and modulated signal performance features are clarified in terms of minimum signal distance, the effect of a Gaussian receiving filter, and spectral power concentration.

Minimum Shift Keying (MSK) is a very attractive modulation and demodulation scheme for satellite communication systems. In this paper, the design, analysis, implementation, and testing of a high-speed MSK modem are described. This MSK modem has a nominal data transmission rate of 100 Mbits/s at an intermediate frequency of 1.7 GHz, and is designed with a new technique which is named "clock-slave carrier synchronization." Phase ambiguities caused by the divide-by-two circuit and carrier recovery loop are resolved by the new technique where the recovered carrier phase is subordinate to decision timing. Implementation is carried out using the remodulation method in the carrier recovery circuit and FM discriminator in the clock recovery circuit. Experimental results show the feasibility of this high-speed MSK modem with little performance degradation from the theoretical predictions. This modem is intended for the experiments through the Japanese Communication Satellite.