A new interference cancellation system was devised to suppress the mutual interference between satellite and terrestrial communication systems and to expand the number of potential earth station locations for effective frequency reuse. This system basically adopts the sidelobe canceller concept and has main and auxiliary antennas. The originality of this system lies in that the auxiliary channel signal to be combined with the main channel signal is modulated by a low frequency signal, and the amplitude and phase controlling voltages are obtained by means of envelope detection, to get the envelope of the residue, and then by phase detection, using the envelope signal and the low frequency signal. As a result of experiments, more than 40 dB cancellation was achieved over a 50 MHz range for CW, FM(TP, TV) and PSK signals, even if the desired and interference signals are in the cochannel. In the field test on a 45 km path, sufficient cancellation performance and response were obtained even during fading periods.

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.

An experimental one-way multiaddress data communication system accommodating many small receive-only terminals is described. In this system, a digital facsimile is used as the output equipment. A simple one-way transmission protocol adopting the flag synchronization method has been developed so that facsimile equipment of different speeds can be used. The receive-only terminal comprises an antenna, an RF receiver, a demodulator, and a channel selector. The antenna is an offset parabolic type with an effective diameter of 60 cm and uses a printed spiral type primary radiator. Dimensions of the terminal are 70 cm wide, 88 cm deep, and 126 cm high. The satellite channel bit rate is 64 kbits/s in order to transmit multiple facsimile data simultaneously. Experiments using the Japanese "CS" satellite have been carried out to verify the system feasibility. The normal bit error rate was less than 10-6and line errors occurred less than once in three facsimile transmissions.