Abstract: A spread spectrum communications system includes at least one communication station for transmitting a plurality of digital information data sequences via a plurality of communication channels by using the same PN code sequence. The communication station spreads the respective digital information data sequences by the PN code sequence to provide spread spectrum signals, modulates the spread spectrum signals by respective carriers having different frequencies from each other to provide modulated signals, and then transmits the modulated signals via the communication channels respectively. A frequency interval of the carrier frequencies is determined to an even-numbered multiple of a symbol rate of the transmitted digital information data sequences.

Abstract: A method is disclosed for uniquely determining the position of a mobile earth station in a mobile satellite communication system which employs a non-geostationary satellite with a multi-spot beams. A given point of a preknown position on the earth surface is defined as the center coordinate of a three-dimensional coordinate axis, information on the measured distance and Doppler shift amount between a mobile earth station of an unknown position and a non-geostationary satellite is used to repeat the estimation of the position of the mobile earth station a plurality of times, thereby obtaining the position of the earth station with high accuracy.

Abstract: A system for determining and registering the location of mobile terminals in a mobile communication system using non-geosynchrous satellites, in which each land earth station transmits its identification information via spot beams of satellites or together with identification information of a spot beam and that of satellite. A mobile terminal thus receives identification information, and transmits the received identification information together with information on time of reception and the terminal identifying information to the terrestrial network for registering the latest location information. Since the latest location information of mobile terminal is registered in the terrestrial network as mentioned above, a call can be connected to the mobile terminal simply by sending a call announcement message by referring the registered location information. This leads to reduction of the number of circuits that are needed for sending call announcement messages.

Abstract: The non-geosynchronous orbiting satellites each transmit identification information given to each of spot beams irradiated from them. A mobile terminal, when registering its location, receives the spot beam identification information at some moments in time with the predetermined time interval. Then, the mobile terminal transmits the received spot beam identification information and each of their reception time together with the terminal identification information assigned to the mobile terminal. On the basis of an overlapped area of spot beam coverage areas at time when each of identification information is received by the terminal, a terrestrial network estimates and registers the latest location of the mobile terminal.

Abstract: A gas laser device includes a high frequency power source for generating a high frequency output voltage and a pair of electrodes positioned sandwiching a discharge gap through which laser gas circulates. The pair of the electrodes are connected to the high frequency power source for applying the high frequency output voltage across the electrodes to achieve discharge in the discharge gap and to thereby generate laser light. Each of the electrodes includes an electrode element, a capacity coupling control element provided on either side of the electrode element, and a dielectric shell. The dielectric shell surrounds the electrode element and the capacity coupling control element, therefore the discharge occurs between the dielectric shells of a pair of the electrodes. The dielectric constant of the capacity coupling control means is lower than that of the dielectric shell.

Abstract: A spread spectrum communication system has a plurality of transmit ends capable of simultaneous communications and at least one receive end. Each of the transmit ends modulates digital information by a PN code to provide a spread signal, modulates a carrier by the spread signal to provide modulated signal, and then transmits the modulated signal to the receive end. These transmit ends use the same PN code for spreading the respective digital information and use carriers having different frequencies from each other so that spectrums of at least two of the modulated signals overlap each other. The receive end receives signals transmitted from the transmit ends to provide a received signal, frequency-converts the received signal to provide a converted signal, and calculates a correlation between the converted signal and the PN code to recover the digital information transmitted from the desired transmit end.

Abstract: A unique word in a digital communication system is detected on a receiving side by using an acoustic surface wave matched filter (4) having a piezoelectric substrate, an input interdigital electrode (4c) and and output interdigital electrode (4a, 4b) on the substrate. An input signal is applied to the input interdigital electrode in the form of a phase modulated IF band signal. A pattern of the output interdigital electrode is designed depending upon a unique word to be detected where data 1 corresponds to an upper finger (4a) followed by a lower finger (4b), data 0 corresponds to a lower finger (4b) followed by an upper finger (4a) or vice versa, and progagation time of the surface acoustic wave over the spacing (d) between each pairs of fingers (4a, 4b) is equal to a bit time duration of the unique word.

Abstract: A unique word and/or a recovered phase in the demodulator in a multi-phase modulation system and/or a multi-level modulation system is detected by obtaining a plurality of correlation values, performing linear calculations for those correlation values to provide a correlation pattern, and looking at a table if this pattern coincides with one of the predetermined patterns. The invention is useful even when a received signal quality is poor and/or the length of the unique words is short. A plurality of unique word, together with a recovered phase are also recognized by the present invention.

Abstract: An acoustic surface wave filter bank consisting of a single or a plurality of piezoelectric substrates on which a plurality of acoustic surface wave filters each comprising an input interdigital transducer and an output interdigital transducer are fabricated, wherein center frequencies of adjacently located filters are not adjacent to center frequency of present filter so that leaked acoustic surface waves to the present filter from adjacently located filters are strongly attenuated.

Abstract: A communications satellite repeater having input demultiplexers for demultiplexing input beams to a plurality of first channels each having a first bandwidth, switches for interconnecting each input channel to desired output channel on a channel by channel basis, amplifiers, and output multiplexers for multiplexing output channels to output beams is improved by the particular structure of the switch. The present switch (8) has filter banks (9) for providing a plurality of second channels each having a second bandwidth narrower than said first channels by dividing each of said first channels, which can also operate as bandwidth-variable filter banks by multiplexing the adjacent second channels, switches (10) coupled with said filter banks (9) to interconnect said second channels, and multiplexers (11) for multiplexing the second channels at the ouptut of said switches (10) to provide output channels. Thus, each transponder can interconnect a plurality of beams.