Earth station capable of effectively using a frequency band of a satellite

Claim 2

In an earth station for carrying out communication in a satellite communication system through a satellite by the use of an up-link frequency band and a down-link frequency band, said earth station comprising a transmission section responsive to first and second input signals for transmitting first and second transmission signals through said up-link frequency band towards said satellite, the improvement in combination with the foregoing wherein: each of said up-link and said down-link frequency bands has a plurality of frequency subbands spaced apart from one another with frequency gap bands interposed between said frequency subbands; said transmission section comprising: modulating means for modulating a carrier by said first input signal to produce a transmission subband signal occupying a selected one of said frequency subbands of the up-link frequency band; first transmitting means coupled to said modulating means for transmitting said transmission subband signal as said first transmission signal through said selected one of the frequency subbands; spread spectrum processing means for processing said second input signal into a spread spectrum transmission signal having said up-link frequency band; and second transmitting means coupled to said spread spectrum processing means for transmitting said spread spectrum transmission signal as said second transmission signal through said up-link frequency band.

Claim 3

An earth station as claimed in claim 1, said earth station comprising a reception section for receiving a first reception signal through a predetermined one of the frequency subbands of said down-link frequency band and a second reception signal through said down-link frequency band from said satellite to produce first and second output signals corresponding to said first and second input signals, respectively, wherein said reception section comprises: first receiving means for receiving said first reception signal through said predetermined one of said frequency subbands of said down-link frequency band to produce a reception subband signal; first producing means coupled to said first receiving means for producing said first output signal from said reception subband signal; selecting means for selecting the frequency gap bands of said down-link frequency band to produce a frequency gap signal from said second reception signal; and second producing means coupled to said second selecting means for producing said second output signal from said frequency gap signal.

Claim 4

An earth station as claimed in claim 2, said satellite communication system comprisng a base station, at least one fixed substation, and a movable station being capable of communicating with one another through said satellite by the use of said up-link frequency band and said down-link frequency band; said satellite communication system further comprising an additional satellite; said base station, said fixed substation, and said movable station being capable of communicating with one another through said additional satellite by the use of an additional up-link frequency band and an additional down-link frequency band; said earth station being operable as said base station, wherein said reception section further comprises: second receiving means for receiving an additional reception signal through the frequency gap bands of said additional down-link frequency band of said additional satellite to produce an additional frequency gap signal; third producing means coupled to said second receiving means for producing said second output signal from said additional frequency gap signal; detecting means coupled to said second and third producing means for detecting a first arrival time instant of said reception signal and a second arrival time instant of said additional reception signal to produce first and second detection signals, respectively; and calculating means responsive to said first and second detection signals for calculating the location of a selected one of said movable station.

Claim 5

An earth station as claimed in claim 2, wherein said first receiving means comprises selection means for selecting a predetermined one of said frequency subbands of said down-link frequency band to supply said reception subband signal.

Claim 6

An earth station as claimed in claim 2, wherein said selecting means comprises filter means for selecting said frequency gap bands of said down-link frequency band to supply said frequency gap signal

Claim 7

An earth station as claimed in claim 2, wherein said second producing means comprises delay means for delaying said frequency gap signal in a predetermined period to produce a plurality of delayed signals; adding means coupled to said delay means for adding said delayed signals to produce a sum signal; and a demodulator unit responsive to said sum signal for demodulating said sum signal to produce said second output signal.

Claim 8

An earth station as claimed in claim 6, wherein said demodulator unit comprises clock producing means responsive to said sum signal for producing a clock signal sequence; sampling means for sampling said sum signal by using said clock signal sequence to produce a sampled signal; and a demodulator responsive to said sampled signal for demodulating said sampled signal to produce said second output signal.