Patent ID: 7260138

Claim:
A signal transmission device of base station which is used for base station of movable communication system using direct spread CDMA system, having a transmitter in which spread signal transmission data of all transmission channels are additively combined with each other to produce a quantized amplitude data and to change it to a modulation output signal of wireless carrier wave frequency by digital to analog conversion, and a transmission amplification means which amplifies a power of the modulation output signal to transmit waves as a transmission output to a movable station, said transmitter comprising: an additive composite means to produce a quantized amplitude data; a modulation means which converts the amplitude data to an analog base band signal in accordance with a level of its value and implements a modulation to wireless carrier wave frequency to change it to a modulation output; a variable attenuation means capable of controlling an attenuation amount of the modulation output signal level in accordance with a value of control signal to be input; an amplification means which amplifies an electric power in order to output the modulation output signal, of which level is controlled by the variable attenuation means, as a transmitter output to the transmission amplification means; a transmission power inspecting means inspecting the level of the transmitter output to the transmission amplification means and outputting a corresponding digital value as a transmission power data; a first mean value-calculating means calculating a mean value of the amplitude data per a predetermined time provided by the additive composite means and making it a transmission mean value which shows a mean value of the transmission power level to be required; a second mean value-calculating means calculating a mean value of the transmission power data per a predetermined time provided by the transmission power inspecting means and making it a transmission power mean value which shows a mean value of the actual transmission power; and a comparative control means comparing the transmission mean value provided by the first mean value-calculating means with a predetermined maximum transmission power value and, where the transmission mean value is not more than the maximum transmission power value, outputting a data for supplementing, as the control signal to the variable attenuation means, a difference between the transmission mean value and the transmission power mean value provided by second mean value-calculating means, or where the transmission mean value is more than the maximum transmission power value, outputting a data for supplementing, as the control signal to the variable attenuation means, a difference between the maximum transmission power value and the transmission power mean value.