Patent ID: 7058037

Claim:
An RF transmitting device of a mobile radio communication base station system in a CDMA system having a plurality of channel cards providing baseband signals on I/Q channels for multi-frequency assignment and a transmitting antenna, said RF transmitting device comprising: a plurality of digital modulators for digital modulating the baseband signals on the I/Q channels to frequencies according to a frequency assignment, wherein the baseband signals are provided from said plurality of channel cards, wherein each of said digital modulators comprises a digital local oscillator for outputting one of a plurality of local frequencies, and a digital mixer for generating mixed signals by mixing the baseband signals on the I/Q channels with respective ones of the plurality of local frequencies; a digital adder for coupling the mixed signals; a digital to analog converter for converting the coupled mixed signals into an analog-converted multi-frequency signal; an analog frequency up-converting unit for up-converting the analog-converted multi-frequency signal in said digital unit into an IF signal and a secondarily up-converting the converted IF signal into an RF signal, wherein said analog frequency up-converting unit comprises a first frequency up-converter for up-converting the coupled multi-frequency assignment analog signal outputted from said digital unit into an arbitrary IF signal; a band-pass filter for band-pass filtering the coupled multi-frequency assignment IF signal outputted from said first frequency up-converter to an arbitrary frequency bandwidth; and a second frequency up-converter for converting the IF signal filtered in said band-pass filter into an RF signal to thereby output the converted RF signal to said transmitting unit, and wherein said band-pass filter is an SAW filter having the bandwidth of 3.75 MHz, in order to accurately pass the multi-frequency assignment coupled signal; and a transmitting unit for amplifying the secondarily up-converted RF signal to an arbitrary transmitting output level and transmitting the amplified signal via said transmitting antenna.