| 摘要 |
PURPOSE: A 3FA wideband down converter in an IMT(International Mobile Telecommunication)-2000 BTS(Base Transceiver Station) is provided to increase CDMA receiving capacity at two times without additionally increasing a BTS by embodying a down converter capable of being applied to an IMT-2000 system as one module. CONSTITUTION: The first and second amplifiers(100,200) receive a wideband(3FA) RF(Radio Frequency) signal from a front end unit(1) and amplify the received wideband(3FA) RF signal. A band pass filter(300) receives the wideband(3FA) RF signal from the second amplifier(200) and filters a noise except for an original signal. A mixer(400) mixes the wideband(3FA) RF signal outputted from the band pass filter(300) with a local frequency and outputs a wideband(3FA) IF(Intermediate Frequency) signal. A tuning attenuator(500) receives the wideband(3FA) IF signal and adjusts the cell coverage of the wideband(3FA) IF signal. A low pass filter(600) receives wideband(3FA) IF signal from the tuning attenuator(500) and removes a higher noise. The third and fourth amplifiers(700,800) receive the wideband(3FA) IF signal from the low pass filter(600). A channel band pass filter(900) receives the wideband(3FA) IF signal from the fourth amplifier(800) and removes a noise of carrier both sides. A coupler(1000) receives the wideband(3FA) IF signal from the channel band pass filter(900) and divides the received wideband(3FA) IF signal into two paths(a,b). An A/D converter(1100) receives the wideband(3FA) IF signal from the output terminal(a) of the coupler(1000), converts the received wideband(3FA) IF signal into a digital signal, and divides the converted digital signal according to frequency bands(FA0,FA1,FA2). A digital down converter(1200) receives the three narrow band(FA0,FA1,FA2) IF signal from the A/D converter(1100), performs a digital filtering operation, performs a QPSK demodulation, and outputs the demodulated signal to a channel card(2). |
