2.1 GHz direct-conversion GaAs quadrature modulator IC for W-CDMA base station

In a W-CDMA base station, communication quality directly depends on RF-block dynamic range. Direct-conversion modulation is an effective method to enhance the system dynamic range by eliminating the intermediate frequency (IF) blocks. In this method, baseband signals are directly quadrature-modulated at radio frequencies (RF), and the dynamic range of the RF block depends mainly on RF characteristics of the quadrature modulator (QMOD). This type of modulation, however, has difficulty in obtaining modulating accuracy and low adjacent-channel leakage power ratio (ACPR). Especially lower ACPR is required in the WCDMA system, because the channel is required to have -4 MHz spread and 5 MHz carrier spacing.