A 1.9-GHz-band GaAs direct-quadrature modulator IC with a phase shifter

A 1.9-GHz-band direct-quadrature modulator IC has been successfully developed for digital portable telephone use. In the 1.9-GHz high-frequency band, both image and carrier rejections as low as -40 dBc have been obtained with a low-power dissipation of 110 mW at a single power supply of 3.1 V, corresponding to a phase error below 1.1. In order to reduce undesired sideband spectral components required for digital modulation, a newly developed circuit configuration that combines a quadrature phase shifter with drivers for amplitude imbalance compensation and makes spectrum efficiency and low-power dissipation possible is used. The modulator IC may be used in enhanced digital mobile radiocommunication systems such as digital portable telephones.>