A 2-V 2-GHZ SI-BIPOLAR DIRECT-CONVERSION QUADRATURE MODULATOR

A 2-GHz Si-bipolar direct-conversion quadrature modulator with a wide bandwidth is described, It operates at a low supply-voltage of 2 V and features a ''current-folded'' double-balanced mixer with a two-stacke d-transistor configuration, and a tunable RC/CR 90 degrees phase shift er that reduces the amplitude imbalance and the phase error over a wid e bandwidth (0.8 to 2 GHz). The modulator is implemented using 18-GHz Si-bipolar technology and dissipates only 68 mW at 2 V. The image rati o at 2 GHz is about -37 dBc, corresponding to a phase error of 1.6 deg rees. Moreover, both second order and third-order products, and local signal leakage are less than -40 dBc.