A compact CMOS 2 V low-power direct-conversion quadrature modulator merged with quadrature voltage-controlled oscillator and RF amplifier for 1.9 GHz RF transmitter applications

A compact 2 V CMOS low-power direct-conversion quadrature modulator merged with quadrature voltage-controlled oscillator (VCO) and RF amplifier for 1.9 GHz RF transmitter applications is described. The circuit is implemented by using 0.35 /spl mu/m DPTM CMOS technology and dissipates only 19 mW under 2 V power supply voltage. The low power operation is enabled by the current reuse technique used among quadrature modulator, quadrature VCO, and RF amplifier. Due to small signal path mismatch, the unwanted lower sideband is below -50 dB when the 0 dB normalized desired upper sideband is set at 1.97 GHz. Moreover, the LO feedthrough, second-order intermodulation, and third-order intermodulation are less than -50 dB. The tuning range of the quadrature VCO is 270 MHz from 1.95 GHz to 2.22 GHz.