A 3 V 1.9 GHz CMOS low-distortion direct-conversion quadrature modulator with a RF amplifier

A 3 V 1.9 GHz CMOS low-distortion direct-conversion quadrature modulator with an RF amplifier is described. The circuit is implemented using 0.5 /spl mu/m DPDM CMOS technology and dissipates only 95 mW (including power dissipation of RF amplifier) under 3 V power supply voltage. The unwanted lower sideband is below -80 dBc when the 0 dB normalized desired upper sideband is set at 1.9 GHz, corresponding to a small signal path mismatch. Moreover, the LO feedthrough and the second-order intermodulation are less than -80 dB. The third-order intermodulation of -60 dB is obtained. A current reuse technique is employed to save the power dissipation of RF amplifier such that the current in the negative resistor is reused in the gain stage. The gain of RF amplifier is 23 dB at 1.9 GHz center frequency. The power dissipation of RF amplifier is only 9 mW and smaller than in recent work.