A RF transmitter is operable to transmit a signal at a frequency specified by the Bluetooth protocol. A passive upconversion mixer, which comprises a pair of MOSFET switches, is utilized inside the RF transmitter. The passive upconversion mixer is operable to receive analog local oscillator (LO) signals to be utilized for controlling operation of each of the pair of MOSFET switches to transmit signals with maximum gain. A MOS threshold voltage VTH and a DC component of a received baseband signal, VBB—DC, are determined for each of the pair of MOSFET switches. The determined VTH and the determined VBB—DC of the received baseband signal are combined such as VTH+VBB—DC and compared with a DC component of the received LO signals, VLO—DC. The VLO—DC is set equal to VTH+VBB—DC, accordingly, to provide maximum gain from the passive upconversion mixer for signal transmission.