Methods and apparatuses are presented for harmonic reject upconverting a baseband signal using at least one quadrature passive upconversion mixer. In some embodiments, an apparatus may include a first quadrature passive mixer configured to receive a first baseband input and a first LO input, and a second quadrature passive mixer configured to receive a second baseband input and a second LO input. A first output of said first passive mixer may be directly connected to a first output of said second passive mixer and together coupled to a first amplifier input. A second output of said first passive mixer may be directly connected to a second output of said second passive mixer and together coupled to a second amplifier input. The transmitter may be configured to output an upconverted signal with at least one rejected harmonic spurious mixing product based on the first and second amplifier inputs.