A truly balanced operation of a 5.2-GHz Gilbert micromixer with a single-ended input and a single-ended output is demonstrated using 2-μm GaInP/GaAs HBT technology. Because the micromixer has a single-ended input, a passive LC current combiner is used to convert the mixer-differential output into a single-ended output. A cross-coupled LC oscillator with oscillation frequency of 4.3 GHz and a cascode buffer amplifier are also integrated in the same chip. The fully integrated upconversion micromixer has conversion gain of -2.5 dB and OP1dB of -12.5 dBm when input IF = 0.9 GHz and thus output RF = 5.2 GHz. The IF input return loss is better than 25 dB for frequencies up to 6 GHz. while the RF output return loss is better than 12 dB for frequencies from 5.15 to 5.35 GHz.