Abstract: A 2. 8-6GHz on-chip double-balanced passive mixer is presented in this paper, which is fabricated in WIN′s GaAs 0. 15 μm pHEMT process. Spiral-shaped Marchand baluns of different sizes are utilized in the LO and RF ports of the mixer to reduce chip size and improve port matching without any redundant circuit. As demonstrated in measurement results, the mixer′s conversion loss and return reflection are less than 8 dB and -10 dB, respectively, its RF-LO isolation is better than 40 dB, as well as its IP1dB is better than 10 dBm and IIP3 is better than 17 dBm. The measurement results agree well with the simulation ones, and the overall size of the chip is 1. 4 mm×1. 1 mm.