This article presents a double-balanced up-conversion ring mixer based on complementary switches operating at millimeter-wave frequencies. Complementary-switching relieves the mixer from the need for a differential Local-Oscillator (LO) signal, simplifying the design and improving the circuit performance. A prototype, capable of operation between 18 GHz and 32 GHz, is implemented in a 22 nm FD-SOI CMOS technology offering n-and p-type transistors with comparable performance. Furthermore, the presented circuit also exploits the back-gate control voltage offered by the process to minimize the transistors threshold voltage, reducing the minimum LO power required to saturate the mixer gain. Measurements showed a conversion gain of-5.5 dB, an output power at 1 dB gain compression (o1dBCp) of-7 dBm, and a Radio-Frequency (RF) bandwidth of 10 GHz. These results were demonstrated for an LO power of 3 dBm at 23.5 GHz or 28 GHz, a DC power of 2.2mW, and all the mixer ports matched to 50 Ω. The active area of the chip is 0.11mm2, the smallest so far demonstrated for ring mixers. These performances translate in the best-reported figure of merit, which relates gain, RF up-converted power, and required DC and LO power.