This paper presents a high-linearity down-conversion mixer covering 24-30 GHz with a frequency doubler at the local oscillator (LO) port. Thanks to the doubler, the required LO frequency band is shrunk which ranges from 10 to 13 GHz. The core structure of the mixer uses a passive double-balanced structure to achieve high linearity, and a transimpedance amplifier (TIA) is developed to improve the impedance matching at the IF port and compensate for the insertion loss of the core. Post-layout simulation results show that the frequency conversion loss is less than 1 dB, and the input 1 dB compression point (IP 1dB ) is greater than 0 dBm when the LO power is 0 dBm. The return loss of RF/IF port is better than 10 dB/15 dB in the entire frequency band, respectively. The circuit consumes 32mW from a 1 V power supply and occupies a layout area of 1200×850 μm 2 including testing pads.