Two-Tone Intermodulation Measurement of W-band Amplifiers based on High-Linearity Frequency Down-Conversion

a two-tone intermodulation measurement system for W-band power amplifiers is constructed based on a high-linearity frequency down-conversion by using a subharmonic diode mixer. The linearity performance of the subharmonic diode mixer is measured, along with a diode harmonic mixer operated at 6th LO harmonic. A pair of W-band signal sources is combined to form a two-tone signal for measurement. The output signal of the device under test is coupled to the mixer for down conversion. The down-converting signal is them measured by a microwave signal analyzer. With suitable arrangement, the measured power level can be ranged from 0 dBm to -50 dBm, the measurement error over various power level is less than 0.33 dB. The estimated error contributed by the IMD terms introduced by the mixer is less than 0.17dB.