The AV1271X series harmonic mixer is mainly designed for millimeter-wave frequency extension of the microwave spectrum analyzer. Compared with its foreign counterparts, it covers a wider local power range to ensure the accuracy of amplitude measurement. The AV1271X series harmonic mixer can be used in frequency extension for AV4032, AV4033, HP70000, HP8560, and HP8566 series microwave spectrum analyzers. Besides, it may serve as the front end of the millimeter-wave signal receiver.