A 220-GHz Third-Harmonic Mixer Based on Balanced Structure and Hybrid Transmission Line

This paper proposes a novel 220-GHz third-harmonic mixer, which using a waveguide-fin-coplanar waveguide-microstrip line hybrid transmission line as the carrier circuit, based on the balanced structure and the co-directional diode pair. The hybrid transmission line is designed to allow the mixing signals to be input in the correct direction in order to achieve the third-harmonic mixing. Then, high isolation between the radio-frequency (RF) port and the local oscillator (LO) port is performed through the mode orthogonality of the balanced structure. The metal slots on the fin line are used as the matching network for the RF signal to enable the RF signal into the diode pair with low loss. The experimental test results show that the conversion loss of the third-harmonic mixer is better than 18.5 dB in the range of 210–230 GHz and has a tiny fluctuation in the broad range of intermediate frequency (IF).