Design of W-Band Wide Intermediate Frequency Fundamental Mixer Based on Finline

This paper presents a wideband intermediate frequency (IF) mixer based on finline in the W-band. The mixer adopts a local oscillator (LO) anti-parallel configuration. The LO signal is input through a waveguide-to-microstrip probe transition, while the RF signal is input through a waveguide-to-single-sided symmetrical finline transition. The two mixing diodes are anti-parallel connected between the finline and microstrip line. By utilizing the orthogonal electric field characteristics between the finline and microstrip line, as well as the high-pass characteristic of the LO waveguide, the need for RF and LO filtering at the input ports is eliminated, reducing circuit length. The mixer incorporates a suspended microstrip line dual-sided coupling structure as the connecting line in the LO-IF duplex structure, eliminating the transmission nulls in the IF passband and increasing the bandwidth of the IF signal transmission. Simulation results demonstrate that the conversion loss of the mixer in the 65-110 GHz is within the range of 5 dB to 7.6 dB, and the IF signal can reach up to 40 GHz.