AbstractIn this paper, a new millimeter‐wave gain equalizer based on metallic rectangular waveguide is presented, which is implemented by E‐plane microstrip‐line probe, metal rectangular waveguide resonator, waveguide coupling groove, and thin‐film resistor. The proposed gain equalizer has good tunability, high Q factor, and high power capacity. To demonstrate its performance, a modified gain equalizer, operating 90 to 97 GHz, is designed and fabricated. The final equalizer has achieved better performance and satisfied the need of actual application under a working range from 90 to 97 GHz.