ABSTRACTThis paper presents the design of a D‐band [110–170 GHz] thermoelectric power sensor for millimeter‐wave applications. The sensor is based on a transition between a rectangular waveguide and a coplanar waveguide, a matched load and a thermopile; a series of nickel/chromium thermocouple junctions. The sensor exhibits satisfactory performance, maintaining a return loss lower than −18 dB and an efficiency of over 80% through the entire D‐band. The sensitivity of the power sensor is about 0.1 mV/mW at 170 GHz.