Microwave diode models included in commercial simulators use a large set of parameters, so they are often difficult to set up in order to match the actual response of a specific device. In this paper a simple model for a zero-bias microwave Schottky diode is presented. Noise characteristics are determined by measurements and then incorporated to the large signal model offered by the manufacturer in the diode datasheet. Using this model a diode power detector in large signal operation is simulated with commercial software, achieving excellent agreement with the measurement results, both in terms of power sensitivity and noise spectrum.