Abstract <p>A polarization-modulation method for determining the pitch angle of an aircraft using emitted horizontally polarized beacon signals is considered. The polarization modulator placed in the microwave channel of the airborne receiving antenna is a Faraday rotator for the polarization plane of received beacon signals. The pitch angle is determined by the second-harmonic phase of the polarization-plane rotation frequency, which is contained in the envelope spectrum of the receiver output signal. A prototype of the experimental setup implementing this method is described. Results of aircraft pitch angle measurements are presented, and the measurement accuracy is estimated.</p>