Radio-electric helicopter distance and angle measuring system - has ground based responder supplying information to on board interrogator via pulse width modulation

摘要

An interrogator on a helicopter contains a transmitter comprising a voltage controlled oscillator which transmits via an antenna. The signals are received at a responder which decodes the signal to cause transmission of pressure and direction signals via pulse width modulation. The signals are filtered (21) detected and applied to an frequency to voltage converter to receive the information. A period meter measures the timing of the signals to determine distance and speed from the responder. The system also has barometers to indicate altitude differences between two nearby points, allowing the local relief to be established.