Passive wireless sensors include an antenna. The antenna receives a combined signal. The combined signal includes a low frequency modulating signal modulated on a high frequency carrier wave. A demodulator receives the combined signal and extracts the modulating signal. A sensor receives the extracted modulating signal and produces an output signal with a time delay indicative of a property to be sensed. A modulator receives the output signal and the high frequency carrier wave and modulates the output signal onto the high frequency carrier wave to create a combined output signal broadcast by the antenna.