Abstract: An electromagnetic, reflective type, active proximity sensor includes a transmitter, the transmitter including a voltage controlled oscillator circuit, a transmitter circular waveguide and a transmitter polarization circuit. The voltage controlled oscillator circuit generates an output signal which is modulated such that the frequency of the output signal varies over time between a range of frequencies. The frequency varying, output signal is provided to the transmitter circular waveguide and propagated to the transmitter polarization circuit where it is circularly polarized in a first circular direction. The circularly polarized, frequency varying, output signal is radiated by the transmitter to the target, where it strikes the target and reflects back toward the sensor to form return signals. The return signals, upon being reflected, rotate in a second circular direction opposite to the first circular direction.

Abstract: A low power, low cost, millimeter wave (MMW) proximity sensor that provides over a 6:1 increase in minimum detection range (55 mm minimum) compared to standard 18 mm inductive proximity sensors preferably includes a low cost MMW Gunn oscillator, MMW detector and analog processing/driver circuitry. The sensor is preferably designed for 3-wire operation and will fit in a standard 18 mm tube.