| 摘要 |
A sensor front end is disclosed that is able to discriminate objects based on their range from the sensor. The sensor includes an antenna that transmits a sensor signal and, if an object is present receives a reflected signal therefrom. A pulsed oscillator provides a pulsed first signal having a first frequency and phase, and wherein the pulsed oscillator provides the pulsed first signal for a predetermined pulse duration and with a predetermined pulse repetition frequency. The pulsed oscillator provides the p0pul sed first signal to a first input port of a dual mode mixer that is further coupled to the antenna via a second port. The dual mode mixer transmits a portion of the pulsed first signal from the first input port to the second port and thus to the antenna to be transmitted as the sensor signal. In addition, the dual mode mixer then provides a mixed signal as an output at a third port. Thus, the pulsed first signal provides both the signal to be transmitted as the sensor signal and the local oscillator signal for the mixer as well. The dual mode mixer will only provide a mixed signal output if the received reflected signal is present in the dual mode mixer concurrently with the pulsed first signal. Accordingly, an object can only be detected when the range to the object is such that the signal propagation time to and from the object is less than or equal to the predetermined pulse length of the pulsed first signal.
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