Smart blind spot sensor

  • US 5,325,096 A
  • Filed: 08/25/1993
  • Issued: 06/28/1994
  • Est. Priority Date: 08/14/1992
  • Status: Expired due to Term
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First Claim
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1. A system for detecting the presence of targets moving at slow speeds relative to the vehicle upon which the system is mounted and adjacent to, and on at least one side of, the vehicle upon which the system is mounted, including:

  • (a) a transceiver for emitting signals along side a vehicle upon which the system is mounted and for receiving reflections of the emitted signals;

    (b) a Doppler circuit, coupled to the transceiver, for generating a Doppler signal having a frequency equal to the difference between the emitted signal and the received reflections;

    (c) a signal processing section including;

    (1) an amplifier, coupled to the Doppler circuit, for amplifying the Doppler signal such that only targets within a range of approximately 15 feet of the transceiver are detected;

    (2) a sample and hold circuit, coupled to the amplifier, for sampling the output of the amplifier during periods concurrent with the emission of the emitted signals and generating a signal having a voltage level that is proportional to the phase difference between the emitted signal and received reflections;

    (3) a low pass filter, coupled to the output of the sample and hold circuit, for filtering high frequency components and signals which represent objects moving rapidly relative to the vehicle upon which the system is mounted from the signal output by the sample and hold circuit;

    (4) square wave generator coupled to the low pass filter for generating a square wave output having a frequency equal to the filtered signal;

    (5) malfunction detector circuit, coupled to the output of the square wave generator and the output of the sample and hold circuit, for sensing the level of the direct current offset of the signal generated by the sample and hold circuit, to determine when the system is operating within specified limits, and indicating a malfunction in the detection system when the system is not operating within the specified limits;

    (6) a persistence period circuit, coupled to the square wave generator, for generating an output equivalent to the output of the square wave generator when an object is present for a predefined minimum persistence period;

    (d) an indicator circuit, coupled to the persistence period circuit, for receiving the output of the persistence circuit and indicating to an operator of the vehicle on which the system is mounted, the presence of an object which is detected for a period which is longer than the persistence period.

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