METHOD OF AND AN APPARATUS FOR ELIMINATING MISLEADING DOPPLER SIGNALS IN A DOPPLER RADAR SPEED-MEASURING SYSTEM

• US 3,618,084 A
• Filed: 11/25/1969
• Issued: 11/02/1971
• Est. Priority Date: 11/25/1968
• Status: Expired due to Term

• Current Assignee: Kurt Piechocki, Rudolf Balsiger
• Original Assignee: Kurt Piechocki, Rudolf Balsiger
• Inventors: Balsiger, Rudolf, Piechocki, Kurt
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US04/879,799
• Time in Patent Office: 707 Days
• Field of Search: 343/7A,8
• US Class Current: 342/91
• CPC Class Codes: G01S 13/92 for velocity measurement

Abstract

Method and apparatus for eliminating misleading Doppler signals in a Doppler radar speed-measuring system in which a measured value derived from the doppler frequency is differentiated to detect portions of the Doppler frequency in excess of a given threshold value which varies with the detected speed, and timing means is provided for controlling the period of time of receipt of proper Doppler signals, the time period of control also being varied in accordance with the measured speed.

Claims

1. A method of eliminating misleading Doppler frequency signals in a Doppler radar speed-measuring system in which a measured value derived from the Doppler frequency is passed on to control a speed indication stage only if it is a proper signal comprising detecting the time differential of said measured value derived from the Doppler frequency, preventing passage of said Doppler frequency signals to said speed indication stage when said time differential exceeds a given tolerance range, and varying said tolerance range in accordance with the level of said measured value.

2. A method according to claim 1, wherein said tolerance range is varied proportionally to said measured value.

3. A method according to claim 1, wherein said tolerance range us varied substantially proportionally to the square of said measured value.

4. A method according to claim 1, wherein passage of said Doppler frequency signals to said speed indication stage is prevented where said time differential exceeds said tolerance range at least once within a predetermined time interval.

5. A method according to claim 4, further including the step of varying said predetermined time interval in inverse proportion to said measured value and hence to the speed of the vehicle under observation.

6. An apparatus for eliminating misleading Doppler frequency signals in a Doppler radar speed-measuring system comprising differentiating means for differentiating a measured value signal derived from the Doppler frequency signals, threshold circuit means connected to the output of said differentiating means for generating a control signal only in response to the differentiated measured value signal falling within a given tolerance range, said control signal enabling measurement of speed from said Doppler frequency signals, control means responsive to the level of said measured Value signal for varying said tolerance range of said threshold circuit means.

7. An apparatus as claimed in claim 6, wherein said control means includes means for varying said tolerance range in proportion to the level of said measured value signal.

8. An apparatus as claimed in claim 6, wherein said control means includes means for varying said tolerance range in proportion to the square of said measured value.

9. An apparatus as claimed in claim 6, wherein said measured value signal is an analog of said Doppler frequency signals and said differentiating means includes a differentiator receiving said measured value signal at its input and providing a time differential signal at its output.

10. An apparatus as claimed in claim 9, wherein a limiter is connected at the input of said differentiator.

11. An apparatus as claimed in claim 10, wherein a phase reversal stage is connected to the output end of the differentiator.

12. An apparatus as claimed in claim 11, wherein said threshold circuit means includes a switching transistor circuit and diode means connecting said differentiating means to said switching transistor circuit and biased in response to the level of said measured value signal for controlling the conduction of said switching transistor circuit.

13. An apparatus as claimed in claim 12, wherein said limiter, the differentiator, the phase reversal stage, the threshold circuit means with its speed-dependent tolerance range and switching transistor circuit are connected in series.

14. An apparatus as claimed in claim 9, wherein two diodes are connected antiparallel and are connected at one end to a fixed potential and are galvanically connected at another end to an emitter terminal of a transistor in said differentiator.

15. An apparatus as claimed in claim 6, further including timing means responsive to the output of said threshold circuit means for enabling measurement of speed from said Doppler signals only after generation of said control signal continuously for a given period of time.

16. An apparatus as claimed in claim 15, wherein said timing means includes means connected in receipt of said measured value signal for varying said give time period in inverse proportion to the level of said measured value signal.

17. An apparatus as claimed in claim 6, further including a timing circuit including a capacitor and a resistance for discharging the capacitor, one terminal of the capacitor being connected to a source of constant potential and the other terminal being connected to a switching point which is connected to a first switch circuit connected to the output of the threshold circuit means, to the input of a second switch circuit via a diode and to one end of said resistance, to other end of said resistance being galvanically connected to a terminal at said measured value, the output of said second switching means providing a control for passage of said Doppler frequency signals.

18. An apparatus as claimed in claim 9, wherein said threshold circuit means includes a switching transistor circuit and diode means connecting said differentiating means to said switching transistor circuit and biased in response to the level of said measured value signal for controlling the conduction of said switching transistor circuit.

19. An apparatus as defined in claim 18, further including a timing circuit connected to the output of said switching transistor circuit for permitting measurement of the Doppler frequency only after receipt of said control signal at the output of said switching transistor circuit continuously for a given time period.

20. An apparatus as claimed in claim 19, wherein said timing means includes means connected in receipt of said measured value signal for varying said given time period in inverse proportion to the level of said measured value signal.