Sensor system

• US 6,255,984 B1
• Filed: 08/30/1999
• Issued: 07/03/2001
• Est. Priority Date: 02/28/1997
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Kreppold, Bernhard, Heide, Patric, Vossiek, Martin
• Primary Examiner(s): Gregory, Bernarr E.
• Application Number:
  US09/380,345
• Time in Patent Office: 673 Days
• Field of Search: 342/21, 342/22, 342/27, 342/28, 342/118-144, 342/175, 342/195, 342/202, 342/165, 342/169, 342/170-174, 342/200, 342/201
• US Class Current: 342/128
• CPC Class Codes: G01S 13/34 using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
• CPC Class Codes: G01S 7/4008 of transmitters
• CPC Class Codes: G01S 7/4056 specially adapted to FMCW

Abstract

FMCW doppler radar, in which a reference signal is generated from the transmit signal via a delay line and a mixer. A measuring signal which is received and mixed with the transmit signal is detected and digitized at the times of the zero crossings of the reference signal. In this way, the measuring signal can be evaluated at time intervals of equal phase of the reference signal. A downstream algorithm enables the generation of a strictly linearly frequency-modulated transmit signal. With this mechanism, phase errors of conventional radar systems are eliminated.

Claims

1. A sensor system comprising:

a signal source that generates a frequency-modulated (FM) signal that propagates in the manner of a wave,

a transceiver and a mixer, wherein said mixer mixes a signal coming from said transceiver with said FM signal, into a measuring signal,

a delay circuit, which chronologically delays said FM signal and mixes it with said FM signal, for purposes of generating a reference signal,

a detector circuit, which defines definite phases of said reference signal and which comprises two comparators which are arranged so that one comparator can be actuated with said reference signal, and the other comparator can be actuated with said reference signal shifted 180°

in phase, and

a measuring signal detector circuit for detecting said measuring signal at the instants of said definite phases and which determine a correction therefrom, with which said correction the modulation of said signal source is linearized.

2. The sensor system according to claim 1, wherein outputs of said comparators are conducted to monostable flip-flops (monoflops).

3. The sensor system according to claim 1, wherein said outputs of said comparators are conducted to a differentiator.

4. The sensor system according to claim 1

wherein said signal source is configured to deliver a linearly frequency-modulated signal.

5. The sensor system according to claim 1 comprising:

an evaluation circuit with a clock counter which is controlled by an output signal of detector circuit, wherein said evaluation circuit is so arranged and of such a nature that it calculates a correction signal from values delivered by said clock counter, wherein said correction signal is fed to said signal source, and

a frequency trimming circuit which trims the frequency of said FM signal such that the absolute value of said correction signal remains below a predefined limit.

6. The sensor system according to claim 5, wherein said evaluation circuit can generate a modulation which is mirrored with respect thereto for stored values of a modulation.

7. The sensor system according to claim 5, wherein

said evaluation circuit comprises a digital signal processor, and

said sensor system comprises a digital-analog converter, which converts a digitally computed correction signal into an analog correction signal.

8. The sensor system according to claim 1, wherein

said delay circuit comprises a surface wave component and an additional mixer, wherein

said additional mixer is so arranged as to be able to mix, into reference signal, a signal coming from said surface wave component and said FM signal.

9. The sensor system according to claim 1 comprising:

an analog-digital converter that has a trigger,

an arrangement comprising said detector circuit and said analog-digital converter,

wherein said arrangement produces an output signal from said detector circuit which controls said trigger, and

said analog-digital converter converts said measuring signal to a digital output signal in cycle with said detector circuit control, and

an evaluation circuit allowing an evaluation of said measuring signal from said output signal.

10. The sensor system according to claim 9 wherein said evaluation circuit allows a correction of a signal medium delivered by said signal source.