Fmcw Radar with Restricted Emission Time to Avoid Aliasing Effects

• US 20070216568A1
• Filed: 11/20/2002
• Published: 09/20/2007
• Est. Priority Date: 11/28/2001
• Status: Abandoned Application

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Kunert, Martin
• Application Number:
  US10/496,960
• Publication Number:
  US 20070216568A1
• Time in Patent Office: Days
• US Class Current: 342/107
• 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

Abstract

The invention relates to a radar system comprising an evaluation device (10) which determines the speed and/or the distance of at least one object to be located, on the basis of a spectral analysis of a measuring signal (h(t)) consisting of an emission signal and a reception signal (R(t)). According to the invention, means (12) are used to limit the emission time (τ_{a on}) of the emission signal (T(t)) in order to avoid aliasing effects.

Claims

1. Radar system with an evaluation device (10) which, on the basis of a spectral analysis of a measuring signal (h(t)) formed from an emission signal (T(t)) and a reception signal (R(t)), determines the speed and/or distance of at least one object to be located

characterized in that

means (12) are provided which limit the emission time (τ

<sub>a—

on</sub>) of the emission signal (T(t)) to avoid aliasing effects.

2. Radar system according to claim 1

characterized in that

through limiting of the emission time (τ

<sub>a—

on</sub>) of the emission signal (T(t)) a pulse-shaped emission signal (T(t)) is generated whose emission pulse length (τ

<sub>a—

on</sub>) determines the maximum measuring range.

3. Radar system according to claim 2

characterized in that

the emission pulse length (τ

<sub>a—

on</sub>) of the emission signal (T(t)) is variable.

4. Radar system according to claim 2 or 3

characterized in that

to determine the maximum measuring range changing take place between at least two emission pulse lengths (τ

<sub>a—

on</sub>)

5. Radar system according to one of the preceding claims

characterized in that

the measuring signal is a digital measuring signal (h(t)).

6. Radar system according to claim 5

characterized in that

the digital measuring signal (h(t)) is obtained from a mixer out-put signal (i(t)) of a mixer (20).

7. Radar system according to claim 6

characterized in that

the digital measuring signal (h(t)) is supplied by an analog-digital converter (14) whose sampling frequency is variable.

8. Radar system according to claim 7

characterized in that

the mixer output signal (i(t)) is buffered by a sample and hold circuit (18) before being routed to the analog-digital converter (14).

9. Radar system according to claim 8

characterized in that

the sample time (τ

<sub>s—

on</sub>) of the sample and hold circuit (18) can be set independently of the emission pulse length (τ

<sub>a—

on</sub>).

10. Radar system according to claim 8 or 9

characterized in that

the sample time (τ

<sub>s—

on</sub>) of the sample and hold circuit (18) is delayed with respect to the emission pulse length (τ

<sub>a—

on</sub>).

11. Radar system according to one of the claims 8 to 10

characterized in that

the sample time (τ

<sub>s—

on</sub>) of the sample and hold circuit (18) is less than or the same as the emission pulse length (τ

<sub>a—

on</sub>).

12. Radar system according to one of the claims 8 to 11

characterized in that

the input of the sample and hold circuit (18) is taken outside the sample time (τ

<sub>a—

on</sub>) to a low-resistance operating point.

13. Radar system according to one of the preceding claims

characterized in that

the emission signal is a frequency-modulated emission signal (T(t)).

14. Radar system according to claim 13

characterized in that

the frequency of the frequency-modulated emission signal (T(t)) is varied at least at times, in particular for determining the distance from an object to be located.

15. Radar system according to claim 13 or 14

characterized in that

the frequency of the frequency-modulated emission signal (T(t)) is continuously varied.

16. Radar system according to claim 13 or 14

characterized in that

the frequency of the frequency-modulated emission signal (T(t)) is varied in discrete frequency stages.

17. Radar system according to claim 16

characterized in that

the discrete frequency stages can be started up in any sequence.

18. Radar system according to claim 13

characterized in that

the frequency of the frequency-modulated emission signal (T(t)) is kept constant at least at times, in particular for determining the speed of an object to be located.

19. Radar system according to one of the preceding claims

characterized in that

the settable emission time (τ

<sub>a—

on</sub>) is matched to measuring ranges required in the area of motorized vehicles and is in particular between 20 ns and 200 ns.