Radar apparatus

• US 20030016163A1
• Filed: 07/11/2002
• Published: 01/23/2003
• Est. Priority Date: 07/11/2001
• Status: Active Grant

• Current Assignee: Fujitsu Ten Limited (DENSO Corporation)
• Original Assignee: Fujitsu Ten Limited (DENSO Corporation)
• Inventors: Isaji, Osamu
• Granted Patent: US 6,597,308 B2
• Time in Patent Office: Days
• US Class Current: 342/70
• CPC Class Codes: G01S 13/345 using triangular modulation
• CPC Class Codes: G01S 13/931 of land vehicles
• CPC Class Codes: G01S 2013/9329 cooperating with reflectors or transponders
• CPC Class Codes: G01S 7/35 Details of non-pulse systems
• CPC Class Codes: G01S 7/4008 of transmitters

Abstract

A modulation signal generation circuit performs frequency modulation of a VCO with a triangular wave for operation as an FM-CW radar. A signal processing circuit gives a modulation signal for detection generated from the modulation signal generation circuit to the VCO. A high-frequency signal subjected to frequency modulation in the VCO is transmitted as a radio wave from a transmission antenna and is reflected on a target and the reflected radio wave is received at a reception antenna. The reception signal and the high-frequency signal are mixed by a mixer to provide a beat signal and frequency shift corresponding to a voltage V1 is detected from the frequency of the beat signal. If the voltage V1 of the modulation signal for detection is switched, the frequency shift corresponding to different voltage V1 can be provided and the frequency modulation characteristic can be detected.

Claims

1. A radar apparatus for performing frequency modulation of a high-frequency signal, transmitting the frequency-modulated signal, and receiving a reflected radio wave to detect a target, the radar apparatus comprising:

a high frequency generation section for generating the high-frequency signal;

a modulation signal generation section for generating and giving a modulation signal to the high frequency generation section to modulate the high frequency signal;

a mixing section for mixing the high-frequency signal and the reception signal of the reflected radio wave; and

a signal processing section for controlling the modulation signal generation section so as to give a modulation signal for detection changing among a plurality of predetermined signal levels and retained for a predetermined time for each signal level to the high frequency generation section, detecting frequency of a differential signal between the high-frequency signal and the reception signal, inputted from the mixing section, and detecting a frequency modulation characteristic of the high frequency generation section based on the relationship between a signal level of the modulation signal for detection and the frequency of the differential signal.

2. The radar apparatus according to claim 1, further comprising a modulation characteristic correction section for correcting the modulation signal based on the frequency modulation characteristic detected by the signal processing section so that the frequency modulation characteristic is not placed out of a predetermined normal range.

3. The radar apparatus according to claim 1, further comprising a width calculation section for calculating frequency modulation width, which is a difference between frequency of the differential signal when the signal level of the modulation signal is the maximum value and frequency of the differential signal when the signal level is the minimum value based on the frequency modulation characteristic detected by the signal processing section.

4. The radar apparatus according to claim 3, wherein the width calculation section includes a counter for counting the frequency of the difference.

5. The radar apparatus according to claim 3, further comprising a width correction section for correcting the modulation signal based on the frequency modulation width calculated by the width calculation section so that the frequency modulation width has a predetermined value.

6. The radar apparatus according to claim 2, wherein one of the modulation characteristic correction section and the width correction section performs the correction when the level of the reception signal of the reflected radio wave is equal to or greater than a predetermined level.

7. The radar apparatus according to claim 2, further comprising a temperature detection section,

wherein one of the modulation characteristic correction section and the width correction section performs the correction when a temperature detected by the temperature detection section has a predetermined temperature.

8. The radar apparatus according to claim 2, wherein one of the modulation characteristic correction section and the width correction section performs the correction when a distance to the target is in a predetermined distance range.

9. The radar apparatus according to claim 2, wherein one of the modulation characteristic correction section and the width correction section performs the correction when relative speed of the target is in a predetermined speed range.

10. The radar apparatus according to claim 1, wherein the signal processing section detects the frequency modulation characteristic when an input level of the reflected radio wave from the target is equal to or greater than a predetermined reference level at a normal radar operation time.

11. The radar apparatus according to claim 1, wherein the signal processing section detects the frequency modulation characteristic when a distance to the target is in a predetermined distance range.

12. The radar apparatus according to claim 1, wherein the signal processing section detects the frequency modulation characteristic just after detecting the target initially after a radar operation starts and determines whether or not a normal modulation operation for the high frequency generation section is performed.

13. The radar apparatus according to claim 1, further comprising a reference signal source for generating a reference signal to decrease a frequency with respect to the differential signal between the high-frequency signal and the reception signal, the differential signal inputted to the signal processing section from the mixing section,

wherein the signal processing section detects the frequency modulation characteristic based on the inputted differential signal with the frequency decreased by the reference signal.

14. The radar apparatus according to claim 13,

wherein the reference signal source comprises:

a basic signal generation section for generating a basic signal, which is a source of the reference signal; and

a frequency division section for dividing the frequency of the basic signal generated from the basic signal generation section according to one of frequency dividing ratios that can be switched to convert the basic signal into the reference signal.

15. The radar apparatus according to claim 13, wherein the reference signal source includes a plurality of reference signal generation sections and selects one of the reference signal generation sections to generate the reference signal.

16. The radar apparatus according to claim 13, wherein the reference signal source comprises a signal arithmetic section for generating the reference signal by performing arithmetic processing according to a preset program.

17. The radar apparatus according to claim 13, wherein the reference signal source supplies a clock signal for a signal arithmetic processing to the signal processing section.

18. The radar apparatus according to claim 13, wherein a frequency of the reference signal is set so that a difference from the frequency of the reception signal from the target is within a beat signal band at a time of a radar operation.

19. The radar apparatus according to claim 18, wherein the signal processing section performs at least a part of processing of the beat signal.

20. The radar apparatus according to claim 1, wherein the signal processing section changes a predetermined time for holding a signal level of the modulation signal for detection in response to a distance to the target.

21. The radar apparatus according to claim 1, wherein the signal processing section changes a predetermined time for holding a signal level of the modulation signal for detection in response to a relative speed of the target.

22. The radar apparatus according to claim 1, wherein the signal processing section detects the frequency of the differential signal between the high-frequency signal and the reception signal considering a Doppler shift based on a relative speed of the target.