Communications: directive radio wave systems and devices (e.g. – Testing or calibrating of radar system – By monitoring
Reexamination Certificate
2004-03-03
2004-12-14
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Testing or calibrating of radar system
By monitoring
C342S070000, C342S104000, C342S105000, C342S109000, C342S118000, C342S128000, C342S165000, C342S175000, C342S195000, C342S196000
Reexamination Certificate
active
06831595
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority of Japanese Patent Application number 2003-068860, filed on Mar. 5, 2003.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radar apparatus equipped with an abnormality detection function, and more particularly to an FM-CW radar apparatus equipped with a function for detecting an abnormality in the frequency modulation width.
2. Description of the Related Art
An FM-CW radar radiates forward a transmit wave frequency-modulated by a modulating signal of a triangular waveform alternating cyclically between an upsweep section and a downsweep section, and produces a beat signal by mixing the wave reflected from a target with a portion of the transmitted wave. When the frequency of the beat signal in the downsweep section is denoted by f
b
(down) and the frequency of the beat signal in the upsweep section by f
b
(up), the beat frequency f
r
due to the distance to the target and the beat frequency f
d
due to the relative velocity of the target are respectively calculated as
f
r
=(
f
b
(down)+
f
b
(up))/2 (1)
f
d
=(
f
b
(down)−
f
b
(up))/2 (2)
From these, the distance R to the target and the relative velocity V of the target can be respectively calculated as
R=c·f
r
·T
/4
&Dgr;F
(3)
V=c·f
d
·/2
f
0
(4)
(where c is the velocity of light, T is the period of the triangular wave, &Dgr;F is the frequency modulation width (frequency shift width), and f
0
is the center frequency.) Therefore, the values of f
b
(down) and f
b
(up) associated with each target are determined from the peaks appearing in the beat signal spectrum in the frequency domain obtained by Fourier transforming the beat signal, and the distance and the relative velocity of the target are determined by calculating the equations (1) to (4).
Here, the equation (3) can be rewritten as
f
r
=4
&Dgr;F·R/C·T
Therefore, if the modulation width &Dgr;F decreases, for example, to 50% for some reason, such as a failure, f
r
also decreases to 50% of the normal value; accordingly, the distance R calculated from the equation (3) also decreases to 50% of the actual distance, resulting in the generation of a false distance.
A possible method for detecting such a failure that causes &Dgr;F to change would be to directly monitor the transmission frequency by using a frequency dividing circuit and a counter.
This method, however, would require that a circuit for monitoring the transmission frequency be added in the FM-CW radar construction, and would thus lead to a substantial increase in cost.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to provide a radar apparatus equipped with a function for detecting an abnormality in the frequency modulation width at low cost.
A radar apparatus equipped with an abnormality detection function according to the present invention comprises: a distance measuring unit measuring a distance to a target; relative velocity measuring unit measuring a relative velocity with respect to the target; and a unit detecting a discrepancy between the measured distance and the measured relative velocity, based on the distance to the target measured by the distance measuring unit, the relative velocity measured by the relative velocity measuring unit with respect to the same target, and the elapsed time.
REFERENCES:
patent: 3735399 (1973-05-01), Sletten et al.
patent: 3935572 (1976-01-01), Broniwitz et al.
patent: 4180816 (1979-12-01), Endo et al.
patent: 5371718 (1994-12-01), Ikeda et al.
patent: 5590044 (1996-12-01), Buckreub
patent: 5920280 (1999-07-01), Okada et al.
patent: 6082666 (2000-07-01), Windhorst et al.
patent: 6278399 (2001-08-01), Ashihara
patent: 6335700 (2002-01-01), Ashihara
patent: 6384768 (2002-05-01), Kai
patent: 6414628 (2002-07-01), Ashihara
Christie Parker and Hale, LLP
Fujitsu Ten Limited
LandOfFree
Radar apparatus equipped with abnormality detection function does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Radar apparatus equipped with abnormality detection function, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Radar apparatus equipped with abnormality detection function will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3283045