Communications: directive radio wave systems and devices (e.g. – Return signal controls external device – Radar mounted on and controls land vehicle
Reexamination Certificate
1999-09-21
2001-04-17
Sotomayor, John B. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Return signal controls external device
Radar mounted on and controls land vehicle
C342S092000, C342S107000, C342S158000
Reexamination Certificate
active
06218981
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a radar device for vehicle used for measuring, for example, following-on distances.
2. Discussion of Background
A FM-CW radar device as illustrated in
FIG. 11
is known as a radar device for vehicle, wherein the radar device is miniaturized using an antenna for transmitting and receiving to improve applicability to a vehicle. In
FIG. 11
, numerical reference
1
designates an oscillator; numerical reference
2
designates a power divider; numerical reference
3
designates a transmitting amplifier; numerical reference
4
designates a circulator; numerical reference
5
designates a transmitting and receiving antenna composed of a hone antenna
51
and a reflecting mirror antenna
52
; numerical reference
6
designates a target object; numerical reference
7
designates a receiving amplifier; numerical reference
8
designates a mixer; numerical reference
9
designates a filter; numerical reference
10
designates an automatic gain control (AGC) amplifier; numerical reference
11
designates an A/D converter; numerical reference
12
designates a signal processing unit; numerical reference
13
designates an antenna scanning motor; and numerical reference
14
designates a steering angle sensor. A transmitting means is composed of numerical references
1
through
5
; a receiving means is composed of numerical references
4
,
5
,
7
and
8
; a signal processing means is composed of numerical references
9
through
12
; and a scanning means is composed of numerical references
13
and
52
.
An operation of thus constructed conventional device will be described. The signal processing unit
12
outputs linear voltage signals for frequency modulation. The oscillator
1
generates electromagnetic waves subjected to frequency modulation by the voltage signals for frequency modulation. The electromagnetic waves are divided into two parts by a power divider
2
, wherein one of the parts is inputted in the mixer
8
. The other part of the electromagnetic waves is amplified by the transmitting amplifier
3
. Thereafter, it passes through the circulator
4
and outputted into space from the transmitting and receiving antenna
5
. The electromagnetic waves outputted to space from the transmitting and receiving antenna
5
are reflected by the target object
6
and inputted in the transmitting and receiving antenna
5
as receiving electromagnetic waves having a delay time Td with respect to the transmitted electromagnetic waves. Further, when the target object
6
has a relative velocity with respect to the radar device, the receiving electromagnetic waves are inputted in the transmitting and receiving antenna
5
with a Doppler shift fd with respect to the transmitting electromagnetic waves. The electromagnetic waves received by the transmitting and receiving antenna
5
are amplified by the receiving amplifier
7
. Thereafter, these electromagnetic waves are mixed with the transmitting electromagnetic waves by the mixer
8
to output beat signals corresponding to the delay time Td and the Doppler shift fd. The obtained beat signals pass through the filter
9
and are inputted in the A/D converter
11
after being amplified in the AGC amplifier
10
. The signal processing unit
12
calculates a relative range and a relative velocity for the target object
6
from the beat signals.
In the next, a method of calculating the relative range and the relative velocity will be described.
FIG. 12
is an example of calculating a relative range and a relative velocity using the above-mentioned radar device, wherein an ordinate represents a frequency f and an abscissa represents a time t. In
FIG. 12
, a transmitting electromagnetic wave
100
is subjected to frequency modulation with a frequency bandwidth in sweeping B and a modulation period Tm. The receiving electromagnetic waves
101
,
102
has a delay time Td between a reflection of the transmitting electromagnetic wave by the target object
6
existing at a position of a range R and an input in the transmitting and receiving antenna
5
. Further, when the target object
6
has a relative velocity, the receiving electromagnetic waves have a Doppler shift of fd with respect to the transmitting electromagnetic waves. At this time, a difference of frequency between a transmitting signal, i.e. the transmitting electromagnetic wave, and a receiving signal, i.e. the receiving electromagnetic waves, in case that a frequency of the receiving signal is increased and a difference of frequency fbd between the transmitting signal and the receiving signal, i.e. the receiving electromagnetic waves, in case that a frequency of the receiving signal is decreased are outputted from the mixer
8
as beat signals. These beat signals are subjected to an analogue-digital conversion by the A/D converter
11
, taken in the signal processing unit
12
as data, and subjected to a fast Fourier transformation (FFT) to obtain the above-mentioned fbu and fbd and receiving levels M thereof, wherein the receiving levels of fbu and fbd are usually the same M.
The relative range R and the relative velocity V of the target object is obtainable by the following Equation 1.
R
=
TmC
4
B
(
fbu
+
fbd
)
,
V
=
λ
4
(
fbu
-
fbd
)
[
Equation
1
]
where reference C designates the light velocity of 3.0×10
8
m/s; and
reference &lgr; designates a wavelength of carrier wave, wherein &lgr;=4.0×10
−3
m when a fundamental frequency of the carrier wave is f
0
=77 GHz.
Incidentally, in case that a plurality of target objects exists, fbu and fbd of an identical target object is selected among a plurality of differences of frequency fbu between the transmitting signal and the receiving signal in case that the frequency of the receiving signal is increased or among a plurality of differences of frequency fbd between the transmitting signal and the receiving signal in case that the frequency of the receiving signal is decreased, and relative ranges R and relative velocities V respectively for the plurality of target objects are obtained by Equation 1.
In the next, a method of operating a direction of the target object
6
by the signal processing unit
12
using the receiving level M will be described. Conventionally, in operating a direction, typical methods such as a mono pulse method, a sequential roving method, and a conical scanning method are disclosed in, for example, JP-B-7-20016. The sequential roving method will be described. This method equal to a method of measuring angle in an ample range by normalizing a difference of two receiving levels of radar beam having different axes as disclosed in JP-A-7-92258.
After measuring a range, a relative velocity, and a receiving level M
1
in a predetermined direction &thgr;
1
, the signal processing unit
12
similarly measures a range, a relative velocity, and a relative velocity M
2
in a next direction &thgr;
2
by operating the motor
13
. Among these plurality of detected data, the same data of the ranges and the relative velocities are selected to measure an angle based on a relationship of magnitude between the receiving level M
1
and the receiving level M
2
.
Specifically, a sum pattern S(&thgr;) and a difference pattern D(&thgr;) are obtained from antenna beam patterns B
1
(&thgr;) and B
2
(&thgr;) in the predetermined two directions &thgr;
1
and &thgr;
2
as follows:
S
(&thgr;)=
B
1
(&thgr;)+
B
2
(&thgr;) Equation 4
D
(&thgr;)=
B
1
(&thgr;)−
B
2
(&thgr;) Equation 5
In the next, a discriminatior DS(&thgr;) standardized by S(&thgr;) is obtained.
DS
(&thgr;)=
D
(&thgr;)/
S
(&thgr;) Equation 6
where within a half bandwidth &thgr;s of S(&thgr;) is monotonously increased or decreased.
By defining a center between the predetermined two directions &thgr;
1
and &thgr;
2
as &thgr;o, and the half bandwidth of S(&thgr;) as &thgr;s, an inclination k of DS(&thgr;) at around an angle &thgr;n standardized by &
Mitsubishi Denki & Kabushiki Kaisha
Sotomayor John B.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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