Communications: directive radio wave systems and devices (e.g. – Return signal controls external device – Radar mounted on and controls land vehicle
Reexamination Certificate
1999-09-30
2001-03-20
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
C342S109000, C342S111000, C342S194000, C342S196000
Reexamination Certificate
active
06204803
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a radar apparatus mounted on a vehicle such as an automobile, and used to constitute, for instance, a vehicle-to-vehicle safety distance warning system. More specifically, the present invention is directed to a peak value correction of an amplitude level, capable of correcting a peak value of an amplitude level of a detected spectrum as a correct value.
As this sort of radar apparatus, an FMCW radar apparatus is known. That is, since a transmitting/receiving common antenna is employed, a compact FMCW radar apparatus can be constructed and thus, can be easily mounted on an automobile.
FIG. 4
is a block diagram for representing an arrangement of a conventional on-vehicle radar apparatus. In
FIG. 4
, reference numeral
1
indicates an oscillator, reference numeral
2
shows a power divider, reference numeral
3
represents a transmitter amplifier, and reference numeral
4
denotes a circulator. Also, reference numeral
5
indicates a transmitting/receiving common antenna, and this antenna is arranged by an electromagnetic radiator
51
and a reflection mirror
52
. Furthermore, reference numeral
6
indicates a target object, reference numeral
7
indicates a receiver amplifier, reference numeral
8
represents an IQ detecting mixer, reference numeral
9
shows a filter, and reference numeral
10
indicates an AGC amplifier. Further, reference numeral
11
represents an A/D converter, reference numeral
12
shows a signal processing apparatus, reference numeral
13
indicates an antenna scanning motor, and reference numeral
14
represents an handle angle sensor.
Next, operations of the conventional radar apparatus with employment of the above-described arrangement will now be explained. The signal processing apparatus
12
outputs a linear voltage signal for an FM modulation. In response to this FM-modulating voltage signal, the oscillator
1
produces an FM-modulated electromagnetic wave. This electromagnetic wave is divided into two wave portions by the power divider
2
. One divided electromagnetic wave portion is entered into the IQ detecting mixer
8
. After the other divided electromagnetic wave portion is amplified by the transmitter amplifier
3
, the amplified electromagnetic wave portions radiated via the circulator
4
from the transmitting/receiving common antenna
5
to the space. The electromagnetic wave which is radiated as a transmission electromagnetic wave from the transmitting/receiving common antenna
5
to the space is reflected from the target object
6
, and then is entered into the transmitting/receiving common antenna
5
as a reception electromagnetic wave having a delay time “Td” with respect to the transmission when the target object
6
owns a relative speed, the reception electromagnetic wave having a Doppler shift “fd” with respect to the transmission electromagnetic wave is inputted to the transmitting/receiving common antenna
5
. After the electromagnetic wave received by the transmitting/receiving common antenna
5
is amplified by the receiver amplifier
7
, the amplified electromagnetic wave is mixed with the electromagnetic wave produced from the oscillator
1
by the IQ detecting mixer
8
, so that a beat signal corresponding to both the delay time “Td” and the Doppler shift “fd” is outputted. The resulting beat signal is filtered by the filter
9
, and the filtered signal is amplified by the AGC amplifier
10
, and thereafter, the amplified signal is entered into the A/D converter
11
. Based upon the A/D-converted beat signal, the signal processing apparatus
12
calculates a distance measured from the target object
6
and a relative speed.
Next, a description will now be made of a method for calculating a distance and a relative speed.
FIG. 5
is an explanatory diagram for explaining an example of a method for calculating a distance and a relative speed by a conventional on-vehicle radar apparatus. In
FIG. 5
, a transmission electromagnetic wave is FM-modulated by a frequency sweeping bandwidth “B” and a modulation period “Tm”. A reception electromagnetic wave owns delay time “Td” defined by such that the transmission electromagnetic wave is reflected from a target object
6
located at a distance “R” and then the reflected transmission electromagnetic wave is entered into the transmitting/receiving antenna
5
. Also, when the target object
6
owns a relative speed “V”, a reception electromagnetic wave is Doppler-shifted by “fd” with respect to a transmission electromagnetic wave. At this time, both a frequency difference “Fbu” between a transmission signal and a reception signal when a frequency is increased, and another frequency difference “Fbd” between a transmission signal and a reception signal when a frequency is decreased are outputted as a beat signal from an IQ detecting mixer
8
. This beat signal is acquired via an A/D converter
11
into a signal processing apparatus as data. This acquired beat signal is processed by way of the FFT (Fast Fourier Transform) so as to obtain the frequency differences “Fbu” and “Fbd”, and also a peak value “M” of amplitude levels thereof, as shown in FIG.
6
. It should be understood that the peak value of “M” is a value equivalent to a reception strength, and will be referred to as a “reception strength” hereinafter.
A method for obtaining the frequency differences “Fbu” and “Fbd”, and also the reception strength “M” will now be summarized as follows: That is, when the FFT process operation is carried out, the amplitude signals with respect to the respective abscissa time and ordinate time can be converted into the amplitudes of the frequency components with respect to the respective abscissa frequency and ordinate frequency. In the case that the frequency difference “Fbu” and the reception strength “M” are acquired, generally speaking, such a peak point where a level of amplitude becomes a peak is found out, and an amplitude level value of this peak and a frequency value thereof are assumed as the reception strength “M” and the frequency difference “Fbu”. This frequency acquisition is similarly applied to another frequency “Fbd”. In general, the reception strengths of the frequency differences “Fbu” and “Fbd” are identical to each other, and become “M”.
Based upon the above-described items “Fbu”, “Fbd”, “Tm”, and “B”, the light velocity “C(=3.0×10
8
m/s)”, and a wavelength “&lgr;” of a carrier wave (if a basic frequency of a carrier wave is defined as f
0
=77 GHz, then a wavelength “&lgr;” is given as &lgr;=4.0×10
−3
m), the distance “R” and the relative speed “V” of the target object
6
are calculated by the below-mentioned formulae (1) and (2):
R
=(
TmC/
4
B
)×(
Fbu+Fbd
) (1)
V
=(&lgr;/4)×(
Fbu−Fbd
) (2)
Also, in the case that a plurality of target objects are located, based upon a plurality of frequency differences “Fbu” between transmission signals and reception signals when a frequency is increased, and a plurality of frequency differences “Fbd” between transmission signals and reception signals when a frequency is decreased, both “Fbu” and “Fbd” of the same object are selected. Then, the distance “R” and the relative speed “V” are obtained from the above-described formulae (1) and (2).
Next, operations of the IQ detecting mixer
8
will now be explained in detail. In
FIG. 4
, the electromagnetic wave produced from the oscillator
1
is distributed to the power divider
2
, and is further subdivided by ½ into two electromagnetic wave portions by the power divider P/D at the input unit of the IQ detecting mixer
8
, and then, these two electromagnetic wave portions are entered as LO (local) signals into mixers
81
and
82
. Also, the received electromagnetic wave is amplified by the reception amplifier
7
, and thereafter, the amplified electromagnetic wave is subdivided by ½ into two electromagnetic wave portions by the power divider P/D. One subdivided electromagnetic wave portion is directly entered into
Mitsubishi Denki & Kabushiki Kaisha
Sotomayor John B.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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