United States Patent [19]
`Agravante et al.
`
`111111
`
`lllllllllllllllllllllllllllllllllllllllllllllllllllllllllllll
`5,767,793
`Jun. 16, 1998
`
`US005767793A
`[11] Patent Number:
`[451 Date of Patent:
`
`[54] COMPACT VEHICLE BASED REAR AND
`SIDE OBSTACLE DETECTION SYSTEM
`INCLUDING MULTIPLE ANTENNAE
`
`5,315,303
`5,339,075
`5,341,344
`
`5/1994 Tsou et al ................................ 342t27
`8/1994 Abst et al. .............................. 340/903
`8/1994 O'Brien et al ..
`
`[75]
`
`Inventors: Hiroshi H. Agravante. Long Beach;
`Bruce L Hauss. Los Angeles; Philip J,
`Moffa, Torrance. all of Calif.
`
`[73] Assignee: TRW Inc .. Redondo Beach. Calif.
`
`[21] Appl. No.: 426,376
`
`Apr. 21, 1995
`
`[22] Filed:
`Int. Cl.6
`....................................................... GOSG 1/16
`[51]
`[52] U.S. Cl ........................... 3401903; 340/401; 340/435;
`180/167; 180/169: 342no; 342129
`[58] Field of Search ..................................... 340/903. 901,
`340/435. 436; 180/169. 167; 342/70, 71.
`72. 29. 41
`
`[56]
`
`References Cited
`
`U.S. PATENI' DOCUMENfS
`
`3,697,985 10/1972 Faris et al ............................... 343/510
`3,846,796
`ll/1974 Oishi et al ................................ 342n2
`6/1977 Young ..................................... 340/903
`4,028,662
`7/1980 Adachi .................................... 3431713
`4,210,357
`9/1982 Tagami et al ...................... 343n UM
`4,349,823
`7/1985 Takeuchi ................................. 340/903
`4,528,563
`8/1987 Miller et al. ............................ 340/903
`4,684,295
`7/1989 Shibata et al ........................... 3431713
`4,845,506
`4,910,523
`3/1990 Huguenin et al ....................... 3421179
`4,920,520
`4/1990 Gobel et al ..
`5,008,678
`4/1991 Herman ................................... 3421158
`5,028,920
`7/1991 Dombrowski ................ , .......... 3401904
`5,087,918
`2/1992 May et al ................................. 342/85
`5/1992 Wen et al ............................... 3421175
`5,115,245
`5,202.692
`4/1993 Huguenin et al ....................... 3421179
`8/1993 Qualizza ................................. 3401436
`5,235,316
`5,281 ,947
`1/1994 Durley et al. ........................... 340/433
`
`OTHER PUBUCft:fiONS
`
`Automotive Radar: A Brief Review, Dale M. Grimes Pro(cid:173)
`ceedings of the IEEE. vol. 62. No. 6. Jun. 1974.
`
`Primary Examiner-Jeffery Hofsass
`Assistant Examiner-Julie Lieu
`Attome.}\ Agent, or Firm-Michael S. Yatsko
`
`[57]
`
`ABSTRACT
`
`A rear and side object detection system for a vehicle based
`on monolithic millimeter wave integrated circuit technology.
`A multiple antenna configuration is employed that defines
`six sensing regions to the right. left and the rear of the
`vehicle. A sixth sensing region is defined at the right side of
`the vehicle, a second sensing region is defined at the right
`side and rear of the vehicle and overlaps the sixth sensing
`region. a fourth sensing region and a first sensing region
`extend from the rear on both sides of the vehicle in the
`adjacent lanes, a third sensing region is defined at the left
`side of the vehicle and a fifth sensing region is defined at the
`left side and rear of the vehicle and overlaps the second and
`third sensing regions. A right side warning signal is issued
`if an object is detected in a right side detection zone defined
`by the sixth sensing region or a portion of the second sensing
`region that does not overlap the fourth or fifth sensing
`regions. likewise. a left side warning signal is issued if an
`object is detected in a left side detection zone defined by the
`third region and a portion of the fifth sensing region that
`does not overlap the second or first sensing regions. A
`back-up warning signal is issued if an object is detected in
`an overlap region between the second and fifth sensing
`regions.
`
`2 Claims, 4 Drawing Sheets
`
`136
`
`134
`
`IPR2016-00293 - Ex. 1005
`Toyota Motor Corp., Petitioner
`
`1
`
`

`
`U.S. Patent
`
`Jun. 16, 1998
`
`Sheet 1 of 4
`
`5,767,793
`
`16
`
`FIG. I
`
`40
`
`54
`
`.
`
`FIG. 2
`
`2
`
`

`
`,..--28
`
`82 \o------
`
`DATA
`OUT
`DATA
`IN- n
`
`DSP
`
`DATA
`OUT
`DATA
`IN
`
`DSP
`
`72
`
`16
`
`FIG. 3
`
`•
`
`0 • 00.
`~ ...... a
`
`~
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`~
`.....
`!"
`.....
`~
`
`00
`1:1"'
`m.
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`N
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`.~:;..
`
`Ol
`'41 .....:1
`Q'\
`.....:1
`'41 .....:1
`~
`
`3
`
`

`
`MIXER
`OUTPUT
`
`TO AGC
`AMPLIFlER
`
`102
`
`)
`SAMPLE
`DATA
`
`,-100
`108
`
`SPECTRUM
`ESTIMATION
`
`--
`
`1 06"'\.
`AGC
`1--
`-~ONTROL
`
`'
`
`TOTAL ENERGY
`ESTIMATE
`\....104
`
`FIG. 4
`
`TO CENTRA
`CONTRO
`UNIT
`
`-
`
`126
`)
`OUTPUT
`TARGET
`RANGE,
`SPEED
`
`120
`
`I
`ADAPTIVE
`THRESHOLDJ
`
`RANGE ONLY
`
`12
`
`PARAMETER
`ESTIMATION
`20
`
`c--
`
`24
`
`TARGET
`DECISION
`
`•
`
`~ • 00.
`~ = g .....
`-~
`
`1--'
`!"
`1--'
`
`~
`QO
`
`g:
`l
`w
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`.r;.
`
`Ol
`"' .......
`="
`.......
`"' .......
`\0
`~
`
`,-108
`114
`
`112
`
`FIG. 5
`
`1 16
`
`118
`
`NOISE
`EQUAUZATION
`
`AVERAGE
`WITH PAST
`SPECTRA
`
`110
`
`SAMPLED --1 TIME
`
`MIXER
`OUTPUT
`
`WINDOW
`FUNCTION
`
`4
`
`

`
`U.S. Patent
`
`Jun. 16, 1998
`
`Sheet 4 of 4
`
`5,767,793
`
`10
`
`136
`
`130
`
`FIG. 6
`
`136
`
`134
`
`FIG. 7
`
`5
`
`

`
`5,767,793
`
`1
`COMPACT VEHICLE BASED REAR AND
`SIDE OBSTACLE DETECTION SYSTEM
`INCLUDING MULTIPLE ANTENNAE
`
`BACKGROUND OF THE INVENI10N
`
`1. Field of the Invention
`This invention relates generally to a rear and side object
`detection system for a vehicle and. more particularly. to a
`rear and side object detection system for a vehicle that
`incotporates an antenna configuration that defines overlap(cid:173)
`ping antenna fields around the vehicle where the antenna
`fields combine to give an accurate detection of obstacles
`within a desirable obstacle detection region.
`2. Discussion of the Related Art
`For current vehicle transportation, there is a significant
`number of incidences involving vehicle collisions with
`obstacles, such as other vehicles. when the vehicle is chang(cid:173)
`ing travel lanes or merging. and when the vehicle is oper(cid:173)
`ating in reverse. The main reason why the lane change/ 20
`merge and reverse operation incidences occur is because the
`vehicle operator is unaware of the obstacles in the vehicle's
`intended path. Many factors relate to why the vehicle
`operator would be unaware of the obstacles. These factors
`include operator fatigue. carelessness. distraction by other 25
`conditions. and blocked vision. This suggests that many of
`these crash incidences can be avoided by vehicle based
`countermeasures that inform the vehicle operator of the
`presence of an obstacle when the vehicle operator initiates a
`lane change or back-up maneuver.
`Currently. progress is being made in the applicable tech(cid:173)
`nological fields to achieve an effective rear and side object
`detection system that informs a vehicle operator of an
`impending collision with many types of objects that may be
`present within the vehicle's intended path. In most practical 35
`detection systems of this type. radar technology is utilized.
`Particularly. a radio wave signal at a desirable frequency is
`emitted from the detection system to define a desirable
`sensing zone around the vehicle. and reflected signature
`signals from objects within the zone are received by the 4Q
`system to be analyzed. Positional information from the
`signature signals and the relative timing between the trans(cid:173)
`mitted radio wave signal and the reflected signature signals
`provide an indication of the location. distance and speed of
`the objects. A background discussion of typical obstacle 45
`detection systems known in the art can be found in U.S. Pat.
`Nos. 5.087.918; 5.008.678; 4.349.823 and 3.697.985.
`It does not appear that the current technology has reached
`a level that would make radar detection systems feasible in
`a wide variety of mass produced vehicles. This is because of
`a number of necessary design criteria required for a practical
`detection system. Generally. the detection system must be
`low cost and readily adaptable to various types of vehicles
`with respect to consumer demands and industry standards.
`More importantly. the detection system must be reliable in
`that the system must give a warning indication of an obstacle
`of the type that may cause a collision for a high percentage
`of the times, and not provide a warning or nuisance signal
`for those objects that do not provide a chance of collision.
`To achieve reliable object detection. the detection system 60
`must accurately define sensing zones around the vehicle.
`The requirement for highly defined sensing zones can be
`realized by understanding the following situation. The
`detection system must emit a signal of a sufficient power that
`will cause a small child to generate a significant reflection
`signature signal if the child is behind the vehicle in a
`potentially hazardous position. However. it would be unde-
`
`2
`sirable to provide a warning signal of a metal obstacle that
`was significantly distanced from the back of the vehicle
`where it would not be a potential collision hazard. Because
`the metal object would provide a much greater reflection
`5 signature than the child when at the same distance for the
`same power level. the design of the system must define the
`sensing zones to separate these two events to be practical.
`To detect objects in the proximity of a vehicle to be
`effective against lane change/merge and back-up collisions.
`10 the detector system must be able to cover specific areas to
`the left. right and back of the vehicle. In order to create this
`necessary coverage without sacrificing aesthetics and to
`avoid packaging problems. a multiple detector system con(cid:173)
`figuration is necessary. However, it becomes important from
`15 a design standpoint to limit the number of power sources and
`antenna in the system because of space and cost constraints.
`What is needed is a rear and side obstacle detection
`system that accurately defines effective sensing areas around
`a vehicle so as to give a high probability of detection when
`a potential collision causing obstacle is within the sensing
`areas, and prevent the system from indicating an obstacle is
`present when one is not present in the sensing areas. It is
`therefore an object of the present invention to provide such
`a rear and side object detection system.
`SUMMARY OF THE INVENI10N
`In accordance with the teaching of the present invention.
`a rear and side obstacle detection system that provides a
`warning of an obstacle that is within specified sensing
`30 regions around a vehicle is disclosed. A multiple antenna
`configuration is employed that defines six sensing regions to
`the right. left and rear of the vehicle. The antenna configu(cid:173)
`ration is designed such that the sensing regions accurately
`sense strategic areas around the vehicle that are limited to
`adjacent lanes on either side of the vehicle and an appro(cid:173)
`priate back-up area behind the vehicle. A sixth sensing
`region is defined at the right side of the vehicle. a second
`sensing region is defined at the right side and rear of the
`vehicle and overlaps the first sensing region. a fourth sensing
`region and a first sensing region extend from the rear on both
`sides of the vehicle along the adjacent lanes. a third sensing
`region is defined at the left side of the vehicle. and a fifth
`sensing region is defined at the left side and rear of the
`vehicle and overlaps the second and third sensing regions.
`A right side warning signal is given if an obstacle is
`detected in a right side detection zone defined by the sixth
`sensing region or a portion of the second sensing region that
`doesn't overlap the fourth or fifth sensing regions. Likewise.
`a left side warning signal is given if an obstacle is detected
`so in a left side detection zone defined by the third sensing
`region and a portion of the fifth sensing region that does not
`overlap the second or first sensing regions. A back-up
`warning signal is given if an obstacle is detected in an
`overlap region between the second and fifth sensing regions.
`55 The fourth and first sensing regions detect obstacles that are
`traveling at a speed that will cause the obstacle to enter the
`right or left side detection zones within a predetermined
`period of time so as to issue an appropriate right or left side
`warning signal.
`In one embodiment, the detection system comprises two
`sensing units positioned at the rear of the vehicle on the left
`and right sides. Each of the sensing units incorporates three
`antenna arrays specially designed ~o define the six sensing
`regions. The sensors are based on monolithic millimeter
`65 wave integrated circuit technology such that a single power
`source associated with each unit provides power to the three
`antenna arrays.
`
`6
`
`

`
`5,767,793
`
`3
`Additional objects, advantages, and features of the present
`invention will become apparent from the following descrip(cid:173)
`tion and appended claims. taken in conjunction with the
`accompanying drawings.
`
`BR1EF DESCRIPTION OF THE DRAWINGS
`
`F1G. 1 is a rear view of a vehicle incorporating a rear and
`side obstacle detection system according to an embodiment
`of the present invention:
`F1G. 2 is a blown apart perspective view of one sensor
`associated with the rear and side obstacle detection system
`of F1G. 1;
`F1G. 3 shows a block diagram of the rear and side obstacle
`detection system of the present invention;
`F1G. 4 shows a block diagram of the operation of the rear
`and side obstacle detection system of the invention;
`F1G. 5 shows a block diagram of a spectrum estimation
`device of the invention.
`F1G. 6 is a top view of the vehicle of F1G. 1 depicting a
`plurality of sensing regions established by the rear and side
`obstacle detection system around the vehicle according to an
`embodiment of the present invention; and
`F1G. 7 is a perspective view of the vehicle of F1G. 6
`depicting the plurality of sensing regions.
`
`20
`
`DEI'All..ED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`The following description of the preferred embodiments 30
`directed to a rear and side obstacle detection system for
`detecting obstacles around a vehicle is merely exemplary in
`nature and is in no way intended to limit the invention or its
`applications or uses.
`F1G. 1 shows a rear view of a vehicle 10. The vehicle 10
`is intended to represent any type of vehicle adaptable to
`operate on a conventional highway system. The vehicle 10
`includes a left side sensor 12 positioned within a left end of
`a bumper 14 associated with the vehicle 10 and a right side
`sensor Hi positioned within a right end of the bumper 14. As
`will be discussed in detail below. the sensors 12 and 16 emit
`a radio wave signal that defines sensing regions (see F1GS.
`6 and 7) around a left side 18. a right side 20 and a rear area
`22 of the vehicle 10. The sensors 12 and 16 are shown
`positioned at opposite ends of the bumper 14 as one possible
`strategic location to define the desirable sensing area.
`However. as will be appreciated by those skilled in the art
`from the discussion of Applicant's embodiments and the
`prior art, the sensors 12 and 16 can be positioned at other
`locations on the vehicle 10 without significantly effecting
`the sensing regions around the vehicle 10. For example. the
`left side sensor 12 can be positioned at some location on the
`left side 18 of the vehicle 10. and the right side sensor 16 can
`be positioned at some location on the right side 20, as well
`as being positioned at other locations on the rear area 22 of
`the vehicle 10. without departing from the scope of the
`invention. U.S. patent application Ser. No. 08/177.266 to
`Chen et al .. assigned to the assignee of the instant
`application. and herein incorporated by reference. discloses
`sensors of the types of sensors 12 and 16 being positioned
`within side view mirrors 24 of the vehicle 10.
`F1G. 2 shows a blown apart perspective view of the
`components of the sensor 12 according to an embodiment of
`the present invention. ll will be understood that the sensor 16
`includes the identical components of the sensor 12. F1G. 3
`shows a block diagram of a rear and side detection system
`28 according to one embodiment of the present invention
`
`10
`
`15
`
`4
`incorporating the sensors 12 and 16. The sensor 12 includes
`a base member 30 on which is secured various sensor
`components. A connector lead frame 32 is provided to
`connect the sensor 12 to other circuit components, such as
`5 a system controller 34 and a vehicle battery (not shown). An
`intermediate frequency (IF) printed circuit board 40 is
`positioned on the base member 30 to provide connections
`from the lead frame 32 to an integrated circuit chip board 42.
`The chip board 42 includes a monolithic millimeter wave
`integrated circuit (MMIC) 44. a patch antenna array 46. a
`first end-fire slot antenna array 48 and a second end-fire slot
`array antenna 50. A cover 54 covers the sensor 12 and acts
`as a suitable protective layer to the sensor 12 from the
`environmental conditions that would exist at the rear of the
`vehicle 10. Additionally. the cover 54 is aesthetically
`matched to the design of the vehicle 10. U.S. patent appli(cid:173)
`cation Ser. No. 08/177.266 referenced above depicts an
`alternate configuration of the different layers and compo(cid:173)
`nents of a sensor of the type of the sensor 12 that is within
`the scope of the present invention.
`The reason for the particular configuration of the antenna
`arrays 46, 48 and 50 will become apparent from the discus(cid:173)
`sion below. It is stressed. however. that these antenna arrays
`are used by way of a non-limiting example in that other
`25 types of antennas. including dipoles and feed horns. can be
`incorporated within the scope of the invention. U.S. patent
`application Ser. No. 081177.266 referenced above discusses
`other types of antenna configurations that may be suitable
`for the purposes described herein.
`The sensor 12 utilizes MMIC technology to provide a
`suitable transceiver 58 for the purposes described herein.
`U.S. Pat. No. 5.315.303 issued to Tsou et al. assigned to the
`assignee of the instant application and herein incorporated
`by reference. discloses a monolithic millimeter wave inte-
`35 grated circuit transceiver and associated circuitry that is
`applicable for the purposes of the present invention. A
`general description of the operation of the sensors 12 and 16
`will be given below that is adequate to describe the embodi(cid:173)
`ments of the invention. However, it will be understood that
`40 a more detailed discussion of the operation of the sensor 12
`can be gleaned from a detailed analysis of U.S. Pat. No.
`5.315.303.
`An appropriate voltage signal is applied from the vehicle
`battery through the controller 34 to voltage regulators 60
`45 within the sensor 12. A temperature control device 62
`monitors the temperature of the sensor 12. The sensor 12 is
`activated when an input signal from the controller 34 is
`applied to a digital signal processor (DSP) 64. The DSP 64
`applies an output signal to a sweep generator 66 to generate
`so an appropriate voltage signal. The voltage signal is applied
`to a voltage controlled oscillator (VCO) 68. The VCO 68
`generates a millimeter wave frequency signal at the desir(cid:173)
`able frequency that is applied to a series of amplifiers 70.
`The amplified millimeter wave frequency signal is then
`55 systematically applied to a series of antenna 72 through a
`rotating switch 74 to radiate the frequency signal into space.
`The antenna 72 are intended to represent the patch antenna
`array 46 and the end-fire slot antenna arrays 48 and 50.
`Signals that are reflected off of objects within the antenna
`60 fields defined by the antenna 72 are received by the antenna
`72 and applied to a mixer 76 through the switch 74. The
`mixer 76 mixes the reflected signal with the frequency signal
`from the VCO 68 for timing purposes. The mixed signal
`from the mixer 76 is applied to an analog-to-digital con-
`65 verter 78 through a series of amplifiers 80. The digital signal
`representation of the reflected signal is applied to the DSP 64
`for signal processing in a manner that will be discussed in
`
`7
`
`

`
`5,767,793
`
`5
`greater detail below. If the DSP 64 determines that a warning
`signal should be issued as a result of the reflected signal. the
`DSP 64 will output an appropriate signal to the controller 34
`that will in turn activate a suitable warning device (not
`shown).
`The sensors 12 and 16 provide object detection and
`range/velocity measurement functions of detected objects,
`and the controller 34 performs the final warning decision
`processing as well as overall system control. self-test and
`vehicle interfacing. Further. the controller 34 provides watch 10
`dog functions and overall system diagnostics. A series of
`input and output lines 82 are connected to the controller 34.
`Input lines are provided to provide input signals to the
`controller 34 of when the sensors 12 and 16 should be
`activated. 1n one example, a determination of whether an 15
`obstacle exists at the right side of the vehicle 10 will be made
`when a right turn signal (not shown) is switched on, a
`determination of whether an obstacle exists on the left side
`of the vehicle will be made when a left turn signal (not
`shown) is switched on. and a determination of whether an 20
`obstacle exists at the rear of the vehicle 10 will occur when
`the vehicle 10 is switched into reverse. 1n an alternate
`example, the sensors 12 and 16 can be continuously acti(cid:173)
`vated to provide an indication as to whether an obstacle is
`around the rear and side of the vehicle 10 at all times of 25
`vehicle use. Indications of whether obstacles are present
`when the sensors 12 and 16 are activated is applied through
`the controller 34 to various types of warning devices (not
`shown), such as audible alarms and visual signals. For
`different applications. different levels of warnings can be 30
`given. For example, the system 28 can be designed such that
`a visual warning signal is given whenever an obstacle is
`within the range of the antenna 72, and a visual signal and
`an audible alarm can be given when an obstacle is in a zone
`that is critical for a particular left. right or back-up maneuver 35
`in response to activation of the left and right turn signals and
`the reverse gear.
`The system 28 uses millimeter wave radar signals with a
`FM-CW chitped wave form. The FM-CW approach is well
`suited to low peak power MMIC transmitters. and is com- 40
`patible with the current generation of low cost digital signal
`processors. Millimeter wave frequencies are desired to uti(cid:173)
`lize small antenna, and to accommodate a 500 MHz band(cid:173)
`width to enable one foot range resolution. One foot range
`resolution is desirable to fine tune the antenna coverage 45
`using range cutting to faithfully follow the desired detection
`areas. The patch antenna array 46 and the slot antenna arrays
`48 and 50 transmit an appropriate millimeter wave radar
`signal. and receive reflected signals.
`1n one embodiment. the radar signals are emitted at 20 50
`mW having greater than a 23 dB signal-to-noise ratio. This
`yields signal pulse detection probabilities of approximately
`98% and negligible false alarms for targets with fluctuating
`cross sections. Five chirped pulses are transmitted within a
`5 msec update period and a proximity detection criteria of 55
`three out of five return pulses exceeding adaptive thresholds
`(discussed below) in order to declare a detection. To provide
`the necessary processing capabilities, the controller 34
`includes a suitable microprocessor such as the Motorola
`MC68HC05B6 8-bit microcontroller having 6k bytes of 60
`masked read only memory (ROM), 512 bytes of erasable
`programmable read only memory (EPROM) and 256 bytes
`of random access memory (RAM). The DSP 64 can be a
`Texas Instruments TMC320C10 16-bit processor including
`3k bytes of masked ROM and 288 bytes of RAM. The 65
`millimeter wave radar signal can be transmitted at various
`millimeter wave frequencies in the GHz frequency bands.
`
`6
`For example, suitable frequency bands include 37.5-38.5
`GHz. 76-77 GHz, 92-95 GHz. 140 GHz and 153 GHz.
`These components and parameters are just examples of
`suitable devices and system operations as it will be appre-
`5 dated by those skilled in the art that others will be equally
`applicable within the scope of the invention.
`FIG. 4 shows a block diagram of a system 100 depicting
`the operation of a portion of the DSP 64 when it receives a
`reflected signature signal. The discussion below will be
`general in nature as adequate for the present invention. A
`more detailed description of this operation can be found in
`U.S. patent application Ser. No. 08/173.540, filed Dec. 23.
`1993. assigned to the assignee of the instant application, and
`herein incorporated by reference. The system 100 includes a
`data sampling device 102 that samples an output of the
`mixer 76 through the analog-to-digital processor 78. The
`mixer 76 combines the transmitted signal with the reflected
`signal to generate a mixer output signal related to the range
`of a detected object. If multiple objects are detected. the
`mixer output signal will be a sum of frequencies correspond(cid:173)
`ing to each object. An output of the data sampling device 102
`is applied to an energy estimation device 104 that estimates
`a total energy of the sampled mixer output signal. An
`automatic gain control device 106 generates a gain control
`signal for an automatic gain amplifier (not shown) associ(cid:173)
`ated with the sensor 12.
`A spectrum estimation device 108 receives the sample
`data signal from the sample data device 102 to estimate the
`spectrum of the sampled mixer output signal. A more
`detailed block diagram of the spectrum estimation device
`108 is shown in FIG. 5. A time domain window device 110
`multiplies the sampled mixer output signal generated by the
`sample data device 102 with a time domain window
`function, for example a raised cosine function. to generate a
`windowed signal. The time domain window device 110
`decreases spectrum leakage and outputs the windowed sig(cid:173)
`nal to a fast fourier transform (FFT) device 112 which
`generates a frequency spectrum signal. The frequency spec(cid:173)
`trum signal includes a series of spectral components.
`The frequency spectrum signal is applied to a magnitude
`determining device 114 that calculates the magnitude of the
`spectral components, and generates a magnitude range pro(cid:173)
`file signal. The magnitude range profile signal includes a
`plurality of range bins where each range bin is associated
`with a spectral component and contains the magnitude of the
`associated spectral component. The magnitude of each
`spectra-component is related to signal strength at a particular
`frequency. Signal strength relates to the presence or absence
`of objects at a given range. 1n addition. the frequency of a
`peak of the frequency signal is related to the distance of a
`target.
`The magnitude range profile signal is then applied to a
`noise equalization device 116. Because the sampled mixer
`signal has a noise characteristic which increases with
`decreasing frequency, the magnitude range profile signal is
`equalized by the noise equalization device 116 to produce an
`equalized range profile signal having a noise floor that is
`constant with respect to frequency. The equalized range
`profile signal is applied to an averaging or integration device
`118 which integrates the equalized range profile signal with
`prior equalized range profile signals to increase the signal(cid:173)
`to-noise ratio so as to increase the detection probability.
`The averaging device 118 generates an integrated range
`profile signal which is applied to an adaptive threshold
`device 120. The adaptive threshold device 120 defines a
`moving window that includes a plurality of range bins. The
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`5,767,793
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`7
`adaptive threshold device 120 evaluates the signal strength
`of each range bin and generates target flags in the range bins
`to indicate the presence or absence of an object. The
`adaptive threshold device 120 is implemented with one form
`of a constant false alarm rate algorithm to have a predictable
`false alarm rate based on the signal-to-noise ratio of the
`system 100. This algorithm determines the amplitude thresh(cid:173)
`old which potential objects must be above to be recognized.
`Anything below the threshold is discarded as noise. The
`threshold changes in both range and time, and thus is
`adaptive to changing conditions of clutter. object size and
`distance. Various types of adaptive threshold techniques are
`discussed with reference to U.S. patent application Ser. No.
`08/173,540 referenced above.
`For the lane change target prediction mode of operation,
`a 2D parameter estimation device 122 determines target
`distance and velocity. The 2D parameter estimation device
`122 performs computations on a 2D object space array
`generated by the adaptive threshold device 120, and gener(cid:173)
`ates a 2D estimation signal including components related to
`the speed of and distance to possible detected objects. Only
`objects greater than the threshold range profile signal are
`analyzed and only the object paths which correlate closely
`enough to constant velocity motion pass the thresholding.
`An object is valid if it persists over enough thresholding
`intervals. and if its path is correlated to a relatively non(cid:173)
`accelerating path. This estimate is then used to determine if
`the object will be within side detection zones within one
`second as will be discussed below. The algorithm utilizes the
`transform from two dimensional range-time space to range(cid:173)
`time velocity space. This algorithm has superior clutter
`rejection properties and rejects objects that are out of the
`allowed velocity limits.
`For rear and side object detection where only range is
`needed. the 2D parameter estimation algorithm is not
`performed. and the process moves to a target detection
`decision device 124. A target decision algorithm determines
`whether the object is valid and if it should be sent on to the
`controller 34. If the target decision device 124 determines
`that an object is present that may cause a potential collision,
`the target decision device 124 outputs a signal to an output
`target range and speed device 126 to give the appropriate
`object range and speed data to the controller 34.
`FIG. 6 shows a top view and FIG. 7 shows a perspective
`view of the vehicle 10 and a plurality of sensing regions
`defined by the sensors 12 and 16 at the left side 18, the right
`side 20 and the rear area 22 of the vehicle 10. Each antenna
`array of the sensors 12 and 16 radiates a frequency signal
`into space that is limited to a particular shape and distance
`so as to define a sensing region such that a reflected signal
`from an object in the sensing region is detected by the
`antenna array that created the region. Particularly. the patch
`antenna array 46 of the sensor 12 is configured to define a
`sensing region 130. the end-fire slot antenna array 48 is
`configured to define a sensing region 132. and the end-fire
`slot antenna array 50 is configured to define a sensing region
`134. Likewise. the patch antenna array of the sensor 16 is
`configured to define a sensing region 136 and the end-fire
`slot antenna arrays of the sensor 16 are configured to define
`sensing regions 138 and 140. As would be well understood
`to those skilled in the art. the types of antenna arrays
`discussed herein can be accurately designed at particular
`power levels to be limited to desirable antenna fields. The
`shape of the sensing regions 132, 134, 138 and 140 gener(cid:173)
`ated by the end-fire slot antenna arrays are typical 90° beam
`width antenna fields produced by a dipole antenna.
`1n one example, the end-fire slot antenna arrays are
`configured to give a 15° beam width in the vertical direction
`
`8
`to limit the vertical coverage of the sensing regions 132. 134.
`138 and 140 to the height of the vehicle 10, and a 90° beam
`width in the horizontal direction. The sensing regions 132.
`134, 138 and 140 extend out from the vehicle 10 to a
`5 distance within the range of about nine feet to about twelve
`feet to limit the coverage area to the adjacent lanes. The
`power of the sensors 12 and 16 can be adjusted to increase
`or decrease this area for specific applications. The patch
`antenna arrays have a 15° beam width with a 13° bore sight
`10 angle to provide for long range coverage without spill over
`into either the lane occupied by the vehicle 10 or two lanes
`over on either side of the vehicle 10. 1n this example. the
`regions