11:5
`United States Patent
`5,905,457
`(11) Patent Number:
`
`Rashid
`[45] Date of Patent:
`May18, 1999
`
`US005905457A
`
`[54] VEHICLE RADAR SAFETY APPARATUS
`
`[76]
`
`rentor:
`‘
`.
`Inventor: cures rary jeoue Merrily,
`osevilie,
`Nuen.
`
`[21] Appl. No.: 08/022,372
`
`[22]
`
`Filed:
`
`Feb. 25, 1993
`
`Related U.S. Application Data
`[63] aee apoleiion Nes oleae me
`pee gs A ACODE, weet
`sks
`2) COTANathpare ©
`application No. 07/595,995, Oct. 11, 1990, abandoned.
`Tints Cl! sessment GOIS 13/93
`[51]
`PQ] WS, Ce seers: 342/70; 342/71; 343/785
`:
`abe
`;
`
`[58] Field of Search oo. 342/70 sivasage
`
`>
`
`[56]
`
`
`
`4,628,317 12/1986 Nishikawaet al. ......c 340/903
`4,660,050
`4/1987 Phillips ......
`.
`4,673,937
`6/1987 Davis ..
`4.703.429
`10/1987 Sakata ....
`4,855,748
`8/1989 Brandaoetall.
`4,914,733
`4/1990 Gralnick.....
`4,916,450
`4/1990 Davis .........
`4,945,550
`7/1990 Krauseetal.
`5,008,844
`4/1991 Kyriakosetal.
`§,053,979 LO/L991 Eto cece ceeeeteees 364/565
`OTHER PUBLICATIONS
`“Two Groups are Developing Radar—Based Collision—
`Avoidance Systems for Autos”, Electronics, vol. 50, No. 4,
`pp. TE-SE,Feb. 17, 1977.
`“Millimeter Wave Components & Subsystems’, Alpha
`Industries, Inc., 1987, pp. 5-2, 5-3 and 5-4.
`
`
`
`Primary Examiner—Gilketto Baron,Ir
`
`Attorney, Agent, or Firm—Young & Basile, PC
`[57]
`ABSTRACT
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`Avehicle radar safety apparatus employsa radar for detect-
`ing an object in front and/or to the rear and sides of a vehicle
`2,804,160
`8/1957 Rashid occ 180/82.1
`
`3,153,230
`10/1964 Van Krevelen et
`and for producing an indication of the distance and closing
`3,383,678
`5/1968 Palmer .
`speed between the vehicle and the detected object. A signal
`3:683,387
`8/1972. Meek ssssesessvsscssscscesssesssscaersiass 343/761
`processing unit sums the vehicle speed and the closing speed
`3,689,882
`9/1972 Dessailly .
`between the vehicle and detected object and compares the
`3,697,985
`10/1972 Faris et al... 343/5 PD
`
`summedoutput with a signal corresponding to the distance
`3,701,160
`... 343/755
`10/1972 Bequin .....
`
`between the vehicle and the detected object to provide an
`3,710,383
`....
`1/1973 Cherry et al.
`343/7 ED
`3,725,921
`4/1973 Weidmanetal. .
`output to a display indicating the vehicle’s capability of
`3,778,826
`12/1973 Flannery et al.
`.
`stopping prior to colliding with the detected object. The
`
`
`3,795,426—3/1974 SISSON wees ctseteeeeeeeeee 303/21 F
`output from the signal processing unit is optionally applied
`cece 180/98
`3,820,622
`6/1974 Powell woes
`to an accelerator and/or brake control circuit to automati-
`
`.....
`3,856,105
`12/1974 Lewiset al.
`. 180/98
`cally slow downthe vehicle. A brake pedal override switch
`3/1975 McCormidket al. we. 343/6.5
`3,870,994
`is connectedto the accelerator and brake controls to override
`3,898,652
`8/1975 Rashid .....ccccccccceeeceeenee 343/6 R
`the accelerator and/or brake controls when the vehicle
`4,060,805
`11/1977 McComas o.ceecessecereeeereeserene 343/6.5
`4,106,023
`8/1978 Baghdady .
`operator depresses the vehicle brake pedal. The radar
`4,128,839
`12/1978 McComas ..ccessreeeeeeenees 343/112
`includes a horn antenna having a plano-convex dielectric
`
`... 343/708
`4,148,040
`4/1979 Lundenetal.
`lens mounted at an exterior end. The lens has an exterior
`4,203,113
`5/1980 Baghdady .
`4,259,743
`3/1981 Kaneko et al. eee 342/70 X
`4,293,859
`10/1981 Sergent........
`. 343/702
`4,318,103
`3/1982 Roettele et al. wee 343/18 E
`4,382,291
`5/1983 Nakauchi .
`4,A77,816
`10/1984. Cho? ssesescssssesssessscesvecsescseveessieses 343/786
`4,543,577
`9/1985 Tachibana etal. .
`4,621,705
`11/1986 EIN vesecccccccscesseescesscssssscsscssee 180/169
`
`convex surface shaped to reduce side lobe generation of the
`transmitted radar wave so as to transmit a radar wave of a
`minimal beam width at a specified operating frequency and
`effective radar antenna diameter.
`
`8 Claims, 7 Drawing Sheets
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`2l2
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`207
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`UNIFIED 1007
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`UNIFIED 1007
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`1
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`

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`U.S. Patent
`
`May18, 1999
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`Sheet 1 of 7
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`5,905,457
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`U.S. Patent
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`May18, 1999
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`Sheet 2 of 7
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`U.S. Patent
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`May18, 1999
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`Sheet 3 of 7
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`U.S. Patent
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`Sheet 4 of 7
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`5,905,457
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`May18, 1999
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`May18, 1999
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`Sheet 5 of 7
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`U.S. Patent
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`May18, 1999
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`Sheet 6 of 7
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`5,905,457
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`U.S. Patent
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`May18, 1999
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`Sheet 7 of 7
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`5,905,457
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`5,905,457
`
`1
`VEHICLE RADAR SAFETY APPARATUS
`
`CROSS REFERENCE TO CO-PENDING
`APPLICATION
`
`This application is a continuation-in-part application of
`United States patent application Ser. No. 07/812,053 filed on
`Dec. 17, 1991 in the name of Charles E. Rashid and entitled
`“Vehicle Radar Safety Apparatus”. Now abandoned whichis
`a C-I-P of Ser. No. 07/595,995 filed Oct. 11, 1990 now
`abandoned.
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`
`This invention relates, in general, to vehicle safety appa-
`ratus and, more specifically to vehicle safety apparatus for
`locating an object surrounding a moving vehicle and to
`provide an indication of the vehicle’s capability of stopping
`to avoid collision with the detected object.
`2. State of the Art
`
`Radar systems for controlling a vehicle in response to the
`detection of an object surrounding the vehicle are known.
`U.S. Pat. No. 3,898,652 discloses such a vehicle radar
`system in whichfront, rear and side sensors are mounted on
`a vehicle. A radar means is connected to each of the sensors
`
`and calculates the distance and closing speed to an object
`detected by one of the sensors, particularly the front or rear
`sensors. The vehicle velocity is used to calculate a distance
`which, under existing conditions,
`is the minimum safe
`distance the vehicle should be with respect to the detected
`object if the detected object immediately stops, so as to
`provide an indication of the moving vehicle’s capability of
`stopping without collision with the detected object.
`The radar system providesan indication to the operator of
`the vehicle of the vehicle’s capability of stopping prior to
`collision with the detected object. The indicatoris preferably
`a visual indicator in the form of a light on a display console
`mounted in the vehicle. This radar system also provides for
`automatic control of the vehicle accelerator and/or brakes to
`automatically slow the vehicle down to avoid collision an
`with object detected in front or to the rear of the vehicle.
`The existing road conditions, whether wet, dry oricy, is
`also a factor in the computation of the safe operating
`distance of the vehicle and is input to the radar control
`apparatus via a switch mounted on the operator console.
`The radar employed for the front and rear sensors in this
`system is a Doppler radar. While the vehicle safety and
`protection system disclosed in this patent is effective in
`detecting and controlling the vehicle within sate operating
`limits to avoid a collision with a detected object, it has been
`found that certain improvements could be made to this
`system to improve its efficiency and to provide greater
`operator control over the system.
`The Doppler radar employed in this patented system is
`large and requires a considerable amount of space in the
`vehicle. The large diameter radar and low operating fre-
`quencies is necessary to provide the desired narrow beam
`directly in front of or to the rear of the vehicle so as to avoid
`detecting objects to the sides of the vehicle which do not
`prevent
`a potential collision situation to the vehicle.
`Specifically, the radar in this patent as well as other similar
`prior art vehicle radar systems has an effective diameter of
`six inches at an operating frequency of 10 to 24 GHz. This
`effective diameter and operating frequency creates a radar
`beam having a 6° beam width whichis particularly suited for
`vehicle applications as 6° covers one road lane width at the
`
`10
`
`15
`
`25
`
`30
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`range of the radar. However, the six-inch diameter radar is
`large and unwieldy and cannoteasily be mountedin existing
`vehicles due to minimal available space at the front and/or
`rear of such vehicles. However, merely employing a smaller
`effective diameter radar at a higher operating frequency,
`such as 24 GHz,hasthe effect of increasing the beam width
`to approximately 18°. This is unsuitable for vehicle appli-
`cations as 18° would cover up to three lanes of roadway and
`thereby detect objects to the sides of the vehicle in front or
`back of the vehicle which do not pose a potential collision
`situation.
`
`it would be desirable to provide a vehicle radar
`Thus,
`safety system which is capable of employing a smaller
`diameter radar than that previously employed in vehicle
`radar systems. It would also be desirable to provide such a
`small diameter radar in a vehicle radar system which is
`capable of operating at a high frequency and yet provides a
`sufficiently narrow radar beam. It would also be desirable to
`provide a vehicle radar safety apparatus which enables the
`operator of the vehicle to selectively control various oper-
`ating features of the radar system. Finally,
`it would be
`desirable to provide a vehicle radar system which automati-
`cally compensates for existing road conditions,1.e., wet or
`dry.
`
`SUMMARY OF THE INVENTION
`
`The present invention is a vehicle radar safety apparatus
`whichprovides an indication to the driver of a vehicle of the
`presence of objects in front of the vehicle and, optionally, ta
`the rear and sides of the vehicle, as well as providing an
`indication of the vehicle’s capability of stopping prior to
`colliding with a detected object to the front and/or rear of the
`vehicle.
`
`The vehicle radar safety apparatus comprises a front
`sensor means mounted on the vehicle for detecting objects
`to the front of the vehicle. A vehicle velocity sensor means
`providesan indication of the velocity of the vehicle. A signal
`processing means receives the outputs of the front sensor
`meansand the vehicle velocity sensor means for producing
`a first output indicative of the vehicle’s capability of stop-
`ping prior to colliding with an object detected by the front
`sensor meansin front of the vehicle.
`
`The signal processing means includes a radar means
`coupled to the front sensor means for producing a distance
`or range outpul indicative of the distance of the object
`detected by the front sensor from the vehicle. The signal
`processing means also includes a closing speed generating
`means coupled to the radar means for producing a signal
`indicative of the closing speed between the detected object
`and the vehicle. A vehicle velocity computer means is
`coupled to the vehicle velocity sensor means for producing
`a velocity output. Means are provided for summing the
`closing speed and the vehicle velocity and providing a
`summed output indicative thercof. Mcans, responsive to the
`summed output and the range output of the radar means,are
`provided for generating the first output when the summed
`output exceeds the range output.
`In a preferred embodiment, the radar means includes a
`horn antenna having a small effective diameter when oper-
`ating at a predetermined operating frequency. The horn
`antenna has first and second spaced ends and a side wall
`tapering inwardly from the second endto the first end. Radar
`transmitting and receiving means are mounted in signal
`communication with the first end of the horn antenna. A
`dielectric lens is mounted in the second end of the horn
`antenna and has an exterior surface shaped to reduce side
`
`9
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`

`5,905,457
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`3
`lobe generation in the transmitted radar waveso as to reduce
`the beam width of the transmitted radar wave.
`
`10
`
`15
`
`the lens has a generally
`In a preferred embodiment,
`plano-convex shape with a planarfirst surface facing thefirst
`end of the horn antenna and a convex surface facing outward
`from the second end of the horn antenna. The convex surface
`is formed at a predetermined radius of curvature.
`In a
`specific example, when the radar transmitter is operated at a
`frequency of 24.125 GHz and the horn antenna has an
`effective diameter of substantially three inches, a dielectric
`lens having a convex surface with a radius of curvature
`greater than one-half of the effective diameterofthe lens, is
`effective to transmit a radar wave over a specified range
`having a beam width of 6°. This 6° beam width is sufficient
`to cover only one lane of roadway at the range of the radar
`and thereby prevents the detection of objects or vehicles
`located in adjacentlanesor to the sides of the lane on which
`the vehicle employing the radar apparatus of the present
`invention is located.
`The vehicle radar safety apparatus of the present inven-
`tion also optionally includes speed control means, respon-
`sive to the signal processing means,for automatically apply-
`ing the vehicle brakes and/or moving the vehicle accelerator
`to a position to slowthe vehicle upon generation ofthe first
`output from the signal processing means. The speed control
`means preferably comprises an accelerator control means,
`mounted in the vehicle and coupled to the vehicle
`accelerator, for moving the accelerator in a direction to slow
`the vehicle in response to the first output from the signal
`processing means. Brake control means, coupled to the
`vehicle brake system, are also mounted in the vehicle for
`applying the vehicle brakes in response to the first output
`from the signal processing means.
`In vehicles having automatic cruise control, the vehicle
`radar safety apparatus also includes the speed control means
`generating a signal in response to the first output from the
`signal processing means for deactivating the automatic
`cruise control.
`
`The speed control means mayoptionally include a brake
`pedal depression sensing means for sensing depression of
`the vehicle brake pedal. The brake pedal sensing means
`gencratcs an output signal indicative of depression of the
`vehicle brakes, which output signal is input to the signal
`processing means to deactivate the brake and/or accelerator
`control means.
`
`The vehicle radar safety system also includes a water
`sensor means, mounted on the vehicle, for generating an
`output signal indicative of the presence of water in the path
`of movementofthe vehicle. ‘he signal processing means,in
`response to the output signal from the water sensor means,
`increases the distance threshold at which the first output is
`generated by the signal processing means. Further, a selector
`switch is mounted on the operator control and display
`console to sclectively switch the vchicle radar safety appa-
`ratus between a warning system and a warning and auto-
`matic brake and accelerator control system. This selector
`switch is input to the signal processing means which dis-
`ables the automatic accelerator and brake control meansfor
`a predetermined amountof time, i.e., twenty seconds.
`In addition to the front sensor means, the radar means may
`be coupled to the rear sensor for detecting the presence of an
`abject to the immediate rear of the vehicle. The vehicle radar
`safety system operates in substantially the same manner as
`described above to control the accelerator and brakes of the
`vehicle and/or provide only a warning indication to the
`operator of the presence of a vehicleto the rear of the vehicle
`
`45
`
`50
`
`55
`
`60
`
`65
`
`10
`
`4
`when the vehicle is in reverse. Optionally, the rear sensor
`and signal processing means may provide only a warning
`indication to the operator vehicle without any automatic
`accelerator and/or brake control.
`
`Side sensors in the form of proximity radars may also be
`mounted on the vehicle for indicating the presence of an
`object to the side of the vehicle. This is particularly suited
`for the side “blind spots” on the vehicle and provides an
`indication to the operator of the vehicle of the presence of
`objects to either side of the vehicle.
`The vehicle radar safety apparatus of the present inven-
`tion uniquely enables a small effective diameter radar to be
`operated at high operating frequencies sufficient to detect
`objects to the front and/orrear of the vehicle while providing
`such a radar in a smaller diameter than previously thought
`possible in vehicle radar systems. The radar also operates at
`frequencies heretofore not possible in vehicle radar appli-
`cations with the desired small effective radar diameter and
`narrow beam width.
`
`The vehicle radar safety apparatus of the present inven-
`tion also provides the operator of the vehicle with control
`over the with regard to providing a selection between
`warning and active accelerator and brake control system or
`merely a warning system. The vehicle radar system of the
`present invention also automatically adapts for changing
`road conditions, Le., wet or dry.
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`The various features, advantages and other uses of the
`present invention will become more apparentbyreferring to
`the following detailed description and drawing in which:
`FIG. 1 is a block diagram of a vehicle and the location of
`the sensors of the vehicle in accordance with the present
`invention;
`FIG. 2 is a block diagram of the vehicle radar safety
`system of the present invention;
`FIG. 3 is a front elevational view of the operator control
`and display console of the present invention;
`FIG. 4 is a block diagram of a proximity radar used in one
`embodimentof the present invention;
`FIG. 5 is a schematic diagram of the vehicle velocity
`computer employed in the present invention;
`FIG. 6 is a block and schematic diagram of the Doppler
`radar and control logic employed in the vehicle radar safety
`system;
`FIG. 7 is a schematic diagram of the signal processing
`unit used in the vehicle radar safety system;
`FIG. 8 is an exploded, side elevational, cross sectional
`view showing the construction of the horn antenna
`employed in the radar means of the present invention;
`FIG. 9 is a side elevational view of the lens employed in
`the radar means of the present invention; and
`FIG. 10 is a schematic diagram of the RF power supply
`circuit employed in the radar meansof the present invention.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`Referring now to the drawing, and to FIGS. 1 and 2 in
`particular, there is illustrated a vehicle radar safety apparatus
`for detecting the presence of object near a moving vehicle
`and for indicating to the operator of the vehicle the vchicle’s
`capability of stopping prior to colliding with the detected
`object. As shown in FIG. 1, a vehicle 10 has a plurality of
`sensors mounted thereon for detecting objects in the vicinity
`
`10
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`5,905,457
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`5
`of the vehicle 10. Front sensor 12 is mounted in the front of
`the vehicle 10 for detecting objects in front ofthe vehicle 10.
`Optional rear sensor 14 is mounted on the rear of the vehicle
`10 to detect objects to the rear of the vehicle 10. Optional
`side sensors 16 and 18 are mounted on the sides of the
`vehicle 10, at approximately the middle of the sides of the
`vehicle 10, to detect objects to the side of the vehicle 10,
`such as objects in a blind spot normally occurring on the
`sides of the vehicle 10.
`
`the side sensors 16 and 18 are
`As shown in FIG. 2,
`connected to an operator control and display console 20
`which is mountedin the vehicle 10 in a convenient location
`
`10
`
`6
`of which passes through a circulator 52 andfilter 54 to an
`antenna 56. The signal radiated by the antenna 56is reflected
`off of an object and is received by the antenna 56 and the
`filter 54 and passes through the circulator 52 to a mixer 58,
`preamplifier 60, and amplifier 62. The output of the amplifier
`62 is applied to an indicator, not shown, on the operator
`control and display console 20.
`As shown in FIG. 3,
`the operator display and control
`console 20 includes a display 66 for indicating the distance
`computed by the Doppler radar 22 between the vehicle 10
`and an object detected in front of the vehicle. The display 66
`may be any type of display, such as a digital or analog
`display. Also mounted on the operator display and control
`console 20 is a bar display 68 formed of a plurality of
`serially-arranged, light-emitting diodes (LED’s) 68a, 68b,
`etc. The LED’s 68a, 685,etc., are sequentially illuminated
`by the control system computer 30, as described hereafter, to
`provide an indication to the operator of the vehicle 10 of
`howfast the vehicle 10 is approaching a point from an object
`detected in front of the vehicle 10 at which the vehicle 10
`
`will be incapable of stopping prior to colliding with the
`detected object. An on/off switch 70 is mounted on the
`operator control and display console 20 for activating and
`de-activating the vehicle radar safety system of the present
`invention. A slide switch 72 is mounted on the console 20
`
`and provides an operator selection between aggressive and
`non-aggressive driving conditions. The operation of the
`switch 72 will be described in greater detail hereafter. A
`disable for time switch 44 is mounted on the console 20 to
`disable the automatic accelerator and brake control means
`
`34 for a predetermined amount of time, such as twenty
`seconds, as described hereafter. A metric select switch 73 is
`coupled to the display 66 and the radar means 22 to convert
`the display 66 output to meters.
`A typical circuit for the vehicle velocity computing means
`or computer 28 is depicted in FIG. 5. The vehicle velocity
`detection means or transducer 26 produces an electrical
`signal having a frequency of f,,. This signal is applied to an
`amplifier 82 and a comparitor 83, the output of which is
`applied to a monostable multivibrator 84. The output of the
`multivibrator 84 is applied across a diode 85 which gener-
`ates a voltage signal to an amplifier 90, the output of which
`is connected to a second amplifier 92. The output of the
`second amplifier 92 is connected to a drive transistor 94
`which provides a signal 96 to turn on the Doppler radar 22
`and to illuminate an LED 97in the console 20. The output
`signal 96 to the Doppler radar 22 is generated only when the
`vehicle velocity exceeds a predetermined value, such as ten
`miles per hour, as set by the reference input to the compari-
`tor 83. At speeds lower than this preset value, the vehicle
`radar safety system of the present invention will be inactive,
`despite the on/off switch 70 being in the “on” position. This
`is due to the fact that any collision between the vehicle 10
`and an object at speeds below the preset value are considered
`to be relatively safe. Of course, other preset trigger speeds
`may also be employed.
`The on/off switch 70 is connected to a conventional power
`supply circuit to generate the voltage level signals needed to
`operate the electronic components of the vehicle radar safety
`system.
`FIG. 6 depicts the Doppler radar means 22 which detects
`the range and closing speed between the vehicle 10 and
`abjects to the front and, optionally, to the rear of the vehicle
`10. The radar means 22 operates in a continuous wave
`Doppler mode with opening Doppler rejection and includes
`an RF power supply and squarewave generator 106, when
`activated by signal 96 indicating that the vehicle 10 is above
`
`so as to be easily visible to the operator of the vehicle 10.
`Front sensor 12 and rear sensor 14 are antennas connected
`to a Doppler radar means 22 which is part of a signal
`processing control means 24. A vehicle velocity sensing
`means, such as a transducer 26, is mounted on the vehicle
`and generates an output signal indicative of the velocity of
`the vehicle 10. This output signal is applied to a vehicle
`velocity computing means 28 which computes the velocity -
`of the vehicle based on the output of the vehicle velocity
`sensing meansor transducer 26. One output from the vehicle
`velocity computing means 28 is applied to the operator
`control and display console 20. Another outputof the vehicle
`velocity computing means 28 is applied to a control system
`computing means or computer 30.
`The control system computer 30 computes the distance
`required for the vehicle 10 to stop based on existing road
`conditions and the velocity of the vehicle and comparesthis
`computed value with the range or distance of an objected
`detected in front of the vehicle 10. The range or distance
`between the object detected by the front sensor 12 and the
`vehicle 10 is computed by the Doppler radar means 22.
`Based on this comparison, the control system computer 30
`generates a first output which is indicative of the vehicle’s
`ability to stop prior to colliding with the detected object.
`This output is applied to the operator control and display
`console 20 which provides an indication to the operator of
`the vehicle that the vehicle is approaching a distance from
`the object in front of it at which it will not be able to stop
`if the object in front of it is stationary or suddenly stops.
`One output 32 of the control system computer 30 is
`optionally applied to an accelerator and brake control means
`34 which generates a signal to suitable accelerator and brake
`control actuators shown in general by reference numbers 36
`and 37, respectively,
`to automatically move the vehicle
`accelerator to a position to slow down the vehicle and/or
`apply the vehicle brakes.
`Also input to the signal processing unit or means 24, and
`described in greater detail hereafter, is a gear shift position
`detection means or transducer 38. The gear shift position
`detection means or transducer 38 is input to the Doppler
`radar 22 and provides a signal indicative of the direction of
`movement of the vehicle 10. A water sensor means 40 is
`
`15
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`input to the control system computer 30 and detects the
`presence of water on the road surface. This signalis utilized
`by the control system computer 30 to increase the threshold
`distance at which a signal is provided to the operator of the
`vehicle 10 indicating that
`the vehicle is approaching a
`collision point with a detected object. Also input to the
`control system computer are a brake override switch 42 and
`a disable for time switch 44, both of which will be described
`in greater detail hereafter.
`Referring now to FIG. 4, there is depicted an example of
`the circuitry employed with a typical side sensor 16 or 18.
`The side sensor 16 includes a radar transmitter 50, the output
`
`60
`
`65
`
`11
`
`11
`
`

`

`5,905,457
`
`7
`a predetermined speed, supplies a squarewave RF signal
`through a modulator 108 to a radar transmitter 100. The
`transmitter 100 emits microwave energy through a horn
`antenna 101 which constitutes the front sensor 12 and which
`defines the degrees of beam width of the transmitted energy.
`A return signal reflected off of an object is received by the
`antenna 101 and a receiver 102. The receiver 102 output and
`the output of the modulator 108 are inputto a filter 104.
`FIG. 10 depicts the RF power supply and squarewave
`generator circuit 106 which is contained on a circuit board
`218 mounted along with a heat sink 219 about the horn
`antenna 101 as shownin FIG. 8. Input power from a suitable
`source 220 is supplied through a transformer and filter
`network to provide output power at leads 222 to the trans-
`mitter 100. This poweris regulated by an adjustable voltage
`regulator 224, IC Chip No. LM7230N, which provides an
`adjustable output voltage. This voltage is precisely set by a
`potentiometer 226 to generate the preferred +5 V output
`powerto the transmitter 100. Powerto the transmitter 100 is
`initiated by the input 96 as described hereafter.
`The input 96 also activates a crystal oscillator 228 which
`through a flip-flop 230 and associated gating circuitry sup-
`plies the specified frequencyto the transmitter 100 on leads
`232. By way of cxample,this frequency is 24.150 GHz +25
`MHz.
`In a mannersimilar to the circuit shown in FIG. 4 for the
`
`side sensors 16, 18, the transmitter 100 output is modulated
`in a circular mannerat the rate of 1,000 cycles per micro-
`second by sweeping the voltage applied to the varactorofthe
`transmitter 100 with a triangular waveform. The modulated
`transmitter 100 output passes through a circulator 221, FIG.
`8, before being applied to the radar antenna 101. The
`circulator 221 functions to transmit the radar wave as well
`
`to receive a radar wavereflected off of an object detected in
`the direction of movement, i.e., front or rear, of the vehicle.
`When receiving a reflected radar signal, the circulator 221
`passes such received signal to a detector means 233, such as
`a Gunn diode, which is connected across terminals 234 in
`FIG. 10. The output of the diode 233 is connected to filters
`104 described hereafter.
`
`An identical Doppler radar means 22 is also provided for
`the rcar sensor 14 as shown in FIG. 6. The RF powersupply
`and squarewave generator 106 is energized by a (+V) signal
`through the ON/OFF switch 70 and an output signal from the
`gear shift selector 36 when the vehicle 10 is in reverse.
`The squarewave generator 106 and modulator 108 gen-
`erate a squarewave signal whichis transmitted by the front
`sensor 12, for example,at a frequency of f,. The transmitted
`signal from the front sensor 12 is reflected off of an object
`located in front of the vehicle 10 andis received by the front
`sensor 12 at a frequencyf, greater than f,, if the vehicle 10
`is moving faster than the detected object. The reflected
`signal is at a frequency f, whichisless than f, if the object
`is movingfaster than the vehicle. The difference between fy
`and f, or f, and f, is indicative of the distance and the
`relative velocity or closing speed betweenthe vehicle 10 and
`the detected object.
`As shown in FIG. 8, the horn antenna 101 has first and
`second spaced ends 200 and 202, respectively. A side wall
`204 of the horn antenna 101 is shaped in the form of a funnel
`and tapers inwardly from the second end 202 to the first end
`200. The transmitter 100, circulator 221 and detector diode
`233 arc mounted in signal communication with thefirst end
`200 of the horn antenna 101. The circuit board 218 and heat
`219 are mounted to the transmitter housing adjacentthe first
`end 200.
`
`8
`The second end 202 of the horn antenna 101 has a
`separate inclined portion 206 which is adapted to fittingly
`receive one end of a dielectric lens 208. The dielectric lens
`
`208 is fixedly mounted in the inclined portion 206 at the
`second end 202 of the horn antenna 101 by suitable means,
`such as a pressfit, adhesives,etc.
`The dielectric lens 208 is formed of any suitable material
`whichis transparent to microwave radiation. In a preferred
`example, the diclectric lens 208 is formed of Rexolite 1442,
`sold by C-LEC Plastics, Inc., Beverly, NJ.
`As shown in FIGS. 8 and 9, the dielectric lens 208 has a
`first surface 210 which faces the first end 200 of the horn
`antenna 101 whenthe dielectric lens 208 is mounted in the
`second end 202 of the horn antenna 101 and an opposed
`second surface 212. The second surface 212 which faces
`outward from the second end 202 of the horn antenna 101
`and is an exterior surface on the dielectric lens 208 is shaped
`to reduce side lobe generationin the transmitted radar wave
`from the horn antenna 101. In a preferred embodiment, the
`dielectric lens 208 has a generally plano-convex shape with
`a substantially planar first surface 210 and a convex second
`or exterior surface 212. The radius of curvature (R.) of the
`second surface 212 is preferably greater than one-half of the
`effective diameter of the diclectric lens 208. This specified
`convex shape for the exterior surface 212 of the dielectric
`lens 208 effectively reduces side lobe generation in the
`transmitted radar wave so as to reduce the beam width of the
`
`transmitted radar wave. An annular inclined edge portion
`207 is formed adjacentthe first end 210 of the dielectric lens
`208 to conform to the inclined portion 206 at the second end
`202 of the horn antenna 101 and enable a secure mounting
`of the dielectric lens 208 in the second end 202 of the horn
`antenna 101.
`
`In a specific example, which is provided only to explain
`the unique features of the radar means 22 of the present
`invention and is not meantto limit the novel features of the
`
`radar meansto the specified dimensions, the dielectric lens
`208 is formed to have an effective diameter of substantially
`three inches, i.e.,