Abstract:
This invention provides a ground-speed measuring apparatus for a vehicle that can detect a velocity along the movement of the vehicle (in the fore direction), a velocity across the movement of the vehicle (in the athwartships direction), a side-skid angle of the vehicle, and an angular velocity of the vehicle. A ground-speed measuring apparatus comprising three or more transceivers each of which contains a transmitter for transmitting a wave and a receiver for receiving a reflection of the wave transmitted from the transmitter, wherein at least three of said transceivers are placed outside a cylindrical area whose axis of symmetry passes through a point on the floor of the vehicle, three straight lines which respectively pass through said transceivers perpendicularly thereto intersect with each other or skewed in said cylindrical area, and the transmitter of each transceiver is at a preset angle with the floor of the vehicle.

Description:
CLAIM OF PRIORITY  
       [0001]     The present application claims priority from Japanese application serial no. 2003-186083, filed on Jun. 30, 2003, and Japanese application serial no. 2004-167900, filed on Jun. 7, 2004, the contents of which are hereby incorporated by reference into this application.  
       FIELD OF THE INVENTION  
       [0002]     This invention relates to a ground-speed measuring apparatus for a vehicle and a method of mounting thereof on a vehicle.  
       BACKGROUND OF THE INVENTION  
       [0003]     A Janus-type Doppler ground-speed measuring apparatus has been well known as an apparatus for measuring ground speeds of vehicles (e.g. “Microwave Front End for True Ground Speed Measurements” by J. Kehrbeck et al., Journal of Navigation, pp. 88-96, Vol. 48, No. 1, 1995). The Janus-type system has two Doppler ground-speed measuring apparatus in the fore and aft directions of a vehicle to reduce deterioration in precision of detection due to assembling errors, road conditions, and unbalancing of loads in the fore and aft directions.  
         [0004]     Japanese Application Patent Laid-open Publication No. Hei 11-352225 discloses a ground speed measuring apparatus that enables measurement of speeds in fore, aft, and athwartship directions of the vehicle by employing three radio beams originated from transmitting means which are disposed on vertices of a certain equilateral triangle.  
       SUMMARY OF THE INVENTION  
       [0005]     The above Janus-type Doppler ground-speed measuring apparatus, however, cannot measure the velocity in the athwartship direction of the vehicle because the Janus-type is designed to measure velocities only in the fore direction of the vehicle.  
         [0006]     Further, the ground speed measuring apparatus of Japanese Application Patent Laid-open Publication No. Hei 11-352225 has a problem that, when the vehicle or the body rotates in the yawing direction (in a plain parallel to the road surface) around the center  02  of an equilateral triangle as shown in  FIG. 12 , it is impossible to measure a velocity component in the yawing direction (angular velocity).  
         [0007]     This invention is made to solve the above problem. An object of this invention is to provide an apparatus that can measure velocities in the fore, aft, and athwartship directions, side-skid angles of the vehicle, and angular velocities of the vehicle.  
         [0008]     In an aspect of the invention, a ground-speed measuring apparatus comprises three or more transceivers each of which contains a transmitter for transmitting a wave and a receiver for receiving a reflection of the wave transmitted from the transmitter, wherein  
         [0009]     at least three of said transceivers are placed outside a cylindrical area whose axis of symmetry passes through a point on the floor of the vehicle,  
         [0010]     three straight lines which respectively pass through said transceivers perpendicularly thereto intersect with each other or skewed in said cylindrical area, and  
         [0011]     the transmitter of each transceiver is at a preset angle with the floor of the vehicle. 
     
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0012]      FIG. 1  shows a top view of a ground speed measuring apparatus which is an embodiment of this invention.  
         [0013]      FIG. 2  shows a side view of a ground speed measuring apparatus which is an embodiment of this invention.  
         [0014]      FIG. 3  shows a ground speed measuring apparatus which is an embodiment of this invention.  
         [0015]      FIG. 4  shows an example of coordinate axes used for vehicle control.  
         [0016]      FIG. 5  shows an example of flow chart to measure velocities in accordance with this invention.  
         [0017]      FIG. 6  shows an example of installation of the ground speed measuring apparatus which is an embodiment of this invention.  
         [0018]      FIG. 7  shows an example of a vehicle having the ground speed measuring apparatus which is an embodiment of this invention.  
         [0019]      FIG. 8  shows examples of vehicles having the ground speed measuring apparatus which is embodiments of this invention.  
         [0020]      FIG. 9  shows an example of a mounting structure of the ground speed measuring apparatus which is an embodiment of this invention.  
         [0021]      FIG. 10  shows an example of a mounting structure of the ground speed measuring apparatus which is an embodiment of this invention.  
         [0022]      FIG. 11  shows an example of a mounting structure of the ground speed measuring apparatus which is an embodiment of this invention.  
         [0023]      FIG. 12  shows a top view of a ground speed measuring apparatus of a prior art.  
         [0024]      FIG. 13  shows an example construction of a ground-speed measuring apparatus which is an embodiment of this invention.  
         [0025]      FIG. 14  shows a variation of the embodiment of  FIG. 13 .  
         [0026]      FIG. 15  shows an example construction of a transceiving means which is an embodiment of this invention.  
         [0027]      FIG. 16  shows another construction of a transceiving means which is another embodiment of this invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     This invention will be described in further detail by way of embodiments.  
         [0029]      FIG. 1  shows a ground speed measuring apparatus which is an embodiment of this invention. Peculiarly,  FIG. 1  shows a top view of a Doppler type ground speed measuring apparatus. The x- and y-axes of the apparatus mounted on a vehicle represent the same axes of  FIG. 4 .  
         [0030]     In  FIG. 1 , transceiving means  100 ,  101 , and  102  respectively transmit waves and receive their reflections upon the road surface. C is a circle of a radius r with a point O 1  as the center. The transceiving means  100 ,  101 , and  102  are placed on points P 0 , P 1 , and P 2  on the circle C so that they may respectively transmit waves tangentially to the circle (when viewed from the above).  
         [0031]     Although transceiving means  100 ,  101 , and  102  seem to transmit waves in the in-plane direction in parallel with the circle C in  FIG. 1 , they substantially transmit waves to the road surface. Therefore, the transceivers  200 ,  201 , and  202  of the transceiving means are respectively disposed at a depression angle θ with a plane including the circle C. Here,  203  represents a vehicle structure (such as a chassis) and  204  represents the road surface.  
         [0032]     In  FIG. 1 , the dotted circle C, the x-axis, the y-axis, the dotted lines S 0 , S 1 , and S 2  are given to explain the positional relationship of the transceiving means  100 ,  101 , and  102  for the sake of convenience.  
         [0033]     Referring to  FIG. 3  and  FIG. 5 , we explain below an example of calculating velocities in the fore, aft, and athwartship directions of a vehicle and a side-skid angle by the ground speed measuring apparatus of  FIG. 1 .  
         [0034]      FIG. 3  shows an example of functional block diagram of the transceiving means  100 ,  101 , and  102 . This example assumes that the transceiving means  100 ,  101 , and  102  transmit and receive radio waves. Referring to  FIG. 2 , the transceiver  200  comprises a transmitter  301  and a receiver  302 . The transmitter  301  receives a radio wave modulated at a transmission frequency due to a modulation signal from the modulator  303  and emits the radio wave to the road surface. The radio wave reflected upon the road surface is received by the receiver  302  and frequency-converted by the mixing circuit  305 . The mixing circuit  305  mixes this signal with a signal coming from the oscillator  304  and sends the resulting low-frequency signal to the analog circuit  306 . This low-frequency signal is amplified by the analog circuit  306 , converted into a digital signal (as sample data) by the analog/digital (A/D) converter  307 , and fed to the FFT processor section  308 . The FFT processor section  308  performs a fast Fourier transform on the digital signal (sample data). The result represents the frequency spectrum of the received beat signal in all frequency bands. The signal processor section  309  detects peaks in the result of the FFT processing, applies a Doppler frequency fd to the detected peak, and calculates a velocity v by Equation 1 below. 
   v =( c·fd )/(2· ft )  (Equation 1)  
         [0035]     wherein fd is a Doppler frequency. c is the velocity of light. ft is the frequency of the transmitted wave.  
         [0036]     In  FIG. 1 , the transmitting direction of the transceiving means  101  and  102  are the angle of θ 1  and θr on the basis of the transmitting direction of the transceiving means  100 , respectively. Moreover, the speed calculated by Equation 1 based on the signal obtained by the transceiving means  100 - 102  is v 1 , v 2 , and v 3 , respectively. As these velocities v 1 , v 2 , and v 3  are velocity components at the depression angle θ with a plane in parallel with the road surface (see  FIG. 2 ), step S 501  converts these velocities v 1 , v 2 , and v 3  into velocity components in a plane in parallel with the road surface by Equations 2 to 4. 
 
 V 1 =v 1/cos θ  (Equation 2) 
 
 V 2= v 2/cos θ  (Equation 3) 
 
 V 3= v 3/cos θ  (Equation 4) 
 
         [0037]     Step S 502  calculates the output offset (Vw) of respective transceiving means from velocities V 1 , V 2 , and V 3  and the angular velocity component (yaw rate) around the z-axis of the vehicle using Equation 5. 
 
 Vw =(sin θ1( V 1 cos θ r−V 2)−sin θ r ( V 1 cos θ1− V 3))/(sin θ1(cos θ r− 1)−sin θ r (cos θ1−1))  (Equation 5) 
 
         [0038]     When the angular velocity is represented by w, Vw is equal to rw. Therefore, we can get the angular velocity (yaw rate) w from Equation 5.  
         [0039]     Step S 503  calculates the differences between the velocities V 1  to V 3  and the output variations of the transceiving means  100  to  102  due to the influence of the rotational motion of the vehicle by Equations 6 to 8. 
 
 VF=V 1− Vw (Equation 6) 
 
 VL=V 2− Vw   (Equation 7) 
 
 VR=V 3− Vw   (Equation 8) 
 
         [0040]     Where VF, VL, and VR respectively represent differences between velocities V 1  to V 3  and the angular velocity (the output offset).  
         [0041]     The next steps S 504  and S 505  calculate the velocity in the fore direction of the vehicle (the first x-axis velocity Vx 1 ) and the velocity in the aft direction of the vehicle (the second x-axis velocity Vx 2 ). Here, Vx 1  is equal to VF as Vx 1  and VF are is in the same direction.  
         [0042]     The second x-axis velocity Vx 2  is the composition of fore and aft velocity components of VL and VR which are calculated from the outputs of the transceiving means  11  and  12 . This is expressed by Equation 9. 
 
 Vx 2=|−( VR  cos θ r+VL  cos θ1)|  (Equation 9) 
 
         [0043]     Step S 506  calculates the velocity Vx in the x-axis (in the fore and aft directions of the vehicle) from the first and second x-axis velocities Vx 1  and Vx 2 ). This is expressed by Equation 10. 
 
 Vx =( Vx 1+ Vx 2)/2  (Equation 10) 
 
         [0044]     Step S 507  calculates the ratio (Rx) of the second x-axis velocity Vx 2  to the first x-axis velocity Vx 1 . This is expressed by Equation 11. 
 
 Rx=Vx 2/ Vx 1  (Equation 11) 
 
         [0045]     Step S 508  calculates the y-axis velocity Vy (in the athwartship direction of the vehicle). The y-axis velocity is calculated as the composition of y-axis velocity components of VL and VR (by Equation 12) but must be compensated as the y-axis velocity is affected by pitching of the vehicle (tilting in the fore and aft directions of the vehicle). 
 
 Vy=VR  sin θ r−VL  sin θ1  (Equation 12) 
 
         [0046]     The fore and aft tilting of the vehicle is reflected on the x-axis velocity ratio (Rx). Rx=1 indicates that the vehicle is running ideally without any pitching. Rx&gt;1 indicates that the vehicle is pitching forward and Rx&lt;1 indicates that the vehicle is pitching backward. Therefore, Vy corrected by Equation 13 is used as a new y-axis velocity Vy. 
 
Vy←Vy/Rx  (Equation 13) 
 
         [0047]     Step S 509  calculates the side-skid angle β from the x-axis velocity Vx and the y-axis velocity Vy. This is expressed by Equation 14. 
 
β=arctan( Vy/Vx )  (Equation 14) 
 
         [0048]     As described above, we reduced influences of pitching of the vehicle on velocities in the fore, aft, and athwartship directions and increased the accuracy in measurement of ground velocities of the vehicle by calculating the velocities including the fore-aft pitching of the vehicle.  
         [0049]     In this way, the ground-speed measuring apparatus of this invention can measure velocities in the fore, aft, and athwartship directions, and side-skid angles of the vehicle. Even when the movement of the vehicle contains a rotation around the vehicle center O 1 , the ground-speed measuring apparatus of this invention can measure velocities in the fore, aft, and athwartship directions, side-skid angles of the vehicle, and angular velocities of the vehicle without losing the rotational velocity component. Therefore, this apparatus can work both as a velocity sensor and an angular velocity sensor and need not an additional angular velocity sensor as in the case with conventional ground speed measuring apparatus. This can also has an effect to reduce the manufacturing cost of the apparatus. Further, when these three transceiving means are disposed on the vertices of an equilateral triangle, θ 1  becomes equal to θr and the computation can be simplified.  
         [0050]     This invention does not always limit the layout of the transceiving means to that of  FIG. 1 . For example, the transceiving means  100  to  102  can be respectively turned by preset angles from the positions shown in  FIG. 6 (A) around the center O 1 . However, one of the transceiving means must face to the fore or aft direction of the vehicle (the x-axis direction) when the equations of this embodiment are used. When none of the transceiving means face to the fore or aft direction of the vehicle, Vx 1  is not equal to VF and the velocity VF has velocity components in the fore-aft and athwartship directions. Therefore these velocity components must be calculated individually. However, also in this case, it is possible to measure velocities in the fore, aft, and athwartship directions, side-skid angles of the vehicle, and angular velocities of the vehicle similarly in principle.  
         [0051]     Further, this embodiment disposes the transceiving means so that they may transmit waves tangentially to the circle and clockwise around the center of the circle (when viewed from the top). The similar effect can be obtained also when the transceiving means are disposed to transmit waves counterclockwise.  
         [0052]     Furthermore, although this embodiment disposes three transceiving means on a circle, it is also possible to dispose the transceiving means on concentric circles (having a point O 1  as the center) as shown in  FIG. 6 (B). In this case, the offsets are corrected by Equation 5 and the similar effect can be obtained. As long as three transceiving means are disposed to satisfy a preset relative positional condition, the wave transmission directions can be determined independently of the movement of the vehicle. Therefore, they can be mounted on the vehicle with less limitation.  
         [0053]     Below will be explained an embodiment which uses the ground speed measuring apparatus of this invention for vehicle control.  
         [0054]     In automobile fields, ABS (Anti-lock Brake System) and ESP (Electronic Stability Program) have been well known as safety means to stabilize an unstable vehicle (against a sliding, etc.). Similarly, an active suspension control has been well known to make vehicle riding comfortable.  
         [0055]     The Antilock Brake System (ABS) controls to prevent wheels from being locked during sudden “panic” braking and the Electronic Stability Program (ESP) controls to prevent the vehicle from skidding during driver&#39;s steering control. The active suspension control means has actuators on the suspensions and causes the actuators to damp swaying of the vehicle.  
         [0056]     These kinds of vehicle control require input information such as ground speeds and/or angular velocities of the vehicle. As employing a Janus type Doppler ground-speed measuring apparatus which is described above in “Prior Art” as a means to detect ground speeds and an angular velocity sensor such as a gyro sensor as a means to detect angular velocities, the current vehicle control system must be equipped with a plurality of sensors and enter their information of detection into the controller. This increases their installation spaces, limits their mounting positions, makes their wiring complicated, and increases their manufacturing cost.  
         [0057]     Contrarily, the ground-speed measuring apparatus of this invention enables simultaneous measurement of both ground speeds and angular velocities by a single unit and can solve the above problems. Some embodiments will now be described more fully in detail with reference to the accompanying drawings.  
         [0058]      FIG. 7  shows an example of Electronic Stability Program (ESP) installed in a car.  FIG. 8 (A) and  FIG. 8 (B) respectively show an example of active suspension system installed in a train and an example of active suspension system installed in a car.  
         [0059]     Referring to  FIG. 7, 705  represents the ground-speed measuring apparatus of this invention.  701  to  704  respectively represent a brake caliper on each wheel.  706 ,  707 ,  708 , and  709  respectively represent a controller, a hydraulic unit, a master cylinder, and a steering sensor in this order. The dotted lines represent signal lines and the solid lines represent hydraulic lines.  
         [0060]     In this measuring system, the ground-speed measuring apparatus  705  detects velocities of the vehicle and angular velocities of the vehicle around the z-axis. The steering sensor  709  detects steering angles of the vehicle. The controller uses these kinds of detected information to individually control the braking forces for the brake calipers  701  to  704  on wheels. Substantially, if the vehicle is over-steered when taking a curve, the controller controls to brake the outer front wheel to prevent spinning. If the vehicle is under-steered, the controller controls to brake the inner rear wheel to turn the car body inwards or gives different braking forces to inner and outer wheels to stabilize the turning. Although this system uses oil pressure to drive the brake calipers, electrically-driven actuators can be used.  
         [0061]     Referring to  FIGS. 8, 801  and  851  respectively represent the ground-speed measuring apparatus of this invention.  802  and  852  respectively represent a controller.  803 ,  804 ,  853 , and  854  are actuators.  811 ,  812 , and  862  represent signal lines and/or power transmission lines.  
         [0062]     A running vehicle is subject to vibrations  831  or  881  (yawing) around the z-axis of the vehicle due to road surface conditions, wheel structures, and so on. This yawing gives various influences to passengers and loads on the vehicle. To suppress the yawing, the ground-speed measuring apparatus of this invention detects the vehicle velocity and the angular velocity around the z-axis (to be abbreviated simply as an angular velocity) and drives the actuators  803 ,  804 ,  853 , and  854  to counteract the detected angular velocity.  
         [0063]     The above ESP and active suspension control have been typical now, but the conventional ESP and active suspension controlling system uses a gyro sensor or the like to detect angular velocities and a ground speed measuring apparatus which is described in “Prior Art” to detect the ground velocity.  
         [0064]     Contrarily, the ground speed measuring apparatus of this invention can measure the angular velocities and ground velocities simultaneously by a single unit. Of course, no additional sensor such as a gyro sensor is required to detect angular velocities. This can reduce its manufacturing cost. Further, this can make the apparatus compact, reduce the installation space, and shorten wires between the controller ( 706 ,  802 , or  852 ) and sensors. Furthermore, it is possible to connect the ground speed measuring apparatus directly to the controller (as shown in  FIG. 8 (B)) or to house the apparatus and the controller in a box (not shown in the figure).  
         [0065]     Still further, the ground speed measuring apparatus of this invention can detect angular velocities more quickly than a gyro sensor. This enables high-accuracy detection of angular velocities and high-accuracy vehicle controlling.  
         [0066]     Next, we explain sample conditions and methods of mounting the ground speed measuring apparatus of this invention.  
         [0067]     In principle, the ground speed measuring apparatus of this invention can be mounted in any manner as long as three transceivers satisfy the positional and angular conditions shown in  FIG. 1  or  FIG. 6  and  FIG. 2   
         [0068]     However, it is very complicated and time-consuming to mount the transceivers individually on the vehicle while satisfying the positional and angular conditions shown in  FIG. 1  or  FIG. 6  and  FIG. 2 . To solve this problem, it is recommended to assemble three transceivers in a unit to satisfy the preset positional and angular conditions and to mount this unit on a vehicle.  
         [0069]      FIG. 9  shows an example of layout of the ground speed measuring apparatus of this invention on a vehicle.  FIG. 9 (A) is a worm&#39;s-eye view of the ground speed measuring apparatus and  FIG. 9 (B) is a perspective worm&#39;s-eye view of the ground speed measuring apparatus.  
         [0070]     In  FIG. 9, 901  is a box housing three transceivers  902  which transmit and receive waves. The transceiving block of each transceivers  902  are exposed outside from notches  904 , respectively. Three transceivers  902  are disposed so that they may transmit waves tangentially to a circle on which they are seated (see  FIG. 1 ) when viewed from the top and that they may be at a preset angle with the road surface as shown in  FIG. 2 .  
         [0071]     This unit configuration makes high-precision mounting and installation of the apparatus easier than the configuration in which three transceivers are mounted individually.  
         [0072]     The unit bottom having notches through which the transceivers  902  are exposed outside can be covered with a cover member  1001  whose material can transmit waves from the transceivers  902  as shown in  FIG. 10 (A) or with a cover member  1001  whose areas  1102  facing to the notches  904  are made of materials that can transmit waves as shown in  FIG. 11 (A). This cover can protect the transceivers  902  against water, dust, sands, and any other contaminants that come from the outside of the vehicle.  
         [0073]     Further, it is possible to make the unit bottom (facing to the road surface of the box  901 ) itself made of a wave-transmittable material instead of covering the unit bottom with the above cover of  FIG. 10 (A) and  FIG. 11 (A). This can make assembling and installation of the ground speed measuring apparatus much simpler and easier.  
         [0074]     Furthermore, it is possible to cover each notch  904  of  FIG. 9  with a separate cover member  1103  as shown in  FIG. 11 (B).  
         [0075]     As shown in  FIG. 10 (B), it is possible to provide a processing section  905  for generating waves and processing transmitted and received signals inside the box (unit)  901  and a connection section for connecting signal and power lines to the vehicle on the outer wall of the box  901 . This configuration enables installation of the ground speed measuring apparatus and connection of its signal and power lines to the vehicle at the same time. This simplifies the installation works of the apparatus greatly. In this embodiment, the processing section  905  can contain all or part of the modulator  303 , the oscillator  304 , a mixing circuit  305 , an analog circuit  306 , an A/D converter  307 , an FFT processing section  308 , and a signal processor  309  shown in  FIG. 3 .  
         [0076]     Referring to  FIG. 13  and  FIG. 14 , we&#39;ll explain an embodiment of the interior of the ground-speed measuring apparatus of  FIG. 9  to  FIG. 11 .  
         [0077]      FIG. 13  ( a ) shows a side view of the ground-speed measuring apparatus of  FIG. 9  to  FIG. 11  and  FIG. 13  ( b ) shows a bottom view of the apparatus. As explained above, three transceiving means  902  ( a ),  902  ( b ), and  902  ( c ) are laid out in place on the common box  901  as shown in  FIG. 1 ,  FIG. 5 , and  FIG. 6 . The transceiving means  902  ( a ),  902  ( b ), and  902  ( c ) are equivalent to the means  200  in  FIG. 2 . Each of the transceiving means  902  ( a ),  902  ( b ), and  902  ( c ) is comprised of a microwave monolithic integrated circuit (MMIC) which contains a modulator  303 , a transmitter  304 , a mixing circuit  305 , and so on, and a transceiving means (equivalent to the transceiving means  100 ,  101 , or  102  of  FIG. 1 ) which contains an analog circuit  306 . Each of the transceiving means  902  ( a ),  902  ( b ), and  902  ( c ) transmits an electric wave, receives its reflection on the ground, generates an intermediate frequency (IF) signal from the transmitted and received signals, amplifies and outputs this IF signal. This IF signal is fed to a signal processing board  1301  in the box  901 . The signal processing board  1301  is equipped with an A/D converter  307 , an FFT processor  308 , and a signal processor  309 , converts the received IF signal to a digital signal, performs a fast Fourier transform (FFT) on the signal, and gets the ground speed and angular velocity of the vehicle from peaks of the result.  
         [0078]     The signal processing board  1301  receives IF signals from three transceiving means  902  ( a ),  902  ( b ), and  902  ( c ). This board  1301  is also equipped with a storage section that stores the location of the ground-speed measuring apparatus on the vehicle (e.g. deviation from the center of rotation of the vehicle) and the mounting angle of the apparatus on the vehicle (e.g. angle between the wave transmission direction and the movement of the vehicle). This board  1301  calculates the ground speed and other values of the vehicle from peaks detected in three IF signals sent from three transceiving means and information related to their installation using the above Equations (1) to (14).  
         [0079]     A power supply board  1302  in the box  901  receives electric power from the outside of the apparatus, converts it to voltages fit to the transceiving means  902  ( a ),  902  ( b ), and  902  ( c ), and sends the voltages to the transceiving means. The box  901  is equipped with a single connector that contains power supply wires from the in-vehicle power supply and output signal wires to output the result of measurement such as a ground speed from the signal processing board to the outside of the apparatus.  
         [0080]     As these three transceiving means share the power supply board  1302  and the signal processing board  1301  in this way, the apparatus can be simplified, down-sized and be placed anywhere under the vehicle floor. Further, although the measuring means using electric waves must have a common ground potential, these three transceiving means can easily have a common ground potential by sharing the power supply board  1302 . Furthermore, this embodiment has the power supply board  1302  and the signal processing board  1301  at an identical horizontal level. This structure can reduce the height of the box  901  and release the dimensional limitation of the box under the vehicle floor.  
         [0081]      FIG. 14  is a variation of the embodiment of  FIG. 13 . Although the embodiment of  FIG. 13  can reduce the height of the box  901  as it has the power supply board  1302  and the signal processing board  1301  at an identical horizontal level, its horizontal dimensions cannot be reduced so much. In contrast, this embodiment piles up these boards  1301  and  1302 . This makes the vertical dimensions of the box  901  a little greater than those of the embodiment but can reduce the horizontal dimensions of the box.  
         [0082]     There are various kinds of vehicles from light cars to heavy-duty trucks and they have various dimensional limitations. For example, a box that is smaller in horizontal dimensions may be preferable for light cars and compact cars whose under-floor areas are limited. Further, a box that is smaller in vertical dimensions may be preferable for off-road vehicles to secure a greater vehicle height. Accordingly, box structures of  FIG. 13  and  FIG. 14  can be selectively used according to the types and uses of vehicles.  
         [0083]     Referring to  FIG. 15 , an embodiment of the transceiving means  902  ( a ),  902  ( b ), and  902  ( c ) will be explained in more detail below. In  FIG. 9  to  FIG. 14 , only the transceiving section  902  (equivalent to the transceiving means  200 ,  201 , and  202  in  FIG. 1  and the transceiving means  200  in  FIG. 3 ) is explained and it seems like a flat plate. Actually, however, it is built up as a transceiving means (equivalent to the transceiving means  100 ,  101 , and  102  in  FIG. 1 ) that includes a circuit to transmit an electric wave from the relevant transceiving section.  
         [0084]     As shown in  FIG. 15 , the transceiving means  1500  is equipped with a high-frequency circuit board  1501 . This high-frequency circuit board  1501  is equipped with a microwave monolithic integrated circuit (MMIC)  1502 . The MMIC  1502  is an integrated circuit comprising a transceiving section  200  (transmitter and receiver), a modulator  303 , a transmitter  304 , and a mixing circuit  305 . It transmits an electric wave, receives its reflection on the ground, and mixes the transmitted and received waves. Further, it amplifies the resulting low-frequency signal (which is also termed as an intermediate frequency (IF) signal). The amplified signal is sent to the signal processing board  1301  of  FIG. 15  and so on. Here, signal wires  1506  and power supply wires  1507  from the high-frequency circuit board  1501  are connected to the connector on the cover  1513 . The high-frequency circuit board  1501  receives power from the outside and transfers signals to and from the outside through this connector.  
         [0085]     As for a Doppler ground-speed measuring apparatus like this embodiment using electric waves, electric waves transmitted from the transceiving means spread wide at a certain angle. When the electric waves spreads, the transceiving means receive innumerable reflected waves of different velocity components in every direction. This may decrease the accuracy of velocity measurement. Therefore, it is ideal that the electric waves are emitted like a straight line ( 1510 ) as shown in  FIG. 15 . However, as the spreading angle of electric waves is approximately in inverse proportion to the width of the transceiving means, the spreading angle of the electric waves may be greater as the transceiving means is made smaller.  
         [0086]     To converge the electric waves that are transmitted from the transceiving antenna, this embodiment provides a primary lens in the wave transmission side of the transceiving section  200  of MMIC  1502 . It is preferable that the primary lens  1503  is shaped convex as shown in  FIG. 15  ( b ). This lens shape can converge the electric waves transmitted from the transceiving section to a predetermined angle. This configuration can increase the accuracy of measurement of a ground speed of the vehicle while reducing the size of the transceiving section.  
         [0087]     Further, this embodiment places a secondary lens  1504  before the primary lens to converge the transmitted waves further ( 1511 ). It is more preferable to mount the ground-speed measuring apparatus on the vehicle with the focus  1512  put on the road surface because the same effect as the electric waves are transmitted in a straight line can be obtained.  
         [0088]      FIG. 16  is a variation of the transceiving means  100 ,  101 , and  102  of  FIG. 1  and others. The embodiment of  FIG. 16  is the same as the embodiment of  FIG. 16  but the embodiment of  FIG. 16  has a power supply board  1601  in the transceiving means  100 . In this case, the common power supply board  1302  like that of  FIG. 13  is not needed but each transceiving means must be equipped with a power supply board  1601 . Each of these power supply boards  1601  receives power from the in-vehicle power supply such as a car battery, converts it to a proper voltage, and supplies it to the high-frequency circuit board  1501  and so on. The power supply board  1601  is connected to the high-frequency circuit board  1501  with the power wires  1604  and the connector  1605 . The power supply board  1601  receives power from the outside of the transceiving means  100  through the power lines  1604  and the connector  1605 .  
         [0089]     Each transceiving means ( 100 ,  101 , or  102 ) of the embodiments of  FIG. 15  and  FIG. 16  contains a high-frequency circuit board  1501  or a set of a high-frequency circuit board  1501  and a power supply board  1601  in a cylindrical structure  100   c  having an opening (whose sectional shape can be any of a circle, a polygon, and an irregular figure). The cylindrical structure  100   c  has flange-like protrusions  100   a  and  100   b  on the inner wall of the structure  100   c . When the high-frequency circuit board  1501  is inserted into the cylindrical structure  100   c , its peripheral edges are stopped and supported by the flange-like protrusion  100   a . In this case, the high-frequency circuit board  1501  is installed with the transceiving antenna and the primary lens projected from the central opening of the flange  100   a . To enable accurate positioning of the high-frequency circuit board  1501  in the structure  100   c , projection  100   a , or the high-frequency circuit board  1501  can have protrusions, dents, or both to be fit to each other. In the embodiment of  FIG. 16 , the power supply board  1601  is butted with the protrusion  100   b . The high-frequency circuit board  1501  is first inserted into the cylindrical structure through the central opening of the flange-like protrusion  100   b  and then the power supply board  1601  is inserted into the cylindrical structure. After the power supply board  1601  is installed, the opening of the structure is closed with a cover  1513 . A connector  1505  can be provided on the cover  1513  to connect signal wires, power wires, or both to the outside. This enables installation of a connector on a place of a simpler shape even when the cylindrical structure has a complicated shape. This makes the production of the apparatus easier.  
         [0090]     Furthermore, the embodiments of  FIG. 15  and  FIG. 16  respectively have a secondary lens  1504  on an opening of the structure opposite to the opening through which the high-frequency circuit board is inserted. This makes adjustment of the mounting angle and location of the secondary lens. When the lens  1504  also works as the cover of the opening, the number of parts of the apparatus can be reduced.  
         [0091]     This invention can improve the measuring performance of a ground speed measuring apparatus and enables a single ground speed measuring apparatus to measure velocities in the fore, aft, and athwartship directions, side-skid angles of the vehicle, and angular velocities of the vehicle.